Protein molecule concentration detector based on whispering gallery mode optical microcavity singular point

Abstract

The present invention relates to a protein molecule concentration detector based on a whispering gallery mode optical microcavity singular point, comprising a microdisk, a special singular point in a non-Hermitian system of the microdisk, namely a singular point (EP) position, with a circular small hole, and a microfluid conduit made of the same material as the microdisk is inserted into the small hole. If a microfluid containing protein molecules of unknown concentration flows into the small hole in the microdisk, the protein molecules in the microfluid will adhere to the inner wall of the small hole, which will inevitably lead to a small decrease in the radius r of the small hole. The decrease in r will cause the system to move away from the EP point, at which time the EP will produce a large amplitude spectral line splitting. Thereafter, the amplitude of the detected spectral line splitting can be converted into protein concentration information, thereby realizing ultra-low concentration protein concentration detection. The present invention has a lower detection limit concentration and is suitable for detecting low-concentration protein solutions.

Description

Technical Field

[0001] The invention belongs to the technical field of optical microcavities, and in particular relates to a protein molecule concentration detector based on a whispering gallery mode optical microcavity singular point. Background Art

[0002] Whispering gallery mode: In a rotationally symmetric geometric structure, electromagnetic waves will undergo continuous total reflection when propagating from a denser medium to a less dense medium. The light will be confined to the annular boundary, producing a phenomenon similar to a whispering gallery. When the optical path of light traveling along the annular boundary inside the microcavity is an integer multiple of the wavelength, it will be in a resonant state. At this time, the rotationally symmetric photonic device composed of the denser medium is called a whispering gallery mode optical microcavity. In a whispering gallery mode optical microcavity, light energy propagates along the inner surface of the microcavity through multiple total reflections, and the photon lifetime is enhanced. Therefore, the whispering gallery mode has a very high quality factor (Q value), and its Q value can exceed 10 9 .

[0003] Singularity point: In a non-Hermitian system (a system that exchanges energy with the outside world), there is a singularity point (EP), which is a special degenerate state unique to the non-Hermitian system. Usually, phenomena such as energy level crossing and energy level repulsion will occur near the EP point. The optical microcavity is a typical open non-Hermitian physical system. The real part of the energy level corresponds to the resonant wavelength or resonant frequency, and the imaginary part of the energy level corresponds to the quality factor and the photon lifetime in the cavity. When at the EP point, the real and imaginary parts are intersected. If the system is affected by a perturbation, the coupled mode pairs will produce drastic frequency shifts and splits. There are two types of splitting: frequency splitting and linewidth splitting. The eigenvalue at the EP point is extremely sensitive to external disturbances on the system, which means that it has the potential to realize highly sensitive sensors.

[0004] Microfluidics: Microfluidics refers to complex fluids that need to be controlled, manipulated, and detected at a microscopic scale.

[0005] Protein is an important component of organisms and controls all aspects of biological activities and metabolism. Therefore, high-sensitivity detection, identification and quantitative analysis of proteins are crucial for medical research and disease diagnosis. For example, testing the concentration of albumin in human urine can help to diagnose diabetes, cardiovascular disease and kidney disease in advance. However, the mass spectrometry, enzyme-linked immunosorbent assay (ELISA) and fluorescent immunoassay methods commonly used in major medical institutions are costly and complicated to operate, and are not effective for detecting low-concentration protein solutions. Therefore, it is necessary to develop a low-cost, stable protein concentration detection device suitable for low-concentration detection. Summary of the invention

[0006] In view of the shortcomings of the prior art, based on the special property of protein adsorbed on solids, a certain thickness of protein molecules will be attached to the surface of the solid placed in the protein aqueous solution after a period of time, and the increase in the thickness of the adsorbed protein molecules gradually decreases over time. This adsorption property is very suitable for protein detection. The present invention uses the optical microcavity of the whispering gallery mode to provide a protein molecule concentration detector based on the singular point of the optical microcavity of the whispering gallery mode, which realizes the concentration detection of protein molecules in microfluids with high sensitivity; it can also be used to detect the concentration of other types of molecules in microfluids.

