An optical sensor based on rare earth doped microbubble cavity

Abstract

The present invention belongs to the field of optical sensing technology and discloses an optical sensor based on a rare-earth-doped microbubble cavity. To predict concentration, the rare-earth-doped microbubble cavity is first pumped with a pump source laser. An immunoglobulin G solution to be tested is then injected into the microfluidic channel of the rare-earth-doped microbubble cavity, and the resulting signal laser spectrum is recorded. The signal laser power is then compared with a standard curve that correlates concentration and signal laser power. The concentration corresponding to the same signal laser power is found, and the concentration of the immunoglobulin G solution to be tested is thus determined. By utilizing the active cavity structure of the rare-earth-doped microbubble cavity to detect biomolecules, the present invention enables the realization of a high-precision biosensor capable of predicting both the concentration of an immunoglobulin solution and the occurrence of specific binding between multiple immunoglobulins.

Description

Technical Field

[0001] The present invention belongs to the field of optical sensing technology, and more specifically, relates to an optical sensor based on a rare earth doped microbubble cavity. Background Art

[0002] With the development of modern science and technology, especially in emerging disciplines such as life sciences, the topics of biomolecular analysis and drug analysis continue to emerge, and the requirements for analytical results are becoming increasingly stringent. Optical sensors are becoming increasingly popular due to their advantages such as non-contact and non-destructive measurement, virtually no interference, high-speed transmission, and remote sensing and remote control capabilities, making them a current research hotspot.

[0003] Whispering gallery mode optical microcavities are optical resonators that localize the light field to a micrometer-scale region. They have an ultra-high quality factor and a small mode volume, and can significantly enhance the interaction between light and matter. They have great application potential in microlasers, optical sensing, nonlinear optics, quantum optics, and other fields. Optical microbubble cavities are hollow, thin shell structures with natural microfluidic channels. They are an excellent platform for realizing biosensors, with advantages such as high sensitivity, low detection limit, and fast detection speed. Sensing mechanisms based on optical microcavities include mode shift, mode splitting, and mode broadening (all of which are passive cavities). Their detection limit and sensitivity are affected by the mode linewidth. On the other hand, rare earth elements have high conversion efficiency and long upper energy level lifetime. The operating wavelength is determined only by their own energy level structure and does not depend on the host material. The emission spectrum covers the ultraviolet to mid-infrared band, making them a commonly used gain medium for solid-state lasers.

[0004] The inventor's research group previously reported a rare-earth-doped optical microcavity and its fabrication method (see Chinese invention patent application CN113497401A). The resulting rare-earth-doped microcavity can be used for ultra-high-sensitivity molecular detection and ultra-long photon lifetime optical storage. Exploring biomolecular applications would undoubtedly greatly expand the application prospects of rare-earth-doped optical microcavities. Summary of the Invention

[0005] To address the aforementioned deficiencies and improvements in the prior art, the present invention aims to provide an optical sensor based on a rare-earth-doped microbubble cavity. By utilizing this active cavity structure, the rare-earth-doped microbubble cavity can detect biomolecules (i.e., immunoglobulin G), enabling the realization of a high-precision biosensor. The present invention utilizes a rare-earth-doped microbubble cavity laser for biomolecule concentration analysis, enabling the prediction of immunoglobulin solution concentrations and the occurrence of specific binding between multiple immunoglobulins.

[0006] To achieve the above objectives, according to one aspect of the present invention, a method for predicting the concentration of an immunoglobulin G solution based on an optical sensor using a rare earth-doped microbubble cavity is provided, characterized in that it comprises the following steps:

[0007] S1: Prepare a clean rare earth ion doped optical microbubble cavity;

[0008] S2: Pumping the rare earth-doped microbubble cavity with a pump source laser to generate a signal laser; wherein the wavelength of the pump source laser is within the absorption band of the rare earth element contained in the rare earth-doped microbubble cavity;

[0009] S3: injecting an immunoglobulin G solution to be tested, whose immunoglobulin type is known but whose concentration is unknown, into the microfluidic channel of the rare earth-doped microbubble cavity, and recording the signal laser spectrum at this time after stabilization as the signal laser spectrum after change;

[0010] According to the signal laser power of the changed signal laser spectrum, the concentration of the immunoglobulin G solution to be tested can be obtained by comparing it with the standard curve of the relationship between concentration and signal laser power and finding the concentration value corresponding to the same signal laser power.

