An organic photoelectrochemical transistor sensor and a preparation method and a detection method thereof

Abstract

The application discloses an organic photoelectrochemical transistor sensor for cortisol detection and a preparation method and a detection method thereof. The organic photoelectrochemical transistor sensor comprises an electrolytic cell loaded with an electrolyte solution, a substrate inserted into the electrolyte solution at one end, and a gate electrode. The substrate is provided with a source electrode and a drain electrode inserted into the electrolyte solution at one end and spacedly distributed. The surface of the source electrode and the drain electrode is coated with an organic semiconductor film. The gate electrode is provided with a photoelectric active layer at one end inserted into the electrolyte solution. The photoelectric active layer is provided with a first antibody specifically combined with cortisol in a sample to be detected. The application further comprises a spare second antibody conjugate specifically combined with cortisol in the sample to be detected. The second antibody conjugate is composed of a second antibody and a MOF material. The material of the photoelectric active layer is a covalent organic framework material. The cortisol detection method based on the organic photoelectrochemical transistor sensor has high sensitivity, simple operation and high detection efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of organic photoelectrochemical transistors, in particular to an organic photoelectrochemical transistor sensor for cortisol detection and a preparation method and detection method thereof. BACKGROUND

[0002] Cortisol, as a kind of steroid hormone, is called "stress hormone", is a potential biomarker for psychological stress assessment, is the final product of the central stress response system, is one of the main glucocorticoids synthesized in the adrenal cortex belt, and is also an important molecule for regulating blood pressure, glucose level and carbohydrate metabolism. When cortisol is excessive, diseases such as depression and anxiety will occur; when cortisol is insufficient, diseases such as adrenal tuberculosis and autoimmune Addison's disease will occur. Therefore, it is crucial for human health to develop a simple, accurate, rapid and sensitive cortisol detection technology.

[0003] The existing clinical cortisol detection method is to collect urine or saliva samples from patients and send them to the laboratory for results. The main methods include traditional standard method, chromatography, surface plasmon resonance (SPR), radioimmunoassay (RIA), enzyme-linked immunosorbent assay (ELISA) and the like. Among them, the standard method uses complex and time-consuming liquid chromatography-tandem mass spectrometry. Chromatography technology is based on analyte adsorption induced by mass transfer, involving multiple pretreatment procedures. The optical technology of surface plasmon resonance (SPR) biosensor has the problems of integration of complex optical components and portability, which is difficult to miniaturize, and most laser instruments are difficult to use for untreated or unpurified samples. Radioimmunoassay (RIA) involves radioisotope labeling, which requires complex pretreatment. Enzyme-linked immunosorbent assay (ELISA) generally requires 90-120 minutes for detection, which is relatively cumbersome, and requires monoclonal antibodies as a match, and the enzyme-substrate reaction is short-term, which requires immediate reading of the micro-well; and due to the cross-reactivity with other steroid hormones of similar structure, the detection selectivity is limited. The existing detection methods all have the problems of complex pretreatment process, long detection time, or high cost, which do not meet the needs of basic detection.

[0004] Therefore, the prior art still needs to be improved and developed. SUMMARY

[0005] In view of the deficiencies of the prior art described above, the purpose of the present application is to provide an organic photoelectrochemical transistor sensor for cortisol detection and a preparation method and detection method thereof, aiming to solve the problems of cumbersome operation and long detection time of the existing methods for detecting cortisol concentration.

[0006] The technical scheme of the present application is as follows:

[0007] An organic photoelectrochemical transistor sensor for cortisol detection includes an electrolytic cell containing an electrolyte solution, a substrate with one end inserted into the electrolyte solution, and a gate electrode. A source electrode and a drain electrode, each with one end inserted into the electrolyte solution and spaced apart, are disposed on the substrate. An organic semiconductor thin film is coated on the surfaces of the source and drain electrodes. A photoactive layer is disposed on the end of the gate electrode inserted into the electrolyte solution, and a first antibody that specifically binds to cortisol in the test sample is disposed on the photoactive layer. The sensor also includes a secondary antibody conjugate that specifically binds to cortisol in the test sample, the secondary antibody conjugate being composed of a second antibody and a metal-organic framework (MOF) material. The photoactive layer is made of a covalent organic framework (COF) material.