[0007] The protein molecule concentration detector based on the whispering gallery mode optical microcavity singular point comprises a microdisk, wherein a circular hole is opened at the special singular point in the non-Hermitian system of the microdisk, and a microfluidic conduit of the same material as the microdisk is inserted into the hole.

[0008] The refractive index of the microdisk is 3.

[0009] The radius of the microdisk was 10 μm.

[0010] The refractive index inside the small hole at the singular point of the micro-disk is the refractive index of water, that is, the value is 1.333.

[0011] The radius of the small hole at the singular point of the micro-disk is 0.9 μm.

[0012] The center of the small hole is 7.15 μm away from the center of the microdisk.

[0013] The diameter of the microfluidic conduit is the same as the diameter of the small hole.

[0014] The beneficial effects of the present invention are:

[0015] 1. Compared with mass spectrometry, enzyme-linked immunosorbent assay (ELISA) and fluorescent immunoassay, which are commonly used in life, the present invention has a lower detection limit concentration. When using an infrared spectrometer with a detection limit of 0.005nm, the detection concentration limit is 9.0×10-10mol / L, which is much stronger than the above methods.

[0016] 2. Compared with the method of using defect-free whispering gallery mode optical microcavity, that is, placing the defect-free whispering gallery mode optical microcavity in a solution, allowing protein molecules to attach to the outer wall of the microcavity, and then detecting the frequency change for detection, the present invention can calculate the reference frequency based on the reference wavelength of the line width splitting diagram; at the same time, if it is a method of one mode and one line, it is easy to be affected, but this method can know that the two lines in the line width splitting diagram will float up and down with the temperature at the same time, so the difference between the two lines does not change much, so this method can overcome the system measurement error caused by temperature, humidity and other environmental factors. Moreover, the sensitivity can be obtained by deriving the results shown in the line width difference diagram. According to the comparison with the single mode, the sensitivity of the present invention is much higher than the above method. When the aperture radius is reduced by 0 to 0.02μm, the sensitivity of the system is above 0.8, and the highest sensitivity is even as high as 1.75.

[0017] 3. The protein molecule concentration detector based on the whispering gallery mode optical microcavity EP point of the present invention mainly consists of a medium microdisk with a hole dug in it, which has a simple structure and a small diameter. The radius of the microdisk is only 10 μm. Considering the microfluidic conduit and necessary waveguide fibers and other devices, the volume will not be very large, so it can be integrated on a chip.

[0018] 4. The protein molecule concentration detector based on the whispering gallery mode optical microcavity EP point of the present invention has a very low minimum concentration detection limit. If an advanced infrared spectrometer with a detection limit of 0.1nm is used, the minimum concentration detection limit is about 2.0×10-8mol / L, and if a common infrared spectrometer with a detection limit of 0.005nm is used, the minimum concentration detection limit is about 9.0×10-10mol / L. If specific adsorption is used on this basis, the minimum concentration detection limit will be even lower.

[0019] 5. The present invention includes a dielectric microdisk with holes dug therein, which has a simple structure. If microfluidic conduits and other necessary waveguide fibers are considered, the volume will not be very large and can be integrated into a chip, which has a wide range of application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic diagram of a protein molecule concentration detector provided by an embodiment of the present invention;

[0021] Figure 2 A schematic diagram of a microplate in a protein molecule concentration detector provided by an embodiment of the present invention;

[0022] Figure 3A graph showing the splitting variation of the full width at half maximum (line width) of the spectral line in two different modes, with the distance between the center of the aperture and the center of the microdisk being 7.15 μm and the radius of the aperture r ranging from 0.94 μm to 0.86 μm, provided in an embodiment of the present invention (wherein mode one is an even mode of (m, l) = (6, 3) and mode two is an even mode of (m, l) = (12, 1));

[0023] Figure 4 A frequency splitting variation diagram of two different modes provided in an embodiment of the present invention, where the distance between the center of the small hole and the center of the microdisk is 7.15 μm and the radius of the small hole r ranges from 0.94 μm to 0.86 μm (wherein mode one is an even mode of (m, l) = (6, 3) and mode two is an even mode of (m, l) = (12, 1));

[0024] Figure 5 A line width variation diagram of a defect-free microdisk with a radius of 10 μm and no pinholes as a comparative example in the (m, l) = (6, 3) even mode when the microdisk radius R ranges from 9.98 μm to 10.07 μm;

