Magnetic iron oxide nanoparticle based sensors and biosensors and methods of use thereof

Abstract

This invention relates to magnetic iron oxide nanoparticle-based sensors and biosensors. This invention also relates to sensing methods utilizing magnetic iron oxide nanoparticle-based sensors. This invention also relates to biosensing methods utilizing magnetic iron oxide nanoparticle-based biosensors. A key approach is to utilize magnetic iron oxide nanoparticles (spherical shape) with appropriate particle size and magnetic properties (superparamagnetic and ferrimagnetic properties) to enhance the efficiency, sensitivity, and selectivity of magnetic nanoparticle-based sensors and biosensors by selecting nanoparticles with suitable particle size and crystallite size. Another key approach is to utilize magnetic iron oxide nanoparticles (cuboid shape) with appropriate particle size and ferrimagnetic properties to enhance the efficiency, sensitivity, and selectivity of magnetic nanoparticle-based sensors and biosensors by selecting nanoparticles with suitable particle size.

Description

MAGNETIC IRON OXIDE NANOPARTICLE BASED SENSORS AND BIOSENSORS AND METHODS OF USE THEREOF CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 63 / 546,142 filed October 27, 2023, the contents of which is incorporated herein by reference in its entirety STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] This invention was made with government support under Grant No. FA9550-20-1- 0349 awarded by the U.S. Air Force Office of Scientific Research. The government has certain rights in the invention. FIELD OF THE INVENTION

[0003] This invention relates to magnetic iron oxide nanoparticle-based sensors and biosensors. This invention also relates to sensing methods utilizing magnetic iron oxide nanoparticle-based sensors. This invention also relates to biosensing methods utilizing magnetic iron oxide nanoparticle-based biosensors. BACKGROUND

[0004] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference. The following description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

[0005] Current biosensor technology relies on the use of superparamagnetic iron oxide nanoparticles in the single-domain size range (<25 nm) or micron-sized magnetic beads as the magnetic labeling signal for biosensing. However, this current biosensor technology has several disadvantages. Single-domain nanoparticle biosensors are limited by weak magnetization and thus 4880-1178-1618.1 Page 1 of 66094876-000022WOPTlow sensitivity. Micron-sized magnetic bead based biosensors exhibit higher magnetization, leading to increased signal sensitivity, but the substantial size difference between micron-sized magnetic beads and biomolecules reduces their selectivity and recognition capabilities. Therefore, there is an ongoing need for magnetic iron oxide nanoparticle based biosensors that overcome these disadvantages. The embodiments of the present invention address these needs. SUMMARY OF THE INVENTION

[0006] In various embodiments, the present invention provides a sensor, comprising: at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises a plurality of iron oxide primary crystals, wherein the plurality of iron oxide primary crystals comprise a plurality of crystallites, wherein the at least one magnetic nanoparticle has a particle size of 49 nm to 420 nm, wherein the plurality of crystallites have a crystallite size of 10 nm to 40 nm, wherein the at least one magnetic nanoparticle has a spherical shape; wherein the plurality of iron oxide primary crystals does not have a core-shell structure; and wherein the at least one magnetic nanoparticle does not have a core-shell structure; or at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises a single iron oxide crystal, wherein the at least one magnetic nanoparticle has a particle size of 19 nm to 207 nm, wherein the at least one magnetic nanoparticle has a polyhedral shape; and wherein the at least one magnetic nanoparticle does not have a core-shell structure; or a combination thereof.

[0007] In various embodiments, the present invention provides a sensor, comprising: at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises a plurality of iron oxide primary crystals, wherein the plurality of iron oxide primary crystals comprise a plurality of crystallites, wherein the at least one magnetic nanoparticle has a particle size of 49 nm to 420 nm, wherein the plurality of crystallites have a crystallite size of 10 nm to 40 nm, wherein the at least one magnetic nanoparticle has a spherical shape; wherein the plurality of iron oxide primary crystals does not have a core-shell structure; and wherein the at least one magnetic nanoparticle does not have a core-shell structure. In some embodiments, the sensor of the present invention further comprises at least one receptor, wherein the at least one receptor is connected to or attached to the at least one magnetic nanoparticle. In some embodiments, the at least one receptor is deoxyribonucleic acid (DNA), antibody, enzyme, cell, aptamer, protein, or peptide, or any combination thereof. In some embodiments, the at least one magnetic nanoparticle4880-1178-1618.1Page 2 of 66094876-000022WOPTis ferromagnetic, ferrimagnetic, or superparamagnetic, or any combination thereof. In some embodiments, the iron oxide is Fe3O4, or Fe2O3, or combination thereof.

[0008] In various embodiments, the present invention provides a sensor, comprising: at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises a single crystal, wherein the at least one magnetic nanoparticle has a particle size of 19 nm to 207 nm, wherein the at least one magnetic nanoparticle has a polyhedral shape, and wherein the at least one magnetic nanoparticle does not have a core-shell structure. In some embodiments, the sensor of the present invention further comprises at least one receptor, wherein the at least one receptor is connected to or attached to the at least one magnetic nanoparticle. In some embodiments, the at least one receptor is deoxyribonucleic acid (DNA), antibody, enzyme, cell, aptamer, protein, or peptide, or any combination thereof. In some embodiments, the at least one magnetic nanoparticle is ferromagnetic, ferrimagnetic, or superparamagnetic, or any combination thereof. In some embodiments, the iron oxide is Fe3O4, or Fe2O3, or combination thereof.

[0009] In various embodiments, the present invention provides a method for detecting an analyte in a test sample, comprising: contacting a sensor of the present invention with a test sample; subjecting the sensor to a magnetic field; and detecting an analyte in the test sample by measuring a change in a magnetic property of the sensor. In some embodiments, the test sample is a biological sample. In some embodiments, the analyte is at least one biomolecule.

[0010] In various embodiments, the present invention provides a method of separating at least one analyte from a test sample, comprising: contacting a sensor of the present invention with a test sample, wherein the test sample comprises at least one analyte; allowing the at least one analyte to bind to the sensor; and magnetically separating the bound analyte from the test sample. In some embodiments, the test sample is a biological sample. In some embodiments, the analyte is at least one biomolecule. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Exemplary embodiments are illustrated in referenced figures. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than restrictive.

[0012] FIG.1 depicts in accordance with various embodiments of the invention, tailoring magnetic properties by control the crystallinity for diverse biosensing platforms.4880-1178-1618.1Page 3 of 66094876-000022WOPT

[0013] FIG. 2A - FIG. 2D depicts in accordance with various embodiments of the invention, (FIG. 2A) SEM Image at Magnification 120 kX, (FIG. 2B) TEM, (FIG. 2C) XRD Patterns, and (FIG. 2D) High-resolution XPS spectra Fe 2p of Highly Crystalline Iron Oxide Nanoparticles with Particle Size 120 nm ± 9 nm.

[0014] FIG. 3A – FIG. 3F depicts in accordance with various embodiments of the invention, tuning the Magnetic Properties of IONPs particle Size Around 160 nm with Having Crystallite Size from 37 nm to 10 nm.

[0015] FIG. 4A – FIG. 4C depicts in accordance with various embodiments of the invention, Superparamagnetic Properties of Large Polycrystalline NPs versus Single-domain NPs (particle size < 25 nm): (FIG.4A) Magnetization versus Field (M-H) and (FIG.4B) Magnetization versus Temperature (M-T) in Zero-field-cooled / Field-cooling (ZFC / FC) protocol.

[0016] FIG. 5A – FIG. 5I depicts in accordance with various embodiments of the invention, TEM images of iron oxide nanocubes (FIG.5A) average particle size 23 nm ± 4 nm, (FIG.5B) average particle size 43 nm ± 3 nm, (FIG.5C) average particle size 51 nm ± 3 nm, (FIG. 5D) average particle size 58 nm ± 4 nm, (FIG.5E) average particle size 69 nm ± 5 nm, (FIG.5F) average particle size 82 nm ± 5 nm, (FIG.5G) average particle size 101 nm ± 17 nm, (FIG.5H) average particle size 119 nm ± 15 nm, and (FIG.5I) average particle size 184 nm ± 23 nm.

[0017] FIG. 6 depicts in accordance with various embodiments of the invention, using different additives in solvothermal synthesis to control the crystallinity and magnetic properties of iron oxide nanoparticles.

[0018] FIG.7 depicts in accordance with various embodiments of the invention, synthesis procedure for highly crystalline iron oxide nanospheres. DETAILED DESCRIPTION OF THE INVENTION

[0019] All references cited herein are incorporated by reference in their entirety as though fully set forth. Unless defined otherwise, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0020] One skilled in the art will recognize many methods and materials similar or equivalent to those described herein, which could be used in the practice of the present invention. Other features and advantages of the invention will become apparent from the following detailed4880-1178-1618.1Page 4 of 66094876-000022WOPTdescription, taken in conjunction with the accompanying drawings, which illustrate, by way of example, various features of embodiments of the invention. Indeed, the present invention is in no way limited to the methods and materials described. For purposes of the present invention, the following terms are defined below. For convenience, certain terms employed herein, in the specification, examples and appended claims are collected here.

[0021] Unless stated otherwise, or implicit from context, the following terms and phrases include the meanings provided below. Unless explicitly stated otherwise, or apparent from context, the terms and phrases below do not exclude the meaning that the term or phrase has acquired in the art to which it pertains. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It should be understood that this invention is not limited to the particular methodology, protocols, and reagents, etc., described herein and as such can vary. The definitions and terminology used herein are provided to aid in describing particular embodiments, and are not intended to limit the claimed invention, because the scope of the invention is limited only by the claims.

[0022] As used herein the term “comprising” or “comprises” is used in reference to compositions, methods, systems, articles of manufacture, apparatus, and respective component(s) thereof, that are useful to an embodiment, yet open to the inclusion of unspecified elements, whether useful or not. It will be understood by those within the art that, in general, terms used herein are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). Although the open- ended term “comprising,” as a synonym of terms such as including, containing, or having, is used herein to describe and claim the invention, the present invention, or embodiments thereof, may alternatively be described using alternative terms such as “consisting of” or “consisting essentially of.”

[0023] Unless stated otherwise, the terms “a” and “an” and “the” and similar references used in the context of describing a particular embodiment of the application (especially in the context of claims) can be construed to cover both the singular and the plural. The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual4880-1178-1618.1Page 5 of 66094876-000022WOPTvalue is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (for example, “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the application and does not pose a limitation on the scope of the application otherwise claimed. The abbreviation, “e.g.” is derived from the Latin exempli gratia, and is used herein to indicate a non-limiting example. Thus, the abbreviation “e.g.” is synonymous with the term “for example.” No language in the specification should be construed as indicating any non- claimed element essential to the practice of the application.

[0024] “Optional" or “optionally” means that the subsequently described circumstance may or may not occur, so that the description includes instances where the circumstance occurs and instances where it does not.

[0025] In some embodiments, the numbers expressing quantities of reagents, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0026] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and / or patentability. When any such inclusion or deletion occurs, the specification4880-1178-1618.1Page 6 of 66094876-000022WOPTis herein deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims.

[0027] In various embodiments, compounds of the present invention as disclosed herein may be synthesized using any synthetic method available to one of skill in the art. Non-limiting examples of synthetic methods used to prepare various embodiments of compounds of the present invention are disclosed in the Examples section herein.

[0028] Biosensing technologies have utilized magnetic particles (MPs) as labeling agents, in combination with magnetic detectors, for detecting and quantifying biological entities in various biomedical applications. In the present invention, we describe the use of magnetic iron oxide nanoparticles (IONPs) with tunable magnetic properties across a wide range of biosensing platforms. We have identified crystallinity (specifically, crystallite size) in polycrystalline nanoparticles (NPs) as a dominant factor in determining the magnetic properties of these NPs. By selecting appropriate structures (particle size and crystallite size) for IONPs with the desired properties, magnetic NPs can significantly enhance the sensitivity and selectivity of biosensing techniques. Consequently, polycrystalline IONPs in the multi-domain size range are suitable for diverse biosensor designs. First, the highly crystalline IONPs with enhanced ferrimagnetic (FM) properties offer a substantial improvement in magnetic signal. Second, large superparamagnetic (SPM) IONPs (particle sizes between 150 nm and 400 nm) have been shown to be efficient substitutes for commercial SPM magnetic beads and single-domain SPM NPs (particle size < 25 nm) due to their superior magnetization capabilities. Third, the present invention provides a versatile tool for using magnetic IONPs with customized magnetic strength, whether FM or SPM, to potentially suit all types of biosensing designs. A primary concept of the present invention emphasizes the significance of employing magnetic particles of appropriate particle size, crystallite size, and tailored properties to improve both the sensitivity and selectivity in biosensing.

[0029] Magnetic iron oxide particles, ranging in size from nano to micro, have found extensive use in various biosensing platforms integrated with diverse magnetic detection methods. Depending on the design of the sensing system, magnetic particles (MPs) can play different roles, serving as magnetic markers, platforms for magnetic separation, and force transducers. Consequently, the demand for designing and fabricating magnetic nanoparticles (NPs) with appropriate sizes and magnetic properties is essential, as it undoubtedly enhances the sensitivity and selectivity of biosensing.4880-1178-1618.1Page 7 of 66094876-000022WOPT

[0030] To date, two common types of MPs are widely used in biosensing: (1) single- domain superparamagnetic (SPM) NPs (particle size < 25 nm) and (2) micron-sized SPM particles (particle size > 1 μm). While the former offers several advantages, such as the ease of forming stable colloidal solutions and compatibility with biological entities (e.g., DNA, RNA, proteins, enzymes), their weak magnetization due to their small particle size limits sensitivity and magnetic separation capabilities. The latter, exemplified by commercially available products like Dynabeads® M280, M270, and M450, are commonly used in biosensing, bio-separation, and bio- purification, thanks to their better magnetization capabilities arising from their larger particle size. However, micron-sized particles generally suffer from disadvantages, including a low surface-to- volume ratio, a significant size disparity with biological entities (microscale versus nanoscale), and gravity-driven segregation that limits their potential in biosensing. For example, micron-sized MPs can facilitate non-specific biological interactions in protein detection and hinder the use of MPs for in vivo applications, as the small biomolecules tethered to the large MPs can interfere with movement, binding, and recognition. Therefore, the particle size of SPM beads has a significant impact on the sensitivity of bio-detection. To overcome these problems, we envision that magnetic NPs in the multi-domain particle size range, typically ranging in diameter from 100 nm to 400 nm, can address the current limitations of both single-domain NPs and micron-sized particles.

[0031] While SPM particles are the most commonly used in biosensing, recent research underscores the importance of ferrimagnetic / ferromagnetic properties in multiple biosensing designs. Strongly ferrimagnetic (FM) IONPs exhibit advantages in signal enhancement and hold undiscovered potential in sensing. There is still debate over whether the use of SPM or FM nanoparticles is suitable for biosensing. In many cases, FM is highlighted to improve sensitivity and lower the detection limit. Despite concerns about particle clustering among FM particles due to strong dipole interactions, significant progress has been made in preparing stable colloidal solutions of FM particles, holding promise for the integration of strong FM NPs in biosensing. Therefore, a comprehensive strategy to control the magnetic properties of NPs across a wide range of magnetic behaviors (FM / SPM) with varying levels of magnetic strength (strongly FM, moderately-to- weakly FM, and SPM) is valuable in advancing current biosensing technologies based on magnetic particles. This strategy is exclusively described in various embodiments of the present invention through the utilization of polycrystalline IONPs with controllable particle size4880-1178-1618.1Page 8 of 66094876-000022WOPTand crystallite size. FIG.1 demonstrates the approach for fine-tuning the magnetic properties of multi-domain IONPs by controlling their crystallinity.

[0032] In summary, in various embodiments the present invention focuses on the utilization of magnetic IONPs with tunable magnetic strength achieved by controlling the crystallinity of NPs, catering to a wide array of biosensing platforms. These magnetic NPs possess polycrystalline structures with particle sizes ranging from 100 nm to 400 nm. In the context of this disclosure, the term particle size, abbreviated as “ps” or “PS”, refers to “average diameter” for spherical nanoparticles and the “average edge length” for cubic nanoparticles. The term “crystallite size” is abbreviated as “cs” or “CS”, denoting the average crystallite size, also known as the “grain size” of polycrystalline nanoparticles. In some embodiments, the average diameter may be abbreviated by the letter “D”. In some embodiments, the crystallinity is quantified by calculating the crystallite size (grain size) using the Scherrer formula. The applications of these magnetic nanoparticles can be categorized as follows:

[0033] Biosensing platforms that benefit from permanent magnetic properties (strong ferromagnetic / ferrimagnetic responses). For this purpose, highly crystalline IONPs with enhanced ferrimagnetic properties prove to be advantageous.

[0034] Biosensing platforms are designed to harness the superparamagnetic (SPM) properties of MPs. In this context, the large SPM IONPs outlined in the present invention exhibit significant advantages over single-domain SPM NPs and micron-sized SPM particles. They offer superior magnetization capabilities and help minimize the size gap with biological entities.

[0035] Biosensing platforms tailored for moderate magnetic signals or requiring customized magnetic strength. The strategy of finely tuning the crystallite size of nanoparticles can be adapted to tailor the nanoparticles for these specific sensing designs.

[0036] Additional details about nanoparticle structures, their properties, and their applications in biosensing are presented herein below.

[0037] Magnetic Nanoparticles

[0038] Highly Crystalline Nanoparticles with Enhanced Ferrimagnetic Properties

[0039] In FIG. 2A – FIG. 2B, Scanning Electron Microscopy (SEM) images display the uniform shape and particle size distribution of the NPs of the present invention, while Transmission Electron Microscopy (TEM) images provide a more detailed view of their structure, revealing larger particles composed of smaller primary crystals. The average particle size of the4880-1178-1618.1Page 9 of 66094876-000022WOPTnanoparticles was 120 nm ± 9 nm, and the crystallite size was determined through X-ray Diffraction (XRD) analysis, yielding a value of 37 nm. The XRD pattern was successfully matched with the JCPDS file 00-088-0315 for the Fe3O4phase (magnetite). All diffraction peaks are clearly visible and exhibit sharpness, indicating a highly crystalline structure. These peaks have been indexed with lattice planes, as specified in FIG. 2C. Additionally, high-resolution X-ray photoelectron spectroscopy (XPS) was employed to further confirm the presence of the dominant Fe3O4phase in the NPs. The highly crystalline Fe3O4nanoparticles, with primary crystallite sizes of ≥ 24 nm and particle sizes ranging from 50 nm to 400 nm, exhibit enhanced ferrimagnetic properties (see Table 1). The highly crystalline Fe3O4nanoparticles, with primary crystallite sizes of ≥ 24 nm and particle sizes ranging from 49 to 420 nm, exhibit enhanced ferrimagnetic properties (see Table 1).

