Bifunctional SPR biosensor based on anisotropic material and method thereof

Abstract

The invention discloses a bifunctional SPR (Surface Plasmon Resonance) biosensor based on an anisotropic material. The bifunctional SPR biosensor comprises a Kretschmann prism coupling structure, the Kretschmann prism coupling structure comprises a prism layer, a coupling dielectric layer, an anisotropic functional layer, a metal layer and a sensing dielectric layer; the prism layer comprises an incident surface, a reflecting surface and a detection surface; the incident surface receives irradiation of detection light, and the reflecting surface outputs the detection light reflected by the detection surface; the detection surface of the prism layer is sequentially covered with a coupling dielectric layer, an anisotropic functional layer, a metal layer and a sensing dielectric layer, the anisotropic functional layer is a two-dimensional material layer with in-plane optical anisotropy, and the anisotropic functional layer comprises a first crystal orientation and a second crystal orientation; the performance optimization mode of the SPR biosensor under surface plasma resonance is switched by changing the crystal orientation of the anisotropic functional layer in the plane; when the anisotropic functional layer is in the first crystal orientation or the second crystal orientation, the SPR biosensor is in an optimized high sensitivity mode or an optimized high quality factor mode.

Description

Technical Field

[0001] This invention relates to the fields of optical sensing and biosensing technology, and in particular to a bifunctional SPR biosensor based on anisotropic materials and its method. Background Technology

[0002] Surface plasmon resonance (SPR) biosensors are widely used in biomolecular interaction analysis and clinical diagnostics due to their advantages such as label-free operation and real-time monitoring. Their core performance indicators include sensitivity (S) and quality factor (FOM). Traditional SPR sensors have fixed structures, and their S and FOM are often mutually constrained, making dynamic optimization difficult to meet different detection needs. For example, high sensitivity is required for detecting low concentrations of analytes, while high FOM is needed for high-precision measurement. Users often need to replace sensors with different designs or use complex external tuning devices to achieve detection with different focuses, which is cumbersome and costly. In recent years, some studies have attempted to introduce anisotropic materials into SPR structures to enhance performance, but most have focused on improving single indicators by utilizing their fixed-orientation characteristics. How to utilize the anisotropic properties of materials to achieve active and convenient switching of performance modes on the same sensor, enabling it to intelligently adapt to different detection scenarios while maintaining compatibility with both wavelength and angle detection modes, is a pressing technical problem to be solved in this field. Summary of the Invention

[0003] Purpose of the invention: In order to overcome the shortcomings of the prior art, the present invention provides a dual-function SPR biosensor and method based on anisotropic materials. By introducing anisotropic functional layers into the SPR biosensor, it is possible to dynamically switch between an optimized high-sensitivity model and an optimized high-quality factor model while being compatible with both wavelength and angle detection modes.

[0004] Technical Solution: To achieve the above objectives, the present invention provides a dual-functional SPR biosensor based on anisotropic materials, comprising a Kretschmann prism coupling structure; the Kretschmann prism coupling structure comprises a prism layer, a coupling medium layer, an anisotropic functional layer, a metal layer, and a sensing medium layer; the prism layer comprises an incident surface, a reflecting surface, and a detection surface; the incident surface receives the illumination of the probe light, and the reflecting surface outputs the probe light reflected by the detection surface; the detection surface of the prism layer is sequentially covered by the coupling medium layer, the anisotropic functional layer, the metal layer, and the sensing medium layer, wherein the anisotropic functional layer is a two-dimensional material layer with in-plane optical anisotropy, and the anisotropic functional layer comprises a first crystal orientation and a second crystal orientation.

[0005] The performance optimization mode of the SPR biosensor under surface plasmon resonance is switched by changing the in-plane crystal orientation of the anisotropic functional layer; when the anisotropic functional layer is in the first crystal orientation, the SPR biosensor is in the optimized high sensitivity mode; when the anisotropic functional layer is in the second crystal orientation, the SPR biosensor is in the optimized high quality factor mode.

[0006] Furthermore, the first crystal orientation of the anisotropic functional layer is the X-axis direction of the anisotropic functional layer, and the second crystal orientation of the anisotropic functional layer is the Y-axis direction of the anisotropic functional layer.

