Resonant cavity biosensor operating in a visible range and comprising photonic crystals

Abstract

The present invention relates to a photonic-based optical resonant cavity biosensor (1) which is used in the analysis of biological systems, operates in visible range and is able to perform sensing through color.

Description

[0001] RESONANT CAVITY BIOSENSOR OPERATING IN A VISIBLE RANGE AND COMPRISING PHOTONIC CRYSTALS

[0002] Technical Field

[0003] The present invention relates to a photonic-based optical resonant cavity biosensor which is used in the analysis of biological systems, operates in a visible range and is able to perform sensing through color.

[0004] Background of the Invention

[0005] Today, exposure to various harmful external factors that can adversely affect human health such as carcinogenic chemicals, radiation, microbiological objects containing bacterial or viral infections can cause many diseases. Various biosensor technologies have been developed for the early diagnosis and treatment of these diseases and for the rapid conclusion of this diagnosis-treatment process. Especially in the field of biosensors and nanomedicine, it is very important to examine cells and tissues at the nano and micro level for rapid diagnosis and rapid treatment of diseases. It is also vital to design chemical and biological analysis systems in small sizes in order to realize less reagent consumption and low-cost portable systems. For this reason, the science and technology of photonics, which can offer powerful solutions and alternative approaches especially for nano-sensing due to its physical nature that is based on the interaction of light and matter, has a significant potential. In this context, photonic crystals (PC) which comprise various modifiable optical media for biosensor applications can be used in photonics technology.

[0006] Photonic-based biosensor technology designed with PC provides an innovative and rapid measurement opportunity for the analysis of components in a biological system. Since the dielectric constants of biological molecules are greater than those of air and water, the propagation of electromagnetic waves varies as they pass through a biological system. Due to the variation in the propagation of electromagnetic waves, analytes that can be used for medical applications can be easily identified and detected. In this way, optical biosensors can have the ability to identify various biological analytes such as proteins, antibodies, DNA, blood, diseased tissue, etc. Changes in various optical properties, especially the dielectric constant and refractive index, vary in proportion to the amount or type of biological recognition element present in the sensing unit. By converting this change into various measurable physical parameters, sensing can be performed.

[0007] PCs are periodic nanoscale structures that affect the motion of photons in the same way that the periodic potential in a crystal affects the motion of electrons by defining allowed and forbidden electronic energy bands. In general, PCs are composed of materials with alternating low and high dielectric constant in one, two or three dimensions (ID, 2D or 3D) and periodic dielectric and metal-dielectric nanostructures in order to modify the propagation of electromagnetic waves within the structure. With this periodicity, the transmission of light within certain frequency or wavelength ranges, called the photonic band gap (PBG), can be limited. With this aspect, PC-based cavity sensors have a similar working principle to sensors with a metal-coated mirror guide.

[0008] In photonic sensing technology, two sensing strategies that are based on the change in resonant wavelength or intensity values have been reported. The resonant wavelength can be achieved by the practical realization of multiple beam interference in an optical cavity sandwiched between two layers, where a reflectance band is formed by the designed PBG characteristic of the PC. The two reflecting PC surfaces are facing each other and aligned so as to be as parallel as possible, such as Fabry-Perot. The change in resonant wavelength is determined for different analyte values that will be present in the optical cavity and the analysis of the analyte is carried out by calibration based on the amount of shift. Alternatively, the intensity is reduced while the dielectric parameters of the analytes are changed. There are several reported methods for sensing the refractive index change of various biosensors, such as the brass grating, Mach-Zehnder interferometer and micro-ring resonator. Therefore, these systems are also referred to as refractive index sensors.

[0009] Since biosensing process with resonant wavelength utilizes the phenomenon of reflectance within the optical cavity, a change in the refractive index of the measurement sample present in the cavity can be made by illuminating the system with PCs with white light and by spectroscopically identifying the resonant modes. In this way, problems such as creating a adverse effect on the sample material and the time-consuming preceding process can be eliminated and results can be acquired rapidly, since no labeling with fluorescence or similar material is required. Furthermore, the measurement accuracy can be improved by obtaining high contrast with high light intensity by the modification of the resonant reflectance. This method can also be used for biological, biochemical, chemical and refractive index analysis of gases and liquids.

