Single-molecule Raman fiber optic tweezers based on core-shell microlens and manufacturing method thereof

Abstract

The present invention discloses a single-molecule Raman fiber optic tweezers based on core-shell microlenses and a method for making the same. The tweezers comprise a Raman spectrometer, a fiber coupler, a fiber laser, a fiber probe, and a core-shell microlens suspension for accommodating a sample to be tested, with the front end of the fiber probe extending into the core-shell microlens suspension. Embodiments of the present invention utilize the whispering gallery resonance effect of the core-shell microlenses to amplify the Raman signal of the sample, thereby enabling detection of nanoscale biological samples in a biological environment. The present invention can accomplish detection without the introduction of exogenous substances and is highly biocompatible. Based on the miniaturization of the core-shell microlens fiber optic probe, single-molecule Raman spectroscopy can be detected in confined biological environments. The present invention has the ability to capture individual biomolecules while amplifying the Raman scattering signal of the molecules, making it suitable for in situ detection of biomacromolecules or nanoscale bacteria or viruses in a biological environment.

Description

Technical Field

[0001] The present invention relates to the field of biomedical detection, and in particular to single-molecule Raman fiber optic tweezers based on core-shell microlenses and a manufacturing method thereof. Background Art

[0002] Raman microscopes are widely used in research in the field of biomedical testing, but their bulky instruments are difficult to apply to narrow biological environments such as blood vessels, intestines, and esophagus. In order to precisely achieve the accuracy of Raman spectroscopy detection of biomacromolecules and to achieve the detection accuracy of Raman spectroscopy of biomacromolecules at the level of single molecules, there are three technical problems: First, since the size of biomacromolecules is at the nanoscale, the diameter of the Raman scattering spot also needs to be at the nanoscale to achieve accurate detection of individual biomacromolecules. Secondly, a small and flexible optical probe that can penetrate deep into the living environment is needed to achieve the detection of biomacromolecules in the living environment. Finally, due to the size of biomacromolecules, their Raman scattering signals are usually relatively weak, making it difficult to effectively collect the Raman scattering signals of the target object in a complex biological environment. Summary of the Invention

[0003] The present invention aims to address at least one of the technical problems existing in the prior art. To this end, the present invention proposes a single-molecule Raman fiber tweezers based on a core-shell microlens and a method for fabricating the same. These tweezers feature a simple structure, a compact and flexible probe, and are capable of amplifying the Raman scattering signal of biomacromolecules at the detection location, enabling the detection of nanoscale biological samples in biological environments.

[0004] According to an embodiment of the first aspect of the present invention, a single-molecule Raman fiber tweezers based on a core-shell microlens comprises: a Raman spectrometer; a fiber coupler, the Raman spectrometer being connected to a first end of the fiber coupler; a fiber laser, the fiber laser being connected to a second end of the fiber coupler via an isolator; a fiber probe, the third end of the fiber coupler being connected to an interface end of the fiber probe; and a core-shell microlens suspension for containing a sample to be tested, the front end of the fiber probe extending into the core-shell microlens suspension.

[0005] A single-molecule Raman fiber tweezers based on a core-shell microlens according to an embodiment of the first aspect of the present invention has at least the following beneficial effects:

[0006] The embodiments of the present invention utilize the whispering gallery resonance effect of the core-shell microlens to amplify the Raman signal of the sample, thereby realizing the detection of nanoscale biological samples in a biological environment. The embodiments of the present invention can complete the detection without the introduction of exogenous substances and have high biocompatibility. Based on the miniaturization of the core-shell microlens fiber probe, single-molecule Raman spectroscopy detection can be performed in a narrow biological environment. The present invention has the ability to capture single biological molecules and amplify the Raman scattering signal of the molecules at the same time, and can be used for in situ detection of biological macromolecules or bacteria or viruses at the nanoscale in biological environments.

[0007] According to some embodiments of the present invention, the wavelength of the laser emitted by the fiber laser is 785 nm.