[0008] The organic photoelectrochemical transistor sensor for cortisol detection, wherein the covalent organic framework (COF) material is one or more of the following: a polymer of trialdehyde phloroglucinol and 2-chloro-1,4-p-phenylenediamine (TpPa-Cl), a polymer of 2,6-dialdehyde-1,5-dihydroxynaphthalene and tris(4-aminophenyl)amine (D-TA), a polymer of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 2,5-dihydroxyterephthalic acid (TTA-DHTA), and aminotetraphenylporphyrin (TAPP).

[0009] The organic photoelectrochemical transistor sensor for cortisol detection, wherein the metal-organic framework material is one or more of ZIF-8, Cu-MOF, MIL-101, and NH2-UIO-66.

[0010] The organic photoelectrochemical transistor sensor for cortisol detection is wherein the material of the organic semiconductor thin film layer is at least one of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid, polypyrrole, polythiophene, polyaniline, polycarbazole and their copolymers.

[0011] The organic photoelectrochemical transistor sensor for cortisol detection, wherein the gate electrode material is one or more of Ti, Pt, Au, ITO and FTO.

[0012] A method for fabricating an organic photoelectrochemical transistor sensor for cortisol detection, comprising the steps of:

[0013] A source electrode and a drain electrode are fabricated on a substrate, and an organic semiconductor thin film is fabricated on the surface of the source electrode and the drain electrode for later use;

[0014] A gate electrode is provided, a photoactive layer is prepared on the gate electrode, and a first antibody that specifically binds to cortisol in the sample to be tested is dropped onto the photoactive layer, so that the first antibody binds to the photoactive layer.

[0015] A secondary antibody conjugate that specifically binds to cortisol in the sample to be tested is provided for use, the secondary antibody conjugate being composed of a secondary antibody and a metal-organic framework material;

[0016] The substrate and the gate electrode, which is provided with a photoactive layer and a first antibody, are inserted into an electrolytic cell containing an electrolyte solution to obtain the organic photoelectrochemical transistor sensor for cortisol detection.

[0017] The method for preparing the organic photoelectrochemical transistor sensor for cortisol detection, wherein when the secondary antibody conjugate is formed by combining a second antibody with ZIF-8-MOF material, the preparation steps include:

[0018] The second antibody was dissolved in a dimethylimidazole solution and stirred at room temperature to obtain a mixed solution;

[0019] Zinc acetate solution was added to the mixture and stirred. The mixture was then centrifuged, followed by washing the precipitate with PBS solution. The precipitate was then collected by centrifugation to remove free protein. After purification with ethanol, the precipitate was dispersed in PBS solution containing 1 wt% BSA to obtain the secondary antibody conjugate ZIF-8-Ab2.

[0020] A detection method for cortisol using an organic photoelectrochemical transistor sensor, comprising the steps of:

[0021] After a photoactive layer is placed on the gate electrode, the first channel step current generated by the gate electrode under light irradiation is measured.

[0022] After the first antibody was bound to the photoactive layer, the second channel step current generated by the gate electrode under light irradiation was measured.

[0023] The sample to be tested is dropped onto the gate electrode, so that the cortisol in the sample to be tested specifically binds to the first antibody. The third channel step current generated by the gate electrode under light irradiation is measured.

[0024] The prepared secondary antibody conjugate is dropped onto the gate electrode, so that the second antibody in the secondary antibody conjugate specifically binds to the cortisol in the sample to be tested, and the fourth channel step current generated by the gate electrode under light irradiation is measured.

[0025] The concentration of cortisol in the sample to be tested is calculated based on the changes in the first channel step current, the second channel step current, the third channel step current, and the fourth channel step current.

[0026] The detection method of the organic photoelectrochemical transistor sensor for cortisol detection, wherein the irradiation wavelength of the light is 425 nm.