[0007] Furthermore, the material of the anisotropic functional layer is α-phase molybdenum trioxide, and the thickness of the anisotropic functional layer is 100nm-500nm.

[0008] Furthermore, the material of the coupling medium layer is a low-refractive-index optical medium, specifically the fluoropolymer CYTOP, and the thickness of the coupling medium layer is between 80nm and 120nm.

[0009] Furthermore, the metal layer includes one of gold and silver, and the thickness of the metal layer is between 50nm and 100nm.

[0010] Furthermore, the metal layer is a stepped metal layer.

[0011] Furthermore, the sensing medium layer is provided with a target to be detected, and two detection modes are performed on the target: wavelength detection and angle detection.

[0012] Furthermore, when performing wavelength detection on the target, the SPR biosensor can dynamically switch between optimizing high sensitivity mode and optimizing high quality factor mode; when performing angle detection on the target, the SPR biosensor can dynamically switch between optimizing high sensitivity mode and optimizing high quality factor mode.

[0013] Furthermore, the operating method of the bifunctional SPR biosensor based on anisotropic materials involves switching the performance optimization mode of the SPR biosensor under surface plasmon resonance according to the detection requirements of wavelength detection or angle detection; including the following steps:

[0014] Step 1: Determine whether the current detection requirement is to detect minute changes in refractive index or to detect high-precision resonance signals.

[0015] Step 2: When the detection requirement is to detect minute changes in refractive index, the anisotropic functional layer is adjusted to the first crystal orientation, and the SPR biosensor is in optimized high-sensitivity mode.

[0016] Step 3: When the detection requirement is to detect a high-precision resonance signal, the anisotropic functional layer is adjusted to the second crystal orientation, and the SPR biosensor is optimized for a high-quality factor mode.

[0017] Beneficial Effects: This invention, a dual-functional SPR biosensor and method based on anisotropic materials, innovatively utilizes the in-plane anisotropy of the anisotropic functional layer. It achieves active switching from high-sensitivity mode to high-quality factor mode on the same sensor through simple physical rotation. This solves the problem of fixed performance indicators in traditional sensors, enabling a single sensor to intelligently adapt to multiple detection needs, such as high-sensitivity screening and high-precision quantification, greatly improving the flexibility and cost-effectiveness of the equipment. The SPR biosensor operates stably in both wavelength and angle detection modes, and its performance mode switching function is effective in both modes, providing richer detection methods and data cross-validation capabilities. Performance switching is achieved solely by rotating the anisotropic layer, representing zero-power or low-power mechanical tuning, eliminating the need for complex external electrical, thermal, and optical field control systems, thus reducing the complexity and cost of the sensor system. By optimizing the layer thickness parameters, the SPR biosensor can achieve a sensitivity exceeding 8000 nm / RIU in high-sensitivity mode and a quality factor exceeding 500 / RIU in high-quality factor mode, demonstrating superior overall performance. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of a bifunctional SPR biosensor based on anisotropic materials.

[0019] Figure 2 This is a spectrum of wavelength detection sensing capability in high-sensitivity mode.

[0020] Figure 3 This is a spectrum of wavelength detection sensing capability in high quality factor mode.

[0021] Figure 4 A spectrum of angle detection sensing capability in high-sensitivity mode.

[0022] Figure 5 A spectrum of angle detection sensing capability in high-quality factor mode.

[0023] Figure 6 The wavelength detection sensing capability spectrum is obtained by rotating the anisotropic functional layer to 30°.

[0024] Figure 7 The wavelength detection sensing capability spectrum is obtained by rotating the anisotropic functional layer to 60°.

[0025] Figure 8 To detect the sensing capability spectrum when the anisotropic functional layer is rotated to an angle of 30°.

[0026] Figure 9 To detect the sensing capability spectrum when the anisotropic functional layer is rotated to an angle of 60°. Detailed Implementation

[0027] The invention will now be further described with reference to the accompanying drawings.