[0040] Table 1. Magnetic Properties Fe3O4Nanospheres with Large Crystallite Size. Average Crystallite size MS(emu / g) HC(Oe) Mr(emu / g) *

[0041] Tuning Magnetic Properties from Enhanced Ferrimagnetic to Superparamagnetic Properties

[0042] FIG.3A – FIG.3F illustrates the ability to finely adjust the magnetic properties of NPs by controlling their crystallinity. SEM images from FIG. 3B to FIG. 3F depict NPs with uniform morphology and similar average particle sizes. Table 2 provides data on polycrystalline IONPs of similar particle sizes but varying levels of crystallinity (crystallite size). This dataset4880-1178-1618.1Page 10 of 66094876-000022WOPTsupports the concept that magnetic properties can be manipulated by controlling crystallinity (crystallite size) without altering the particle size of the NPs. Efficient control over the magnetic properties of NPs can be achieved within both the superparamagnetic and ferrimagnetic regimes, offering different levels of magnetic strength. Samples with particle sizes around 160 nm demonstrate the capability to manipulate various levels of magnetic strength in both ferrimagnetic and superparamagnetic regimes. Similarly, NPs of particles sizes around 175 nm, 220 nm, and approximately 380 nm exhibit the potential to efficiently control the magnetic behavior of NPs, whether ferrimagnetic or superparamagnetic, across a wide range of particle sizes.

[0043] Table 2. Magnetic Properties of Polycrystalline Iron Oxide Nanoparticles with Tunable Crystallinity. Average Average Magnetization* Coercivity Magnetic Particle Crystallite Size (nm) (emu / g) (Oe) Behaviord

[0044] Excellent Superparamagnetic Properties with High Magnetization

[0045] We have identified the potential of the polycrystalline superparamagnetic (SPM) IONPs presented in various embodiments of the present invention disclosed herein. These NPs4880-1178-1618.1Page 11 of 66094876-000022WOPTexhibit SPM behavior with strong magnetization capability even under low magnetic fields. FIG. 4A provides a comparison of the magnetization of polycrystalline SPM IONPs with single-domain SPM IONPs. The single-domain IONPs, with a particle size of 17 nm, were synthesized through the thermal decomposition of iron oleate. It is evident that the larger polycrystalline SPM IONPs achieve nearly three times higher magnetization values compared to the single-domain NPs. Furthermore, when compared to commercial magnetic beads such as M280, M270, and MyOne®, the polycrystalline SPM NPs clearly demonstrate higher magnetization. Additionally, the polycrystalline SPM NPs exhibit greater magnetization than magnetite microspheres and CoFe2O4microspheres reported in the literature. The increased magnetization of the polycrystalline IONPs can be attributed to the strong interaction between primary crystals due to their close proximity. The magnetization versus temperature of SPM IONPs is presented in FIG.4B – FIG.4C. For the polycrystalline SPM IONPs, a broad feature in the Zero-Field-Cooled (ZFC) curve illustrates the strong interactions between primary crystals, with the maximum of ZFC remaining below 300K, indicating SPM properties. In contrast, the single-domain IONPs exhibit a sharp transition with maxima below 300K, confirming their SPM properties and a sharp transition between ferromagnetic (FM) and SPM regimes.

[0046] In various embodiments of the present invention, superparamagnetic (SPM) particles having a particle size ranging from 150 nm to 400 nm, characterized by their polycrystalline structures (with a crystallite size of ≤ 15 nm), are envisioned as excellent replacements for the commonly used single-domain SPM NPs (particle sized < 25 nm) and micro- sized SPM particles in biosensors. The polycrystalline SPM particles described in the present invention disclosed herein address the existing limitations of these SPM particles in terms of signal sensitivity, selectivity, and detection limits.

[0047] Tuning Ferrimagnetic Properties of Nanocubes by Size Selecting

[0048] In various embodiments, nanocubes may possess stronger ferrimagnetic properties than nanospheres. In addition, in various embodiments the nanocubes may have larger surface contact area than the spherical shaped nanospheres. For example, magnetic properties of nanocubes will change with particle size change as specified in Table 3. Thus, selecting the particle size for nanocubes as shown in Table 3 is a guide to picking nanocubes for sensing and biosensing with different ferrimagnetic properties. Magnetic Properties of Fe3O4Cubic NPs with4880-1178-1618.1Page 12 of 66094876-000022WOPTVarious Particle Sizes are shown in Table 3. It is also important to mention that the nanocube particle is a single crystal.

[0049] Table 3. Magnetic Properties of Fe3O4Cubic NPs with Various Particle Sizes Average Body- Volume Equivalent- MSHC(Oe) MrParticle Diagonal (nm3) volume (emu / g) (emu / g)

[0050] Magnetic Nanoparticles For Biosensing

[0051] Magnetic particles have been integrated into various biosensing detection methods. These methods include surface-based approaches such as giant magnetoresistance (GMR), giant magnetoimpedance (GMI), tunneling magnetoresistance (TMR), and planar hall effect (PHE), as well as volumetric techniques like nuclear magnetic resonance (NMR), magnetic resonance imaging (MRI), superconducting quantum (SQUID), and other methods such as atomic magnetometers, flux gate sensors, and frequency mixing magnetic detection. Some of these methods are suitable only for superparamagnetic (SPM) nanoparticles, while several techniques are adaptable for all types of magnetic particles (MPs). In general, GMR, SQUID, NMR, and MRI are the most common detection techniques, prominently used in diagnostic technologies and studies of biochemistry and biophysics. Given the ability to adjust the magnetic properties of iron4880-1178-1618.1Page 13 of 66094876-000022WOPToxide nanoparticles (IONPs), as described in various embodiments of the present invention, these IONPs can be suitable for various existing magnetic detection platforms.

[0052] To demonstrate the potential applications the various embodiments of the present invention in biosensing technologies, the following examples are presented to illustrate how magnetic nanoparticles can be utilized across various biosensing platforms. It's important to note that these examples are (1) merely illustrative and (2) not limiting in terms of the potential applications for the present invention disclosed herein. The non-limiting uses of MPs are categorized into three main areas:

[0053] Biosensing platforms that benefit from permanent magnetic properties (strong ferromagnetic / ferrimagnetic responses).

[0054] Biosensing platforms specifically designed to utilize the superparamagnetic (SPM) properties of MPs.

[0055] Biosensing platforms tailored for moderate magnetic signals or those that require customized magnetic strength.

[0056] The present invention introduces a novel approach involving the use of magnetic iron oxide nanoparticles (IONPs) with adjustable magnetic properties for a wide range of biosensing applications. These IONPs offer the flexibility to control their magnetic properties by adjusting their particle size and crystallite size. This control spans a broad spectrum of magnetic behaviors, providing various levels of magnetic strength. We categorize the utilization of magnetic IONPs for biosensing into three main groups: (1) those with stronger ferrimagnetic properties, (2) those displaying superparamagnetic properties, and (3) those with moderate ferromagnetic (FM) properties or customizable FM properties. The application of these magnetic particles, as described in the present invention, is expected to be compatible with all existing magnetic detection methods. The core idea here underscores the importance of using magnetic particles with the optimum particle size, crystallite size, and the desired properties to enhance both the sensitivity and selectivity of biosensing.

[0057] In various embodiments, the present invention provides a strategy for using magnetic particles (MPs) with adjustable magnetic properties, ranging from strongly ferrimagnetic (FM) to superparamagnetic (SPM) behaviors for various biosensing platforms. In various embodiments, magnetic particles are polycrystalline iron oxide nanoparticles with sizes ranging from 120 to 400 nm and crystallite sizes between 10 and 40 nm. The magnetic properties of these4880-1178-1618.1Page 14 of 66094876-000022WOPTnanoparticles are fine-tuned by controlling both size and crystallite size. Without limitation, the application of magnetic particles in biosensing can be categorized into three main groups: 1. Highly crystalline nanoparticles with enhanced FM properties are ideal for biosensing platforms that demand a permanent and robust magnetic signal. 2. Highly magnetized superparamagnetic nanoparticles can serve as substitutes for single-domain SPM nanoparticles (size < 25 nm) and SPM microbeads. 3. Magnetic particles with moderate-to-weak FM properties or customizable magnetic strength are valuable for biosensing platforms that require a versatile tool to optimize the performance of the sensing system.

[0058] Magnetic iron oxide nanoparticles are appealing nanomaterials for biosensing. However, there is currently no versatile tool available that provides the capability to select magnetic particles (MPs) with the optimum size and magnetic properties to enhance sensitivity and selectivity in biosensing. As the demand for developing high-performance biosensing systems for diagnostic, therapeutic, and biochemical research continues to rise, our invention offers a versatile solution for choosing efficient MPs in biosensors, considering both size and magnetic properties. The strategy is centered on the use of appropriate MPs (in terms of structure and properties), which aids in advancing current biosensing technologies that rely on the utilization of MPs.

[0059] Current technology relies on the use of superparamagnetic iron oxide nanoparticles in the single-domain size range (<25 nm) or micron-sized magnetic beads as the magnetic labeling signal for biosensing. While single-domain NPs are limited by weak magnetization and thus low sensitivity, micron-sized magnetic beads exhibit higher magnetization, leading to increased signal sensitivity. However, the substantial size difference between magnetic beads and biomolecules reduces the selectivity and recognition capabilities of biosensors. Furthermore, many magnetic detection methods achieve better sensitivity and lower detection limits when ferrimagnetic / ferromagnetic nanoparticles are used as the labeling agents. To overcome all of these limitations associated with the utilization of magnetic particles in biosensing, this invention describes a strategy for using polycrystalline iron oxide nanoparticles with tunable sizes and crystallite sizes across a wide range of biosensing platforms. The NPs presented in this invention address the limitations of both single-domain superparamagnetic NPs and microbeads. Additionally, the use of polycrystalline iron oxide nanoparticles with adjustable sizes and crystallite sizes enables the attainment of the desired magnetic properties in various biosensors.4880-1178-1618.1Page 15 of 66094876-000022WOPTThe central concept here emphasizes the importance of choosing magnetic particles with the optimum size and the desired properties to enhance both the sensitivity and selectivity of biosensing.

[0060] Various Non-Limiting Embodiments of the Invention

[0061] Embodiments include those listed below.

[0062] Embodiment 1. A sensor, comprising: a magnetic nanoparticle, wherein the magnetic nanoparticle comprises iron oxide, wherein the magnetic nanoparticle has a particle size of 49 nm to 420 nm, and wherein the magnetic nanoparticle has a crystallite size of 10 nm to 40 nm.

[0063] Embodiment 2. The sensor of embodiment 1, further comprising a receptor.

[0064] Embodiment 3. The sensor of embodiment 2, wherein the receptor is deoxyribonucleic acid (DNA), antibody, enzyme, cell, aptamer, protein, peptide, or any combination thereof.

[0065] Embodiment 4. The sensor of any one of embodiments 1-3, wherein the magnetic nanoparticle is a nanosphere.

[0066] Embodiment 5. A sensing method for detecting an analyte in a test sample, comprising: contacting the sensor of any one of embodiments 1-4 with a test sample; subjecting the sensor to a magnetic field; and detecting an analyte in the test sample by measuring a change in a magnetic property of the sensor.

[0067] Embodiment 6. A biosensor, comprising: a magnetic nanoparticle, wherein the magnetic nanoparticle comprises iron oxide, wherein the magnetic nanoparticle has a particle size of 49 nm to 420 nm, and wherein the magnetic nanoparticle has a crystallite size of 10 nm to 40 nm.

[0068] Embodiment 7. The biosensor of embodiment 6, further comprising a bioreceptor.

[0069] Embodiment 8. The biosensor of embodiment 7, wherein the bioreceptor is deoxyribonucleic acid (DNA), antibody, enzyme, cell, aptamer, protein, peptide, or any combination thereof.

[0070] Embodiment 9. The biosensor of any one of embodiments 6-8, wherein the magnetic nanoparticle is a nanosphere.

[0071] Embodiment 10. A biosensing method for detecting an analyte in a test sample, comprising: contacting the biosensor of any one of embodiments 6-9 with a test sample; subjecting4880-1178-1618.1Page 16 of 66094876-000022WOPTthe biosensor to a magnetic field; and detecting an analyte in the test sample by measuring a change in a magnetic property of the biosensor.

[0072] Embodiment 11. A sensor, comprising: a magnetic nanoparticle, wherein the magnetic nanoparticle comprises iron oxide, and wherein the magnetic nanoparticle has a particle size of 19 nm to 207 nm.

[0073] Embodiment 12. The sensor of embodiment 11, further comprising a receptor.

[0074] Embodiment 13. The sensor of embodiment 12, wherein the receptor is deoxyribonucleic acid (DNA), antibody, enzyme, cell, aptamer, protein, peptide, or any combination thereof.

[0075] Embodiment 14. The sensor of any one of embodiments 11-13, wherein the magnetic nanoparticle is a nanocube.

[0076] Embodiment 15. A sensing method for detecting an analyte in a test sample, comprising: contacting the sensor of any one of embodiments 11-14 with a test sample; subjecting the sensor to a magnetic field; and detecting an analyte in the test sample by measuring a change in a magnetic property of the sensor.

[0077] Embodiment 16. A biosensor, comprising: a magnetic nanoparticle, wherein the magnetic nanoparticle comprises iron oxide, and wherein the magnetic nanoparticle has a particle size of 19 nm to 207 nm.

[0078] Embodiment 17. The biosensor of embodiment 16, further comprising a bioreceptor.

[0079] Embodiment 18. The biosensor of embodiment 17, wherein the bioreceptor is deoxyribonucleic acid (DNA), antibody, enzyme, cell, aptamer, protein, peptide, or any combination thereof.

[0080] Embodiment 19. The biosensor of any one of embodiments 16-18, wherein the magnetic nanoparticle is a nanocube.

[0081] Embodiment 20. A biosensing method for detecting an analyte in a test sample, comprising: contacting the biosensor of any one of embodiments 16-19 with a test sample; subjecting the biosensor to a magnetic field; and detecting an analyte in the test sample by measuring a change in a magnetic property of the biosensor.

[0082] Additional embodiments include those listed below.4880-1178-1618.1Page 17 of 66094876-000022WOPT

[0083] In various embodiments, the present invention provides a sensor, comprising: a magnetic nanoparticle, wherein the magnetic nanoparticle comprises iron oxide, wherein the magnetic nanoparticle has a particle size of 49 nm to 420 nm, and wherein the magnetic nanoparticle has a crystallite size of 10 nm to 40 nm.

[0084] In various embodiments, the present invention provides a biosensor, comprising: a magnetic nanoparticle, wherein the magnetic nanoparticle comprises iron oxide, wherein the magnetic nanoparticle has a particle size of 49 nm to 420 nm, and wherein the magnetic nanoparticle has a crystallite size of 10 nm to 40 nm.

[0085] In various embodiments, the present invention provides a sensor, comprising: a magnetic nanoparticle, wherein the magnetic nanoparticle comprises iron oxide, and wherein the magnetic nanoparticle has a particle size of 19 nm to 207 nm.

[0086] In various embodiments, the present invention provides a biosensor, comprising: a magnetic nanoparticle, wherein the magnetic nanoparticle comprises iron oxide, and wherein the magnetic nanoparticle has a particle size of 19 nm to 207 nm.

[0087] In various embodiments, the present invention provides a sensing method for detecting an analyte in a test sample, comprising: contacting the sensor of the present invention with a test sample; subjecting the sensor to a magnetic field; and detecting an analyte in the test sample by measuring a change in a magnetic property of the sensor.

[0088] In various embodiments, the present invention provides a biosensing method for detecting an analyte in a test sample, comprising: contacting the biosensor of the present invention with a test sample; subjecting the biosensor to a magnetic field; and detecting an analyte in the test sample by measuring a change in a magnetic property of the biosensor.

[0089] Additional embodiments include those listed below.

[0090] Embodiment 21. A sensor, comprising: at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises iron oxide, wherein the at least one magnetic nanoparticle has a particle size of 49 nm to 420 nm, wherein the at least one magnetic nanoparticle has a crystallite size of 10 nm to 40 nm, and wherein the at least one magnetic nanoparticle does not have a core-shell structure.

[0091] Embodiment 22. The sensor of embodiment 21, wherein the iron oxide is Fe3O4.

[0092] Embodiment 23. The sensor of embodiment 21 or embodiment 22, further comprising at least one receptor.4880-1178-1618.1Page 18 of 66094876-000022WOPT

[0093] Embodiment 24. The sensor of embodiment 23, wherein the at least one receptor is deoxyribonucleic acid (DNA), antibody, enzyme, cell, aptamer, protein, or peptide, or any combination thereof.

[0094] Embodiment 25. The sensor of any one of embodiments 21-24, wherein the at least one magnetic nanoparticle is a nanosphere.

[0095] Embodiment 26. The sensor of any one of embodiments 21-25, wherein the at least one magnetic nanoparticle is ferromagnetic, ferrimagnetic, or superparamagnetic, or any combination thereof.

[0096] Embodiment 27. A method for detecting an analyte in a test sample, comprising: contacting the sensor of any one of embodiments 21-26 with a test sample; subjecting the sensor to a magnetic field; and detecting an analyte in the test sample by measuring a change in a magnetic property of the sensor.

[0097] Embodiment 28. The method of embodiment 27, wherein the test sample is a biological sample.

[0098] Embodiment 29. A sensor, comprising: at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises iron oxide, wherein the at least one magnetic nanoparticle has a particle size of 19 nm to 207 nm, and wherein the at least one magnetic nanoparticle does not have a core-shell structure.

[0099] Embodiment 30. The sensor of embodiment 29, wherein the iron oxide is Fe3O4.

[0100] Embodiment 31. The sensor of embodiment 29 or embodiment 30, further comprising at least one receptor.

[0101] Embodiment 32. The sensor of embodiment 31, wherein the at least one receptor is deoxyribonucleic acid (DNA), antibody, enzyme, cell, aptamer, protein, or peptide, or any combination thereof.

[0102] Embodiment 33. The sensor of any one of embodiments 29-32, wherein the at least one magnetic nanoparticle is a nanocube.

[0103] Embodiment 34. The sensor of any one of embodiments 29-33, wherein the at least one magnetic nanoparticle is ferromagnetic, ferrimagnetic, or superparamagnetic, or any combination thereof.