[0010] In a photonic-based biosensor, it is expected that there is no absorption in the wavelength range in which the sensing will be performed for all optical elements that constitute the biosensor. Therefore, all optical processes occurring in the sensor are based on reflectance and transmission, and a more accurate sensing can be performed with perfect mode formation, especially in sensors comprising a system such as a PC. The same situation also applies to the biological system that will be analyzed. Visible range (VR) and near-infrared (NIR) spectral ranges are often referred to as the therapeutic / diagnostic window, and it is precisely in this wavelength range that the absorption of water, an important component of many biological tissues, is weak. Furthermore, designing the biosensor in VR creates an analysis system that can be sensed only by eye without the need for any spectral method. In the field of biosensors, especially in inventions and academic studies that work with both PC-based and refractive index change-based sensing, the sensing process is usually in the NIR range and there has been no progress on sensing with the human eye. Therefore, performing sensing process in a visible range is important for a photonic-based biosensor.

[0011] In the design of a biosensor where various biological systems are involved as analytes, it is especially important to evaluate blood tissue and components that constitute blood such as protein, glucose, mineral ions, hormones, albumin, red blood cells, white blood cells and platelets. This is because the physical, chemical and biological properties of blood components vary from person to person and from disease to disease. Hematologic disorders are the main cause of critical diseases such as hepatitis B, malaria, diabetes, leukemia and many more. Efficient identification of irregularity in blood composition enables timely analysis of diseases. Changing the amount of blood components directly affects the optical properties of the biological system. Therefore, this optical modification emerges as a sensing parameter for a photonic -based biosensor. Blood analysis by conventional methods and existing diagnostic techniques is a laboratory analysis in which a blood sample is taken from the human body. It is possible to analyze blood components by using various methods such as flame atomic absorption spectrometry, graphite furnace atomic absorption spectrometry, laboratory anodic stripping voltammetry, portable and inductively coupled plasma mass spectrometry. The time required to analyze blood is approximately 24-72 hours. It also requires more blood samples for detection.

[0012] Existing identification techniques are complex, lengthy and difficult. One sensing approach is based on the light scattering and absorption properties of human blood, which takes into account factors such as osmolality and oxygen saturation that are extremely difficult to determine due to the relatively high concentration of hemoglobin and is based on the Mie scattering principle. Another technique is the double integrating sphere technique, which works in combination with Reverse Monte Carlo Simulation measuring undiluted blood in a visible light wavelength range. In this technique, photon sensing is also very difficult due to the higher concentration of cell units. Conventional techniques and the physical processes they are based on are time-consuming, costly and inconvenient. This situation leads to the need for biosensors that can efficiently identify and examine analytes in a short time. Compared to all conventional methods, a photonic-based biosensor comprising PC is more convenient in terms of blood analysis with much shorter time to result, portability and portability, and detection with very small amounts of blood samples by optical biosensing. There are also two conventional methods for blood analysis, fluorescence-based detection and label-free detection. In fluorescence-based detection, quantitative analysis of blood is very difficult. For the photonic sensing method, there is no need for a fluorescence label and blood analysis is carried out only by knowing the refractive index value of the target biological system.

[0013] The United States patent document no. US20090116033A1, an application included in the state of the art, discloses a refractive index sensor, a micro-sized cavity structure composed of photonic crystals, a light source and a detector. The photonic crystal microcavity structure includes a photonic crystal layer having first holes and a second hole. The first holes are arranged in a pattern of staggered parallel rows. The second hole is located at an approximate center point of the middle row of the pattern rather than a first hole. A diameter of the second hole is less than that of each of the first holes. Some of the first holes disposed at each of opposite ends of a diagonal row having the second hole are omitted to define an input waveguide and an output waveguide. The wavelength to be sensed is adjusted around 1.550 pm.