[0028] like Figure 1 As shown, a dual-functional SPR biosensor based on anisotropic materials includes a Kretschmann prism coupling structure. The Kretschmann prism coupling structure includes a prism layer 1, a coupling medium layer 2, an anisotropic functional layer 3, a metal layer 4, and a sensing medium layer 5. The prism layer 1 includes an incident surface, a reflecting surface, and a detection surface. The incident surface receives the illumination of the probe light, and the reflecting surface outputs the probe light reflected by the detection surface. The detection surface of the prism layer 1 is sequentially covered by the coupling medium layer 2, the anisotropic functional layer 3, the metal layer 4, and the sensing medium layer 5. The anisotropic functional layer 3 is a two-dimensional material layer with in-plane optical anisotropy, and the anisotropic functional layer 3 includes a first crystal orientation and a second crystal orientation. The probe light is p-polarized light.

[0029] By changing the in-plane crystal orientation of the anisotropic functional layer 3, the performance optimization mode of the SPR biosensor under surface plasmon resonance is switched. When the anisotropic functional layer 3 is in the first crystal orientation, the SPR biosensor is in optimized high sensitivity mode; when the anisotropic functional layer 3 is in the second crystal orientation, the SPR biosensor is in optimized high quality factor mode. By introducing anisotropic functional layers and utilizing their in-plane rotation, a dual-function SPR biosensor with intelligently switchable performance has been creatively realized, providing a core device solution for next-generation intelligent, multifunctional biochemical analysis platforms. SPR stands for Surface Plasmon Resonance.

[0030] The simplified fabrication process of the bifunctional SPR biosensor based on anisotropic materials is as follows: First, the prism layer 1 is cleaned by ultrasonically cleaning its detection surface with acetone, ethanol, and deionized water in sequence, and then dried with nitrogen. Next, a coupling medium layer 2 is deposited on the detection surface using spin-coating, with the material being the fluoropolymer CYTOP. The spin-coating speed is controlled to maintain a thickness between 80 nm and 120 nm, and a uniform film is formed after thermosetting. Then, an anisotropic functional layer 3 is prepared, using α-phase molybdenum trioxide as an example. A two-dimensional material film with a thickness of 150 nm to 250 nm is grown on an independent substrate using chemical vapor deposition, and its X-axis and Y-axis orientations are determined by polarized Raman spectroscopy. This film, along with the support layer, is transferred to the surface of the coupling medium layer 2, and precisely rotated and aligned under a polarizing microscope to ensure that the X-axis or Y-axis forms the required angle with the incident surface of the probe light. The support layer is then removed and annealed. Finally, a metal layer 4, made of gold or silver, is deposited at room temperature using electron beam evaporation, with the initial deposition rate controlled at 0.1%. The initial Å / s was increased to 1-2 Å / s after the continuous film was formed, with the final thickness controlled between 50 nm and 70 nm, monitored in real time using a quartz crystal oscillator. Finally, the multilayer structure was assembled into a flow cell, with the sensing medium layer 5 being the liquid or gas to be measured, directly contacting the metal layer 4, thus completing the construction of the entire SPR biosensor.

[0031] The first crystal orientation of the anisotropic functional layer 3 is the X-axis direction of the anisotropic functional layer, and the second crystal orientation of the anisotropic functional layer 3 is the Y-axis direction of the anisotropic functional layer. When the anisotropic functional layer is in the first crystal orientation, it is rotated horizontally by 90 degrees to be in the second crystal orientation; when the anisotropic functional layer is in the second crystal orientation, it is rotated horizontally by 90 degrees to be in the first crystal orientation.

[0032] In practice, the crystal orientation switching of the anisotropic functional layer 3 can be achieved in two independent ways. The first way is through a mechanical rotating sensor: the prism layer and its multilayer film are fixed as a whole on a high-precision electric rotating stage, with the rotation axis of the stage perpendicular to the prism detection surface; according to the preset first or second crystal orientation, the rotating stage is driven to rotate the entire sample horizontally by 90° around the vertical axis, thus completing the crystal orientation switching. If the SPR biosensor has been packaged and put into use, a rotating fixture with an angle scale can be set outside the prism, and the anisotropic functional layer 3 carrier can be directly rotated by magnetic force or mechanical linkage, thus achieving in-situ switching as well.