[0008] According to some embodiments of the present invention, the core-shell microlens suspension is a TiO2 / SiO2 core-shell composite particle suspension.

[0009] According to some embodiments of the present invention, the diameter of the optical fiber probe is 3-5 μm, and the cone angle of the optical fiber probe is 60°-73°.

[0010] A method for manufacturing single-molecule Raman fiber tweezers based on core-shell microlenses according to an embodiment of the second aspect of the present invention comprises the following steps:

[0011] Obtaining a fiber probe, connecting the fiber probe to the third end of a fiber coupler, connecting a Raman spectrometer to the first end of the fiber coupler, and connecting a fiber laser to the second end of the fiber coupler through an isolator;

[0012] preparing a core-shell microlens suspension;

[0013] The core-shell microlens suspension is dropped onto a glass slide, and the front end of the optical fiber probe is inserted into the core-shell microlens suspension.

[0014] The method for manufacturing single-molecule Raman fiber tweezers based on core-shell microlenses according to the second embodiment of the present invention has at least the following beneficial effects:

[0015] The embodiments of the present invention utilize the whispering gallery resonance effect of the core-shell microlens to amplify the Raman signal of the sample, thereby realizing the detection of nanoscale biological samples in a biological environment. The embodiments of the present invention can complete the detection without the introduction of exogenous substances and have high biocompatibility. Based on the miniaturization of the core-shell microlens fiber probe, single-molecule Raman spectroscopy detection can be performed in a narrow biological environment. The present invention has the ability to capture single biological molecules and amplify the Raman scattering signal of the molecules at the same time, and can be used for in situ detection of biological macromolecules or bacteria or viruses at the nanoscale in biological environments.

[0016] According to some embodiments of the present invention, the method for manufacturing the optical fiber probe is as follows:

[0017] Cut the optical fiber into two sections, remove the plastic outer skin and coating layer of the middle section of the optical fiber to obtain a bare section of optical fiber, and then put the optical fiber into a metal tube;

[0018] The exposed optical fiber is melted by a carbon dioxide laser, and then the molten part is pulled thin to form an optical fiber probe.

[0019] According to some embodiments of the present invention, the specific steps of preparing the core-shell microlens suspension are as follows:

[0020] dispersing a titanium precursor in anhydrous ethanol to obtain a titanium precursor solution;

[0021] Adding SiO2 microsphere powder into anhydrous ethanol to obtain an ethanol dispersion of SiO2 microspheres;

[0022] Stirring the titanium precursor solution and adding it dropwise to the ethanol dispersion of the SiO2 microspheres, and then placing the solution into a constant temperature reaction vessel for reaction to obtain an ethanol dispersion of core-shell microparticles;

[0023] The core-shell microparticle ethanol dispersion was taken out and diluted with deionized water to obtain a core-shell microlens suspension.

[0024] According to some embodiments of the present invention, the reaction temperature in the reaction vessel is 28°C-42°C.

[0025] According to some embodiments of the present invention, the diameter of the SiO2 microsphere powder is 3 to 5 μm.

[0026] According to some embodiments of the present invention, the thickness of the core-shell particles in the ethanol dispersion is 0.05-0.1 μm.

[0027] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0029] Figure 1 Schematic diagram of the principle of single-molecule Raman fiber tweezers based on core-shell microlenses in an embodiment of the present invention;

[0030] Figure 2 is a light field intensity distribution diagram in an embodiment of the present invention;

[0031] Figure 3This is a light field intensity curve of the photon nanojet generated by the core-shell microlens in an embodiment of the present invention.

[0032] Figure Number:

[0033] Raman spectrometer 100 , fiber coupler 200 , fiber laser 300 , fiber probe 400 , core-shell microlens suspension 500 , core-shell microlens 510 , isolator 600 , fiber adjustment frame 700 , glass slide 800 , and sample to be tested 900 . DETAILED DESCRIPTION

[0034] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0035] In the description of the present invention, it should be understood that descriptions involving orientation, such as the orientation or positional relationship indicated by up, down, etc., are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0036] In the description of the present invention, "a plurality" refers to more than two. The use of "first" or "second" is solely for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of the indicated technical features, or implicitly indicating the order of the indicated technical features.