[0025] Figure 6 Line width difference diagrams in two different modes when the distance between the center of the small hole and the center of the microdisk provided in the embodiment of the present invention is 7.15 μm and the radius of the small hole r ranges from 0.90 μm to 0.86 μm (wherein mode one is an even mode of (m, l) = (6, 3) and mode two is an even mode of (m, l) = (12, 1));

[0026] Figure 7 The sensitivity of the mode to line width splitting in two different modes is shown in FIG. 1 , when the distance between the center of the small hole and the center of the microdisk is 7.15 μm and the radius of the small hole r ranges from 0.90 μm to 0.86 μm. Figure 6 The graph of the derivative (where mode 1 is the even mode (m,l)=(6,3) and mode 2 is the even mode (m,l)=(12,1));

[0027] in,

[0028] 1-microdisk, 2-microfluidic conduit, 3-small hole. DETAILED DESCRIPTION

[0029] In order to better explain the present invention and facilitate understanding, the technical solutions and effects of the present invention are described in detail below through specific implementation modes in conjunction with the accompanying drawings.

[0030] like Figure 1-2As shown, a protein molecule concentration detector based on the singular point of the whispering gallery mode optical microcavity includes a microdisk 1, a special singular point in the non-Hermitian system of the microdisk 1, namely, a singular point (EP) is provided with a circular hole 3, and the axis of the hole 3 is parallel to the axis of the microdisk 1; a microfluidic conduit 2 made of the same material as the microdisk 1 is inserted into the hole 3, so that the microfluid can pass through the microfluidic conduit 2 into the hole 3; the diameter of the microfluidic conduit 2 is the same as the diameter of the hole 3. Enlarging or reducing the same volume without changing the overall shape will not change the position of the singular point. During detection, the microfluidic conduit 2 is used to allow the microfluid to continue to pass through the hole 3, and the protein will adhere to the hole 3, and then the concentration of the protein molecules can be detected.

[0031] In this embodiment, the radius of the microdisk 1 is 10 μm, and the refractive index n is 3; the radius of the small hole 3 at the singular point of the microdisk 1 is 0.9 μm; the microfluid flowing through the microfluidic conduit 2 is a protein molecule aqueous solution. Since the main component of the microfluid flowing into the small hole 3 is water, the refractive index inside the small hole 3 is the refractive index of water, that is, n water The value is 1.333; the center of the small hole 3 is 7.15 μm away from the center of the microdisk 1. During the detection process, the microdisk 1 is placed in the air, and the outside of the microdisk 1 is air with a refractive index of n air is 1.

[0032] The principle of the protein molecule concentration detector based on the singular point of the whispering gallery mode optical microcavity for protein molecule concentration detection is: the microfluid to be tested is introduced into the microfluid conduit 2, and the microfluid to be tested will flow through the microfluid conduit 2. For the optical microdisk 1 with a quasi-degenerate mode, after a small hole 3 is dug in the microdisk 1, two different modes with high quality factor Q and low quality factor Q are selected, and the coupling phenomenon of the two modes will occur. At the EP point, the reduction of the radius of the small hole 3 will cause the originally coupled modes to split, including frequency splitting and line width splitting; wherein, the line width splitting caused by the reduction of the radius of the small hole 3 is extremely strong. Regulating the size and position of the small hole 3 will move the system to a special singular point in the non-Hermitian system, namely the singular point (EP). When the system is just at the EP point, if a microfluid containing protein molecules of unknown concentration flows into the small hole 3 in the microdisk 1, the protein molecules in the microfluid will adhere to the inner wall of the small hole 3, which will inevitably cause a small reduction in the radius r of the small hole 3. The reduction of r will cause the system to move away from the EP point, and at this time, the EP will produce a large amplitude of spectral line splitting. After that, the detected spectrum line splitting amplitude can be converted into protein concentration information, and ultra-low concentration protein concentration detection can be achieved. As long as the change of line width splitting is detected in the outside world, the reduction degree of the radius of the small hole 3 can be very sensitively detected, thereby converting the protein molecule concentration in the microfluid to achieve the purpose of low concentration protein molecule solution concentration detection.