[0104] Embodiment 35. A method for detecting an analyte in a test sample, comprising: contacting the sensor of any one of embodiments 29-34 with a test sample; subjecting the sensor4880-1178-1618.1Page 19 of 66094876-000022WOPTto a magnetic field; and detecting an analyte in the test sample by measuring a change in a magnetic property of the sensor.

[0105] Embodiment 36. The method of embodiment 35, wherein the test sample is a biological sample.

[0106] Additional embodiments include those listed below.

[0107] In some embodiments, the sensor is a biosensor.

[0108] In some embodiments, the method for detecting an analyte in a test sample, is a biosensing method.

[0109] In some embodiments, the analyte is at least one protein.

[0110] In some embodiments, the magnetic nanoparticle, or the iron oxide nanoparticle, or the magnetic iron oxide nanoparticle has a particle size of 49 nm to 420 nm. In some embodiments, the magnetic nanoparticle, or the iron oxide nanoparticle, or the magnetic iron oxide nanoparticle has a particle size of 49 nm, 50 nm, 51 nm, 52 nm, 53 nm, 54 nm, 55 nm, 56 nm, 57 nm, 58 nm, 59 nm, 60 nm, 61 nm, 62 nm, 63 nm, 64 nm, 65 nm, 66 nm, 67 nm, 68 nm, 69 nm, 70 nm, 71 nm, 72 nm, 73 nm, 74 nm, 75 nm, 76 nm, 77 nm, 78 nm, 79 nm, 80 nm, 81 nm, 82 nm, 83 nm, 84 nm, 85 nm, 86 nm, 87 nm, 88 nm, 89 nm, 90 nm, 91 nm, 92 nm, 93 nm, 94 nm, 95 nm, 96 nm, 97 nm, 98 nm, 99 nm, 100 nm, 101 nm, 102 nm, 103 nm, 104 nm, 105 nm, 106 nm, 107 nm, 108 nm, 109 nm, 110 nm, 111 nm, 112 nm, 113 nm, 114 nm, 115 nm, 116 nm, 117 nm, 118 nm, 119 nm, 120 nm, 121 nm, 122 nm, 123 nm, 124 nm, 125 nm, 126 nm, 127 nm, 128 nm, 129 nm, 130 nm, 131 nm, 132 nm, 133 nm, 134 nm, 135 nm, 136 nm, 137 nm, 138 nm, 139 nm, 140 nm, 141 nm, 142 nm, 143 nm, 144 nm, 145 nm, 146 nm, 147 nm, 148 nm, 149 nm, 150 nm, 151 nm, 152 nm, 153 nm, 154 nm, 155 nm, 156 nm, 157 nm, 158 nm, 159 nm, 160 nm, 161 nm, 162 nm, 163 nm, 164 nm, 165 nm, 166 nm, 167 nm, 168 nm, 169 nm, 170 nm, 171 nm, 172 nm, 173 nm, 174 nm, 175 nm, 176 nm, 177 nm, 178 nm, 179 nm, 180 nm, 181 nm, 182 nm, 183 nm, 184 nm, 185 nm, 186 nm, 187 nm, 188 nm, 189 nm, 190 nm, 191 nm, 192 nm, 193 nm, 194 nm, 195 nm, 196 nm, 197 nm, 198 nm, 199 nm, 200 nm, 201 nm, 202 nm, 203 nm, 204 nm, 205 nm, 206 nm, 207 nm, 208 nm, 209 nm, 210 nm, 211 nm, 212 nm, 213 nm, 214 nm, 215 nm, 216 nm, 217 nm, 218 nm, 219 nm, 220 nm, 221 nm, 222 nm, 223 nm, 224 nm, 225 nm, 226 nm, 227 nm, 228 nm, 229 nm, 230 nm, 231 nm, 232 nm, 233 nm, 234 nm, 235 nm, 236 nm, 237 nm, 238 nm, 239 nm, 240 nm, 241 nm, 242 nm, 243 nm, 244 nm, 245 nm, 246 nm, 247 nm, 248 nm, 249 nm, 250 nm, 251 nm, 252 nm, 253 nm, 254 nm, 255 nm, 256 nm, 257 nm, 258 nm, 259 nm, 260 nm, 261 nm, 262 nm, 2634880-1178-1618.1Page 20 of 66094876-000022WOPTnm, 264 nm, 265 nm, 266 nm, 267 nm, 268 nm, 269 nm, 270 nm, 271 nm, 272 nm, 273 nm, 274 nm, 275 nm, 276 nm, 277 nm, 278 nm, 279 nm, 280 nm, 281 nm, 282 nm, 283 nm, 284 nm, 285 nm, 286 nm, 287 nm, 288 nm, 289 nm, 290 nm, 291 nm, 292 nm, 293 nm, 294 nm, 295 nm, 296 nm, 297 nm, 298 nm, 299 nm, 300 nm, 301 nm, 302 nm, 303 nm, 304 nm, 305 nm, 306 nm, 307 nm, 308 nm, 309 nm, 310 nm, 311 nm, 312 nm, 313 nm, 314 nm, 315 nm, 316 nm, 317 nm, 318 nm, 319 nm, 320 nm, 321 nm, 322 nm, 323 nm, 324 nm, 325 nm, 326 nm, 327 nm, 328 nm, 329 nm, 330 nm, 331 nm, 332 nm, 333 nm, 334 nm, 335 nm, 336 nm, 337 nm, 338 nm, 339 nm, 340 nm, 341 nm, 342 nm, 343 nm, 344 nm, 345 nm, 346 nm, 347 nm, 348 nm, 349 nm, 350 nm, 351 nm, 352 nm, 353 nm, 354 nm, 355 nm, 356 nm, 357 nm, 358 nm, 359 nm, 360 nm, 361 nm, 362 nm, 363 nm, 364 nm, 365 nm, 366 nm, 367 nm, 368 nm, 369 nm, 370 nm, 371 nm, 372 nm, 373 nm, 374 nm, 375 nm, 376 nm, 377 nm, 378 nm, 379 nm, 380 nm, 381 nm, 382 nm, 383 nm, 384 nm, 385 nm, 386 nm, 387 nm, 388 nm, 389 nm, 390 nm, 391 nm, 392 nm, 393 nm, 394 nm, 395 nm, 396 nm, 397 nm, 398 nm, 399 nm, 400 nm, 401 nm, 402 nm, 403 nm, 404 nm, 405 nm, 406 nm, 407 nm, 408 nm, 409 nm, 410 nm, 411 nm, 412 nm, 413 nm, 414 nm, 415 nm, 416 nm, 417 nm, 418 nm, 419 nm, or 420 nm.

[0111] In some embodiments, the at least one magnetic nanoparticle, or the at least one iron oxide nanoparticle, or the at least one magnetic iron oxide nanoparticle has a particle size of 49 nm to 420 nm. In some embodiments, the at least one magnetic nanoparticle, or the at least one iron oxide nanoparticle, or the at least one magnetic iron oxide nanoparticle has a particle size of 49 nm, 50 nm, 51 nm, 52 nm, 53 nm, 54 nm, 55 nm, 56 nm, 57 nm, 58 nm, 59 nm, 60 nm, 61 nm, 62 nm, 63 nm, 64 nm, 65 nm, 66 nm, 67 nm, 68 nm, 69 nm, 70 nm, 71 nm, 72 nm, 73 nm, 74 nm, 75 nm, 76 nm, 77 nm, 78 nm, 79 nm, 80 nm, 81 nm, 82 nm, 83 nm, 84 nm, 85 nm, 86 nm, 87 nm, 88 nm, 89 nm, 90 nm, 91 nm, 92 nm, 93 nm, 94 nm, 95 nm, 96 nm, 97 nm, 98 nm, 99 nm, 100 nm, 101 nm, 102 nm, 103 nm, 104 nm, 105 nm, 106 nm, 107 nm, 108 nm, 109 nm, 110 nm, 111 nm, 112 nm, 113 nm, 114 nm, 115 nm, 116 nm, 117 nm, 118 nm, 119 nm, 120 nm, 121 nm, 122 nm, 123 nm, 124 nm, 125 nm, 126 nm, 127 nm, 128 nm, 129 nm, 130 nm, 131 nm, 132 nm, 133 nm, 134 nm, 135 nm, 136 nm, 137 nm, 138 nm, 139 nm, 140 nm, 141 nm, 142 nm, 143 nm, 144 nm, 145 nm, 146 nm, 147 nm, 148 nm, 149 nm, 150 nm, 151 nm, 152 nm, 153 nm, 154 nm, 155 nm, 156 nm, 157 nm, 158 nm, 159 nm, 160 nm, 161 nm, 162 nm, 163 nm, 164 nm, 165 nm, 166 nm, 167 nm, 168 nm, 169 nm, 170 nm, 171 nm, 172 nm, 173 nm, 174 nm, 175 nm, 176 nm, 177 nm, 178 nm, 179 nm, 180 nm, 181 nm, 182 nm, 183 nm, 184 nm, 185 nm, 186 nm, 187 nm, 1884880-1178-1618.1Page 21 of 66094876-000022WOPTnm, 189 nm, 190 nm, 191 nm, 192 nm, 193 nm, 194 nm, 195 nm, 196 nm, 197 nm, 198 nm, 199 nm, 200 nm, 201 nm, 202 nm, 203 nm, 204 nm, 205 nm, 206 nm, 207 nm, 208 nm, 209 nm, 210 nm, 211 nm, 212 nm, 213 nm, 214 nm, 215 nm, 216 nm, 217 nm, 218 nm, 219 nm, 220 nm, 221 nm, 222 nm, 223 nm, 224 nm, 225 nm, 226 nm, 227 nm, 228 nm, 229 nm, 230 nm, 231 nm, 232 nm, 233 nm, 234 nm, 235 nm, 236 nm, 237 nm, 238 nm, 239 nm, 240 nm, 241 nm, 242 nm, 243 nm, 244 nm, 245 nm, 246 nm, 247 nm, 248 nm, 249 nm, 250 nm, 251 nm, 252 nm, 253 nm, 254 nm, 255 nm, 256 nm, 257 nm, 258 nm, 259 nm, 260 nm, 261 nm, 262 nm, 263 nm, 264 nm, 265 nm, 266 nm, 267 nm, 268 nm, 269 nm, 270 nm, 271 nm, 272 nm, 273 nm, 274 nm, 275 nm, 276 nm, 277 nm, 278 nm, 279 nm, 280 nm, 281 nm, 282 nm, 283 nm, 284 nm, 285 nm, 286 nm, 287 nm, 288 nm, 289 nm, 290 nm, 291 nm, 292 nm, 293 nm, 294 nm, 295 nm, 296 nm, 297 nm, 298 nm, 299 nm, 300 nm, 301 nm, 302 nm, 303 nm, 304 nm, 305 nm, 306 nm, 307 nm, 308 nm, 309 nm, 310 nm, 311 nm, 312 nm, 313 nm, 314 nm, 315 nm, 316 nm, 317 nm, 318 nm, 319 nm, 320 nm, 321 nm, 322 nm, 323 nm, 324 nm, 325 nm, 326 nm, 327 nm, 328 nm, 329 nm, 330 nm, 331 nm, 332 nm, 333 nm, 334 nm, 335 nm, 336 nm, 337 nm, 338 nm, 339 nm, 340 nm, 341 nm, 342 nm, 343 nm, 344 nm, 345 nm, 346 nm, 347 nm, 348 nm, 349 nm, 350 nm, 351 nm, 352 nm, 353 nm, 354 nm, 355 nm, 356 nm, 357 nm, 358 nm, 359 nm, 360 nm, 361 nm, 362 nm, 363 nm, 364 nm, 365 nm, 366 nm, 367 nm, 368 nm, 369 nm, 370 nm, 371 nm, 372 nm, 373 nm, 374 nm, 375 nm, 376 nm, 377 nm, 378 nm, 379 nm, 380 nm, 381 nm, 382 nm, 383 nm, 384 nm, 385 nm, 386 nm, 387 nm, 388 nm, 389 nm, 390 nm, 391 nm, 392 nm, 393 nm, 394 nm, 395 nm, 396 nm, 397 nm, 398 nm, 399 nm, 400 nm, 401 nm, 402 nm, 403 nm, 404 nm, 405 nm, 406 nm, 407 nm, 408 nm, 409 nm, 410 nm, 411 nm, 412 nm, 413 nm, 414 nm, 415 nm, 416 nm, 417 nm, 418 nm, 419 nm, or 420 nm.

[0112] In some embodiments, the at least one magnetic Fe3O4nanosphere has a particle size of 49 nm to 420 nm. In some embodiments, the at least one magnetic Fe3O4nanosphere has a particle size of 49 nm, 50 nm, 51 nm, 52 nm, 53 nm, 54 nm, 55 nm, 56 nm, 57 nm, 58 nm, 59 nm, 60 nm, 61 nm, 62 nm, 63 nm, 64 nm, 65 nm, 66 nm, 67 nm, 68 nm, 69 nm, 70 nm, 71 nm, 72 nm, 73 nm, 74 nm, 75 nm, 76 nm, 77 nm, 78 nm, 79 nm, 80 nm, 81 nm, 82 nm, 83 nm, 84 nm, 85 nm, 86 nm, 87 nm, 88 nm, 89 nm, 90 nm, 91 nm, 92 nm, 93 nm, 94 nm, 95 nm, 96 nm, 97 nm, 98 nm, 99 nm, 100 nm, 101 nm, 102 nm, 103 nm, 104 nm, 105 nm, 106 nm, 107 nm, 108 nm, 109 nm, 110 nm, 111 nm, 112 nm, 113 nm, 114 nm, 115 nm, 116 nm, 117 nm, 118 nm, 119 nm, 120 nm, 121 nm, 122 nm, 123 nm, 124 nm, 125 nm, 126 nm, 127 nm, 128 nm, 129 nm, 130 nm, 1314880-1178-1618.1Page 22 of 66094876-000022WOPTnm, 132 nm, 133 nm, 134 nm, 135 nm, 136 nm, 137 nm, 138 nm, 139 nm, 140 nm, 141 nm, 142 nm, 143 nm, 144 nm, 145 nm, 146 nm, 147 nm, 148 nm, 149 nm, 150 nm, 151 nm, 152 nm, 153 nm, 154 nm, 155 nm, 156 nm, 157 nm, 158 nm, 159 nm, 160 nm, 161 nm, 162 nm, 163 nm, 164 nm, 165 nm, 166 nm, 167 nm, 168 nm, 169 nm, 170 nm, 171 nm, 172 nm, 173 nm, 174 nm, 175 nm, 176 nm, 177 nm, 178 nm, 179 nm, 180 nm, 181 nm, 182 nm, 183 nm, 184 nm, 185 nm, 186 nm, 187 nm, 188 nm, 189 nm, 190 nm, 191 nm, 192 nm, 193 nm, 194 nm, 195 nm, 196 nm, 197 nm, 198 nm, 199 nm, 200 nm, 201 nm, 202 nm, 203 nm, 204 nm, 205 nm, 206 nm, 207 nm, 208 nm, 209 nm, 210 nm, 211 nm, 212 nm, 213 nm, 214 nm, 215 nm, 216 nm, 217 nm, 218 nm, 219 nm, 220 nm, 221 nm, 222 nm, 223 nm, 224 nm, 225 nm, 226 nm, 227 nm, 228 nm, 229 nm, 230 nm, 231 nm, 232 nm, 233 nm, 234 nm, 235 nm, 236 nm, 237 nm, 238 nm, 239 nm, 240 nm, 241 nm, 242 nm, 243 nm, 244 nm, 245 nm, 246 nm, 247 nm, 248 nm, 249 nm, 250 nm, 251 nm, 252 nm, 253 nm, 254 nm, 255 nm, 256 nm, 257 nm, 258 nm, 259 nm, 260 nm, 261 nm, 262 nm, 263 nm, 264 nm, 265 nm, 266 nm, 267 nm, 268 nm, 269 nm, 270 nm, 271 nm, 272 nm, 273 nm, 274 nm, 275 nm, 276 nm, 277 nm, 278 nm, 279 nm, 280 nm, 281 nm, 282 nm, 283 nm, 284 nm, 285 nm, 286 nm, 287 nm, 288 nm, 289 nm, 290 nm, 291 nm, 292 nm, 293 nm, 294 nm, 295 nm, 296 nm, 297 nm, 298 nm, 299 nm, 300 nm, 301 nm, 302 nm, 303 nm, 304 nm, 305 nm, 306 nm, 307 nm, 308 nm, 309 nm, 310 nm, 311 nm, 312 nm, 313 nm, 314 nm, 315 nm, 316 nm, 317 nm, 318 nm, 319 nm, 320 nm, 321 nm, 322 nm, 323 nm, 324 nm, 325 nm, 326 nm, 327 nm, 328 nm, 329 nm, 330 nm, 331 nm, 332 nm, 333 nm, 334 nm, 335 nm, 336 nm, 337 nm, 338 nm, 339 nm, 340 nm, 341 nm, 342 nm, 343 nm, 344 nm, 345 nm, 346 nm, 347 nm, 348 nm, 349 nm, 350 nm, 351 nm, 352 nm, 353 nm, 354 nm, 355 nm, 356 nm, 357 nm, 358 nm, 359 nm, 360 nm, 361 nm, 362 nm, 363 nm, 364 nm, 365 nm, 366 nm, 367 nm, 368 nm, 369 nm, 370 nm, 371 nm, 372 nm, 373 nm, 374 nm, 375 nm, 376 nm, 377 nm, 378 nm, 379 nm, 380 nm, 381 nm, 382 nm, 383 nm, 384 nm, 385 nm, 386 nm, 387 nm, 388 nm, 389 nm, 390 nm, 391 nm, 392 nm, 393 nm, 394 nm, 395 nm, 396 nm, 397 nm, 398 nm, 399 nm, 400 nm, 401 nm, 402 nm, 403 nm, 404 nm, 405 nm, 406 nm, 407 nm, 408 nm, 409 nm, 410 nm, 411 nm, 412 nm, 413 nm, 414 nm, 415 nm, 416 nm, 417 nm, 418 nm, 419 nm, or 420 nm.

[0113] In some embodiments, the magnetic nanoparticle, or the iron oxide nanoparticle, or the magnetic iron oxide nanoparticle has a crystallite size of 10 nm to 40 nm. In some embodiments, the magnetic nanoparticle, or the iron oxide nanoparticle, or the magnetic iron oxide nanoparticle has a crystallite size of 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm,4880-1178-1618.1Page 23 of 66094876-000022WOPT18 nm, 19 nm, 20 nm, 21 nm, 22 nm, 23 nm, 24 nm, 25 nm, 26 nm, 27 nm, 28 nm, 29 nm, 30 nm, 31 nm, 32 nm, 33 nm, 34 nm, 35 nm, 36 nm, 37 nm, 38 nm, 39 nm, or 40 nm.