[0033] The second method involves changing the polarization direction of the incident light using a polarizer: Keeping the crystal orientation of the anisotropic functional layer fixed, a rotatable linear polarizer is placed in the incident light path of the probe light. Since p-polarized light is defined as having an electric field vector parallel to the incident plane, and the azimuth angle of the incident plane relative to the fixed crystal orientation can be artificially changed, the specific operation is as follows: The prism layer and multilayer film are fixed as a whole, and the linear polarizer is rotated so that its transmission axis is at different angles relative to the first crystal orientation of the anisotropic functional layer 3. When the transmission axis is parallel to the first crystal orientation, it is equivalent to the anisotropic functional layer 3 being in the first crystal orientation; rotating the polarizer by 90° so that the transmission axis is parallel to the second crystal orientation is equivalent to the anisotropic functional layer 3 being in the second crystal orientation. This method requires no mechanical rotation of the sensor's internal components; performance mode switching is achieved solely through the rotation of external optical components, and the switching speed is fast and repeatability is good. Both methods can be used individually depending on the actual equipment conditions.

[0034] The anisotropic functional layer 3 is made of α-phase molybdenum trioxide, and the thickness of the anisotropic functional layer is 100 nm to 500 nm. The anisotropic functional layer is made of a natural two-dimensional material with in-plane optical anisotropy, including at least one of α-phase molybdenum trioxide, black phosphorus, or transition metal chalcogenides, preferably α-phase molybdenum trioxide; preferably, the thickness of the anisotropic functional layer is 150 nm to 250 nm.

[0035] The coupling medium layer 2 is made of a low-refractive-index optical medium, including polymer PMMA, fluoropolymer CYTOP, magnesium fluoride, silicon dioxide, etc., with fluoropolymer CYTOP being preferred. The thickness of the coupling medium layer is 80nm-120nm. The coupling medium layer 2 is a low-refractive-index, low-optical-loss medium layer. The material of the coupling medium layer 2 is fluoropolymer CYTOP, and the thickness of the coupling medium layer is 10nm-200nm. Through experiments, the optimal thickness of the coupling medium layer can be obtained, which is 80nm-120nm.

[0036] The metal layer 4 includes either gold or silver, and the thickness of the metal layer is between 50nm and 100nm. The optimal thickness of the metal layer can be obtained through experiments, which is between 50nm and 70nm. Silver is the preferred metal for the metal layer.

[0037] The metal layer 4 is a stepped metal layer, comprising multiple steps. Each step has a different thickness; for example, the stepped metal layer may include three steps: 50nm, 60nm, and 70nm. Within a certain thickness range, as the thickness increases, its impact on sensitivity exhibits a trend of increasing sensitivity followed by decreasing sensitivity. Therefore, the sensitivity of the SPR biosensor can be adjusted by selecting metal layers of different thicknesses. In practical use, when performing wavelength detection on the target, the incident angle is fixed, and the probe light is shifted to different steps during detection, ensuring that the probe light does not deviate from the selected step, thus adjusting the sensitivity of the SPR biosensor. Similarly, when performing angle detection on the target, the incident wavelength is fixed, and the probe light is shifted to different steps, ensuring that the probe light does not deviate from the selected step when the angle is changed, thus adjusting the sensitivity of the SPR biosensor. For some high-concentration samples, high sensitivity can actually interfere with effective detection. Therefore, it is necessary to reduce the sensitivity to effectively detect high-concentration samples. When the sensitivity obtained by changing the crystal orientation of the anisotropic functional layer is still high, it is necessary to increase or decrease the thickness of the metal layer to reduce the sensitivity and achieve detection of high-concentration samples. In the case of stepped metal layers, the spaces where the metal layer is missing due to the stepped shape are filled with a transparent material that does not affect the sensitivity and refractive index, thus avoiding interference with sensitivity adjustment.