[0033] The method of using the above-mentioned protein molecule concentration detector based on the whispering gallery mode optical microcavity singular point is:

[0034] Step 1:

[0035] The protein molecule solution to be tested is injected into the microfluidic conduit 2 of the protein molecule concentration detector connected to the small hole 3 on the microdisk 1, so that the protein molecule solution flows through the small hole 3, and waits for 7 to 12 minutes to allow the protein molecules to adhere to the wall of the small hole 3;

[0036] Step 2:

[0037] Turn on the spectrometer for detecting spectral line splitting, transmit real-time data to the computer through the data interface for data processing, calculate the current degree of spectral line splitting, and then convert the spectral line splitting data into changes in the thickness of the defect circular hole, and then infer the data of the protein solution concentration.

[0038] The whole system is just at the EP point. When the device is used for detection, the protein molecule solution to be tested flows from one end of the microfluidic conduit 2 into the microfluidic conduit 2, passes through the small hole 3 on the microdisk 1, and then flows out from the other end of the microfluidic conduit 2. Because the solid, i.e., the microdisk 1 in the present application, has the property of adsorbing protein molecules, the inner wall of the small hole 3 will be covered by the protein molecules, resulting in a reduction in the radius of the small hole 3, so that the spectrum will produce a line width splitting phenomenon, and the user can calculate the corresponding protein molecule solution concentration according to the spectrum.

[0039] In order to verify the effectiveness of the small hole 3 in the detector being located at the singular point, this embodiment was verified, and the results are as follows: Figure 3 and Figure 4 As shown. Figure 3 As shown in FIG. 1 , in the present embodiment, when the distance between the center of the pinhole 3 and the center of the microdisk 1 is 7.15 μm, and the radius r of the pinhole 3 is from 0.94 μm to 0.86 μm, the line width splitting changes obtained by the spectrometer in two different modes can be seen. From the figure, it can be seen that the two modes, mode 1 (m, l) = (6, 3) even mode and mode 2 (m, l) = (12, 1) even mode, are about to cross when the radius r of the pinhole 3 is between 0.90 μm and 0.91 μm. Figure 4 As shown in the figure, the two lines of the two modes cross near 0.90μm, and the small section of 0.90μm-0.91μm is too smooth, so the position of 0.90μm is the EP point. Figure 4 The frequency splitting variation diagrams obtained by the spectrometer in two different modes are shown, where the distance between the center of the small hole 3 and the center of the microdisk 1 is 7.15 μm and the radius r of the small hole 3 ranges from 0.94 μm to 0.86 μm. It is obvious that the effect of detecting frequency splitting is not obvious when the radius r is less than 0.90 μm, which is far less than Figure 3 The detected linewidth splitting is shown in .

[0040] In order to verify the sensitivity of this method, simulation experiments were carried out. The results are as follows Figure 6 and Figure 7 shown.

[0041] like Figure 6 The line width difference diagram in two different modes, (m,l)=(6,3) even mode and (m,l)=(12,1) even mode, is shown when the distance between the center of the small hole 3 and the center of the microdisk 1 is 7.15μm and the radius r of the small hole 3 ranges from 0.90μm to 0.86μm. It can be seen from the figure that when the radius r of the small hole 3 is in the range of 0.88μm to 0.90μm, the line width difference changes rapidly; when the radius of the small hole 3 decreases from 0.90μm to 0.89μm, the line width difference decreases by about 0.016μm; when it decreases from 0.89μm to 0.88μm, the line width difference decreases by about 0.01μm, and the overall change is large.

[0042] like Figure 7 When the distance between the center of the small hole 3 and the center of the microdisk 1 is 7.15 μm and the radius r of the small hole 3 is from 0.90 μm to 0.86 μm, the line width splitting sensitivity (i.e., the sensitivity to the line width splitting) in two different modes (m, l) = (6, 3) even mode and (m, l) = (12, 1) even mode is Figure 6 The line width difference curve is derived to obtain the speed of line width difference changing with the radius of the small hole 3); it can be seen from the figure that when the radius r of the small hole 3 is in the range of 0.89 to 0.90μm, the line width splitting sensitivity is significantly higher than that in the range of 0.86 to 0.87μm, with a maximum of 1.75. Moreover, the curve is smooth and there is no drastic fluctuation. The sensitivity change is relatively stable, so it can be used for sensing and detecting low-concentration protein molecule solutions.