[0027] Beneficial Effects: This invention provides an organic photoelectrochemical transistor sensor for cortisol detection. By modifying the gate electrode surface with a photoactive layer composed of a covalent organic framework (COF) material, and then adding a first antibody (Ab1) to the surface of the photoactive layer, the first antibody can specifically recognize and capture cortisol. Next, a secondary antibody conjugate (MOF-Ab2) combining a second antibody (Ab2) and MOF material is added, thereby progressively modifying the gate electrode surface to form a sandwich immune structure. The COF material on the gate electrode and the MOF material linked to the specifically recognized secondary antibody form a composite material, improving photoelectric conversion efficiency and thus enhancing the photocurrent signal. Different concentrations of cortisol combined with different amounts of MOF material generate different current signals, allowing for the detection of cortisol through changes in sensor current. This invention's cortisol detection method based on an organic photoelectrochemical transistor sensor exhibits high sensitivity, simple operation, and high detection efficiency, showing promising application prospects in the field of biosensing. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of an organic photoelectrochemical transistor sensor for cortisol detection.

[0029] Figure 2 This is a schematic diagram illustrating the principle of enzyme-free immunoassay for cortisol detection based on MOF materials as signal amplification probes, as described in this invention.

[0030] Figure 3 This is a flowchart illustrating the preparation method of an organic photoelectrochemical transistor sensor for cortisol detection according to the present invention.

[0031] Figure 4 This refers to the photocurrent of the TpPa-Cl / ITO gate electrode in this invention.

[0032] Figure 5 The channel current I in an organic photochemical transistor device under illumination in the "off-on" state. DS The changes.

[0033] Figure 6 To progressively modify the TpPa-Cl / ITO gate electrode with biomolecules DS -T curve.

[0034] Figure 7 The results show the detection results of cortisol at different concentrations. Detailed Implementation

[0035] This invention provides an organic photoelectrochemical transistor sensor for cortisol detection, along with its preparation and detection methods. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention.

[0036] Please see Figures 1-2 This invention provides an organic photoelectrochemical transistor sensor for cortisol detection, as shown in the figure. It includes an electrolytic cell 2 containing an electrolyte solution 1, a substrate 3 with one end inserted into the electrolyte solution 1, and a gate electrode 4. A source electrode 5 and a drain electrode 6, each with one end inserted into the electrolyte solution 1 and spaced apart, are disposed on the substrate 3. An organic semiconductor thin film 7 is coated on the surfaces of the source electrode 5 and the drain electrode 6. A photoactive layer 8 is disposed on the end of the gate electrode 4 inserted into the electrolyte solution 1. A first antibody 10, specifically binding to cortisol 20 in the test sample, is disposed on the photoactive layer 8. It also includes a secondary antibody conjugate 30, specifically binding to cortisol 20 in the test sample, which is composed of a second antibody 31 and an MOF material 32. The photoactive layer 8 is made of a covalent organic framework material.

[0037] Specifically, organic photoelectrochemical transistors (OPTs), as a novel high-sensitivity biosensing technology, combine organic electrochemical transistors with photoelectrochemical analysis methods. They possess advantages such as high sensitivity, low detection limit, miniaturization, and low cost, giving them unique advantages in biosensor applications. Among these advantages, the gate electrode modified with photoactive materials plays a crucial role in the biosensor.

[0038] This invention selects a covalent organic framework (COF) material as the photoactive substance to modify the gate electrode and form a photoactive layer 8. The COF material is a novel porous crystalline material with oxygen vacancies, which can enhance visible light capture at the interband level and reduce photogenerated carrier recombination. Furthermore, it possesses a π-electron conjugated structure, exhibiting broad visible light absorption and excellent photocatalytic performance. Compared to common inorganic materials, the photocurrent of the COF material is the cathode current. Compared to other cathode materials, this material has a large cathode current, and its microstructure is a porous bird's nest shape with a large specific surface area, which is beneficial for adsorbing other particles. The secondary antibody conjugate 30 in this invention is composed of a secondary antibody 31 and a MOF material 32. The MOF material serves as a signal probe to amplify the signal, enabling enzyme-free immunoassay. The MOF material used in this invention is photoactive and can form an interleaved semiconductor with the band structure of the COF material on the gate electrode, promoting charge carrier separation and migration, reducing the barrier effect and electron-hole recombination probability, thereby greatly improving photoelectric efficiency. Furthermore, MOF materials have a large specific surface area and a tunable porous structure, making them suitable for anchoring biomolecules with high loading capacity through van der Waals forces, hydrogen bonds, π-π interactions, electrostatic or hydrophobic interactions, making them ideal matrices for fixing or encapsulating biomolecules.