[0037] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, and connecting should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0038] Reference Figure 1As shown, a single-molecule Raman fiber tweezers based on core-shell microlenses includes: a Raman spectrometer 100, a fiber coupler 200, a fiber laser 300, a fiber probe 400, and a core-shell microlens suspension 500. In this embodiment, the fiber coupler 200 is a Y-shaped fiber coupler 200. The Raman spectrometer 100 is connected to one arm of the left end of the fiber coupler 200. The fiber laser 300 is connected to the other arm of the left end of the fiber coupler 200 via an isolator 600. The right end of the fiber coupler 200 is connected to the interface end of the fiber probe 400. The fiber probe 400 is fixed to a fiber adjustment frame 700. The core-shell microlens suspension 500 containing the sample 900 to be tested is placed on a glass slide 800, and the front end of the fiber probe 400 extends into the core-shell microlens suspension 500.

[0039] The fiber laser 300 is used to emit the capture light and the excitation light. In this embodiment, the wavelength of the fiber laser 300 is 785 nm and the power is 10-60 mW. Of course, fiber lasers 300 with other wavelengths and powers can also be selected.

[0040] The core-shell microlens suspension 500 is a suspension of TiO2 / SiO2 core-shell composite particles. Other microcavity materials, such as silicon compounds, titanium dioxide, crystals, and polymers, can also be used. Due to the electrostatic adsorption force generated on the optical fiber surface, the core-shell microlenses 510 within the core-shell microlens suspension 500 adhere to the tip of the optical fiber probe 400, resulting in a core-shell microlens 510 optical fiber probe. This produces a whispering gallery effect under laser light of a specific wavelength, amplifying the Raman scattering signal of molecules. In this embodiment, the diameter of the optical fiber probe 400 is 3-5 μm, and the cone angle of the optical fiber probe 400 is 60°-73°.

[0041] The embodiments of the present invention utilize the whispering gallery resonance effect of the core-shell microlens 510 to amplify the Raman signal of the sample, thereby enabling the detection of nanoscale biological samples in a biological environment. The embodiments of the present invention can complete the detection without the introduction of exogenous substances and have high biocompatibility. Based on the miniaturization of the core-shell microlens 510 fiber probe, single-molecule Raman spectroscopy can be detected in a narrow biological environment. The present invention has the ability to capture single biological molecules and amplify the Raman scattering signal of the molecules. It can be used for in situ detection of biological macromolecules or bacteria or viruses at the nanoscale in biological environments.

[0042] The present invention also relates to a method for manufacturing single-molecule Raman fiber tweezers based on core-shell microlenses, comprising the following steps:

[0043] S100, obtain the optical fiber probe 400, connect the optical fiber probe 400 to the third end of the optical fiber coupler 200, connect the Raman spectrometer 100 to the first end of the optical fiber coupler 200, and connect the optical fiber laser 300 to the second end of the optical fiber coupler 200 through the isolator 600.

[0044] It should be noted that the optical fiber probe 400 in the embodiment of the present invention is made by using a large-core optical fiber through a melt-tapering method. First, the optical fiber is cut into two sections from the middle, and the plastic outer skin and coating layer of the middle section of the optical fiber are stripped off to obtain a section of bare optical fiber. The optical fiber is then inserted into a metal tube; the bare optical fiber is then melted by a carbon dioxide laser, and the melted part is then thinned to form the optical fiber probe 400.

[0045] It should be noted that the specific steps of the fused tapered method for large-core optical fibers are as follows:

[0046] S101 , selecting an optical fiber type. In this embodiment, the optical fiber is a large-core optical fiber with a core diameter of 100 μm and an FC / PC connector type.