[0014] The European patent document no. EP2146229B1, an application included in the state of the art, discloses an optical element used as a resonant filter capable of resonating and reflecting light having a specific wavelength and an optical filter capable of transmitting light having a specific wavelength to a refractive index sensor. In the invention, a biosensor that detects a change in the index of an analyte and checks antibody reactivity and the like with this detection is designed. Summary of the Invention

[0015] An object of the present invention is to realize a biosensor which senses the changes in the resonant wavelength caused by various biological analyte systems in an optical resonant cavity surrounded by reflective photonic crystals and performs analyte determination with the changes occurring in the resonant wavelengths.

[0016] Detailed Description of the Invention

[0017] The “Resonant Cavity Biosensor Operating in a Visible Range and Comprising Photonic Crystals” realized to fulfd the objectives of the present invention is shown in the figures attached, in which:

[0018] Figure 1 is a block diagram showing the working principle of the inventive photonic -based biosensor designed.

[0019] Figure 2 is the structure of the optical cavity of the inventive photonic -based biosensor designed.

[0020] Figure 3 is a) the structure and b) the reflectance and transmittance spectra of the (MgFi / MoOs)8one-dimensional photonic crystal (1D-PC) system that forms the optical cavity of the inventive photonic-based biosensor.

[0021] Figure 4 is the structure of the analyte and reference cavities located in the optical cavity of the inventive photonic-based biosensor.

[0022] Figure 5 shows the transmittance characteristics of the inventive optical cavity in Figure 5 -a and the cavity mode in which the resonant occurs in Figure 5-b.

[0023] Figure 6 is the resonant wavelengths generated in the inventive optical cavity by using different blood components as analytes.

[0024] Figure 7 is the resonant wavelengths generated in the inventive optical cavity by using analytes with healthy and cancerous cell components. Figure 8 is the change of resonant wavelengths generated in the cavity as a function of the refractive index of the analyte located in the analyte cavity of the inventive photonic-based biosensor.

[0025] The components illustrated in the figures are individually numbered, where the numbers refer to the following:

[0026] 1. Biosensor

[0027] 2. Optical Cavity Resonator (Resonant Cavity, Optical Resonator)

[0028] 2.1 Substrate

[0029] 2.2 Photonic Crystal

[0030] 2.2.1. MgFi (Magnesium Fluoride)

[0031] 2.2.2. MoOs (Molybdenum Trioxide)

[0032] 2.3 Reference Cavity

[0033] 2.4 Analyte Cavity

[0034] 3. White Light Source

[0035] 4. Optical Analysis System

[0036] The inventive optical resonant cavity biosensor (1) which senses the changes in the resonant wavelength caused by biological analyte systems and performs analyte determination with the changes occurring in the resonant wavelengths comprises at least one optical cavity resonator (2) which includes the analyte in one part and a reference sample of the analyte in another part; and comprises photonic crystals (PC) and the substrate (2.1) having the structure forming the cavity gap, the photonic crystal (2.2) used as a mirror for reflectance and mode formation, the MgF2 (2.2.1) having low refractive index and the MoOs (2.2.2) having high refractive index, the reference cavity (2.3) housing the reference sample and enabling the analysis of the analyte to be carried out according to this reference, and the analyte cavity (2.4) housing the analyte sample and enabling its analysis to be carried out according to the reference sample; at least one white light source (3) which is configured to be optically integrated into the optical cavity resonator (2); and at least one optical analysis system (4) which is configured to examine the electromagnetic wave; to determine the wavelength difference between two wavelengths; to determine the shift value occurring at the resonant wavelength; and to directly perform the determination of the properties in the form of the type, density, additive ratio of the analyte by calibrating the amount of shift.