[0039] This invention modifies the surface of a gate electrode with a photoactive layer composed of COF material, and then drops a first antibody (Ab1) onto the surface of the photoactive layer. The first antibody can specifically recognize and capture cortisol. Next, a secondary antibody conjugate MOF-Ab2, composed of a second antibody (Ab2) and MOF material, is added, thereby progressively modifying the gate electrode surface to form a sandwich immune structure. The COF material on the gate electrode and the MOF material linked to the specifically recognized second antibody form a composite material, improving photoelectric conversion efficiency and thus enhancing the photocurrent signal. Different concentrations of cortisol bind to different amounts of MOF material, generating different current signals. Therefore, cortisol can be detected by changes in the sensor current. This invention's cortisol detection method based on an organic photoelectrochemical transistor sensor has high sensitivity, simple operation, and high detection efficiency, showing promising application prospects in the field of biosensing. It effectively solves the problems of long detection time, complex equipment, high cost, and cumbersome sample processing in existing cortisol detection technologies.

[0040] In some embodiments, the covalent organic framework material is one or more of the following: a polymer of trialdehyde-resorcinol and 2-chloro-1,4-p-phenylenediamine (TpPa-Cl), a polymer of 2,6-dialdehyde-1,5-dihydroxynaphthalene and tris(4-aminophenyl)amine (D-TA), a polymer of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 2,5-dihydroxyterephthalic acid (TTA-DHTA), and aminotetraphenylporphyrin (TAPP), but is not limited thereto. In this embodiment, the covalent organic framework material is a novel type of organic porous framework material composed of light atoms (such as hydrogen, boron, carbon, nitrogen, etc.) linked by covalent bonds. Preferably, the covalent organic framework material is TpPa-Cl, which is derived from TpPa-1 and inherits its narrow band gap and photocatalytic reduction ability. TpPa-Cl is a classic covalent organic framework with many phenyl rings and planar structures. Its villous porous structure can be used as a support for doping other particles and can be used for catalytic applications. Moreover, it not only has oxygen vacancies, which can enhance visible light capture and reduce recombination of photogenerated carriers at the interband level, but also has a π-electron conjugated structure, which has broad visible light absorption and excellent photocatalytic performance.

[0041] In some embodiments, the material of the organic semiconductor thin film layer is at least one of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid, polypyrrole, polythiophene, polyaniline, polycarbazole and copolymers thereof, but is not limited thereto.

[0042] In some embodiments, the gate electrode material is one or more of Ti, Pt, Au, ITO, and FTO, but is not limited thereto.

[0043] In some embodiments, the metal-organic framework (MOF) material is one or more of ZIF-8, Cu-MOF, MIL-101, and NH2-UIO-66, but is not limited thereto. This embodiment chooses MOF material to load the second antibody because MOF materials have a large specific surface area and a tunable porous structure, making them suitable for anchoring biomolecules with high loading capacity through van der Waals forces, hydrogen bonds, π-π interactions, electrostatic or hydrophobic interactions, thus making them ideal matrices for immobilizing or encapsulating biomolecules. Furthermore, MOF materials exhibit photoelectric activity and can form an interleaved semiconductor with the band structure of the COF material on the gate electrode, promoting charge carrier separation and migration, reducing barrier effects and electron-hole recombination probability, thereby significantly improving photoelectric efficiency. Therefore, this embodiment uses MOF material as a signal probe to amplify the signal for enzyme-free immunoassay.

[0044] In some embodiments, a method for fabricating an organic photoelectrochemical transistor sensor for cortisol detection is also provided, such as... Figure 3 As shown, it includes the following steps:

[0045] S10. Prepare a source electrode and a drain electrode on a substrate, and prepare an organic semiconductor thin film on the surface of the source electrode and the drain electrode for later use;

[0046] S20. Provide a gate electrode, prepare a photoelectric active layer on the gate electrode, and drop a first antibody that specifically binds to cortisol in the sample to be tested onto the photoelectric active layer, so that the first antibody binds to the photoelectric active layer.