[0047] S102. Use fiber optic strippers to strip off the coating layer of the middle section of the large-core optical fiber to obtain a section of exposed large-core optical fiber, and then put the large-core optical fiber into a metal tube to protect the large-core optical fiber. In this embodiment, the inner diameter of the metal tube is 0.9-1.0 mm, the wall thickness is 0.08-0.12 mm, and the length is 10-12 cm.

[0048] S103. Place the exposed large-core optical fiber horizontally above the carbon dioxide laser and let it stand for a few minutes to heat the optical fiber to a temperature of about 500°C to melt the large-core optical fiber. Then, draw the molten portion at a speed of 3 to 5 mm / s to form an optical fiber with a diameter of 3 to 5 μm, a length of 10 μm, and a cone angle of 60° to 73°. This will yield the desired optical fiber probe 400.

[0049] S200, preparing a core-shell microlens suspension 500, taking a TiO2 / SiO2 core-shell composite particle suspension as an example, the specific steps are as follows:

[0050] S201. Dispersing a titanium precursor in anhydrous ethanol to obtain a titanium precursor solution; wherein the titanium precursor is titanium alkoxide (TBT), and the concentration of the titanium precursor solution is about 0.01 mol / L.

[0051] S202. Add SiO2 microsphere powder to anhydrous ethanol to obtain an ethanol dispersion of SiO2 microspheres; wherein the diameter of the SiO2 microsphere powder is 3 to 5 μm.

[0052] S203. Using a thermostatic agitator, the titanium precursor solution prepared in step S201 is added dropwise to the ethanol dispersion of SiO2 microspheres prepared in step S202 while stirring. The mixture is then placed in a thermostatic reaction vessel. The reaction temperature in the reaction vessel is 28°C-42°C. In this embodiment, the reaction is carried out at 30°C for about 24 hours. The prepared microlenses are characterized by transmission electron microscopy to ensure that the thickness of the core-shell structure is within the specified range. The thickness of the TiO2 shell is controlled to be 0.05-0.1 μm, thereby obtaining an ethanol dispersion of core-shell particles.

[0053] S204 , taking out the core-shell microparticle ethanol dispersion and diluting it with deionized water, and then diluting it with deionized water to a concentration of 4.0×10 4 core-shell microlenses 510 per microliter to obtain a core-shell microlens suspension 500 .

[0054] It should be noted that each single particle in core-shell microlens suspension 500 can be considered a microlens with a core-shell structure, with the refractive indices of the core and shell being 2-2.5 and 1.4-1.5, respectively. In the present invention, this microlens functions as a whispering gallery microcavity that couples with the tapered optical fiber to produce a whispering gallery effect. It should be understood that, in addition to TiO2, materials for making this type of microcavity also include silicon compounds, titanium dioxide, crystals, and polymers.

[0055] S300 , placing a glass slide 800 on the stage, dropping the core-shell microlens suspension 500 onto the glass slide, and inserting the front end of the optical fiber probe 400 into the core-shell microlens 510 solution to obtain a core-shell microlens 510 optical fiber probe.

[0056] Through steps S100 to S300, a single-molecule Raman fiber tweezers based on a core-shell microlens of the present invention can be obtained. The specific workflow is described below:

[0057] Turn on the fiber laser 300 and direct laser light into the fiber probe 400 through the fiber coupler 200. The tip of the fiber probe 400 generates an optical gradient force, capturing a core-shell microlens 510 in the core-shell microlens suspension 500. Due to the electrostatic adsorption force generated on the fiber surface, the core-shell microlens 510 adheres to the tip of the fiber probe. Due to the principle of total internal reflection of light, coupled with the evanescent field and the microsphere, light of a specific wavelength resonates within the microcavity, forming a stable standing wave, known as the whispering gallery effect. Furthermore, because the focal point of the tapered fiber is larger than the diameter of the microlens, an optical potential well is generated at the tip of the core-shell microlens 510, resulting in a core-shell microlens 510 fiber probe. Other microlenses, such as biological microlenses, can also produce a whispering gallery effect under specific laser wavelengths, provided that their shape, size, and refractive index meet the requirements.