[0037] The optical cavity resonator (2) included in the inventive biosensor (1) is configured to comprise mirrors or various optical systems that form the resonator for electromagnetic waves. The optical cavity resonator (2) is configured to enable the electromagnetic wave confined in the cavity to be reflected multiple times by generating modes having specific resonant frequencies. The optical cavity resonator (2) is configured to enable modes to be decomposed into longitudinal and transverse modes that differ only in frequency. The optical cavity resonator (2) is configured so as to generate standing wave modes. The optical cavity resonator (2) is configured to provide reflectance of the electromagnetic wave by ID-PCs (onedimensional photonic crystals). The optical cavity resonator (2) is configured to enable the ID-PCs to act as individual mirrors. The optical cavity resonator (2) is configured to enable the thickness of the cavity in which the analyte and reference samples are separately located to be determined according to the designed resonant wavelength of the cavity and the sample type. The optical cavity resonator (2) is configured to enable the PCs forming the optical cavity and the structure forming the cavity gap to be grown by deposition methods on the substrate (2.1) with the substrate (2.1) forming the structure thereof. The optical cavity resonator (2) is configured to comprise Silica (SiO2), transparent in the visible range (VR), in the substrate (2.1) forming the structure thereof. The optical cavity resonator (2) is configured to use photonic crystal (2.2) and ID-PCs that are easy to fabricate and manufacture and provide a high degree of accuracy, precision and limit of detection as mirrors for reflectance and mode formation. The manufacturing advantage of ID-PCs is that they are easy to fabricate and manufacture and provide a high degree of accuracy, precision and limit of detection.

[0038] The one-dimensional photonic crystal (2.2) is configured to be designed as (MgFi / MoCh)8by successively arranging the dielectric materials MgFi and MoOs having low and high refractive indices, respectively, preferably in 8 periods. MgFi and MoOs have no absorption characteristics in the VR and their refractive indices do not change along the VR. This enables the mode density that will occur in the optical cavity designed in VR with the MgFi / MoCh 1D-PC system to be stable and less wavelength dependent. It is sufficient to design the MgFi / MoCh 1D-PC system as 8 periods based on the intensity of both reflectance and cavity modes. The fact that the use of more layers will not add any value to the performance of the proposed sensor is known from calculations carried out with the transfer matrix method (TMM); it only increases the size and cost of the sensor. The thickness of MgFi and MoOs (d\igi;2 and d\ioO3) for the 1D-PC system is respectively 100 nm and 65 nm. With these thickness values, the (MgFi / MoCh)81D-PC system gives a PBG characteristic of 175 nm in the VR as in Figure 3 b. Therefore, cavity modes are formed in the optical cavity of the biosensor at the wavelengths within this PBG. The reference cavity (2.3), which forms the structure of the optical cavity resonator (2), is the part that houses the reference sample and enables the analysis of the analyte to be carried out according to this reference. The optical cavity (2) material is made of silica with high transmittance at VR and almost zero absorption properties. As shown in Figure 4, the reference cavity (2.3) resonates at wavelength Xo with the structure of the cavities therein and the electromagnetic wave is allowed to pass through the cavity at this wavelength. The value of Ao shows dependence on the refractive index of the reference sample. The reference cavity (2.4) is the part that houses the analyte sample and enables its analysis to be carried out according to the reference sample. As shown in Figure 4, the biological system in the analyte cavity (2.4) resonates at wavelength A. and the electromagnetic wave is allowed to pass through the cavity at this wavelength. The physical, chemical and biological properties of the components that constitute the biological system to be sensed vary from person to person and from disease to disease. Therefore, the dielectric properties of these components are characteristic and highly useful in identifying diseases for various medical applications. Therefore, the value of A. shows dependence on the refractive index of the analyte sample.

[0039] The white light source (3) included in the inventive biosensor (1) is configured to enable the light falling on the optical cavity (2) to be distributed over a spectrum at least as wide as the amount of shift that will occur in the resonant wavelengths due to the analyte effect. The white light source (3) is configured to be a white colored light source that performs blackbody radiation preferably in the 5000 K-6500 K range, since it operates in the visible range (VR).

[0040] With the designed photonic crystal (2.2) and optical cavity (2), the resonant wavelength, i.e. the cavity mode, is at 531.47 nm in the presence of air in the cavity. The transmittance characteristic of the optical cavity and the cavity mode in which the resonant occurs are respectively given in Figure 5a and b. The PBG value generated by the transmittance characteristic is about 175 nm and the full width at half maximum (FWHM) of the resonant peak is 0.19688 nm.

[0041] The optical analysis system (4) included in the inventive biosensor (1) is configured to provide transmittance characteristics at a wavelength corresponding to a resonant wavelength designed so as to be located within the VR in the optical cavity. The optical analysis system (4) is configured to provide sensing properties of the photonic-based biosensor by determining the location and peak characteristics of the resonant wavelength and by presenting them as measurable values. The optical analysis system (4) is configured to convert analog light signals into digital pixels for direct sensing and rapid analysis by using charged coupling devices (CCD) as detectors.