[0038] The sensing medium layer 5 is used to set the target to be detected, and two detection modes are used: wavelength detection and angle detection. The target to be detected includes a liquid or a gas to be detected. In the SPR biosensor, the sensing medium layer 5 is the liquid or gas sample to be detected, and its thickness is usually determined by the structure of the flow cell or sample cell. It should be noted that the thickness of the sensing medium layer is not arbitrary, but should meet a basic condition: the thickness of the medium to be detected must be greater than the penetration depth of surface plasmons in the sensing medium layer; otherwise, the evanescent field will penetrate into areas outside the medium layer, such as air or the sample cell wall, causing interference to the measurement results. Therefore, under the structural parameters, the penetration depth of the evanescent field into the sensing medium is approximately 300 nm. Therefore, to ensure the accuracy and stability of the measurement, the effective thickness of the sensing medium layer 5 should be at least greater than 300 nm. In practical device design, when using a flow cell structure, the channel height is usually designed to be 100 μm to 1 mm, which is much greater than the penetration depth. Therefore, it is sufficient to ensure that the thickness of the sample covering the metal layer surface is not less than 500 nm to meet most measurement requirements. In summary, there is no strict upper limit requirement for the sensing medium layer 5, but there is a lower limit constraint. Below this lower limit, the sensitivity and quality factor of the sensor will decrease.

[0039] When performing wavelength detection on the target, the SPR biosensor can dynamically switch between optimizing high sensitivity mode and optimizing high quality factor mode; when performing angle detection on the target, the SPR biosensor can dynamically switch between optimizing high sensitivity mode and optimizing high quality factor mode.

[0040] The working method of a dual-functional SPR biosensor based on anisotropic materials involves switching the performance optimization mode of the SPR biosensor under surface plasmon resonance according to the detection requirements of wavelength detection or angle detection; it includes the following steps:

[0041] Step 1: Determine whether the current detection requirement is to detect minute changes in refractive index or to detect high-precision resonance signals;

[0042] Step 2: When the detection requirement is to detect a small change in refractive index, the anisotropic functional layer 3 is adjusted to the first crystal orientation, and the SPR biosensor is in optimized high-sensitivity mode.

[0043] Step 3: When the detection requirement is to detect a high-precision resonance signal, the anisotropic functional layer 3 is adjusted to the second crystal orientation, and the SPR biosensor is optimized for a high-quality factor mode.

[0044] After parameter optimization, the thickness of the coupling medium layer was set to 100 nm, the thickness of the anisotropic functional layer was set to 175 nm, the metal layer was selected as silver, and the thickness of the metal layer was set to 55 nm; the initial refractive index of the sensing medium layer was set to 1.33 to simulate the water environment.

[0045] like Figure 2-3 As shown, when performing wavelength detection on the target, the incident angle of the probe light on the fixed prism layer incident surface is 65.5°, and the refractive index of the target is set to n. s = 1.34, the crystal orientation of the anisotropic functional layer is along the X-axis, and the SPR biosensor is optimized for high sensitivity mode, with a sensitivity S x Approximately 8500 nm / RIU, corresponding to a quality factor (FOM) x Approximately 490 / RIU; The anisotropic functional layer is rotated horizontally by 90 degrees so that its crystal orientation is along the Y-axis. For the SPR biosensor, to optimize the high-quality factor mode, the sensitivity S0 is [value missing]. y Approximately 7500 nm / RIU, quality factor FOM y The performance was significantly improved to approximately 580 / RIU. Changes in sensitivity and quality factor clearly demonstrate the active switching of performance modes achievable by rotating the anisotropic functional layer. By scanning the wavelength of the probe light reflected from the detection surface and monitoring the movement of the minimum reflectivity point, changes in the refractive index of the sensing medium layer were detected, and the switchability of performance optimization was verified in this mode.

[0046] like Figure 4-5 As shown, when performing angle detection on the target, the wavelength of the probe light incident on the fixed prism layer is 632.8 nm, and the refractive index of the target is set to n. s = 1.34. The crystal orientation of the anisotropic functional layer is along the X-axis. In the SPR biosensor's optimized high-sensitivity mode, the anisotropic functional layer is rotated horizontally by 90 degrees, so that its crystal orientation is along the Y-axis. In this optimized high-quality factor mode, the SPR biosensor also produces a clear SPR absorption valley by scanning the incident angle of the probe light. Rotating the anisotropic functional layer also causes changes in the resonance angle shift and the width of the resonance curve, demonstrating the universality of the performance optimization mode switching function, which can adapt to both wavelength detection and angle detection modes.