[0058] When performing Raman spectrum detection, the prepared sample 900 to be tested is placed on a glass slide 800, and the prepared core-shell microlens 510 optical fiber probe is inserted into the sample 900 to be tested. The optical fiber laser 300 is turned on to emit a laser with a wavelength of 785nm. The laser passes through the isolator 600, the optical fiber coupler 200, the optical fiber probe 400 and the core-shell microlens 510 to reach the captured sample 900 to be tested, and stimulates the Raman scattering signal of the sample 900 to be tested. Figure 2 As shown, a 796 nm laser beam passing through the tapered optical fiber and the 3 μm diameter core-shell microlens 510 generates a whispering gallery effect, forming an optical potential well at the front of the core-shell microlens 510. The Raman scattering signal is enhanced by the whispering gallery resonance of the core-shell microlens 510 and then transmitted through the optical fiber probe 400 and the optical fiber coupler 200 to the Raman spectrometer 100.

[0059] refer to Figure 3 As shown, this is a light field intensity curve of the photon nanojet generated by the core-shell microlens 510, with a FWHM of 0.23λ, breaking the diffraction limit. Therefore, the core-shell microlens 510 fiber probe of the present application can achieve ultra-high spatial detection resolution and can be used to detect nano-scale bacteria, viruses, biological macromolecules, etc.

[0060] Among them, the sample to be tested 900 in this embodiment can be a nanoscale biological macromolecule, virus or pathogenic bacteria, which is widely distributed in the human body and nature, and is convenient for detecting diseases and detecting the health status of humans or other animals; the Raman spectrum signal received in the Raman spectrometer 100 can be displayed and further processed by a computer.

[0061] The method for preparing the single-molecule Raman fiber optic tweezers based on core-shell microlenses of the present invention is convenient and quick to operate. After preparation, detection can be completed without introducing exogenous substances, and it has high biocompatibility. The core-shell microlens 510 fiber optic probe of the present invention is prepared based on the fiber optic probe. Due to the miniaturization of the fiber optic probe, single-molecule Raman spectroscopy detection can be performed in narrow biological environments. The core-shell microlens 510 fiber optic probe of the present invention has the ability to capture single biological molecules and amplify the Raman scattering signals of the molecules. It can be used for in situ detection of biological macromolecules or bacteria or viruses with nanometer sizes in biological environments.

[0062] The present invention also relates to an application of single-molecule Raman fiber optic tweezers based on core-shell microlenses, which is applied to the detection of macromolecular organisms.

[0063] The present invention combines fiber optic tweezers with a core-shell microlens 510. The fiber optic tweezers combined with the core-shell microlens 510 can generate a subwavelength optical focal length, enhancing the interaction between light and matter. The resulting optical potential well can more stably capture nanoscale biomolecules. Simultaneously, the whispering gallery resonance effect generated by the core-shell microlens 510 amplifies the Raman scattering signal generated by the molecules. The amplified Raman signal is transmitted via optical fiber to the Raman spectrometer 100, enabling in situ detection of single biological molecules. The present invention can be used to capture and detect biomacromolecules such as DNA and protein molecules. The whispering gallery resonance effect overcomes the problem of weak Raman scattering signals from such detection targets, demonstrating its potential for application in the biomedical field.

[0064] The embodiments of the present invention are described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the scope of the present invention.