[0011] Among them, the standard curve of the relationship between concentration and signal laser power is prepared by preparing multiple standard solutions with known concentration values ​​according to the type of immunoglobulin contained in the immunoglobulin G solution to be detected, and the concentrations of these standard solutions are different from each other; using the same rare earth ion-doped optical microbubble cavity and the same pump source as step S2, and under the same relative position conditions, for each standard solution, one standard solution is injected each time into the microfluidic channel of the rare earth-doped microbubble cavity after being rinsed with phosphate buffered saline (PBS), and the original solution inside the microfluidic channel is discharged. After stabilization, the signal laser spectrum is recorded to obtain a data point of the relationship between concentration value and signal laser power; thus, based on the multiple data points of the relationship between concentration value and signal laser power obtained for multiple standard solutions, a fitting curve of the relationship between concentration and signal laser power can be obtained, and this fitting curve is the standard curve.

[0012] As a further preferred embodiment of the present invention, in the process of obtaining the standard curve, before the first injection of the standard solution, the method further comprises: injecting phosphate buffered saline (PBS) into the microfluidic channel of the rare earth-doped microbubble cavity, and recording the signal laser spectrum at this time after stabilization as the initial state signal laser spectrum;

[0013] Accordingly, each time phosphate buffer (PBS) is used to flush the inside of the microfluidic channel of the rare earth-doped microbubble cavity, specifically, phosphate buffer (PBS) is injected into the microfluidic channel of the rare earth-doped microbubble cavity to discharge the original solution inside the microfluidic channel. After stabilization, the signal laser spectrum at this time is recorded and compared with the initial state signal laser spectrum to ensure that the signal laser spectrum is consistent with the initial state signal laser spectrum to ensure that it is flushed cleanly.

[0014] As a further preferred embodiment of the present invention, in step S3, the immunoglobulin G solution to be detected is obtained by mixing two immunoglobulin solutions in a preset volume ratio and reacting them for a preset time;

[0015] Accordingly, in the process of obtaining the standard curve, the standard solution used is obtained by mixing two immunoglobulin solutions designed with different concentrations in a preset volume ratio and reacting them for a preset time.

[0016] As a further preferred embodiment of the present invention, in step S1, the rare earth ion-doped optical microbubble cavity is obtained by treating a quartz capillary tube using a polymer-assisted melt thermal diffusion method;

[0017] The polymer-assisted melt thermal diffusion method utilizes the film-forming properties of the polymer to uniformly dope the rare earth element into the microbubble cavity, and the polymer is one of polymethyl methacrylate, polyethylene and polypropylene.

[0018] As a further preferred embodiment of the present invention, the rare earth ion is specifically at least one of erbium ion, ytterbium ion and thulium ion.

[0019] According to another aspect of the present invention, a method for predicting whether specific binding occurs between two immunoglobulin G solutions based on an optical sensor using a rare earth-doped microbubble cavity is provided, characterized in that the method comprises the following steps:

[0020] (1) Prepare a clean rare earth ion-doped optical microbubble cavity;

[0021] (2) using a pump source laser to pump the rare earth-doped microbubble cavity to generate a signal laser, wherein the wavelength of the pump source laser is within the absorption band of the rare earth element contained in the rare earth-doped microbubble cavity;

[0022] (3) For two immunoglobulin G solutions, one of the immunoglobulin G solutions is selected to design samples of different concentrations, and the immunoglobulin contained in the immunoglobulin G solution is recorded as component A, and a group of component A immunoglobulin G solutions of different concentrations are obtained; the immunoglobulin contained in the other immunoglobulin G solution is recorded as component B, and the concentration of the component B immunoglobulin G solution is kept fixed; the component A immunoglobulin G solutions of different concentrations are mixed with the component B immunoglobulin G solutions according to a preset volume ratio and reacted for a preset time to obtain a group of test solutions of different concentrations; for each test solution, one test solution is injected into the microfluidic channel of the rare earth-doped microbubble cavity after being rinsed with phosphate buffer solution (PBS), and the original solution in the microfluidic channel is discharged. After stabilization, the signal laser spectrum is recorded to obtain a data point of the relationship between the concentration value and the signal laser power; thus, a fitting curve of the relationship between the concentration and the signal laser power can be obtained based on the multiple data points of the relationship between the concentration value and the signal laser power obtained for multiple test solutions;