[0047] like Figure 6-7 As shown, when the anisotropic functional layer 3 rotates to the midpoint between the first and second crystal orientations, the sensor's sensitivity and quality factor continuously change, thus achieving fine-tuning of performance indicators. When performing wavelength detection on the target, when the anisotropic functional layer 3 rotates to 30°, the sensitivity is 7700 nm / RIU, and the quality factor is 502.6 / RIU. Figure 6 As shown; when the anisotropic functional layer 3 is rotated to 60°, the sensitivity is 7400 nm / RIU and the quality factor is 562.1 / RIU, as... Figure 7 As shown.

[0048] like Figure 8-9 As shown, when performing angle detection on the target, the sensitivity is 111° / RIU and the quality factor is 370 / RIU when the anisotropic functional layer 3 is rotated to 30°. Figure 8 As shown; when the anisotropic functional layer 3 is rotated to 60°, the sensitivity is 120° / RIU, and the quality factor is 276.49 / RIU, as... Figure 9 As shown.

[0049] The above data shows that during the rotation from the first crystal orientation to the second crystal orientation, as the rotation angle increases from 0° to 90°, the sensitivity monotonically changes from approximately 8500 nm / RIU to approximately 7500 nm / RIU, while the quality factor first increases from approximately 490 / RIU to approximately 580 / RIU. An intermediate angle provides a compromise or locally optimal performance combination. Therefore, users can not only switch between the two extreme crystal orientations, but also rotate the anisotropic functional layer 3 to any intermediate angle according to actual detection needs. For example, if a balance between sensitivity and a high signal-to-noise ratio is required, the sensitivity and quality factor can be continuously adjusted. This feature significantly enhances the sensor's adaptability to different detection scenarios. For example, at 30°, near-high sensitivity performance with an improved quality factor can be obtained; at 60°, the quality factor increases significantly while the sensitivity remains high. During operation, simply stop the rotating stage or polarizing lens at the desired angle and lock it in place to perform subsequent measurements.

[0050] The complete working process of the dual-function SPR biosensor includes the following steps: First, the SPR biosensor chip is installed in the angle detection system or wavelength detection system, and the liquid or gas to be detected is introduced into the sensing medium layer.

[0051] When performing wavelength detection on the target, the angle of the incident probe light is kept constant. The optimal fixed angle, such as 65.5°, is typically selected based on performance optimization requirements. The probe light is p-polarized, emitted by a broadband light source, such as a halogen tungsten lamp or a supercontinuum laser. After collimation, the p-polarized light enters from the incident surface of the prism layer, passing sequentially through the coupling medium layer, the anisotropic functional layer, and the metal layer. At the interface between the metal layer and the sensing medium layer, surface plasmons are excited. The reflected probe light is output from the reflecting surface of the prism and received by the spectrometer. The spectrometer records the curve of reflected light intensity versus wavelength. A distinct minimum reflectance value appears on the curve; the wavelength corresponding to this minimum value is the resonant wavelength. When the refractive index of the analyte in the sensing medium layer changes, the resonant wavelength shifts. By continuously acquiring spectra and tracking the amount of resonant wavelength shift, combined with a pre-calibrated sensitivity coefficient, the refractive index change can be quantitatively calculated, thereby inferring the concentration of the biomolecule being measured or incorporating kinetic parameters. The unit of the sensitivity coefficient is nm / RIU.

[0052] When performing angle detection on the target, the wavelength of the incident probe light is kept constant, for example, 632.8 nm. The p-polarized light is typically a monochromatic light source, such as a helium-neon laser. The p-polarized light enters from the incident surface of the prism layer, and a stepper motor controls a rotating stage to drive the prism or reflector, continuously scanning the incident angle within a set range, for example, from 50° to 75°. At each incident angle, the photodetector receives the intensity of the reflected probe light, obtaining a curve showing the reflectivity as a function of the incident angle, known as the SPR curve. The angle corresponding to the minimum reflectivity on the SPR curve is the resonance angle. When the refractive index of the sensing medium changes, the resonance angle shifts. By recording the amount of resonance angle shift and combining it with the sensitivity calibration value, the change in refractive index can be detected. The unit of the sensitivity calibration value is ° / RIU.