Claims

1. A single-molecule Raman fiber tweezers based on core-shell microlenses, characterized in that: include: Raman spectrometer (100); an optical fiber coupler (200), the Raman spectrometer (100) being connected to a first end of the optical fiber coupler (200); a fiber laser (300), the fiber laser (300) being connected to the second end of the fiber coupler (200) via an isolator (600); an optical fiber probe (400), wherein the third end of the optical fiber coupler (200) is connected to the interface end of the optical fiber probe (400); a core-shell microlens suspension (500) for accommodating a sample (900) to be tested, wherein the front end of the optical fiber probe (400) extends into the core-shell microlens suspension (500); The fiber laser (300) passes laser light into the fiber probe (400) through the fiber coupler (200); the front end of the fiber probe (400) captures a core-shell microlens (510) in the core-shell microlens suspension (500) through the generated optical gradient force; after the laser light passes through the fiber probe (400) and the core-shell microlens (510), a whispering gallery effect is generated and an optical potential well is formed at the front end of the core-shell microlens (510); the laser light reaches the sample to be tested (900) through the fiber probe (400) and the core-shell microlens (510), and excites a Raman scattering signal of the sample to be tested (900); the Raman scattering signal is enhanced by the whispering gallery resonance effect of the core-shell microlens (510), and then transmitted to the Raman spectrometer (100) through the fiber probe (400) and the fiber coupler (200).

2. The single-molecule Raman fiber tweezers based on core-shell microlenses according to claim 1, characterized in that: The wavelength of the laser emitted by the optical fiber laser (300) is 785 nm.

3. The single-molecule Raman fiber tweezers based on core-shell microlenses according to claim 1, characterized in that: The core-shell microlens suspension (500) is a TiO2 / SiO2 core-shell composite particle suspension.

4. The single-molecule Raman fiber tweezers based on core-shell microlenses according to claim 1, characterized in that: The diameter of the optical fiber probe (400) is 3 to 5 μm, and the cone angle of the optical fiber probe (400) is 60° to 73°.

5. A method for manufacturing single-molecule Raman fiber tweezers based on core-shell microlenses according to any one of claims 1 to 4, characterized in that: The following steps are involved: Obtaining an optical fiber probe (400), connecting the optical fiber probe (400) to the third end of an optical fiber coupler (200), connecting a Raman spectrometer (100) to the first end of the optical fiber coupler (200), and connecting an optical fiber laser (300) to the second end of the optical fiber coupler (200) via an isolator (600); preparing a core-shell microlens suspension (500); A core-shell microlens suspension (500) is dropped onto a glass slide, and the front end of an optical fiber probe (400) is inserted into the core-shell microlens suspension (500).

6. The method for fabricating single-molecule Raman fiber tweezers based on core-shell microlenses according to claim 5, characterized in that: The manufacturing method of the optical fiber probe (400) is as follows: Cut the optical fiber into two sections, remove the plastic outer skin and coating layer of the middle section of the optical fiber to obtain a bare section of optical fiber, and then put the optical fiber into a metal tube; The exposed optical fiber is melted by a carbon dioxide laser, and the melted portion is then thinned to form an optical fiber probe (400).

7. The method for fabricating single-molecule Raman fiber tweezers based on core-shell microlenses according to claim 5, characterized in that: The specific steps of preparing the core-shell microlens suspension (500) are dispersing a titanium precursor in anhydrous ethanol to obtain a titanium precursor solution; Adding SiO2 microsphere powder into anhydrous ethanol to obtain an ethanol dispersion of SiO2 microspheres; Stirring the titanium precursor solution and adding it dropwise to the ethanol dispersion of the SiO2 microspheres, and then placing the solution into a constant temperature reaction vessel for reaction to obtain an ethanol dispersion of core-shell microparticles; The core-shell microparticle ethanol dispersion is taken out and diluted with deionized water to obtain a core-shell microlens suspension (500).

8. The method for fabricating single-molecule Raman fiber tweezers based on core-shell microlenses according to claim 7, characterized in that: The reaction temperature in the reaction container is any value between 28°C and 42°C.

9. The method for fabricating single-molecule Raman fiber tweezers based on core-shell microlenses according to claim 7, characterized in that: The diameter of the SiO2 microsphere powder is 3 to 5 μm.

10. The method for manufacturing single-molecule Raman fiber tweezers based on core-shell microlenses according to claim 7, characterized in that: The thickness of the core-shell particles in the ethanol dispersion is 0.05 to 0.1 μm.

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