[0023] Based on the degree of change in the signal laser power with concentration in the fitting curve, it can be determined whether specific binding can occur between component A and component B; if a specific binding reaction can occur, the signal laser power changes more dramatically with concentration than if a specific binding reaction cannot occur.

[0024] As a further preference of the present invention, the fitting curve is a linear fitting curve in a two-dimensional coordinate system, and the two-dimensional coordinate system has concentration and signal laser power as coordinate axes, wherein the concentration axis is a logarithmic coordinate axis and the signal laser power axis is a linear coordinate axis in dBm.

[0025] As a further preferred embodiment of the present invention, after step (2) and before step (3), the method further includes: injecting phosphate buffer solution (PBS) into the microfluidic channel of the rare earth-doped microbubble cavity, and recording the signal laser spectrum at this time after stabilization as the initial state signal laser spectrum;

[0026] Correspondingly, in step (3), each time phosphate buffer (PBS) is used to flush the inside of the microfluidic channel of the rare earth-doped microbubble cavity, specifically, phosphate buffer (PBS) is injected into the microfluidic channel of the rare earth-doped microbubble cavity to discharge the original solution inside the microfluidic channel. After stabilization, the signal laser spectrum at this time is recorded and compared with the initial state signal laser spectrum to ensure that the signal laser spectrum is consistent with the initial state signal laser spectrum to ensure that it is flushed cleanly.

[0027] Compared with the prior art, the above technical solutions proposed by the present invention can achieve the following:

[0028] Beneficial effects:

[0029] (1) The present invention proposes for the first time the use of rare earth doped microbubble cavity lasers for biomolecule sensing, which significantly reduces the laser mode linewidth, improves detection sensitivity and lowers the detection limit.

[0030] (2) The present invention utilizes laser signals for sensing. Compared with existing schemes based on mode shifting, mode splitting, and mode broadening, it does not require complex equipment such as tunable lasers, thus saving costs. The present invention uses an active microbubble cavity structure (rare earth elements can serve as gain media and belong to the active layer) for the first time, and confirms that compared with a passive cavity, the optical gain in the active cavity can partially compensate for the intracavity loss, narrow the mode linewidth, and significantly improve the microcavity's response to external signals, thereby increasing the sensing sensitivity and reducing the detection limit.

[0031] (3) The present invention achieves high-precision detection of biomolecule concentration by combining an optical microcavity laser with a biosensor. Taking Example 1 as an example, the absolute value of the sensitivity can reach 3.095 dB / (fg / mL).

[0032] (4) Furthermore, the present invention can also be used to detect whether specific binding can occur between multiple immunoglobulins. In the fitting curve of the relationship between concentration and signal laser power obtained under the same detection conditions, the signal laser power of the immunoglobulins that can undergo specific binding reaction will change more dramatically with concentration than that of the immunoglobulins that cannot undergo specific binding reaction. As will be described later Figure 4 and Figure 5 As exemplified, Figure 4 The mixed reaction in Example 1 resulted in specific binding. Figure 5 The mixed reaction in Example 2 did not undergo specific binding, which was obvious. Figure 4 The fitted curve is steeper and has a higher absolute value of slope (that is, Figure 4 The laser power of the medium signal changes more dramatically with concentration).

[0033] In summary, the present invention uses rare earth doped microbubble cavity lasers for biosensors, which has the advantages of low cost, simple operation, high sensitivity, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a schematic top view of the working platform of the microbubble cavity laser used for biomolecule detection in the present invention.

[0035] Figure 2 This is the output spectrum of the microbubble cavity laser when there is no filler in it (the inset in the figure is a microscopic image of the microbubble cavity).