[0053] In practical biological detection, if it is necessary to detect extremely low concentrations of target molecules, the SPR biosensor can be switched to the optimized high-sensitivity mode to capture weak refractive index change signals; if it is necessary to perform high-precision kinetic analysis of the binding process or distinguish non-specific adsorption, the SPR biosensor can be switched to the optimized high-quality factor mode to improve detection resolution and accuracy by utilizing its sharper resonance peaks.

[0054] The above description is merely a preferred embodiment of the present invention. Those skilled in the art can make several modifications and optimizations based on the above disclosure without departing from the basic principles described above. These modifications and optimizations should be considered within the scope of protection as understood by the present invention.

Claims

1. A bifunctional SPR biosensor based on anisotropic materials, characterized in that: The system includes a Kretschmann prism coupling structure; the Kretschmann prism coupling structure includes a prism layer (1), a coupling medium layer (2), an anisotropic functional layer (3), a metal layer (4), and a sensing medium layer (5); the prism layer (1) includes an incident surface, a reflecting surface, and a detection surface; the incident surface receives the illumination of the detection light, and the reflecting surface outputs the detection light reflected by the detection surface; the detection surface of the prism layer (1) is sequentially covered by the coupling medium layer (2), the anisotropic functional layer (3), the metal layer (4), and the sensing medium layer (5), the anisotropic functional layer (3) is a two-dimensional material layer with in-plane optical anisotropy, and the anisotropic functional layer (3) includes a first crystal orientation and a second crystal orientation; The performance optimization mode of the SPR biosensor under surface plasmon resonance is switched by changing the crystal orientation of the anisotropic functional layer (3) in the plane; when the anisotropic functional layer (3) is in the first crystal orientation, the SPR biosensor is in the optimized high sensitivity mode; when the anisotropic functional layer (3) is in the second crystal orientation, the SPR biosensor is in the optimized high quality factor mode.

2. The bifunctional SPR biosensor based on anisotropic materials according to claim 1, characterized in that: The first crystal orientation of the anisotropic functional layer (3) is the X-axis direction of the anisotropic functional layer, and the second crystal orientation of the anisotropic functional layer (3) is the Y-axis direction of the anisotropic functional layer.

3. The bifunctional SPR biosensor based on anisotropic materials according to claim 1, characterized in that: The material of the anisotropic functional layer (3) is α-phase molybdenum trioxide, and the thickness of the anisotropic functional layer is 100nm-500nm.

4. The bifunctional SPR biosensor based on anisotropic materials according to claim 1, characterized in that: The material of the coupling medium layer (2) is a low refractive index optical medium, which is selected as fluoropolymer CYTOP, and the thickness of the coupling medium layer is 80nm-120nm.

5. The bifunctional SPR biosensor based on anisotropic materials according to claim 1, characterized in that: The metal layer (4) includes one of gold and silver, and the thickness of the metal layer is 50nm-100nm.

6. The bifunctional SPR biosensor based on anisotropic materials according to claim 5, characterized in that: The metal layer (4) is a stepped metal layer.

7. The bifunctional SPR biosensor based on anisotropic materials according to claim 1, characterized in that: The sensing medium layer (5) is set with the target to be detected, and two detection modes are performed on the target: wavelength detection and angle detection.

8. The bifunctional SPR biosensor based on anisotropic materials according to claim 7, characterized in that: When performing wavelength detection on the target, the SPR biosensor can dynamically switch between optimizing high sensitivity mode and optimizing high quality factor mode; when performing angle detection on the target, the SPR biosensor can dynamically switch between optimizing high sensitivity mode and optimizing high quality factor mode.

9. The operating method of the bifunctional SPR biosensor based on anisotropic materials according to claims 1-8, characterized in that: Depending on the detection requirements of wavelength detection or angle detection, switch the performance optimization mode of the SPR biosensor under surface plasmon resonance; including the following steps: Step 1: Determine whether the current detection requirement is to detect minute changes in refractive index or to detect high-precision resonance signals; Step 2: When the detection requirement is to detect a small change in refractive index, the anisotropic functional layer (3) is adjusted to the first crystal orientation, and the SPR biosensor is in optimized high sensitivity mode. Step 3: When the detection requirement is to detect a high-precision resonance signal, the anisotropic functional layer (3) is adjusted to the second crystal orientation, and the SPR biosensor is optimized for a high-quality factor mode.

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