[0043] After Figure 7 According to the analysis, the present invention has a high sensitivity when detecting protein solution with a diameter of 0 to 0.01 μm attached to the inner wall of the small hole 3, that is, when the radius r of the small hole 3 is in the range of 0.90 μm to 0.89 μm, and is suitable for detecting low-concentration protein solution concentration. When the radius of the small hole 3 is reduced from 0.89 μm to 0.88 μm due to the attachment of protein molecules, the sensitivity decreases, but is still very high. If the attachment of protein molecules reduces the radius of the small hole 3 to below 0.88 μm, the sensitivity is relatively low.

[0044] As a comparative example, a defect-free microdisk 1 with a radius of 10 μm and no small holes 3 is selected as a comparative scheme. In this scheme, a protein solution microfluid flows over the outer surface of the microdisk 1, and then the protein molecules adhere to the surface of the microdisk 1, thereby causing the radius of the microdisk 1 to increase; the user determines the increase in the radius of the microdisk 1 by measuring the change in line width, thereby knowing the concentration of the protein solution. Figure 5 The line width variation diagram shown is obtained by the spectrometer in the (m,l)=(6,3) even mode with the radius R of the microdisk 1 ranging from 10.07μm to 9.98μm. It can be seen that the line width variation is generally a straight line, which means that the sensitivity is almost a constant value within the range shown in the figure, and the line width changes by about 0.00015μm for every 0.01μm increase in the radius of the microdisk 1, which is a very small variation.

[0045] After analyzing the comparative embodiment, it is known that the scheme without the small hole 3 has a lower sensitivity. For every 0.01μm increase in the radius of the microdisk 1, the line width only changes by 0.00015μm; and unlike the present invention, the sensitivity is higher when the concentration of the protein solution is low, but it is equal everywhere. The system of the present invention is just at the EP point and has a strong sensing sensitivity. If the external microfluid to be tested flows through the small hole 3 through the microfluid conduit 2, the protein in the protein solution will adhere to the inner wall of the small hole 3, causing the radius r of the small hole 3 to decrease by 0.01μm, then rapid line width splitting will occur, and the line width difference will drop by about 0.016μm, which is much larger than the change in the comparative embodiment. It is easier for the outside world to use a spectrometer to detect the degree of line width splitting, and then calculate the degree of change in the radius of the small hole 3, so as to obtain the concentration of the protein molecule solution.

[0046] When the protein is naturally adsorbed on the inner wall of the small hole 3, the lowest concentration detection limit is about 9.0×10 - 10mol / L. The lowest concentration detection limit of the whispering gallery mode specific adsorption currently studied is only 6.28×10-9mol / L. The present invention has achieved a lowest concentration detection limit lower than the current specific adsorption without adding specific adsorption. If specific adsorption is added, the lowest concentration detection limit will be even lower.

[0047] In addition, the present invention is highly resistant to external factors such as temperature and humidity, because these external factors will simultaneously cause similar changes in the two modes, which results in a small change in their difference. Compared with the above-mentioned method of using a defect-free whispering gallery mode optical microcavity, the ability to resist environmental influences is greatly enhanced.

Claims

1. A protein molecule concentration detector based on the singular point of the whispering gallery mode optical microcavity, characterized by: A microdisk is included, wherein a special singular point in a non-Hermitian system of the microdisk is provided with a circular hole, and a microfluidic conduit made of the same material as the microdisk is inserted into the hole; The refractive index of the microdisk is 3; The radius of the microdisk is 10 μm; The radius of the small hole at the singular point of the microdisk is 0.9 μm; The diameter of the microfluidic conduit is the same as the diameter of the small hole.

2. The protein molecule concentration detector based on whispering gallery mode optical microcavity singular point according to claim 1, characterized in that: The refractive index inside the small hole at the singular point of the micro-disk is the refractive index of water, that is, the value is 1.

333.

3. The protein molecule concentration detector based on whispering gallery mode optical microcavity singular point according to claim 1, characterized in that: The center of the small hole is 7.15 μm away from the center of the microdisk.

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