[0036] Figure 3 This is the initial state spectrum when phosphate buffer solution (PBS) is injected into the microbubble cavity laser.

[0037] Figure 4 This is the signal laser spectrum change obtained in Example 1.

[0038] Figure 5 This is the signal laser spectrum change obtained in Example 2.

[0039] Figure 1 In the figure, the meanings of the reference numerals are as follows: 1 is a pump laser; 2 is a rare earth-doped microbubble cavity; 3 is an immunoglobulin G solution to be tested. DETAILED DESCRIPTION

[0040] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0041] Based on the present invention, the implementation may include the following steps: first, a rare-earth-doped optical microbubble cavity is prepared from a quartz capillary using a polymer-assisted melt thermal diffusion method; then, the rare-earth-doped microbubble cavity is pumped by resonant pumping to generate a signal laser; finally, biomolecule solutions of different concentrations are injected into the microfluidic channel of the rare-earth-doped microbubble cavity laser, thereby changing the effective refractive index of the microbubble cavity optical mode, causing the signal laser power to change, and achieving high-sensitivity detection.

[0042] The rare earth doped optical microbubble cavity used in the following examples is prepared by using a polymer-assisted melt thermal diffusion method to prepare a quartz capillary on a carbon dioxide laser processing platform. The detailed preparation method of the rare earth doped optical microcavity can be directly referred to CN113497401A.

[0043] Example 1

[0044] A biosensor based on a microbubble cavity laser, the specific implementation steps are as follows:

[0045] (1) A rare earth ion erbium-doped optical microbubble cavity 2 was prepared from a quartz capillary by a polymer-assisted melt thermal diffusion method. The diameter of the microbubble cavity was 101 μm and the wall thickness was 1.8 μm. Figure 2 The inset is a microscopic image of the optical microbubble cavity.

[0046] (2) If Figure 1 As shown, a 980nm laser 1 is used as a pump source, and the pump laser is injected into the rare earth doped optical microbubble cavity 2 to obtain Figure 2 The laser output spectrum is shown.

[0047] (3) Phosphate buffered saline (PBS) is injected into the microfluidic channel to flush the microfluidic channel, and the signal laser spectrum at this time is recorded as the initial state.

[0048] (4) Inject the immunoglobulin G solution 3 to be tested into the microfluidic channel of the microbubble cavity (after the new solution is injected, the original solution in the microfluidic channel will be discharged). After stabilization (in this embodiment, the laser spectrum is collected 1 minute after the solution is introduced into the microfluidic channel), record the signal laser power after the change.

[0049] (5) Inject phosphate buffered saline into the microfluidic channel to flush the microfluidic channel (PBS solution is used to flush the immunoglobulin solution remaining in the microfluidic channel), returning the signal laser to its initial state. Whether the initial state is restored after this flushing step requires comparing the obtained signal laser spectrum with the signal laser spectrum recorded in step (3) to ensure that the flushing is complete.

[0050] (6) Repeat steps (3) and (4) to record the changes in signal laser power caused by different concentrations of immunoglobulin G solutions.

[0051] The immunoglobulin G solutions of different concentrations used in this example were obtained by mixing mouse IgG solutions with concentrations of 100 ng / mL, 10 ng / mL, 1 ng / mL, 100 pg / mL, 10 pg / mL, 1 pg / mL, 100 fg / mL, 10 fg / mL, and 1 fg / mL with a goat anti-mouse IgG solution with a concentration of 100 ng / mL in a volume ratio of 1:1 for 5 hours.

[0052] The logarithm of the mouse IgG concentration (unit: fg / mL) in the mouse IgG solution used to prepare the immunoglobulin G solution to be tested is used as the horizontal axis, and the signal laser power (unit: dBm) is used as the vertical axis. The results are shown in FIG. Figure 4 As shown, it can be seen that the signal laser power changes with the concentration of the immunoglobulin G solution, and the laser sensor has a sensitivity of -3.095dB / (fg / mL).