[0042] The change occurring in the resonant wavelengths of the designed photonic-based biosensor (1) in the presence of samples wherein the blood plasma in the reference cavity (2.3) and different components in the analyte cavity (2.4) are predominant is shown in Figure 6. The optical changes caused by blood plasma and its different components in the biological system stand out in the refractive indices of the samples and this causes a shift in the resonant wavelengths. The refractive indices and resonant wavelengths of various blood components and blood plasma are given in Table 1 a. In addition, Table 1 b includes the calculated sensing parameters of the designed biosensor (1) such as quality factor (QF), sensitivity (S), figure of merit (FOM), resolution (R), signal-to-noise ratio (SNR) and detection limit (DL). Furthermore, CIE x and y color coordinates wherein the resonant wavelength and the amount of shift are calculated as sensing parameters according to different analytes in the designed biosensor (1) are presented in Table 1 c.

[0043] Table 1. a) refractive indices and properties of the formed resonant modes; b) sensor parameters; and c) CIE 1931 color coordinates and their changes calculated as sensing parameter of various blood components and blood plasma used as analytes for the photonic-based biosensor (1). b) c)

[0044] The change occurring in the resonant wavelengths of the designed photonic-based biosensor (1) in the presence of samples wherein various cancerous and healthy tissues in the reference cavity (2.3) and different components in the analyte cavity (2.4) are predominant is shown in Figure 7. The optical changes caused by healthy and cancerous analyte cells and their different components in the biological system stand out in the refractive indices of the samples and this causes a shift in the resonant wavelengths. The refractive indices and resonant wavelengths of various healthy and cancerous analyte cells are given in Table 2 a. In addition, Table 2 b includes the calculated sensing parameters of the designed biosensor (1) such QF, S, FOM, R, SNR and DL. Furthermore, CIE x and y color coordinates wherein the resonant wavelength and the amount of shift are calculated as sensing parameters according to different analytes in the designed biosensor (1) are presented in Table 2 c.

[0045] Table 2. a) refractive indices and properties of the formed resonant modes; b) sensor parameters; and c) CIE 1931 color coordinates and their changes calculated as sensing parameter of various healthy and cancerous analyte cells used as analytes for the photonic-based biosensor (1). a) b) c)

[0046] The photonic -based biosensor (1) proposed in the present invention is designed for analyte cells with various blood and cancer components. However, the sensor (1) has the potential to be used for many biological systems because of the optical processes and technique involved therein. In this context, a calibration for the change of the resonance wavelength with the refractive index of the analyte cell was performed and a calibration equation of the biosensor (1) was obtained. In Figure 8, the change of resonant wavelengths generated in the cavity as a function of the refractive index of the analyte located in the analyte cavity of the photonicbased biosensor (1) is given. With n being the refractive index, the resonance wavelength has a linear relationship with the expression X(n)=(69.701)n+(459.12 nm).

[0047] Industrial Application of the Invention

[0048] By means of the inventive biosensor (1), a photonic-based optical resonant cavity biosensor, which is developed for the analysis of different biological systems and operates in a visible range and is able to perform sensing through color, is designed.

[0049] Within these basic concepts; it is possible to develop various embodiments of the inventive biosensor (1); the invention cannot be limited to examples disclosed herein and it is essentially according to claims.

Claims

CLAIMS1. An optical resonant cavity biosensor (1) which senses the changes in the resonant wavelength caused by biological analyte systems and performs analyte determination with the changes occurring in the resonant wavelengths; comprising at least one optical cavity resonator (2) which includes the analyte in one part and a reference sample of the analyte in another part and is configured to be photonic crystal (PC)-based; and characterized by photonic crystals (PC) and the substrate (2.1), the structure that forms the cavity gap; the photonic crystal (2.2) used as a mirror for reflectance and mode formation; the MgFi (2.2.1) having low refractive index; the MoOs (2.2.2) having high refractive index; the reference cavity (2.3) housing the reference sample and enabling the analysis of the analyte to be carried out according to this reference; the analyte cavity (2.4) housing the analyte sample and enabling its analysis to be carried out according to the reference sample; at least one white light source (3) which is configured to be optically integrated into the optical cavity resonator (2); and at least one optical analysis system (4) which is configured to examine the electromagnetic wave; to determine the wavelength difference between two wavelengths; to determine the shift value occurring at the resonant wavelength; and to directly perform the determination of the properties in the form of the type, density, additive ratio of the analyte by calibrating the amount of shift.