[0114] In some embodiments, the at least one magnetic nanoparticle, or the at least one iron oxide nanoparticle, or the at least one magnetic iron oxide nanoparticle has a crystallite size nm to 40 nm. In some embodiments, the at least one magnetic nanoparticle, or the at least one iron oxide nanoparticle, or the at least one magnetic iron oxide nanoparticle has a crystallite size of 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, 20 nm, 21 nm, 22 nm, 23 nm, 24 nm, 25 nm, 26 nm, 27 nm, 28 nm, 29 nm, 30 nm, 31 nm, 32 nm, 33 nm, 34 nm, 35 nm, 36 nm, 37 nm, 38 nm, 39 nm, or 40 nm.

[0115] In some embodiments, the at least one magnetic Fe3O4nanosphere has a crystallite size of 10 nm to 40 nm. In some embodiments, the at least one magnetic Fe3O4nanosphere has a crystallite size of 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, 20 nm, 21 nm, 22 nm, 23 nm, 24 nm, 25 nm, 26 nm, 27 nm, 28 nm, 29 nm, 30 nm, 31 nm, 32 nm, 33 nm, 34 nm, 35 nm, 36 nm, 37 nm, 38 nm, 39 nm, or 40 nm.

[0116] In some embodiments, the magnetic nanoparticle, or the iron oxide nanoparticle, or the magnetic iron oxide nanoparticle has a particle size of 19 nm to 207 nm. In some embodiments, the magnetic nanoparticle, or the iron oxide nanoparticle, or the magnetic iron oxide nanoparticle has a particle size of 19 nm, 20 nm, 21, nm, 22 nm, 23 nm, 24 nm, 25 nm, 26 nm, 27 nm, 28 nm, 29 nm, 30 nm, 31 m, 32 nm, 33 nm, 34 nm, 35 nm, 36 nm, 37 nm, 38 nm, 39 nm, 40 nm, 41 nm, 42 nm, 43 nm, 44 nm, 45 nm, 46 nm, 47 nm, 48 nm, 49 nm, 50 nm, 51 nm, 52 nm, 53 nm, 54 nm, 55 nm, 56 nm, 57 nm, 58 nm, 59 nm, 60 nm, 61 nm, 62 nm, 63 nm, 64 nm, 65 nm, 66 nm, 67 nm, 68 nm, 69 nm, 70 nm, 71 nm, 72 nm, 73 nm, 74 nm, 75 nm, 76 nm, 77 nm, 78 nm, 79 nm, 80 nm, 81 nm, 82 nm, 83 nm, 84 nm, 85 nm, 86 nm, 87 nm, 88 nm, 89 nm, 90 nm, 91 nm, 92 nm, 93 nm, 94 nm, 95 nm, 96 nm, 97 nm, 98 nm, 99 nm, 100 nm, 101 nm, 102 nm, 103 nm, 104 nm, 105 nm, 106 nm, 107 nm, 108 nm, 109 nm, 110 nm, 111 nm, 112 nm, 113 nm, 114 nm, 115 nm, 116 nm, 117 nm, 118 nm, 119 nm, 120 nm, 121 nm, 122 nm, 123 nm, 124 nm, 125 nm, 126 nm, 127 nm, 128 nm, 129 nm, 130 nm, 131 nm, 132 nm, 133 nm, 134 nm, 135 nm, 136 nm, 137 nm, 138 nm, 139 nm, 140 nm, 141 nm, 142 nm, 143 nm, 144 nm, 145 nm, 146 nm, 147 nm, 148 nm, 149 nm, 150 nm, 151 nm, 152 nm, 153 nm, 154 nm, 155 nm, 156 nm, 157 nm, 158 nm, 159 nm, 160 nm, 161 nm, 162 nm, 163 nm, 164 nm, 165 nm, 166 nm, 167 nm, 168 nm, 169 nm, 170 nm, 171 nm, 172 nm, 173 nm, 174 nm, 175 nm, 176 nm, 177 nm, 178 nm, 179 nm, 180 nm, 181 nm, 182 nm,4880-1178-1618.1Page 24 of 66094876-000022WOPT183 nm, 184 nm, 185 nm, 186 nm, 187 nm, 188 nm, 189 nm, 190 nm, 191 nm, 192 nm, 193 nm, 194 nm, 195 nm, 196 nm, 197 nm, 198 nm, 199 nm, 200 nm, 201 nm, 202 nm, 203 nm, 204 nm, 205 nm, 206 nm, or 207 nm.

[0117] In some embodiments, the at least one magnetic nanoparticle, or the at least one iron oxide nanoparticle, or the at least one magnetic iron oxide nanoparticle has a particle size of 19 nm to 207 nm. In some embodiments, the at least one magnetic nanoparticle, or the at least one iron oxide nanoparticle, or the at least one magnetic iron oxide nanoparticle has a particle size of 19 nm, 20 nm, 21, nm, 22 nm, 23 nm, 24 nm, 25 nm, 26 nm, 27 nm, 28 nm, 29 nm, 30 nm, 31 m, 32 nm, 33 nm, 34 nm, 35 nm, 36 nm, 37 nm, 38 nm, 39 nm, 40 nm, 41 nm, 42 nm, 43 nm, 44 nm, 45 nm, 46 nm, 47 nm, 48 nm, 49 nm, 50 nm, 51 nm, 52 nm, 53 nm, 54 nm, 55 nm, 56 nm, 57 nm, 58 nm, 59 nm, 60 nm, 61 nm, 62 nm, 63 nm, 64 nm, 65 nm, 66 nm, 67 nm, 68 nm, 69 nm, 70 nm, 71 nm, 72 nm, 73 nm, 74 nm, 75 nm, 76 nm, 77 nm, 78 nm, 79 nm, 80 nm, 81 nm, 82 nm, 83 nm, 84 nm, 85 nm, 86 nm, 87 nm, 88 nm, 89 nm, 90 nm, 91 nm, 92 nm, 93 nm, 94 nm, 95 nm, 96 nm, 97 nm, 98 nm, 99 nm, 100 nm, 101 nm, 102 nm, 103 nm, 104 nm, 105 nm, 106 nm, 107 nm, 108 nm, 109 nm, 110 nm, 111 nm, 112 nm, 113 nm, 114 nm, 115 nm, 116 nm, 117 nm, 118 nm, 119 nm, 120 nm, 121 nm, 122 nm, 123 nm, 124 nm, 125 nm, 126 nm, 127 nm, 128 nm, 129 nm, 130 nm, 131 nm, 132 nm, 133 nm, 134 nm, 135 nm, 136 nm, 137 nm, 138 nm, 139 nm, 140 nm, 141 nm, 142 nm, 143 nm, 144 nm, 145 nm, 146 nm, 147 nm, 148 nm, 149 nm, 150 nm, 151 nm, 152 nm, 153 nm, 154 nm, 155 nm, 156 nm, 157 nm, 158 nm, 159 nm, 160 nm, 161 nm, 162 nm, 163 nm, 164 nm, 165 nm, 166 nm, 167 nm, 168 nm, 169 nm, 170 nm, 171 nm, 172 nm, 173 nm, 174 nm, 175 nm, 176 nm, 177 nm, 178 nm, 179 nm, 180 nm, 181 nm, 182 nm, 183 nm, 184 nm, 185 nm, 186 nm, 187 nm, 188 nm, 189 nm, 190 nm, 191 nm, 192 nm, 193 nm, 194 nm, 195 nm, 196 nm, 197 nm, 198 nm, 199 nm, 200 nm, 201 nm, 202 nm, 203 nm, 204 nm, 205 nm, 206 nm, or 207 nm.

[0118] In some embodiments, the at least one magnetic Fe3O4nanocube has a particle size of 19 nm to 207 nm. In some embodiments, the at least one magnetic Fe3O4nanocube has a particle size of 19 nm, 20 nm, 21, nm, 22 nm, 23 nm, 24 nm, 25 nm, 26 nm, 27 nm, 28 nm, 29 nm, 30 nm, 31 m, 32 nm, 33 nm, 34 nm, 35 nm, 36 nm, 37 nm, 38 nm, 39 nm, 40 nm, 41 nm, 42 nm, 43 nm, 44 nm, 45 nm, 46 nm, 47 nm, 48 nm, 49 nm, 50 nm, 51 nm, 52 nm, 53 nm, 54 nm, 55 nm, 56 nm, 57 nm, 58 nm, 59 nm, 60 nm, 61 nm, 62 nm, 63 nm, 64 nm, 65 nm, 66 nm, 67 nm, 68 nm, 69 nm, 70 nm, 71 nm, 72 nm, 73 nm, 74 nm, 75 nm, 76 nm, 77 nm, 78 nm, 79 nm, 80 nm, 81 nm,4880-1178-1618.1Page 25 of 66094876-000022WOPT82 nm, 83 nm, 84 nm, 85 nm, 86 nm, 87 nm, 88 nm, 89 nm, 90 nm, 91 nm, 92 nm, 93 nm, 94 nm, 95 nm, 96 nm, 97 nm, 98 nm, 99 nm, 100 nm, 101 nm, 102 nm, 103 nm, 104 nm, 105 nm, 106 nm, 107 nm, 108 nm, 109 nm, 110 nm, 111 nm, 112 nm, 113 nm, 114 nm, 115 nm, 116 nm, 117 nm, 118 nm, 119 nm, 120 nm, 121 nm, 122 nm, 123 nm, 124 nm, 125 nm, 126 nm, 127 nm, 128 nm, 129 nm, 130 nm, 131 nm, 132 nm, 133 nm, 134 nm, 135 nm, 136 nm, 137 nm, 138 nm, 139 nm, 140 nm, 141 nm, 142 nm, 143 nm, 144 nm, 145 nm, 146 nm, 147 nm, 148 nm, 149 nm, 150 nm, 151 nm, 152 nm, 153 nm, 154 nm, 155 nm, 156 nm, 157 nm, 158 nm, 159 nm, 160 nm, 161 nm, 171 172nm, nm, nm, nm, nm, nm, nm, nm, nm, nm, nm, 206 nm, or 207 nm.

[0119] In various embodiments, the present invention provides a sensor, comprising: at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises iron oxide, wherein the at least one magnetic nanoparticle has a particle size of 49 nm to 420 nm, and wherein the at least one magnetic nanoparticle has a crystallite size of 10 nm to 40 nm.

[0120] In various embodiments, the present invention provides a sensor, comprising: at least one iron oxide nanoparticle, wherein the at least one iron oxide nanoparticle comprises a plurality of primary crystals, wherein the plurality of primary crystals comprise a plurality of crystallites, wherein the at least one iron oxide nanoparticle has a particle size of 49 nm to 420 nm, and wherein the plurality of crystallites have a crystallite size of 10 nm to 40 nm.

[0121] In various embodiments, the present invention provides a sensor, comprising: at least one iron oxide nanoparticle, wherein the at least one iron oxide nanoparticle comprises at least one primary crystal, wherein the at least one primary crystal comprises at least one crystallite, wherein the at least one iron oxide nanoparticle has a particle size of 49 nm to 420 nm, and wherein the at least one crystallite has a crystallite size of 10 nm to 40 nm.

[0122] In some embodiments, the magnetic nanoparticle is not a core-shell magnetic nanoparticle. In some embodiments, the magnetic nanoparticle is not a core-shell structure. In some embodiments, the magnetic nanoparticle does not have a core-shell structure. In some embodiments, the magnetic nanoparticle does not have a core / shell structure.4880-1178-1618.1Page 26 of 66094876-000022WOPT

[0123] In some embodiments, the iron oxide nanoparticle is not a core-shell magnetic nanoparticle. In some embodiments, the iron oxide nanoparticle is not a core-shell structure. In some embodiments, the iron oxide nanoparticle does not have a core-shell structure. In some embodiments, the iron oxide nanoparticle does not have a core / shell structure.

[0124] In some embodiments, the magnetic iron oxide nanoparticle is not a core-shell magnetic nanoparticle. In some embodiments, the magnetic iron oxide nanoparticle is not a core- shell structure. In some embodiments, the magnetic iron oxide nanoparticle does not have a core- shell structure. In some embodiments, the magnetic iron oxide nanoparticle does not have a core / shell structure.

[0125] In some embodiments, the at least one magnetic Fe3O4nanosphere does not have a core-shell structure. In some embodiments, the at least one magnetic Fe3O4nanocube does not have a core-shell structure.

[0126] In some embodiments, the Fe3O4nanosphere does not comprise FeO. In some embodiments, the Fe3O4nanosphere does not contain FeO. In some embodiments, the Fe3O4nanosphere does not consist of FeO. In some embodiments, the Fe3O4nanosphere does not consist essentially of FeO. In some embodiments, the Fe3O4nanosphere is not FeO.

[0127] In some embodiments, the Fe3O4nanocube does not comprise FeO. In some embodiments, the Fe3O4nanocube does not contain FeO. In some embodiments, the Fe3O4nanocube does not consist of FeO. In some embodiments, the Fe3O4nanocube does not consist essentially of FeO. In some embodiments, the Fe3O4nanocube is not FeO.

[0128] In some embodiments, the Fe3O4nanocube is a magnetic Fe3O4nanocube. In some embodiments, the Fe3O4nanosphere is a magnetic Fe3O4nanosphere.

[0129] In some embodiments, the primary crystal does not have a core-shell structure. In some embodiments, the iron oxide primary crystal does not have a core-shell structure. In some embodiments, the crystallite does not have a core-shell structure. In some embodiments, the iron oxide crystallite does not have a core-shell structure. In some embodiments, the single iron oxide crystal does not have a core-shell structure. In some embodiments, the single crystal does not have a core-shell structure. In some embodiments, the nanosphere does not have a core-shell structure. In some embodiments, the nanocube does not have a core-shell structure.

[0130] In some embodiments, the at least one primary crystal does not have a core-shell structure. In some embodiments, the plurality of primary crystals does not have a core-shell4880-1178-1618.1Page 27 of 66094876-000022WOPTstructure. In some embodiments, the at least one crystallite does not have a core-shell structure. In some embodiments, the plurality of crystallites does not have a core-shell structure.

[0131] In some embodiments, the iron oxide is Fe3O4, or Fe2O3, or combination thereof. In some embodiments, the iron oxide is Fe3O4. In some embodiments, the iron oxide is Fe2O3. In some embodiments, the iron oxide is a combination of Fe3O4and Fe2O3.

[0132] In some embodiments, the iron oxide is not FeO. In some embodiments, the iron oxide does not comprise FeO. In some embodiments, the iron oxide does not contain FeO. In some embodiments, the iron oxide does not consist of FeO. In some embodiments, the iron oxide does not consist essentially of FeO.

[0133] In some embodiments, the primary crystal comprises iron oxide. In some embodiments, the crystallite comprises iron oxide. In some embodiments, the plurality of primary crystals comprise iron oxide. In some embodiments, the plurality of crystallites comprise iron oxide. In some embodiments, the at least one primary crystal comprises iron oxide. In some embodiments, the at least one crystallite comprises iron oxide.

[0134] In some embodiments, the single iron oxide crystal does not comprise FeO. In some embodiments, the single iron oxide crystal does not contain FeO. In some embodiments, the single iron oxide crystal does not consist of FeO. In some embodiments, the single iron oxide crystal does not consist essentially of FeO. In some embodiments, the single iron oxide crystal is not FeO.

[0135] In some embodiments, the single crystal does not comprise FeO. In some embodiments, the single crystal does not contain FeO. In some embodiments, the single crystal does not consist of FeO. In some embodiments, the single crystal does not consist essentially of FeO. In some embodiments, the single crystal is not FeO.

[0136] In some embodiments, the primary crystal does not comprise FeO. In some embodiments, the primary crystal does not contain FeO. In some embodiments, the primary crystal does not consist of FeO. In some embodiments, the primary crystal does not consist essentially of FeO. In some embodiments, the primary crystal is not FeO.

[0137] In some embodiments, the plurality of primary crystals does not comprise FeO. In some embodiments, the plurality of primary crystals does not contain FeO. In some embodiments, the plurality of primary crystals does not consist of FeO. In some embodiments, the plurality of4880-1178-1618.1Page 28 of 66094876-000022WOPTprimary crystals does not consist essentially of FeO. In some embodiments, the plurality of primary crystals is not FeO.

[0138] In some embodiments, the crystallite does not comprise FeO. In some embodiments, the crystallite does not contain FeO. In some embodiments, the crystallite does not consist of FeO. In some embodiments, the crystallite does not consist essentially of FeO. In some embodiments, the crystallite is not FeO.

[0139] In some embodiments, the plurality of crystallites does not comprise FeO. In some embodiments, the plurality of crystallites does not contain FeO. In some embodiments, the plurality of crystallites does not consist of FeO. In some embodiments, the plurality of crystallites does not consist essentially of FeO. In some embodiments, the plurality of crystallites is not FeO.

[0140] In some embodiments, the magnetic nanoparticle does not comprise FeO. In some embodiments, the magnetic nanoparticle does not contain FeO. In some embodiments, the magnetic nanoparticle does not consist of FeO. In some embodiments, the magnetic nanoparticle does not consist essentially of FeO. In some embodiments, the magnetic nanoparticle is not FeO.

[0141] In some embodiments, the primary crystal is an iron oxide primary crystal. In some embodiments, the plurality of primary crystals is a plurality of iron oxide primary crystals. In some embodiments, the at least one primary crystal is at least one iron oxide primary crystal.

[0142] In some embodiments, the crystallite is an iron oxide crystallite. In some embodiments, the plurality of crystallites is a plurality of iron oxide crystallites. In some embodiments, the at least one crystallite is an iron oxide crystallite.

[0143] In some embodiments, the primary crystal is ferromagnetic, ferrimagnetic, or superparamagnetic, or any combination thereof. In some embodiments, the primary crystal is ferromagnetic. In some embodiments, the primary crystal is ferrimagnetic. In some embodiments, the primary crystal is superparamagnetic. In some embodiments, the primary crystal is ferrimagnetic, or superparamagnetic, or combination thereof.

[0144] In some embodiments, the crystallite is ferromagnetic, ferrimagnetic, or superparamagnetic, or any combination thereof. In some embodiments, the crystallite is ferromagnetic. In some embodiments, the crystallite is ferrimagnetic. In some embodiments, the crystallite is superparamagnetic. In some embodiments, the crystallite is ferrimagnetic, or superparamagnetic, or combination thereof.4880-1178-1618.1Page 29 of 66094876-000022WOPT

[0145] In some embodiments, the single crystal is ferromagnetic, ferrimagnetic, or superparamagnetic, or any combination thereof. In some embodiments, the single crystal is ferromagnetic. In some embodiments, the single crystal is ferrimagnetic. In some embodiments, the single crystal is superparamagnetic. In some embodiments, the single crystal is ferrimagnetic, or superparamagnetic, or combination thereof.