[0053] Example 2

[0054] This embodiment differs from embodiment 1 in that the immunoglobulin G solutions to be tested used in embodiment 2 with different concentrations are obtained by mixing human IgG with concentrations of 100 ng / mL, 10 ng / mL, 1 ng / mL, 100 pg / mL, 10 pg / mL, 1 pg / mL, 100 fg / mL, 10 fg / mL and 1 fg / mL and goat anti-mouse IgG with a concentration of 100 ng / mL in a volume ratio of 1:1 for 5 hours, for comparison of specific detection (it is known in the prior art that the mouse IgG used in embodiment 1 can specifically bind to the goat anti-mouse IgG; while the human IgG used in embodiment 2 cannot specifically bind to the goat anti-mouse IgG). Figure 5 As shown in the figure, the signal laser power changes with the concentration of the immunoglobulin G solution. Compared with Example 1, the maximum response of the laser power is only 6.22dB (as shown in the figure). Figure 5 Among the data points shown, the difference between the maximum value and the minimum value of the ordinate is 6.22 dB).

[0055] It can be seen from Examples 1 and 2 that in Example 1, the mouse IgG and goat anti-mouse IgG molecules in the immunoglobulin G solution specifically bind to each other, resulting in a large change in the refractive index of the immunoglobulin G solutions of different concentrations and a large change in the laser power; while in Example 2, the human IgG and goat anti-mouse IgG molecules in the immunoglobulin G solution cannot specifically bind to each other, resulting in a small change in the refractive index of the immunoglobulin G solutions of different concentrations and a small change in the laser power. It can be seen that the laser sensor of the present invention has a good specific detection effect.

[0056] The above embodiments are merely illustrative. For example, in addition to obtaining the immunoglobulin G solution by mixing two solutions, one of the solutions can also be used directly as the test solution to detect solution concentration. Furthermore, the rare earth element used in the above embodiment is erbium, and the pump laser wavelength is 980 nm, which satisfies the absorption band of the rare earth element. Of course, other rare earth ions can also be used, provided that the pump laser wavelength is within the absorption band of the rare earth element.

[0057] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for predicting the concentration of immunoglobulin G solution based on an optical sensor of a rare earth-doped microbubble cavity, characterized in that: The steps include: S1: Prepare a clean rare earth ion doped optical microbubble cavity; S2: Pumping the rare earth-doped microbubble cavity with a pump source laser to generate a signal laser; wherein the wavelength of the pump source laser is within the absorption band of the rare earth element contained in the rare earth-doped microbubble cavity; S3: injecting an immunoglobulin G solution to be tested, whose immunoglobulin type is known but whose concentration is unknown, into the microfluidic channel of the rare earth-doped microbubble cavity, and recording the signal laser spectrum at this time after stabilization as the signal laser spectrum after change; According to the signal laser power of the changed signal laser spectrum, the concentration of the immunoglobulin G solution to be tested can be obtained by comparing it with the standard curve of the relationship between concentration and signal laser power and finding the concentration value corresponding to the same signal laser power. Among them, the standard curve of the relationship between concentration and signal laser power is prepared by preparing multiple standard solutions with known concentration values ​​according to the type of immunoglobulin contained in the immunoglobulin G solution to be detected, and the concentrations of these standard solutions are different from each other; using the same rare earth ion-doped optical microbubble cavity and the same pump source as step S2, and under the same relative position conditions, for each standard solution, one standard solution is injected each time into the microfluidic channel of the rare earth-doped microbubble cavity after being rinsed with phosphate buffered saline (PBS), and the original solution inside the microfluidic channel is discharged. After stabilization, the signal laser spectrum is recorded to obtain a data point of the relationship between concentration value and signal laser power; thus, based on the multiple data points of the relationship between concentration value and signal laser power obtained for multiple standard solutions, a fitting curve of the relationship between concentration and signal laser power can be obtained, and this fitting curve is the standard curve.

2. The method according to claim 1, wherein In the process of obtaining the standard curve, before the first injection of the standard solution, the method further includes: injecting phosphate buffered saline (PBS) into the microfluidic channel of the rare earth-doped microbubble cavity, and recording the signal laser spectrum at this time after stabilization as the initial state signal laser spectrum; Accordingly, each time phosphate buffer (PBS) is used to flush the inside of the microfluidic channel of the rare earth-doped microbubble cavity, specifically, phosphate buffer (PBS) is injected into the microfluidic channel of the rare earth-doped microbubble cavity to discharge the original solution inside the microfluidic channel. After stabilization, the signal laser spectrum at this time is recorded and compared with the initial state signal laser spectrum to ensure that the signal laser spectrum is consistent with the initial state signal laser spectrum to ensure that it is flushed cleanly.