2. A biosensor (1) according to Claim 1; characterized by the optical cavity resonator (2) which is configured to comprise mirrors or other optical systems that form the resonator for electromagnetic waves.

3. A biosensor (1) according to Claim 1 or 2; characterized by the optical cavity resonator (2) which is configured to enable the electromagnetic wave confined in the cavity to be reflected multiple times by generating modes having specific resonant frequencies.

4. A biosensor (1) according to any one of the preceding claims; characterized by the optical cavity resonator (2) which is configured to enable modes to be decomposed into longitudinal and transverse modes that differ only in frequency.

5. A biosensor (1) according to any one of the preceding claims; characterized by the optical cavity resonator (2) which is configured designed so as to generate standing wave modes.

6. A biosensor (1) according to any one of the preceding claims; characterized by the optical cavity resonator (2) which is configured to provide reflectance of the electromagnetic wave by ID-PCs.

7. A biosensor (1) according to any one of the preceding claims; characterized by the optical cavity resonator (2) which is configured to enable the onedimensional photonic crystals to act as individual mirrors.

8. A biosensor ( 1 ) according to any one of the preceding claims ; characterized by the optical cavity resonator (2) which is configured to enable the thickness of the cavity in which the analyte and reference samples are separately located to be determined according to the designed resonant wavelength of the cavity and the sample type.

9. A biosensor (1) according to any one of the preceding claims; characterized by the optical cavity resonator (2) which is configured to enable the photonic crystals forming the optical cavity and the structure forming the cavity gap to begrown by deposition methods on the substrate (2.1) with the substrate (2.1) forming the structure thereof.

10. A biosensor (1) according to any one of the preceding claims; characterized by the optical cavity resonator (2) which is configured to made of Silica (SiO2), transparent in the visible range (VR), in the substrate (2.1) forming the structure thereof.

11. A biosensor (1) according to any one of the preceding claims; characterized by the optical cavity resonator (2) which is configured to use photonic crystal (2.2) and ID-PCs that are easy to fabricate and manufacture and provide a high degree of accuracy, precision and limit of detection as mirrors for reflectance and mode formation.

12. A biosensor (1) according to any one of the preceding claims; characterized by the optical cavity resonator (2) which is configured to enable the onedimensional photonic crystal (2.2) in its structure to be formed as (MgFi / MoCh)8by successively arranging the dielectric materials MgFi and MoOs having low and high refractive indices, respectively, preferably in 8 periods.

13. A biosensor (1) according to any one of the preceding claims; characterized by the white light source (3) which is configured to enable the light falling on the optical cavity (2) to be distributed over a spectrum at least as wide as the amount of shift that will occur in the resonant wavelengths due to the analyte effect.

14. A biosensor (1) according to any one of the preceding claims; characterized by the white light source (3) which is configured to be a white colored light source that performs blackbody radiation preferably in the 5000 K-6500 K range, since it operates in a visible range.

15. A biosensor (1) according to any one of the preceding claims; characterized by the optical analysis system (4) which is configured to provide transmittance characteristics at a wavelength corresponding to a resonant wavelength designed so as to be located within the visible range (VR) in the optical cavity.

16. A biosensor (1) according to any one of the preceding claims; characterized by the optical analysis system (4) which is configured to provide sensing properties by determining the location and peak characteristics of the resonant wavelength and by presenting them as measurable values.

17. A biosensor (1) according to any one of the preceding claims; characterized by the optical analysis system (4) which is configured to convert analog light signals into digital pixels for direct sensing and rapid analysis by using charged coupling devices as detectors.

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