[0146] In some embodiments, the single crystal is a single iron oxide crystal.

[0147] In some embodiments, the iron oxide nanoparticle is a magnetic iron oxide nanoparticle. In some embodiments, the magnetic nanoparticle is a magnetic iron oxide nanoparticle.

[0148] In some embodiments, the sensor further comprises at least one receptor.

[0149] In some embodiments, the at least one receptor is deoxyribonucleic acid (DNA), antibody, enzyme, cell, aptamer, protein, or peptide, or any combination thereof.

[0150] In some embodiments, the at least one receptor is connected to or attached to the at least one magnetic Fe3O4nanosphere.

[0151] In some embodiments, the at least one receptor is connected to or attached to the at least one magnetic Fe3O4nanocube. In some embodiments, the at least one receptor is connected to or attached to the sensor. In some embodiments, the at least one receptor is connected to or attached to the magnetic nanoparticle. In some embodiments, the at least one receptor is connected to or attached to the iron oxide nanoparticle. In some embodiments, the at least one receptor is connected to or attached to the magnetic iron oxide nanoparticle.

[0152] In some embodiments, the magnetic nanoparticle further comprises at least one receptor. In some embodiments, the at least one receptor is deoxyribonucleic acid (DNA), antibody, enzyme, cell, aptamer, protein, or peptide, or any combination thereof.

[0153] In some embodiments, the magnetic nanoparticle is a nanosphere or a nanocube. In some embodiments, the magnetic nanoparticle is a nanosphere. In some embodiments, the magnetic nanoparticle is a nanocube.

[0154] In some embodiments, the magnetic iron oxide nanoparticle is a nanosphere or a nanocube. In some embodiments, the magnetic iron oxide nanoparticle is a nanosphere. In some embodiments, the magnetic iron oxide nanoparticle is a nanocube.4880-1178-1618.1Page 30 of 66094876-000022WOPT

[0155] In some embodiments, the iron oxide nanoparticle is a nanosphere or a nanocube. In some embodiments, the iron oxide nanoparticle is a nanosphere. In some embodiments, the iron oxide nanoparticle is a nanocube.

[0156] In some embodiments, the sensor is a biosensor. In some embodiments, the receptor is a bioreceptor.

[0157] In some embodiments, the magnetic nanoparticle is iron oxide. In some embodiments, the magnetic nanoparticle comprises iron oxide. In some embodiments, the magnetic nanoparticle consists of iron oxide. In some embodiments, the magnetic nanoparticle consists essentially of iron oxide.

[0158] In some embodiments, the magnetic nanoparticle is Fe3O4. In some embodiments, the magnetic nanoparticle comprises Fe3O4. In some embodiments, the magnetic nanoparticle consists of Fe3O4. In some embodiments, the magnetic nanoparticle consists essentially of Fe3O4.

[0159] In some embodiments, the magnetic nanoparticle is ferromagnetic, ferrimagnetic, or superparamagnetic, or any combination thereof. In some embodiments, the magnetic nanoparticle is ferromagnetic. In some embodiments, the magnetic nanoparticle is ferrimagnetic. In some embodiments, the magnetic nanoparticle is superparamagnetic. In some embodiments, the magnetic nanoparticle is ferrimagnetic, or superparamagnetic, or combination thereof.

[0160] In some embodiments, the plurality of primary crystals is a plurality of iron oxide primary crystals. In some embodiments, the plurality of crystallites is a plurality of iron oxide crystallites.

[0161] In some embodiments, the at least one primary crystal is at least one iron oxide primary crystal. In some embodiments, the at least one crystallite is at least one iron oxide crystallite.

[0162] In some embodiments, the test sample is a biological sample. Exemplary biological samples include, but are not limited to cheek swab; mucus; whole blood, blood, serum; plasma; urine; saliva; semen; lymph; fecal extract; sputum; other body fluid or biofluid; cell sample; tissue sample; tumor sample; and / or tumor biopsy etc. Exemplary biological samples include, but are not limited to, cheek swab; mucus; whole blood, blood, serum; plasma; blood products, urine; saliva; semen; lymph; fecal extract; sputum; other body fluid or biofluid; cell sample; tissue sample; tissue extract; tumor sample; and / or tumor biopsy etc. The term biological sample also includes a mixture of the above- mentioned biological samples. The term “biological sample” also includes untreated or pretreated (or4880-1178-1618.1Page 31 of 66094876-000022WOPTpre-processed) biological samples. In some embodiments, a biological sample can comprise one or more cells from a subject. In some embodiments, a biological sample can be a tumor cell sample, e.g. the sample can comprise cancerous cells, cells from a tumor, and / or a tumor biopsy. In some embodiments, the biological samples comprise derivatives of blood products, including blood, plasma and / or serum. In some embodiments, the biological sample is blood. In some embodiments, the biological sample is plasma. In some embodiments, the biological sample is serum. In some embodiments the biological sample is cerebrospinal fluid (CSF). In some embodiments the biological sample is a tissue extract. In some embodiments the biological sample is a biopsy sample. In some embodiments the biological sample is a biopsy specimen. In some embodiments the biological sample is urine. In some embodiments the biological sample is plasma, serum, cerebrospinal fluid (CSF), a tissue extract, urine, a biopsy specimen, or a biopsy sample. In some embodiments, the biological sample comprises one or more proteins and / or one or more peptides. In some embodiments, the biological sample comprises one or more peptides. In some embodiments, the biological sample comprises one or more proteins.

[0163] The terms “body fluid” or “bodily fluids” are liquids originating from inside the bodies of organisms. Bodily fluids include amniotic fluid, aqueous humour, vitreous humour, bile, blood (e.g., serum), breast milk, cerebrospinal fluid, cerumen (earwax), chyle, chyme, endolymph and perilymph, exudates, feces, female ejaculate, gastric acid, gastric juice, lymph, mucus (e.g., nasal drainage and phlegm), pericardial fluid, peritoneal fluid, pleural fluid, pus, rheum, saliva, sebum (skin oil), serous fluid, semen, smegma, sputum, synovial fluid, sweat, tears, urine, vaginal secretion, and vomit. Extracellular bodily fluids include intravascular fluid (blood plasma), interstitial fluids, lymphatic fluid and transcellular fluid. Immunoglobulin G (IgG), the most abundant antibody subclass, may be found in all body fluids. “Biological sample” also includes a mixture of the above-mentioned body fluids. “Biological samples” may be untreated or pretreated (or pre-processed) biological samples.

[0164] Biological sample collection procedures and devices known in the art are suitable for use with various embodiment of the present invention. Examples of biological sample collection procedures and devices include but are not limited to: phlebotomy tubes (e.g., a vacutainer blood / specimen collection device for collection and / or storage of the blood / specimen), dried blood spots, Microvette® CB300 Capillary Collection Device (Sarstedt), HemaXis blood collection devices (microfluidic technology, Hemaxis), Volumetric Absorptive Microsampling ( such as CE-IVD Mitra® microsampling device for accurate dried blood sampling (Neoteryx®), HemaSpot™-HF Blood4880-1178-1618.1Page 32 of 66094876-000022WOPTCollection Device. Additional biological sample collection procedures and devices include but are not limited to: a tissue sample collection device; standard collection / storage device (e.g., a collection / storage device for collection and / or storage of a biological sample (e.g., blood, plasma, serum, urine, etc.); a dried blood spot sampling device. In some embodiments, the Volumetric Absorptive Microsampling (VAMSTM) samples can be stored and mailed, and an assay can be performed remotely.

[0165] In some embodiments, the biomolecules are nucleic acids, lipids, carbohydrates, polysaccharides, glycolipids, or proteins, or any combination thereof.

[0166] In various embodiments, the magnetic nanoparticles of the present invention do not comprise FeO. In various embodiments, the magnetic nanoparticles of the present invention do not contain FeO. In various embodiments, the magnetic nanoparticles of the present invention do not consist of FeO. In various embodiments, the magnetic nanoparticles of the present invention do not consist essentially of FeO.

[0167] In various embodiments, the primary crystals of the present invention do not comprise FeO. In various embodiments, the primary crystals of the present invention do not contain FeO. In various embodiments, the primary crystals of the present invention do not consist of FeO. In various embodiments, the primary crystals of the present invention do not consist essentially of FeO.

[0168] In various embodiments, the crystallites of the present invention do not comprise FeO. In various embodiments, the crystallites of the present invention do not contain FeO. In various embodiments, the crystallites of the present invention do not consist of FeO. In various embodiments, the crystallites of the present invention do not consist essentially of FeO.

[0169] In various embodiments, the present invention provides a sensor, comprising: at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises at least one iron oxide primary crystal, wherein the at least one iron oxide primary crystal comprises at least one crystallite, wherein the at least one magnetic nanoparticle has a particle size of 49 nm to 420 nm, wherein the at least one crystallite has a crystallite size of 10 nm to 40 nm, wherein the at least one magnetic nanoparticle has a spherical shape; and wherein the at least one magnetic nanoparticle does not have a core-shell structure; or at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises a single iron oxide crystal, wherein the at least one magnetic nanoparticle has a particle size of 19 nm to 207 nm, wherein the at least one magnetic4880-1178-1618.1Page 33 of 66094876-000022WOPTnanoparticle has a polyhedral shape; and wherein the at least one magnetic nanoparticle does not have a core-shell structure; or a combination thereof.

[0170] In various embodiments, the present invention provides a sensor, comprising: at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises at least one iron oxide primary crystal, wherein the at least one iron oxide primary crystal comprises at least one crystallite, wherein the at least one magnetic nanoparticle has a particle size of 49 nm to 420 nm, wherein the at least one crystallite has a crystallite size of 10 nm to 40 nm, wherein the at least one magnetic nanoparticle has a spherical shape; and wherein the at least one magnetic nanoparticle does not have a core-shell structure.

[0171] In various embodiments, the present invention provides a sensor, comprising: at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises a single iron oxide crystal, wherein the at least one magnetic nanoparticle has a particle size of 19 nm to 207 nm, wherein the at least one magnetic nanoparticle has a polyhedral shape; and wherein the at least one magnetic nanoparticle does not have a core-shell structure.

[0172] In some embodiments, the single iron oxide crystal has a polyhedral shape. In some embodiments, the single iron oxide crystal has a cuboid shape. In some embodiments, the single iron oxide crystal has a cube shape.

[0173] In some embodiments, the primary crystal has a spherical shape. In some embodiments, the crystallite has a spherical shape.

[0174] In some embodiments, the magnetic nanoparticle has a polyhedral shape. In some embodiments, the magnetic nanoparticle has a cuboid shape. In some embodiments, the magnetic nanoparticle is a nanocube.

[0175] In some embodiments, the magnetic nanoparticle has a spherical shape. In some embodiments, the magnetic nanoparticle is a nanosphere.

[0176] In some embodiments, the magnetic nanoparticle is not a core-shell magnetic nanoparticle. In some embodiments, the magnetic nanoparticle is not a core / shell magnetic nanoparticle. In some embodiments, the magnetic nanoparticle is not a core-shell structure. In some embodiments, the magnetic nanoparticle is not a core / shell structure. In some embodiments, the magnetic nanoparticle does not have a core-shell structure. In some embodiments, the magnetic nanoparticle does not have a core / shell structure.4880-1178-1618.1Page 34 of 66094876-000022WOPT

[0177] In some embodiments, a biomolecule is a carbohydrate, lipid, nucleic acid, or protein, or any combination thereof. In some embodiments the biomolecule is a carbohydrate. In some embodiments, the biomolecule is a lipid. In some embodiments, the biomolecule is a nucleic acid. In some embodiments, the biomolecule is a protein.

[0178] In some embodiments, the iron oxide primary crystal comprises Fe3O4, or Fe2O3, or combination thereof. In some embodiments, the iron oxide primary crystal is Fe3O4, or Fe2O3, or combination thereof. In some embodiments, the iron oxide primary crystal comprises Fe3O4. In some embodiments, the iron oxide primary crystal is Fe3O4. In some embodiments, the iron oxide primary crystal comprises Fe2O3. In some embodiments, the iron oxide primary crystal is Fe2O3.

[0179] In some embodiments, the crystallite comprises Fe3O4, or Fe2O3, or combination thereof. In some embodiments, the crystallite is Fe3O4, or Fe2O3, or combination thereof. In some embodiments, the crystallite comprises Fe3O4. In some embodiments, the crystallite is Fe3O4. In some embodiments, the crystallite comprises Fe2O3. In some embodiments, the crystallite is Fe2O3.

[0180] In some embodiments, the at least one Fe3O4nanosphere further comprises Fe2O3.

[0181] In some embodiments, the at least one Fe3O4nanocube further comprises Fe2O3.

[0182] In some embodiments, the at least one magnetic nanoparticle comprises Fe3O4, or Fe2O3, or combination thereof. In some embodiments, the at least one magnetic nanoparticle is Fe3O4, or Fe2O3, or combination thereof. In some embodiments, the at least one magnetic nanoparticle comprises Fe3O4. In some embodiments, the at least one magnetic nanoparticle is Fe3O4. In some embodiments, the at least one magnetic nanoparticle comprises Fe2O3. In some embodiments, the at least one magnetic nanoparticle is Fe2O3.

[0183] In some embodiments, the magnetic nanoparticle comprises Fe3O4, or Fe2O3, or combination thereof. In some embodiments, the magnetic nanoparticle is Fe3O4, or Fe2O3, or combination thereof. In some embodiments, the magnetic nanoparticle comprises Fe3O4. In some embodiments, the magnetic nanoparticle is Fe3O4. In some embodiments, the magnetic nanoparticle comprises Fe2O3. In some embodiments, the magnetic nanoparticle is Fe2O3. In some embodiments, the magnetic nanoparticle further comprises Fe3O4. In some embodiments, the magnetic nanoparticle further comprises Fe2O3.4880-1178-1618.1Page 35 of 66094876-000022WOPT

[0184] In some embodiments, the terms “trihydrate sodium acetate” and “sodium acetate trihydrate” have the same meaning and can be used interchangeably. In some embodiments, the terms “anhydrous sodium acetate” and “sodium acetate anhydrous” have the same meaning and can be used interchangeably.

[0185] Additional embodiments include those listed below.

[0186] Embodiment 37. A sensor, comprising: at least one magnetic Fe3O4nanosphere, wherein the at least one magnetic Fe3O4nanosphere comprises a plurality of primary crystals, wherein the plurality of primary crystals comprise a plurality of crystallites, wherein the at least one magnetic Fe3O4nanosphere has a particle size of 49 nm to 420 nm, wherein the plurality of crystallites have a crystallite size of 10 nm to 40 nm, and wherein the at least one magnetic Fe3O4nanosphere does not have a core-shell structure; or at least one magnetic Fe3O4nanocube, wherein the at least one magnetic Fe3O4nanocube has a particle size of 19 nm to 207 nm, and wherein the at least one magnetic Fe3O4nanocube does not have a core-shell structure; or a combination thereof.

[0187] Embodiment 38. The sensor of embodiment 37, further comprising at least one receptor, wherein the at least one receptor is connected to or attached to the at least one magnetic Fe3O4nanosphere; or wherein the at least one receptor is connected to or attached to the at least one magnetic Fe3O4nanocube; or both.

[0188] Embodiment 39. The sensor of embodiment 38, wherein the at least one receptor is deoxyribonucleic acid (DNA), antibody, enzyme, cell, aptamer, protein, or peptide, or any combination thereof.

[0189] Embodiment 40. The sensor of any one of embodiments 37-39, wherein the at least one magnetic Fe3O4nanosphere is ferromagnetic, ferrimagnetic, or superparamagnetic, or any combination thereof.

[0190] Embodiment 41. The sensor of any one of embodiments 37-39, wherein the at least one magnetic Fe3O4nanocube is ferromagnetic, ferrimagnetic, or superparamagnetic, or any combination thereof.

[0191] Embodiment 42. The sensor of any one of embodiments 37-39, wherein the sensor comprises the at least one magnetic Fe3O4nanosphere, wherein the at least one magnetic Fe3O4nanosphere comprises a plurality of primary crystals, wherein the plurality of primary crystals comprise a plurality of crystallites, wherein the at least one magnetic Fe3O4nanosphere has a4880-1178-1618.1Page 36 of 66094876-000022WOPTparticle size of 49 nm to 420 nm, wherein the plurality of crystallites have a crystallite size of 10 nm to 40 nm, and wherein the at least one magnetic Fe3O4nanosphere does not have a core-shell structure.

[0192] Embodiment 43. The sensor of embodiment 42, further comprising at least one receptor, wherein the at least one receptor is connected to or attached to the at least one magnetic Fe3O4nanosphere.

[0193] Embodiment 44. The sensor of embodiment 43, wherein the at least one receptor is deoxyribonucleic acid (DNA), antibody, enzyme, cell, aptamer, protein, or peptide, or any combination thereof.

[0194] Embodiment 45. The sensor of any one of embodiments 42-44, wherein the at least one magnetic Fe3O4nanosphere is ferromagnetic, ferrimagnetic, or superparamagnetic, or any combination thereof.

[0195] Embodiment 46. The sensor of any one of embodiments 37-39, wherein the sensor comprises at least one magnetic Fe3O4nanocube, wherein the at least one magnetic Fe3O4nanocube has a particle size of 19 nm to 207 nm, and wherein the at least one magnetic Fe3O4nanocube does not have a core-shell structure.

[0196] Embodiment 47. The sensor of embodiment 46, further comprising at least one receptor, wherein the at least one receptor is connected to or attached to the at least one magnetic Fe3O4nanocube.

[0197] Embodiment 48. The sensor of embodiment 47, wherein the at least one receptor is deoxyribonucleic acid (DNA), antibody, enzyme, cell, aptamer, protein, or peptide, or any combination thereof.

[0198] Embodiment 49. The sensor of any one of embodiments 46-48, wherein the at least one magnetic Fe3O4nanocube is ferromagnetic, ferrimagnetic, or superparamagnetic, or any combination thereof.

[0199] Embodiment 50. A method for detecting at least one analyte in a test sample, comprising: contacting the sensor of any one of embodiments 37-49 with a test sample, wherein the test sample comprises at least one analyte; subjecting the sensor to a magnetic field; and detecting the at least one analyte in the test sample by measuring a change in a magnetic property of the sensor.4880-1178-1618.1Page 37 of 66094876-000022WOPT

[0200] Embodiment 51. The method of embodiment 50, wherein the test sample is a biological sample.