[0047] S30. Provide a secondary antibody conjugate that specifically binds to cortisol in the sample to be tested, wherein the secondary antibody conjugate is composed of a second antibody and a metal-organic framework material;

[0048] S40. Insert the substrate and the gate electrode with the photoactive layer and the first antibody into an electrolytic cell containing an electrolyte solution to obtain the organic photoelectrochemical transistor sensor for cortisol detection.

[0049] This invention modifies the surface of a gate electrode with a photoactive layer composed of COF material, and then drops a first antibody (Ab1) onto the surface of the photoactive layer. The first antibody can specifically recognize and capture cortisol. Then, a secondary antibody conjugate MOF-Ab2, which is composed of a second antibody (Ab2) and MOF material, is dropped on, thereby modifying the surface of the gate electrode layer by layer to form a sandwich immune structure. The COF material on the gate electrode and the MOF material connected to the specifically recognized second antibody form a composite material, which improves the photoelectric conversion efficiency and thus enhances the photocurrent signal. Different concentrations of cortisol combined with different amounts of MOF material generate different current signals, so cortisol can be detected by the sensor current change.

[0050] The preparation method of the organic photochemical transistor sensor for cortisol detection of the present invention will be described below through specific embodiments:

[0051] 1. Fabrication of source electrode, drain electrode, and organic semiconductor thin film layer of organic photoelectrochemical transistor:

[0052] Cut soda-lime glass was ultrasonically cleaned sequentially with acetone, ethanol, and water. A mask with a pre-designed pattern was then attached to the soda-lime glass. 10 nm chromium (Cr) and 100 nm gold (Au) were deposited onto the soda-lime glass via thermal evaporation to obtain an Au / Cr / glass electrode. A layer of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT:PSS) containing ethylene glycol and diethylenetriamine (DETA) was spin-coated onto this electrode. After spin-coating, the electrode was annealed at 120°C for 20 min. The area outside the Au / Cr electrode was then cleaned, leaving the channel electrode portion, thus obtaining the source and drain electrodes of the organic photoelectrochemical transistor, as well as the organic semiconductor thin film layer located on the surface of the source and drain electrodes.

[0053] 2. Fabrication of TpPa-Cl / ITO gate electrode for organic photoelectrochemical transistors:

[0054] 1 g of trialdehyde phloroglucinol (Tp) powder and 1 g of 2-chloro-1,4-p-phenylenediamine (Pa-Cl) powder were dissolved separately in 550 mL of a mixed solvent containing trimethylolpropene, ethanol, and acetic acid. After mixing the two solutions, 40 μL was immediately drop-coated onto the surface of an ITO electrode and reacted for 20 min. Following the reaction, the electrode was washed with dichloromethane for 5 min. I was measured under illumination. DS -T curve, such as Figure 6 As shown in I1.

[0055] 3. Immobilize the first antibody (Ab1) on the surface of the gate electrode:

[0056] First, the TpPa-Cl / ITO modified gate electrode was immersed in TGA solution for 2 hours, and then immersed in a mixture of 20 mg / mL EDC and 10 mg / mL NHS for 1 hour to activate the carboxyl groups. Next, 30 μL of 0.2 mg / mL Ab1 was added to the gate electrode and incubated at 4°C for 16 hours. The electrode was washed three times each with 10 mM PBS solution (wash buffer) containing 0.05% Tween 20 and ultrapure water to remove unfixed Ab1. Then, the gate electrode was blocked with 40 μL of 3% bovine serum albumin (BSA) (prepared with 10 mM PBS solution) for 2 hours, followed by three washes with wash buffer. I was measured under illumination. DS -T curve, such as Figure 6 As shown in I2.

[0057] 4. The secondary antibody (Ab2) is combined with ZIF-8-MOF material to generate a secondary antibody conjugate:

[0058] 200 μL of 0.5 mg / mL Ab2 was dissolved in 1 mL of 2.5 M dimethylimidazole solution and stirred for 10 min at room temperature. Then, 1 mL of 0.5 M zinc acetate solution was added to the mixture and stirred for 20 min. The mixture was then centrifuged at 4 °C for 15 min (4000 rpm). The precipitate was washed with 1 mL of 10 mM PBS solution and centrifuged again to remove free protein. After purification with ethanol, the protein was finally dispersed in 1 mL of 10 mM PBS solution containing 1 wt% BSA to obtain the bioconjugate ZIF-8-Ab2.