3. The method according to claim 1, wherein: In step S3, the immunoglobulin G solution to be tested is obtained by mixing two immunoglobulin solutions in a preset volume ratio and reacting them for a preset time; Accordingly, in the process of obtaining the standard curve, the standard solution used is obtained by mixing two immunoglobulin solutions designed with different concentrations in a preset volume ratio and reacting them for a preset time.

4. The method according to claim 1, wherein: In step S1, the rare earth ion doped optical microbubble cavity is obtained by treating a quartz capillary tube using a polymer-assisted melt thermal diffusion method; The polymer-assisted melt thermal diffusion method utilizes the film-forming properties of the polymer to uniformly dope the rare earth element into the microbubble cavity, and the polymer is one of polymethyl methacrylate, polyethylene and polypropylene.

5. The method according to claim 1, wherein: The rare earth ion is specifically at least one of erbium ion, ytterbium ion and thulium ion.

6. A method for predicting whether two immunoglobulin G solutions specifically bind to each other based on an optical sensor using a rare earth-doped microbubble cavity, characterized in that: The steps include: (1) Prepare a clean rare earth ion-doped optical microbubble cavity; (2) using a pump source laser to pump the rare earth-doped microbubble cavity to generate a signal laser, wherein the wavelength of the pump source laser is within the absorption band of the rare earth element contained in the rare earth-doped microbubble cavity; (3) For two immunoglobulin G solutions, one of the immunoglobulin G solutions is selected to design samples of different concentrations, and the immunoglobulin contained in the immunoglobulin G solution is recorded as component A, and a group of component A immunoglobulin G solutions of different concentrations are obtained; the immunoglobulin contained in the other immunoglobulin G solution is recorded as component B, and the concentration of the component B immunoglobulin G solution is kept fixed; the component A immunoglobulin G solutions of different concentrations are mixed with the component B immunoglobulin G solutions according to a preset volume ratio and reacted for a preset time to obtain a group of test solutions of different concentrations; for each test solution, one test solution is injected into the microfluidic channel of the rare earth-doped microbubble cavity after being rinsed with phosphate buffer solution (PBS), and the original solution in the microfluidic channel is discharged. After stabilization, the signal laser spectrum is recorded to obtain a data point of the relationship between the concentration value and the signal laser power; thus, a fitting curve of the relationship between the concentration and the signal laser power can be obtained based on the multiple data points of the relationship between the concentration value and the signal laser power obtained for multiple test solutions; Based on the degree of change in the signal laser power with concentration in the fitting curve, it can be determined whether specific binding can occur between component A and component B; if a specific binding reaction can occur, the signal laser power changes more dramatically with concentration than if a specific binding reaction cannot occur.

7. The method according to claim 6, wherein: The fitting curve is a linear fitting curve in a two-dimensional coordinate system, wherein the two-dimensional coordinate system uses concentration and signal laser power as coordinate axes, wherein the concentration axis is a logarithmic coordinate axis and the signal laser power axis is a linear coordinate axis in dBm.

8. The method according to claim 6, wherein: After step (2) and before step (3), the method further includes: injecting phosphate buffer solution (PBS) into the microfluidic channel of the rare earth-doped microbubble cavity, and recording the signal laser spectrum at this time after stabilization as the initial state signal laser spectrum; Correspondingly, in step (3), each time phosphate buffer (PBS) is used to flush the inside of the microfluidic channel of the rare earth-doped microbubble cavity, specifically, phosphate buffer (PBS) is injected into the microfluidic channel of the rare earth-doped microbubble cavity to discharge the original solution inside the microfluidic channel, and after stabilization, the original solution is recorded. Record the signal laser spectrum at this time and compare it with the initial state signal laser spectrum. Make the signal laser spectrum consistent with the initial state signal laser spectrum to ensure that it is rinsed cleanly.

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