[0201] Embodiment 52. The method of embodiment 50 or embodiment 51, wherein the analyte is at least one biomolecule.

[0202] Embodiment 53. The method of embodiment 50 or embodiment 51, wherein the analyte is at least one protein.

[0203] Embodiment 54. A method of separating at least one analyte from a test sample, comprising: contacting the sensor of any one of embodiments 37-49 with a test sample, wherein the test sample comprises at least one analyte; allowing the at least one analyte to bind to or with the sensor; and magnetically separating the bound analyte from the test sample.

[0204] Embodiment 55. The method of embodiment 54, wherein the test sample is a biological sample.

[0205] Embodiment 56. The method of embodiment 54 or embodiment 55, wherein the analyte is at least one biomolecule.

[0206] Embodiment 57. The method of embodiment 54 or embodiment 55, wherein the analyte is at least one protein.

[0207] Additional embodiments include those listed below.

[0208] Embodiment 58. A sensor, comprising: at least one magnetic Fe3O4nanosphere, wherein the at least one magnetic Fe3O4nanosphere comprises a plurality of primary crystals, wherein the plurality of primary crystals comprise a plurality of crystallites, wherein the at least one magnetic Fe3O4nanosphere has a particle size of 49 nm to 420 nm, wherein the plurality of crystallites have a crystallite size of 10 nm to 40 nm, and wherein the at least one magnetic Fe3O4nanosphere does not have a core-shell structure; or at least one magnetic Fe3O4nanocube, wherein the at least one magnetic Fe3O4nanocube has a particle size of 19 nm to 207 nm, and wherein the at least one magnetic Fe3O4nanocube does not have a core-shell structure; or a combination thereof.

[0209] Embodiment 59. The sensor of embodiment 58, further comprising at least one receptor, wherein the at least one receptor is connected to or attached to the at least one magnetic Fe3O4nanosphere; or wherein the at least one receptor is connected to or attached to the at least one magnetic Fe3O4nanocube; or both.4880-1178-1618.1Page 38 of 66094876-000022WOPT

[0210] Embodiment 60. The sensor of embodiment 59, wherein the at least one receptor is deoxyribonucleic acid (DNA), antibody, enzyme, cell, aptamer, protein, or peptide, or any combination thereof.

[0211] Embodiment 61. The sensor of embodiment 58, wherein the at least one magnetic Fe3O4nanosphere is ferromagnetic, ferrimagnetic, or superparamagnetic, or any combination thereof.

[0212] Embodiment 62. The sensor of embodiment 58, wherein the at least one magnetic Fe3O4nanocube is ferromagnetic, ferrimagnetic, or superparamagnetic, or any combination thereof.

[0213] Embodiment 63. The sensor of embodiment 58, wherein the sensor comprises the at least one magnetic Fe3O4nanosphere, wherein the at least one magnetic Fe3O4nanosphere comprises a plurality of primary crystals, wherein the plurality of primary crystals comprise a plurality of crystallites, wherein the at least one magnetic Fe3O4nanosphere has a particle size of 49 nm to 420 nm, wherein the plurality of crystallites have a crystallite size of 10 nm to 40 nm, and wherein the at least one magnetic Fe3O4nanosphere does not have a core-shell structure.

[0214] Embodiment 64. The sensor of embodiment 63, further comprising at least one receptor, wherein the at least one receptor is connected to or attached to the at least one magnetic Fe3O4nanosphere.

[0215] Embodiment 65. The sensor of embodiment 64, wherein the at least one receptor is deoxyribonucleic acid (DNA), antibody, enzyme, cell, aptamer, protein, or peptide, or any combination thereof.

[0216] Embodiment 66. The sensor of embodiment 63, wherein the at least one magnetic Fe3O4nanosphere is ferromagnetic, ferrimagnetic, or superparamagnetic, or any combination thereof.

[0217] Embodiment 67. The sensor of embodiment 58, wherein the sensor comprises at least one magnetic Fe3O4nanocube, wherein the at least one magnetic Fe3O4nanocube has a particle size of 19 nm to 207 nm, and wherein the at least one magnetic Fe3O4nanocube does not have a core-shell structure.

[0218] Embodiment 68. The sensor of embodiment 67, further comprising at least one receptor, wherein the at least one receptor is connected to or attached to the at least one magnetic Fe3O4nanocube.4880-1178-1618.1Page 39 of 66094876-000022WOPT

[0219] Embodiment 69. The sensor of embodiment 68, wherein the at least one receptor is deoxyribonucleic acid (DNA), antibody, enzyme, cell, aptamer, protein, or peptide, or any combination thereof.

[0220] Embodiment 70. The sensor of embodiment 67, wherein the at least one magnetic Fe3O4nanocube is ferromagnetic, ferrimagnetic, or superparamagnetic, or any combination thereof.

[0221] Embodiment 71. A method for detecting at least one analyte in a test sample, comprising: contacting the sensor of embodiment 58 with a test sample; subjecting the sensor to a magnetic field; and detecting the at least one analyte in the test sample by measuring a change in a magnetic property of the sensor.

[0222] Embodiment 72. The method of embodiment 71, wherein the test sample is a biological sample.

[0223] Embodiment 73. The method of embodiment 71, wherein the at least one analyte is at least one biomolecule.

[0224] Embodiment 74. The method of embodiment 71, wherein the at least one analyte is a protein.

[0225] Embodiment 75. A method of separating at least one analyte from a test sample, comprising: contacting the sensor of embodiment 58 with a test sample, wherein the test sample comprises at least one analyte; allowing the at least one analyte to bind to or with the sensor; and magnetically separating the bound analyte from the test sample.

[0226] Embodiment 76. The method of embodiment 75, wherein the test sample is a biological sample.

[0227] Embodiment 77. The method of embodiment 75, wherein the at least one analyte is at least one biomolecule.

[0228] Additional embodiments include those listed below.

[0229] Embodiment 78. A sensor, comprising: at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises a plurality of iron oxide primary crystals, wherein the plurality of iron oxide primary crystals comprise a plurality of crystallites, wherein the at least one magnetic nanoparticle has a particle size of 49 nm to 420 nm, wherein the plurality of crystallites have a crystallite size of 10 nm to 40 nm, wherein the at least one magnetic nanoparticle has a spherical shape; and wherein the at least one magnetic nanoparticle does not have a core-4880-1178-1618.1Page 40 of 66094876-000022WOPTshell structure; or at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises a single iron oxide crystal, wherein the at least one magnetic nanoparticle has a particle size of 19 nm to 207 nm, wherein the at least one magnetic nanoparticle has a polyhedral shape; and wherein the at least one magnetic nanoparticle does not have a core-shell structure; or a combination thereof.

[0230] Embodiment 79. The sensor of embodiment 78, wherein the sensor comprises at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises a plurality of iron oxide primary crystals, wherein the plurality of iron oxide primary crystals comprise a plurality of crystallites, wherein the at least one magnetic nanoparticle has a particle size of 49 nm to 420 nm, wherein the plurality of crystallites have a crystallite size of 10 nm to 40 nm, wherein the at least one magnetic nanoparticle has a spherical shape; and wherein the at least one magnetic nanoparticle does not have a core-shell structure.

[0231] Embodiment 80. The sensor of embodiment 79, further comprising at least one receptor, wherein the at least one receptor is connected to or attached to the at least one magnetic nanoparticle.

[0232] Embodiment 81. The sensor of embodiment 80, wherein the at least one receptor is deoxyribonucleic acid (DNA), antibody, enzyme, cell, aptamer, protein, or peptide, or any combination thereof.

[0233] Embodiment 82. The sensor of embodiment 79, wherein the at least one magnetic nanoparticle is ferromagnetic, ferrimagnetic, or superparamagnetic, or any combination thereof.

[0234] Embodiment 83. The sensor of embodiment 79, wherein the iron oxide is Fe3O4, or Fe2O3, or combination thereof.

[0235] Embodiment 84. The sensor of embodiment 78, wherein the sensor comprises at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises a single iron oxide crystal, wherein the at least one magnetic nanoparticle has a particle size of 19 nm to 207 nm, wherein the at least one magnetic nanoparticle has a polyhedral shape, and wherein the at least one magnetic nanoparticle does not have a core-shell structure.

[0236] Embodiment 85. The sensor of embodiment 84, further comprising at least one receptor, wherein the at least one receptor is connected to or attached to the at least one magnetic nanoparticle.4880-1178-1618.1Page 41 of 66094876-000022WOPT

[0237] Embodiment 86. The sensor of embodiment 85, wherein the at least one receptor is deoxyribonucleic acid (DNA), antibody, enzyme, cell, aptamer, protein, or peptide, or any combination thereof.

[0238] Embodiment 87. The sensor of embodiment 84, wherein the at least one magnetic nanoparticle is ferromagnetic, ferrimagnetic, or superparamagnetic, or any combination thereof.

[0239] Embodiment 88. The sensor of embodiment 84, wherein the iron oxide is Fe3O4, or Fe2O3, or combination thereof.

[0240] Embodiment 89. A method for detecting an analyte in a test sample, comprising: contacting the sensor of embodiment 78 with a test sample; subjecting the sensor to a magnetic field; and detecting an analyte in the test sample by measuring a change in a magnetic property of the sensor.

[0241] Embodiment 90. The method of embodiment 89, wherein the test sample is a biological sample.

[0242] Embodiment 91. The method of embodiment 89, wherein the analyte is at least one biomolecule.

[0243] Embodiment 92. The method of embodiment 91, wherein the biomolecule is a carbohydrate, lipid, nucleic acid, or protein, or any combination thereof.

[0244] Embodiment 93. A method of separating at least one analyte from a test sample, comprising: contacting the sensor of embodiment 78 with a test sample, wherein the test sample comprises at least one analyte; allowing the at least one analyte to bind to the sensor; and magnetically separating the bound analyte from the test sample.

[0245] Embodiment 94. The method of embodiment 93, wherein the test sample is a biological sample.

[0246] Embodiment 95. The method of embodiment 93, wherein the analyte is at least one biomolecule.

[0247] Embodiment 96. The method of embodiment 95, wherein the biomolecule is a carbohydrate, lipid, nucleic acid, or protein, or any combination thereof.

[0248] Additional embodiments include those listed below.

[0249] Embodiment 97. A sensor, comprising: at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises a plurality of iron oxide primary crystals, wherein the plurality of iron oxide primary crystals comprise a plurality of crystallites, wherein the at least4880-1178-1618.1Page 42 of 66094876-000022WOPTone magnetic nanoparticle has a particle size of 49 nm to 420 nm, wherein the plurality of crystallites have a crystallite size of 10 nm to 40 nm, wherein the at least one magnetic nanoparticle has a spherical shape; and wherein the at least one magnetic nanoparticle does not have a core- shell structure; or at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises a single iron oxide crystal, wherein the at least one magnetic nanoparticle has a particle size of 19 nm to 207 nm, wherein the at least one magnetic nanoparticle has a polyhedral shape; and wherein the at least one magnetic nanoparticle does not have a core-shell structure; or a combination thereof.

[0250] Embodiment 98. The sensor of embodiment 97, wherein the sensor comprises at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises a plurality of iron oxide primary crystals, wherein the plurality of iron oxide primary crystals comprise a plurality of crystallites, wherein the at least one magnetic nanoparticle has a particle size of 49 nm to 420 nm, wherein the plurality of crystallites have a crystallite size of 10 nm to 40 nm, wherein the at least one magnetic nanoparticle has a spherical shape; and wherein the at least one magnetic nanoparticle does not have a core-shell structure.

[0251] Embodiment 99. The sensor of embodiment 98, further comprising at least one receptor, wherein the at least one receptor is connected to or attached to the at least one magnetic nanoparticle.

[0252] Embodiment 100. The sensor of embodiment 99, wherein the at least one receptor is deoxyribonucleic acid (DNA), antibody, enzyme, cell, aptamer, protein, or peptide, or any combination thereof.

[0253] Embodiment 101. The sensor of embodiment 98, wherein the at least one magnetic nanoparticle is ferromagnetic, ferrimagnetic, or superparamagnetic, or any combination thereof.

[0254] Embodiment 102. The sensor of embodiment 98, wherein the iron oxide is Fe3O4, or Fe2O3, or combination thereof.

[0255] Embodiment 103. The sensor of embodiment 97, wherein the sensor comprises at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises a single iron oxide crystal, wherein the at least one magnetic nanoparticle has a particle size of 19 nm to 207 nm, wherein the at least one magnetic nanoparticle has a polyhedral shape, and wherein the at least one magnetic nanoparticle does not have a core-shell structure.4880-1178-1618.1Page 43 of 66094876-000022WOPT

[0256] Embodiment 104. The sensor of embodiment 103, further comprising at least one receptor, wherein the at least one receptor is connected to or attached to the at least one magnetic nanoparticle.

[0257] Embodiment 105. The sensor of embodiment 104, wherein the at least one receptor is deoxyribonucleic acid (DNA), antibody, enzyme, cell, aptamer, protein, or peptide, or any combination thereof.

[0258] Embodiment 106. The sensor of embodiment 103, wherein the at least one magnetic nanoparticle is ferromagnetic, ferrimagnetic, or superparamagnetic, or any combination thereof.

[0259] Embodiment 107. The sensor of embodiment 103, wherein the iron oxide is Fe3O4, or Fe2O3, or combination thereof.

[0260] Embodiment 108. A method for detecting an analyte in a test sample, comprising: contacting the sensor of any one of embodiments 97-107 with a test sample; subjecting the sensor to a magnetic field; and detecting an analyte in the test sample by measuring a change in a magnetic property of the sensor.

[0261] Embodiment 109. The method of embodiment 108, wherein the test sample is a biological sample.

[0262] Embodiment 110. The method of embodiment 108, wherein the analyte is at least one biomolecule.

[0263] Embodiment 111. A method of separating at least one analyte from a test sample, comprising: contacting the sensor of any one of embodiments 97-107 with a test sample, wherein the test sample comprises at least one analyte; allowing the at least one analyte to bind to the sensor; and magnetically separating the bound analyte from the test sample.

[0264] Embodiment 112. The method of embodiment 111, wherein the test sample is a biological sample.

[0265] Embodiment 113. The method of embodiment 111, wherein the analyte is at least one biomolecule.

[0266] Additional embodiments include those listed below.

[0267] In some embodiments, the plurality of iron oxide primary crystals does not have a core-shell structure. In some embodiments, each of the iron oxide primary crystals in the plurality of iron oxide primary crystals does not have a core-shell structure. In some embodiments, each of the iron oxide primary crystals in the plurality of iron oxide primary crystals does not comprise4880-1178-1618.1Page 44 of 66094876-000022WOPTFeO. In some embodiments, each of the iron oxide primary crystals in the plurality of iron oxide primary crystals does not contain FeO.

[0268] In some embodiments, the plurality of crystallites does not have a core-shell structure. In some embodiments, each of the crystallites in the plurality of crystallites does not have a core-shell structure. In some embodiments, each of the crystallites in the plurality of crystallites does not comprise FeO. In some embodiments, each of the crystallites in the plurality of crystallites does not contain FeO.

[0269] In some embodiments, the at least one iron oxide primary crystal does not have a core-shell structure. In some embodiments, the at least one iron oxide primary crystal does not comprise FeO. In some embodiments, the at least one iron oxide primary crystal does not contain FeO.

[0270] In some embodiments, the at least one crystallite does not have a core-shell structure. In some embodiments, the at least one crystallite does not comprise FeO. In some embodiments, the at least one crystallite does not contain FeO.

[0271] Additional embodiments include those listed below.

[0272] Embodiment 114. A sensor, comprising: at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises a plurality of iron oxide primary crystals, wherein the plurality of iron oxide primary crystals comprise a plurality of crystallites, wherein the at least one magnetic nanoparticle has a particle size of 49 nm to 420 nm, wherein the plurality of crystallites have a crystallite size of 10 nm to 40 nm, wherein the at least one magnetic nanoparticle has a spherical shape; wherein the plurality of iron oxide primary crystals does not have a core-shell structure; and wherein the at least one magnetic nanoparticle does not have a core-shell structure; or at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises a single iron oxide crystal, wherein the at least one magnetic nanoparticle has a particle size of 19 nm to 207 nm, wherein the at least one magnetic nanoparticle has a polyhedral shape; and wherein the at least one magnetic nanoparticle does not have a core-shell structure; or a combination thereof.

[0273] Embodiment 115. The sensor of embodiment 114, wherein the sensor comprises at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises a plurality of iron oxide primary crystals, wherein the plurality of iron oxide primary crystals comprise a plurality of crystallites, wherein the at least one magnetic nanoparticle has a particle4880-1178-1618.1Page 45 of 66094876-000022WOPTsize of 49 nm to 420 nm, wherein the plurality of crystallites have a crystallite size of 10 nm to 40 nm, wherein the at least one magnetic nanoparticle has a spherical shape; wherein the plurality of iron oxide primary crystals does not have a core-shell structure; and wherein the at least one magnetic nanoparticle does not have a core-shell structure.

[0274] Embodiment 116. The sensor of embodiment 115, further comprising at least one receptor, wherein the at least one receptor is connected to or attached to the at least one magnetic nanoparticle.

[0275] Embodiment 117. The sensor of embodiment 116, wherein the at least one receptor is deoxyribonucleic acid (DNA), antibody, enzyme, cell, aptamer, protein, or peptide, or any combination thereof.

[0276] Embodiment 118. The sensor of embodiment 115, wherein the at least one magnetic nanoparticle is ferromagnetic, ferrimagnetic, or superparamagnetic, or any combination thereof.

[0277] Embodiment 119. The sensor of embodiment 115, wherein the iron oxide is Fe3O4, or Fe2O3, or combination thereof.

[0278] Embodiment 120. The sensor of embodiment 114, wherein the sensor comprises at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises a single iron oxide crystal, wherein the at least one magnetic nanoparticle has a particle size of 19 nm to 207 nm, wherein the at least one magnetic nanoparticle has a polyhedral shape, and wherein the at least one magnetic nanoparticle does not have a core-shell structure.

[0279] Embodiment 121. The sensor of embodiment 120, further comprising at least one receptor, wherein the at least one receptor is connected to or attached to the at least one magnetic nanoparticle.

[0280] Embodiment 122. The sensor of embodiment 121, wherein the at least one receptor is deoxyribonucleic acid (DNA), antibody, enzyme, cell, aptamer, protein, or peptide, or any combination thereof.