[0059] 5. Forming a sandwich structure of primary antibody-antigen-secondary antibody on the gate electrode:

[0060] 30 μL of cortisol at different concentrations was dropped onto the surface of the gate electrode and incubated at 37 °C for 2 h. Then, uncaptured cortisol was washed away with washing buffer. I was measured under light irradiation. DS -T curve, such as Figure 6 As shown in Figure I3. 30 μL of the secondary antibody conjugate ZIF-8-Ab2 was added to the gate electrode and incubated at 37°C for 2 hours, forming a sandwich structure. Unbound secondary antibody conjugates were washed away with washing buffer, and I was measured under illumination. DS -T curve, such as Figure 6 As shown in I4.

[0061] In some embodiments, a detection method using an organic photoelectrochemical transistor sensor for cortisol detection is also provided, comprising the steps of:

[0062] S100. After a photoactive layer is provided on the gate electrode, the first channel step current generated by the gate electrode under light irradiation is measured.

[0063] S200. After binding the first antibody to the photoactive layer, the second channel step current generated by the gate electrode under light irradiation was measured.

[0064] S300. The sample to be tested is dropped onto the gate electrode, so that the cortisol in the sample to be tested specifically binds to the first antibody, and the third channel step current generated by the gate electrode under light irradiation is measured.

[0065] S400. The prepared secondary antibody conjugate is dropped onto the gate electrode, so that the second antibody in the secondary antibody conjugate specifically binds to the cortisol in the sample to be tested, and the fourth channel step current generated by the gate electrode under light irradiation is measured.

[0066] S500: Calculate the concentration of cortisol in the sample to be tested based on the changes between the first channel step current, the second channel step current, the third channel step current, and the fourth channel step current.

[0067] This embodiment uses a 425nm infrared laser as the excitation source and a soda-lime glass substrate. Source and drain electrodes are fabricated on the substrate using thermal evaporation. Biomolecules are progressively modified onto the gate electrode surface, forming a sandwich immune structure through specific binding. The COF material on the gate electrode and the MOF material linked to the secondary antibody form a composite material, improving photoelectric conversion efficiency and thus enhancing the photocurrent signal. The detection principle is as follows: Figure 2 As shown. In this embodiment, the I of the gate electrode DS The -T curve was measured in 0.01M PBS solution, V G =0V,V DS =0.1V, the gate electrode is modified with the photoactive material TpPa-Cl-COF, a mixed solution of Tp and Pa-Cl is dropped onto the surface of the ITO electrode, and an orange TpPa-Cl-COF film is generated in situ at room temperature. The photocurrent is as follows. Figure 4 As shown. Figure 5 As shown, the organic photoelectrochemical transistor device under illumination conditions I DS The changes in the steps can be analyzed and detected more intuitively on the object under test. For example... Figure 6 As shown, the gate electrode generates a certain channel current I1 under 425nm wavelength light irradiation. When the primary antibody (Ab1) is immobilized on the gate electrode, the channel current step decreases to I2 due to steric hindrance. When cortisol specifically binds to the primary antibody (Ab1), the channel current step further decreases to I3. When the prepared secondary antibody conjugate (MOF-Ab2) specifically binds to the cortisol antigen, the channel current step increases to I4. Different concentrations of cortisol bind to different amounts of MOF material, thus causing different changes in channel current, achieving highly sensitive, rapid, and accurate detection of cortisol. The detection results for different concentrations of cortisol are shown below. Figure 7 As shown, from Figure 7 It can be seen that the detection range of the detection method provided in this embodiment is 1×10⁻⁶. -12 g / mL - 1×10 -6 g / mL, the limit of detection is 1×10⁻⁶ g / mL. -12 g / mL.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An organic photoelectrochemical transistor sensor for cortisol detection, characterized in that, The device includes an electrolytic cell containing an electrolyte solution, a substrate with one end inserted into the electrolyte solution, and a gate electrode. A source electrode and a drain electrode, each with one end inserted into the electrolyte solution and spaced apart, are disposed on the substrate. The surfaces of the source and drain electrodes are coated with an organic semiconductor thin film. A photoactive layer is disposed on the end of the gate electrode inserted into the electrolyte solution, and a first antibody that specifically binds to cortisol in the test sample is disposed on the photoactive layer. The device also includes a spare secondary antibody conjugate that specifically binds to cortisol in the test sample. The secondary antibody conjugate is composed of a second antibody and a metal-organic framework material. The photoactive layer is made of a covalent organic framework material. The covalent organic framework material is one or more of the following: a polymer of trialdehyde phloroglucinol and 2-chloro-1,4-p-phenylenediamine, a polymer of 2,6-dialdehyde-1,5-dihydroxynaphthalene and tris(4-aminophenyl)amine, a polymer of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 2,5-dihydroxyterephthalic acid, and aminotetraphenylporphyrin. The metal-organic framework material is one or more of ZIF-8, Cu-MOF, MIL-101, and NH2-UIO-66.