[0281] Embodiment 123. The sensor of embodiment 120, wherein the at least one magnetic nanoparticle is ferromagnetic, ferrimagnetic, or superparamagnetic, or any combination thereof.

[0282] Embodiment 124. The sensor of embodiment 120, wherein the iron oxide is Fe3O4, or Fe2O3, or combination thereof.

[0283] Embodiment 125. A method for detecting an analyte in a test sample, comprising: contacting the sensor of any one of embodiments 114-124 with a test sample; subjecting the sensor4880-1178-1618.1Page 46 of 66094876-000022WOPTto a magnetic field; and detecting an analyte in the test sample by measuring a change in a magnetic property of the sensor.

[0284] Embodiment 126. The method of embodiment 125, wherein the test sample is a biological sample.

[0285] Embodiment 127. The method of embodiment 125, wherein the analyte is at least one biomolecule.

[0286] Embodiment 128. A method of separating at least one analyte from a test sample, comprising: contacting the sensor of any one of embodiments 114-124 with a test sample, wherein the test sample comprises at least one analyte; allowing the at least one analyte to bind to the sensor; and magnetically separating the bound analyte from the test sample.

[0287] Embodiment 129. The method of embodiment 128, wherein the test sample is a biological sample.

[0288] Embodiment 130. The method of embodiment 128, wherein the analyte is at least one biomolecule.

[0289] Additional embodiments include those listed below.

[0290] Embodiment 131. A sensor, comprising: at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises at least one iron oxide primary crystal, wherein the at least one iron oxide primary crystal comprises at least one crystallite, wherein the at least one magnetic nanoparticle has a particle size of 49 nm to 420 nm, wherein the at least one crystallite has a crystallite size of 10 nm to 40 nm, wherein the at least one magnetic nanoparticle has a spherical shape; wherein the at least one iron oxide primary crystal does not have a core- shell structure; and wherein the at least one magnetic nanoparticle does not have a core-shell structure; or at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises a single iron oxide crystal, wherein the at least one magnetic nanoparticle has a particle size of 19 nm to 207 nm, wherein the at least one magnetic nanoparticle has a polyhedral shape; and wherein the at least one magnetic nanoparticle does not have a core-shell structure; or a combination thereof.

[0291] Embodiment 132. The sensor of embodiment 131, wherein the sensor comprises at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises at least one iron oxide primary crystal, wherein the at least one iron oxide primary crystal comprises at least one crystallite, wherein the at least one magnetic nanoparticle has a particle size of 49 nm to4880-1178-1618.1Page 47 of 66094876-000022WOPT420 nm, wherein the at least one crystallite has a crystallite size of 10 nm to 40 nm, wherein the at least one magnetic nanoparticle has a spherical shape; wherein the at least one iron oxide primary crystal does not have a core-shell structure; and wherein the at least one magnetic nanoparticle does not have a core-shell structure.

[0292] Embodiment 133. The sensor of embodiment 132, further comprising at least one receptor, wherein the at least one receptor is connected to or attached to the at least one magnetic nanoparticle.

[0293] Embodiment 134. The sensor of embodiment 133, wherein the at least one receptor is deoxyribonucleic acid (DNA), antibody, enzyme, cell, aptamer, protein, or peptide, or any combination thereof.

[0294] Embodiment 135. The sensor of embodiment 132, wherein the at least one magnetic nanoparticle is ferromagnetic, ferrimagnetic, or superparamagnetic, or any combination thereof.

[0295] Embodiment 136. The sensor of embodiment 132, wherein the iron oxide is Fe3O4, or Fe2O3, or combination thereof.

[0296] Embodiment 137. The sensor of embodiment 131, wherein the sensor comprises at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises a single iron oxide crystal, wherein the at least one magnetic nanoparticle has a particle size of 19 nm to 207 nm, wherein the at least one magnetic nanoparticle has a polyhedral shape, and wherein the at least one magnetic nanoparticle does not have a core-shell structure.

[0297] Embodiment 138. The sensor of embodiment 137, further comprising at least one receptor, wherein the at least one receptor is connected to or attached to the at least one magnetic nanoparticle.

[0298] Embodiment 139. The sensor of embodiment 138, wherein the at least one receptor is deoxyribonucleic acid (DNA), antibody, enzyme, cell, aptamer, protein, or peptide, or any combination thereof.

[0299] Embodiment 140. The sensor of embodiment 137, wherein the at least one magnetic nanoparticle is ferromagnetic, ferrimagnetic, or superparamagnetic, or any combination thereof.

[0300] Embodiment 141. The sensor of embodiment 137, wherein the iron oxide is Fe3O4, or Fe2O3, or combination thereof.

[0301] Embodiment 142. A method for detecting an analyte in a test sample, comprising: contacting the sensor of any one of embodiments 131-141 with a test sample; subjecting the sensor4880-1178-1618.1Page 48 of 66094876-000022WOPTto a magnetic field; and detecting an analyte in the test sample by measuring a change in a magnetic property of the sensor.

[0302] Embodiment 143. The method of embodiment 142, wherein the test sample is a biological sample.

[0303] Embodiment 144. The method of embodiment 142, wherein the analyte is at least one biomolecule.

[0304] Embodiment 145. A method of separating at least one analyte from a test sample, comprising: contacting the sensor of any one of embodiments 131-141 with a test sample, wherein the test sample comprises at least one analyte; allowing the at least one analyte to bind to the sensor; and magnetically separating the bound analyte from the test sample.

[0305] Embodiment 146. The method of embodiment 145, wherein the test sample is a biological sample.

[0306] Embodiment 147. The method of embodiment 145, wherein the analyte is at least one biomolecule.

[0307] Additional embodiments include those listed below.

[0308] Embodiment 148. A sensor, comprising: at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises a plurality of iron oxide primary crystals, wherein the plurality of iron oxide primary crystals comprise a plurality of crystallites, wherein the at least one magnetic nanoparticle has a particle size of 49 nm to 420 nm, wherein the plurality of crystallites have a crystallite size of 10 nm to 40 nm, wherein the at least one magnetic nanoparticle has a spherical shape; and wherein the at least one magnetic nanoparticle does not have a core-shell structure; or at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises a single iron oxide crystal, wherein the at least one magnetic nanoparticle has a particle size of 19 nm to 207 nm, wherein the at least one magnetic nanoparticle has a polyhedral shape; and wherein the at least one magnetic nanoparticle does not have a core-shell structure; or a combination thereof.

[0309] Embodiment 149. The sensor of embodiment 148, wherein the sensor comprises at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises a plurality of iron oxide primary crystals, wherein the plurality of iron oxide primary crystals comprise a plurality of crystallites, wherein the at least one magnetic nanoparticle has a particle size of 49 nm to 420 nm, wherein the plurality of crystallites have a crystallite size of 10 nm to 404880-1178-1618.1Page 49 of 66094876-000022WOPTnm, wherein the at least one magnetic nanoparticle has a spherical shape; and wherein the at least one magnetic nanoparticle does not have a core-shell structure.

[0310] Embodiment 150. The sensor of embodiment 149, further comprising at least one receptor, wherein the at least one receptor is connected to or attached to the at least one magnetic nanoparticle.

[0311] Embodiment 151. The sensor of embodiment 150, wherein the at least one receptor is deoxyribonucleic acid (DNA), antibody, enzyme, cell, aptamer, protein, or peptide, or any combination thereof.

[0312] Embodiment 152. The sensor of embodiment 149, wherein the at least one magnetic nanoparticle is ferromagnetic, ferrimagnetic, or superparamagnetic, or any combination thereof.

[0313] Embodiment 153. The sensor of embodiment 149, wherein the iron oxide is Fe3O4, or Fe2O3, or combination thereof.

[0314] Embodiment 154. The sensor of embodiment 148, wherein the sensor comprises at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises a single iron oxide crystal, wherein the at least one magnetic nanoparticle has a particle size of 19 nm to 207 nm, wherein the at least one magnetic nanoparticle has a polyhedral shape, and wherein the at least one magnetic nanoparticle does not have a core-shell structure.

[0315] Embodiment 155. The sensor of embodiment 154, further comprising at least one receptor, wherein the at least one receptor is connected to or attached to the at least one magnetic nanoparticle.

[0316] Embodiment 156. The sensor of embodiment 155, wherein the at least one receptor is deoxyribonucleic acid (DNA), antibody, enzyme, cell, aptamer, protein, or peptide, or any combination thereof.

[0317] Embodiment 157. The sensor of embodiment 154, wherein the at least one magnetic nanoparticle is ferromagnetic, ferrimagnetic, or superparamagnetic, or any combination thereof.

[0318] Embodiment 158. The sensor of embodiment 154, wherein the iron oxide is Fe3O4, or Fe2O3, or combination thereof.

[0319] Embodiment 159. A method for detecting an analyte in a test sample, comprising: contacting the sensor of any one of embodiments 148-158 with a test sample; subjecting the sensor to a magnetic field; and detecting an analyte in the test sample by measuring a change in a magnetic property of the sensor.4880-1178-1618.1Page 50 of 66094876-000022WOPT

[0320] Embodiment 160. The method of embodiment 159, wherein the test sample is a biological sample.

[0321] Embodiment 161. The method of embodiment 159, wherein the analyte is at least one biomolecule.

[0322] Embodiment 162. A method of separating at least one analyte from a test sample, comprising: contacting the sensor of any one of embodiment 148-158 with a test sample, wherein the test sample comprises at least one analyte; allowing the at least one analyte to bind to the sensor; and magnetically separating the bound analyte from the test sample.

[0323] Embodiment 163. The method of embodiment 162, wherein the test sample is a biological sample.

[0324] Embodiment 164. The method of embodiment 162, wherein the analyte is at least one biomolecule.

[0325] Additional embodiments include those listed below.

[0326] Embodiment 165. A sensor, comprising: at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises at least one iron oxide primary crystal, wherein the at least one iron oxide primary crystal comprises at least one crystallite, wherein the at least one magnetic nanoparticle has a particle size of 49 nm to 420 nm, wherein the at least one crystallite has a crystallite size of 10 nm to 40 nm, wherein the at least one magnetic nanoparticle has a spherical shape; and wherein the at least one magnetic nanoparticle does not have a core- shell structure; or at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises a single iron oxide crystal, wherein the at least one magnetic nanoparticle has a particle size of 19 nm to 207 nm, wherein the at least one magnetic nanoparticle has a polyhedral shape; and wherein the at least one magnetic nanoparticle does not have a core-shell structure; or a combination thereof.

[0327] Embodiment 166. The sensor of embodiment 165 , wherein the sensor comprises at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises a t least one iron oxide primary crystal, wherein the at least one iron oxide primary crystal comprises at least one crystallite, wherein the at least one magnetic nanoparticle has a particle size of 49 nm to 420 nm, wherein the at least one crystallite has a crystallite size of 10 nm to 40 nm, wherein the at least one magnetic nanoparticle has a spherical shape; and wherein the at least one magnetic nanoparticle does not have a core-shell structure.4880-1178-1618.1Page 51 of 66094876-000022WOPT

[0328] Embodiment 167. The sensor of embodiment 166, further comprising at least one receptor, wherein the at least one receptor is connected to or attached to the at least one magnetic nanoparticle.

[0329] Embodiment 168. The sensor of embodiment 167, wherein the at least one receptor is deoxyribonucleic acid (DNA), antibody, enzyme, cell, aptamer, protein, or peptide, or any combination thereof.

[0330] Embodiment 169. The sensor of embodiment 166, wherein the at least one magnetic nanoparticle is ferromagnetic, ferrimagnetic, or superparamagnetic, or any combination thereof.

[0331] Embodiment 170. The sensor of embodiment 166, wherein the iron oxide is Fe3O4, or Fe2O3, or combination thereof.

[0332] Embodiment 171. The sensor of embodiment 165, wherein the sensor comprises at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises a single iron oxide crystal, wherein the at least one magnetic nanoparticle has a particle size of 19 nm to 207 nm, wherein the at least one magnetic nanoparticle has a polyhedral shape, and wherein the at least one magnetic nanoparticle does not have a core-shell structure.

[0333] Embodiment 172. The sensor of embodiment 171, further comprising at least one receptor, wherein the at least one receptor is connected to or attached to the at least one magnetic nanoparticle.

[0334] Embodiment 173. The sensor of embodiment 172, wherein the at least one receptor is deoxyribonucleic acid (DNA), antibody, enzyme, cell, aptamer, protein, or peptide, or any combination thereof.

[0335] Embodiment 174. The sensor of embodiment 171, wherein the at least one magnetic nanoparticle is ferromagnetic, ferrimagnetic, or superparamagnetic, or any combination thereof.

[0336] Embodiment 175. The sensor of embodiment 171, wherein the iron oxide is Fe3O4, or Fe2O3, or combination thereof.

[0337] Embodiment 176. A method for detecting an analyte in a test sample, comprising: contacting the sensor of any one of embodiments 165-175 with a test sample; subjecting the sensor to a magnetic field; and detecting an analyte in the test sample by measuring a change in a magnetic property of the sensor.

[0338] Embodiment 177. The method of embodiment 176, wherein the test sample is a biological sample.4880-1178-1618.1Page 52 of 66094876-000022WOPT

[0339] Embodiment 178. The method of embodiment 176, wherein the analyte is at least one biomolecule.

[0340] Embodiment 179. A method of separating at least one analyte from a test sample, comprising: contacting the sensor of any one of embodiments 165-175 with a test sample, wherein the test sample comprises at least one analyte; allowing the at least one analyte to bind to the sensor; and magnetically separating the bound analyte from the test sample.

[0341] Embodiment 180. The method of embodiment 179, wherein the test sample is a biological sample.

[0342] Embodiment 181. The method of embodiment 179, wherein the analyte is at least one biomolecule. EXAMPLES

[0343] The following examples illustrate some embodiments and aspects of the invention. It will be apparent to those skilled in the relevant art that various modifications, additions, substitutions, and the like can be performed without altering the spirit or scope of the invention, and such modifications and variations are encompassed within the scope of the invention as defined in the claims which follow. The following examples do not in any way limit the invention.

[0344] Example 1: Specific Protein Detection

[0345] In Example 1, MPs in category (1) are suitable.

[0346] In various embodiments, biosensors of the present invention having strong ferrimagnetic properties are useful for protein detection.

[0347] Example 2: Surface-based Biosensing Platforms

[0348] A recent study reported enhanced biosensing potential of Fe3O4nanocubes compared to Fe3O4nanospheres. Without being bound by theory, this improved biosensing capability of the nanocubes can be attributed to two key factors: (1) the stronger ferrimagnetic properties of Fe3O4nanocubes due to their more monocrystalline structures and (2) the larger surface contact area of the nanocubes when compared to their spherical counterparts. To evaluate the sensing signal, we used two biosensing platforms, namely GMR and atomic magnetometer in force-induced remnant magnetization spectroscopy, which unequivocally demonstrated the4880-1178-1618.1Page 53 of 66094876-000022WOPTstronger signal generated by the Fe3O4nanocubes as opposed to the nanospheres. Despite the significant potential of Fe3O4nanocubes, their integration into biosensing technologies is limited due to the challenges associated with their synthesis. While there are numerous reports discussing the technical challenges of the synthetic methods, issues related to reproducibility, and the small- scale synthesis of nanocubes the synthesis of polycrystalline Fe3O4nanospheres presents no technical difficulties and provides a substantial scale of nanoparticles, often in the hundreds of milligrams. Consequently, enhancing the crystallinity to boost the ferrimagnetic properties of IONPs serves as a viable solution for this sensing platform.

[0349] Furthermore, for magnetoresistance sensors like GMR and TMR, detection relies on the stray field generated by the magnetic particles (MPs). Superparamagnetic (SPM) NPs with weak magnetization often suffer from several drawbacks, including an unstable sensing signal and a low signal-to-noise ratio. Therefore, the use of ferromagnetic (FM) NPs may be better suited to produce a stable signal and achieve a high signal-to-noise ratio. In various embodiments, the present invention provides a method for employing FM NPs with varying levels of FM strength, offering the means for optimizing magnetoresistance-based sensors.

[0350] In Example 2, MPs in categories (1) and (3) are suitable.

[0351] Example 3: Diagnostic Magnetic Resonance

[0352] In addition to the direct detection of magnetic particles using techniques such as GMR, SQUID, and atomic magnetometers, magnetic nanoparticles can also serve as proximity sensors, causing changes in the relaxation rate of nearby water molecules. This alteration in the relaxation rate, often referred to as the magnetic resonance signal, can then be detected using magnetic resonance imaging (MRI) or nuclear magnetic resonance (NMR) methods. These biosensing platforms fall under the category of diagnostic magnetic resonance, emphasizing the use of superparamagnetic NPs. As previously discussed, polycrystalline superparamagnetic NPs have demonstrated superior magnetization capabilities at low magnetic fields compared to single- domain NPs and micron-sized MPs. Consequently, without being bound by theory, it is expected that the polycrystalline superparamagnetic NPs will induce significant changes in relaxation time, facilitating efficient detection.

[0353] In Example 3, MPs in category (2) are suitable.4880-1178-1618.1Page 54 of 66094876-000022WOPT

[0354] Example 4: MPs Serve as Separation Platforms in Biosensors

[0355] Magnetic particles (MPs) are also valuable for isolating biomolecule samples attached to their surfaces from liquid suspensions. By carefully controlling the surface functionalization of MPs, the separation process can be made specific, effectively eliminating unwanted biomolecules. To achieve this, MPs must first be dispersed in a solution to bind with the target biomolecules, followed by efficient magnetic separation. In general, superparamagnetic (SPM) MPs represent the most practical choice for separation platforms. Additionally, magnetic properties ranging from moderate to weak ferromagnetic (FM) can also be suitable for this purpose. For instance, in cases where separation platforms require extremely low concentrations of MPs, the magnetic separation of SPM particles may be less efficient, leaving residues behind after the process. On the other hand, while increasing the spatial gap can minimize the dipole moment-induced particle clustering in the case of FM particles at low concentrations, their FM properties can enable more efficient magnetic separation.

[0356] In Example 4, MPs in categories (2), (3) are suitable.

[0357] Example 5: Other Biosensors (Electrochemical, Optical, Piezoelectrical Sensing)

[0358] In addition to biosensors that rely on magnetic properties as their primary component, various types of biosensor systems use electrochemical, optical, and piezoelectric signals as their main sensing principles, combined with magnetic nanoparticles to enhance sensor performance. Depending on the biosensor's design, the magnetic particles (MPs) with diverse magnetic properties and a wide range of available particle sizes described in the present invention are suitable choices. Furthermore, the MPs described in various embodiments of the present invention provide unique advantages in optimizing the MP system's structure and properties, ultimately aiding in achieving the highest level of performance in biosensing.