2. The organic photoelectrochemical transistor sensor for cortisol detection according to claim 1, characterized in that, The material of the organic semiconductor thin film layer is at least one of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid, polypyrrole, polythiophene, polyaniline, polycarbazole and their copolymers.

3. The organic photoelectrochemical transistor sensor for cortisol detection according to claim 1, characterized in that, The gate electrode material is one or more of Ti, Pt, Au, ITO, and FTO.

4. A method for preparing an organic photoelectrochemical transistor sensor for cortisol detection as described in any one of claims 1-3, characterized in that, Including the following steps: A source electrode and a drain electrode are fabricated on a substrate, and an organic semiconductor thin film is fabricated on the surface of the source electrode and the drain electrode for later use; A gate electrode is provided, a photoactive layer is prepared on the gate electrode, and a first antibody that specifically binds to cortisol in the sample to be tested is dropped onto the photoactive layer, so that the first antibody binds to the photoactive layer. A secondary antibody conjugate that specifically binds to cortisol in the sample to be tested is provided for use, the secondary antibody conjugate being composed of a secondary antibody and a metal-organic framework material; The substrate and the gate electrode, which is provided with a photoactive layer and a first antibody, are inserted into an electrolytic cell containing an electrolyte solution to obtain the organic photoelectrochemical transistor sensor for cortisol detection.

5. The method for preparing the organic photoelectrochemical transistor sensor for cortisol detection according to claim 4, characterized in that, When the secondary antibody conjugate is prepared by binding a second antibody to ZIF-8-MOF material, the preparation steps include: The second antibody was dissolved in a dimethylimidazole solution and stirred at room temperature to obtain a mixed solution; Zinc acetate solution was added to the mixture and stirred. The mixture was then centrifuged, followed by washing the precipitate with PBS solution. The precipitate was then collected by centrifugation to remove free protein. After purification with ethanol, the precipitate was dispersed in PBS solution containing 1 wt% BSA to obtain the secondary antibody conjugate ZIF-8-Ab2.

6. A detection method for cortisol using an organic photoelectrochemical transistor sensor as described in any one of claims 1-3, characterized in that, Including the following steps: After a photoactive layer is placed on the gate electrode, the first channel step current generated by the gate electrode under light irradiation is measured. After the first antibody was bound to the photoactive layer, the second channel step current generated by the gate electrode under light irradiation was measured. The sample to be tested is dropped onto the gate electrode, so that the cortisol in the sample to be tested specifically binds to the first antibody. The third channel step current generated by the gate electrode under light irradiation is measured. The prepared secondary antibody conjugate is dropped onto the gate electrode, so that the second antibody in the secondary antibody conjugate specifically binds to the cortisol in the sample to be tested, and the fourth channel step current generated by the gate electrode under light irradiation is measured. The concentration of cortisol in the sample to be tested is calculated based on the changes in the first channel step current, the second channel step current, the third channel step current, and the fourth channel step current.

7. The detection method of the organic photoelectrochemical transistor sensor for cortisol detection according to claim 6, characterized in that, The wavelength of the light irradiation is 425nm.

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