[0359] In Example 5, MPs in category (1), (2), (3) are suitable.

[0360] Additional Materials and Additional Examples

[0361] Additional Materials (Examples A-C). Iron(III) chloride hexahydrate (97%, Alfa Aesar) was used as precursor for synthesis of Iron oxide nanospheres. Ethylene glycol (99%,4880-1178-1618.1Page 55 of 66094876-000022WOPTSigma Aldrich) and Diethylene glycol (99%, ACROS Organics) were used as solvents. Sodium acetate (99%, anhydrous) was purchased from ACROS. Organic and sodium acetate trihydrate (99%) was purchased from Fisher. Sodium acrylate (97%) was purchased from Sigma Aldrich. Surfactant polyethylene glycol-400 were purchased from Olin Mathieson Chemical Corporation. Deionized water with resistance of 18 MΩ-cm (Academic Milli-Q Water System, Millipore Corporation). Pressure vessel used for synthesis of spherical IONSs was used with volume of 65 mL from ChemGlass. For synthesis of Fe3O4nanocubes, iron(III) acetylacetonate (99.9%), oleic acid (90%), and benzyl ether (98%), and 1-octadecene (90%) were all purchased from Sigma Aldrich. Sodium oleate (97%) and 1-tetradecene (97%) were purchased from TCI. All chemicals were used for synthesis without any further purification.

[0362] Example A. Synthesis of Highly Crystalline Iron Oxide Nanospheres. A synthetic solvothermal method for fabricating highly crystalline Fe3O4nanospheres was developed. FIG.7 illustrates the procedure for synthesizing highly crystalline Fe3O4nanospheres. Pressure vessels used for the synthesis of iron oxide nanospheres were cleaned in an aqua regia solution (3:1 HCl:HNO3) and then dried overnight at 60°C. Initially, a 40 mL mixture of a binary solvent system containing ethylene glycol (EG) and diethylene glycol (DEG) was prepared. To produce nanoparticles with different particle sizes (average diameters), various ratios of the bi- solvent system EG / DEG (mL) were used: 10 / 30, 15 / 25, 20 / 20, and 30 / 10, giving nanospheres with average diameters (particle sizes) of approximately 50 nm, 120 nm, 220 nm, and 390 nm, respectively. The process involved charging 1.35 g of FeCl3·6H2O into a pressure vessel with 20 mL of the solvent mixture and stirring for 15 minutes to dissolve the chemicals. Subsequently, 3.6 g of NaAc·3H2O was added to the remaining half of the solvent mixture, and vigorous stirring continued for 30 minutes to form a homogeneous mixture. An aliquot of 1200 μL PEG(400) was then injected into the mixture, followed by heating it to 188°C. Only under the synthetic condition using 10 / 30 EG / DEG mL was 1 mL of PEG(400) surfactant employed. The Teflon cap of the pressure vessel was securely screwed on, and a safety shield was used to cover the surroundings throughout the reaction. The ramping rate was maintained at approximately 4.8°C / min, and the reaction time was set to 5 hours under vigorous stirring at least 540 rpm. The resulting product, which had a black color, was allowed to cool naturally to room temperature and was washed three times with ethanol, followed by magnetic separation. During each washing cycle, the iron oxide nanoparticles in ethanol were sonicated for 15 minutes. In addition to solvent compositions, we4880-1178-1618.1Page 56 of 66094876-000022WOPTobserved that stirring speed and ramping rate were two factors affecting the particle size of the nanoparticles, as well as the homogeneity of their spherical morphology. By increasing the stirring speed by 20%, the conditions for synthesizing IONSs with an average particle size of 120 nm and 220 nm were adjusted to yield average particle sizes of 140 nm and 255 nm, respectively. Conversely, by increasing the ramp rate, the synthesis conditions could be altered to reduce the average particle size of the nanoparticles. For instance, conditions to prepare nanoparticles with a particle size of 120 nm (ramping rate ~ 4.8°C / min) were adjusted to produce IONSs with an average particle size of 89 nm by using a ramping rate of 11°C / min. Therefore, the combination of stirring speed adjustments, ramp rates, and variations in solvent mixtures (EG & DEG) allowed for the production of IONSs with desired average particle sizes. Overall, this synthetic procedure efficiently yielded spherical nanoparticles with homogeneous, spherical-like morphology, characterized by large crystallite sizes (ranging from 24 nm to 37 nm) and a uniform particle size distribution. Among different solvent compositions, we noted that a 15 / 25 (mL) EG / DEG ratio produced IONSs with the best crystalline structure and an average crystallite size of approximately 34 nm to 37 nm.

[0363] Additionally, we noticed that the amount of water contained in trihydrate sodium acetate plays an important role in controlling the average particle size of NPs and their crystallinity. Instead of using 3.6 g of NaAc.3H2O (which contains 2.17 g of NaAc and 1.43 mL of water), we achieved similar results (particle size and crystallite size) by using a combination of 2.17 g of NaAc (anhydrous chemical) and 1.43 mL of deionized water. Varying the amount of water can be used to change the particle size and crystallite size of NPs. For example, by adding an extra 0.54 mL of water, the synthetic conditions for preparing 220-nm nanospheres yielded Fe3O4NPs with an average particle size of 175 nm and the crystallite size of 34 nm. Similarly, adding 0.54 mL of DI water to the synthetic conditions for a target size of 120 nm gave NPs with a particle size of 93 nm and a crystallite size of 34 nm. Therefore, adding water can be used to fabricate IONSs with different particle sizes and crystallite sizes. Experiments involving the addition of different amounts of water or the use of anhydrous NaAc are presented in Table 4.

[0364] Table 4. Control Experiments Involving Addition of Water and Anhydrous NaAc.4880-1178-1618.1Page 57 of 66094876-000022WOPTEG DEG Additives Added H2O (mL) Average Particle Crystallite Size (mL) (mL) Size (nm) (nm)

[0365] Example B. Synthesis of Iron Oxides Nanospheres with Tunable Crystallite Sizes. To reduce the crystallinity of IONSs, we employed two approaches: replacing NaAc·3H2O with anhydrous NaAc or adding an extra amount of sodium acrylate (Na-acrylate) to decrease the average crystallite size (see FIG.6). Generally, when we replaced 3.6 g of NaAc·3H2O with 3.6 g of anhydrous NaAc while keeping other parameters constant, the average particle size of NPs increased, but the crystallite size was significantly reduced to less than 20 nm, as shown in Table 4. Similarly, to synthesize highly crystalline IONSs, we used anhydrous sodium acetate in4880-1178-1618.1Page 58 of 66094876-000022WOPTcombination with variations in the EG / DEG ratio and adjustments to stirring speed and ramping rate, giving rise to various NP particle sizes with small crystallite sizes (less than 20 nm). We prepared different sets of IONSs with similar particle sizes around 175 nm, 230 nm, and 380 nm but with varying crystallite sizes. Additionally, the addition of extra sodium acrylate, such as 100 mg or 200 mg, proved effective in finely reducing the average crystallite size of IONSs while maintaining a consistent average particle size. For instance, when we added 100 mg or 200 mg of sodium acrylate to the synthetic conditions for IONSs (particle size 160 nm, crystallite size 26 nm), we were able to produce IONSs with similar particle sizes while reducing the average crystallite sizes to 19 nm and 10 nm, respectively. However, the addition of sodium acrylate led to a broadening of the particle size distribution and deviations from spherical morphology in the synthesized nanoparticles.

[0366] Example C. Synthesis of Iron Oxide Nanocubes. The thermal decomposition of Fe(acac)3in benzyl ether solvent, supported by oleic acid surfactant, was used to prepare Fe3O4nanocubes with a fast ramping rate in a short refluxing time (30 min). A two-neck round-bottom flask with a volume of 100 mL was used for all syntheses. The flask was cleaned with aqua regia (3:1 HCl:HNO3), followed by a piranha solution (3:1 H2SO4:H2O2), and then dried in the oven overnight at 150°C to completely remove all organic residues. Nanocube average particle sizes (edge length) ranging from 43 nm to 120 nm were synthesized by adjusting the stirring speed, concentration of precursors, and oleic acid surfactant. Smaller Fe3O4nanocubes (average particle size 23 nm ± 4 nm) were prepared by thermal decomposition with the addition of 4-biphenyl carboxylic acid. Growing large-size Fe3O4nanocubes requires a stable medium over a longer period. Consequently, nanocubes with a particle size of 184 nm were synthesized using a tri- solvent system and two surfactants (sodium oleate and oleic acid) with a refluxing time of 1 hour. All synthetic conditions were conducted with a customized high-power 140 mW (J-KEM) heating mantle. The maximum heating power was used in all conditions with a heating rate of approximately ~28 to 30°C / min, and the refluxing time was maintained for 30 minutes. Nitrogen (N2) degassing was performed for 2 hours prior to the reaction, and minimum N2bubbling was maintained during the reaction.

[0367] Materials Characterization (Examples A-C). Scanning electron microscope (SEM) LEO-1525 and FEI Dual Beam 235 Focused Ion Beam was used for imaging the nanoparticles at operating voltage 15 kV. All samples were dissolved in ethanol and drop-casted4880-1178-1618.1Page 59 of 66094876-000022WOPTon a clean surface of silicon wafer. Transmission electron microscope (TEM) JEOL JEM-2010 was used for imaging nanoparticles and Selected Area Electron Diffraction of TEM was used to analyze the crystalline nature of the samples. The accelerating voltage of TEM was 200 kV. TEM grids 300-mesh holey carbon-coated copper grids were used. X-ray Diffractometer (Smart Lab, Rigaku) using Cu Kα irradiations operated at 45 kV and 44 mA with a 0.01° step size was used for characterization of phase composition and determine crystallinity. Samples were drop-casted on a clean glass slide surface for measurement from 5 to 90° (2θ) in 20 mins. Full width at half maximum (FWHM) and θ of the most prominent peak of (311) planes at diffracted angle 2θ at 35.5° was used to calculate the average crystallite size. The average crystallite size was calculated by Debye-Scherrer formula, ^ ൌ^^ஒୡ୭^^with K = 0.9 for spherical particles, λ = 0.15406 nm, β = FWHM (radians), and θ is the angle (radians). X-ray photoelectron spectroscopy (XPS) -PHI 5700 X-ray photoelectron with a monochromatic Al Kα X-ray source was used to characterize the iron oxide powder samples. C 1s at binding energy 284.8 eV is used for calibration. Dried powder samples with known mass (from 10 – 12 mg) were loaded in capsule for measure magnetic properties by vibrating sample magnetometer (VSM) (LakeShore VSM 7300 Series with Controller LakeShore 735 and Gaussmeter LakeShore 450 and Software Version 3.8.0). Magnetization versus field (M-H) measurements were swept in the range of field ± 3k Oe. A superconducting quantum interference device (SQUID) MPMS3 by Quantum Design in DC mode was used to record the magnetization versus temperature (M-T) of superparamagnetic samples. The M-T measurement was recorded following the common zero-field-cooling / field- cooling (ZFC / FC) protocol.

[0368] The various methods and techniques described above provide a number of ways to carry out the application. Of course, it is to be understood that not necessarily all objectives or advantages described can be achieved in accordance with any particular embodiment described herein. Thus, for example, those skilled in the art will recognize that the methods can be performed in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objectives or advantages as taught or suggested herein. A variety of alternatives are mentioned herein. It is to be understood that some preferred embodiments specifically include one, another, or several features, while others specifically4880-1178-1618.1Page 60 of 66094876-000022WOPTexclude one, another, or several features, while still others mitigate a particular feature by inclusion of one, another, or several advantageous features.

[0369] Furthermore, the skilled artisan will recognize the applicability of various features from different embodiments. Similarly, the various elements, features and steps discussed above, as well as other known equivalents for each such element, feature, or step, can be employed in various combinations by one of ordinary skill in this art to perform methods in accordance with the principles described herein. Among the various elements, features, and steps some will be specifically included and others specifically excluded in diverse embodiments.

[0370] Although the application has been disclosed in the context of certain embodiments and examples, it will be understood by those skilled in the art that the embodiments of the application extend beyond the specifically disclosed embodiments to other alternative embodiments and / or uses and modifications and equivalents thereof.

[0371] Preferred embodiments of this application are described herein, including the best mode known to the inventors for carrying out the application. Variations on those preferred embodiments will become apparent to those of ordinary skill in the art upon reading the foregoing description. It is contemplated that skilled artisans can employ such variations as appropriate, and the application can be practiced otherwise than specifically described herein. Accordingly, many embodiments of this application include all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the application unless otherwise indicated herein or otherwise clearly contradicted by context.

[0372] All patents, patent applications, publications of patent applications, and other material, such as articles, books, specifications, publications, documents, things, and / or the like, referenced herein are hereby incorporated herein by this reference in their entirety for all purposes, excepting any prosecution file history associated with same, any of same that is inconsistent with or in conflict with the present document, or any of same that may have a limiting affect as to the broadest scope of the claims now or later associated with the present document. By way of example, should there be any inconsistency or conflict between the description, definition, and / or the use of a term associated with any of the incorporated material and that associated with the present document, the description, definition, and / or the use of the term in the present document shall prevail.4880-1178-1618.1Page 61 of 66094876-000022WOPT

[0373] It is to be understood that the embodiments of the application disclosed herein are illustrative of the principles of the embodiments of the application. Other modifications that can be employed can be within the scope of the application. Thus, by way of example, but not of limitation, alternative configurations of the embodiments of the application can be utilized in accordance with the teachings herein. Accordingly, embodiments of the present application are not limited to that precisely as shown and described.

[0374] Various embodiments of the invention are described above in the Detailed Description. While these descriptions directly describe the above embodiments, it is understood that those skilled in the art may conceive modifications and / or variations to the specific embodiments shown and described herein. Any such modifications or variations that fall within the purview of this description are intended to be included therein as well. Unless specifically noted, it is the intention of the inventors that the words and phrases in the specification and claims be given the ordinary and accustomed meanings to those of ordinary skill in the applicable art(s).

[0375] The foregoing description of various embodiments of the invention known to the applicant at this time of filing the application has been presented and is intended for the purposes of illustration and description. The present description is not intended to be exhaustive nor limit the invention to the precise form disclosed and many modifications and variations are possible in the light of the above teachings. The embodiments described serve to explain the principles of the invention and its practical application and to enable others skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Therefore, it is intended that the invention is not limited to the particular embodiments disclosed for carrying out the invention.

[0376] While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that, based upon the teachings herein, changes and modifications may be made without departing from this invention and its broader aspects and, therefore, the appended claims are to encompass within their scope all such changes and modifications as are within the true spirit and scope of this invention.4880-1178-1618.1Page 62 of 66094876-000022WOPT

Claims

CLAIMS What is claimed is:

1. A sensor, comprising: at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises a plurality of iron oxide primary crystals, wherein the plurality of iron oxide primary crystals comprise a plurality of crystallites, wherein the at least one magnetic nanoparticle has a particle size of 49 nm to 420 nm, wherein the plurality of crystallites have a crystallite size of 10 nm to 40 nm, wherein the at least one magnetic nanoparticle has a spherical shape; wherein the plurality of iron oxide primary crystals does not have a core-shell structure; and wherein the at least one magnetic nanoparticle does not have a core-shell structure; or at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises a single iron oxide crystal, wherein the at least one magnetic nanoparticle has a particle size of 19 nm to 207 nm, wherein the at least one magnetic nanoparticle has a polyhedral shape; and wherein the at least one magnetic nanoparticle does not have a core-shell structure; or a combination thereof.

2. The sensor of claim 1, wherein the sensor comprises at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises a plurality of iron oxide primary crystals, wherein the plurality of iron oxide primary crystals comprise a plurality of crystallites, wherein the at least one magnetic nanoparticle has a particle size of 49 nm to 420 nm, wherein the plurality of crystallites have a crystallite size of 10 nm to 40 nm, wherein the at least one magnetic nanoparticle has a spherical shape; wherein the plurality of iron oxide primary crystals does not have a core-shell structure; and wherein the at least one magnetic nanoparticle does not have a core-shell structure.

3. The sensor of claim 2, further comprising at least one receptor, wherein the at least one receptor is connected to or attached to the at least one magnetic nanoparticle.4880-1178-1618.1Page 63 of 66094876-000022WOPT4. The sensor of claim 3, wherein the at least one receptor is deoxyribonucleic acid (DNA), antibody, enzyme, cell, aptamer, protein, or peptide, or any combination thereof.

5. The sensor of claim 2, wherein the at least one magnetic nanoparticle is ferromagnetic, ferrimagnetic, or superparamagnetic, or any combination thereof.

6. The sensor of claim 2, wherein the iron oxide is Fe3O4, or Fe2O3, or combination thereof.

7. The sensor of claim 1, wherein the sensor comprises at least one magnetic nanoparticle, wherein the at least one magnetic nanoparticle comprises a single iron oxide crystal, wherein the at least one magnetic nanoparticle has a particle size of 19 nm to 207 nm, wherein the at least one magnetic nanoparticle has a polyhedral shape, and wherein the at least one magnetic nanoparticle does not have a core-shell structure.

8. The sensor of claim 7, further comprising at least one receptor, wherein the at least one receptor is connected to or attached to the at least one magnetic nanoparticle.

9. The sensor of claim 8, wherein the at least one receptor is deoxyribonucleic acid (DNA), antibody, enzyme, cell, aptamer, protein, or peptide, or any combination thereof.

10. The sensor of claim 7, wherein the at least one magnetic nanoparticle is ferromagnetic, ferrimagnetic, or superparamagnetic, or any combination thereof.

11. The sensor of claim 7, wherein the iron oxide is Fe3O4, or Fe2O3, or combination thereof.

12. A method for detecting an analyte in a test sample, comprising: contacting the sensor of any one of claims 1-11 with a test sample; subjecting the sensor to a magnetic field; and detecting an analyte in the test sample by measuring a change in a magnetic property of the sensor.4880-1178-1618.1Page 64 of 66094876-000022WOPT13. The method of claim 12, wherein the test sample is a biological sample.

14. The method of claim 12, wherein the analyte is at least one biomolecule.

15. A method of separating at least one analyte from a test sample, comprising: contacting the sensor of any one of claims 1-11 with a test sample, wherein the test sample comprises at least one analyte; allowing the at least one analyte to bind to the sensor; and magnetically separating the bound analyte from the test sample.

16. The method of claim 15, wherein the test sample is a biological sample.

17. The method of claim 15, wherein the analyte is at least one biomolecule.4880-1178-1618.1Page 65 of 66094876-000022WOPT

Images