Method for preparing metal organic framework / bismuth vanadate composite material based on electro-deposition method and application of metal organic framework / bismuth vanadate composite material in biomarker detection

Abstract

The invention discloses a method for preparing a metal organic framework / bismuth vanadate composite material based on an electro-deposition method and application of the metal organic framework / bismuth vanadate composite material in detection of biomarkers. According to the composite material, bismuth vanadate prepared by an electrochemical deposition method is used as a substrate, and a porphyrin-based metal organic framework subjected to one-step electrochemical deposition is subjected to surface modification to form a heterojunction. The structure significantly accelerates the separation and migration of photon-generated carriers, and improves the photoelectric properties. The metal organic framework (MOFs) film prepared by utilizing an electrochemical deposition method has large specific surface area, high porosity and excellent structure adjusting capability, and can be used for detecting different biomarkers as a photo / electro-active material. Besides, the photoelectrochemical-electrochemical dual-mode detection is utilized, and a signal is amplified by combining the photo-enzyme action, so that huge potential in the photoelectric and electrochemical sensing aspects is shown, low-concentration biomarkers can be effectively detected, and the method has a good application prospect.

Description

Technical Field

[0001] The present invention relates to a method for preparing a metal-organic framework / bismuth vanadate composite material by electrodeposition and its application in detecting biomarkers, belonging to the technical field of biosensors. Background Art

[0002] Myocardial infarction (MI) is one of the main causes of death and disability globally, and early diagnosis is crucial for improving the prognosis of patients. In recent years, miRNAs (microRNAs) have shown great potential as potential biomarkers in the early detection of myocardial infarction. In particular, the expression of specific miRNAs such as miRNA-133a is significantly increased in patients with myocardial infarction, making its detection an important clinical need. As an emerging detection technology, biosensors have the advantages of high sensitivity, rapid response, simple operation, low cost, good reproducibility and stability. Combining biosensor technology with the characteristics of miRNAs can achieve early diagnosis of myocardial infarction and provide important decision-making support for clinical practice.

[0003] Photoelectrochemical (PEC) and electrochemical (EC) biosensors have become the mainstream methods for miRNA detection in recent years due to their high sensitivity, low background noise and easy operation. To further improve the detection performance, dual-mode biosensors developed in recent years combine the two detection modes of PEC and EC and utilize different signal amplification mechanisms, significantly improving the sensitivity and specificity of detection. This multi-mode sensor design provides new possibilities for improving the reliability of detecting complex biological samples and is considered an important direction for future biosensor research.

[0004] Bismuth vanadate is an important photocatalytic material due to its good photoelectric properties. Its moderate bandgap energy enables it to effectively absorb visible light and generate charge carriers, thus promoting electrochemical reactions. Bismuth vanadate has good stability and compatibility in a biological environment and is suitable for application in biosensors. By compounding with other materials, bismuth vanadate can enhance the signal response of PEC and EC sensors and improve the sensitivity.

[0005] Metal-organic frameworks (MOFs) have a large specific surface area, high porosity and good structural tunability. MOFs can be used as photoactive and electroactive materials to construct PEC and EC biosensors. Porphyrin-based metal-organic frameworks (PMOFs) are widely used in electrochemical biosensors due to their good electrocatalytic activity, porous structure and highly ordered metal-ligand interactions.

[0006] Therefore, if bismuth vanadate is combined with porphyrin-based MOF and the advantages of both are combined, it is expected to improve the detection sensitivity and selectivity for miRNA related to myocardial infarction, providing new ideas for enhancing the performance of biosensors. However, there is currently no report on the preparation of biosensors by combining bismuth vanadate with porphyrin-based MOF

[0007] Currently, the commonly used method for preparing porphyrin-based MOF is mostly the hydrothermal method, which has disadvantages such as a long synthesis time, the need for heating, and complex operations. The electrodeposition method usually has advantages such as simple operation, high time efficiency, no need for heating, and strong tunability. However, there is currently no report on the method for preparing porphyrin-based MOF / bismuth vanadate by the electrodeposition method. Traditional biosensors are usually single-mode detection, with problems such as too high a detection limit and insufficient sensitivity for low-concentration detection. Therefore, there is an urgent need to develop a biosensor with simple preparation, safety, and good detection performance for detecting myocardial infarction-related markers Summary of the Invention

[0008] The purpose of the present invention is to provide a method for preparing a metal-organic framework (MOF) / bismuth vanadate composite material by electrodeposition and its application in detecting biomarker; by the electrodeposition method, the metal-organic framework material is modified on the surface of bismuth vanadate, significantly improving the optoelectronic and electrical properties, accelerating the separation and migration rate of photo-generated carriers, being able to effectively detect lower concentrations of biological information markers, and being able to achieve dual-mode sensing and amplify its detection signal through the photo-nanozyme technology

[0009] To solve the above technical problems, the present invention provides a method for preparing a metal-organic framework / bismuth vanadate composite material based on the electrodeposition method, including the following steps

[0010] Step 1: Prepare a mixed solution of ethanol and N,N-dimethylformamide, and disperse a metal nitrate salt, tetrakis(4-carboxyphenyl)porphyrin, and tetrabutylammonium perchlorate in an organic solvent to obtain a metal-organic framework precursor solution

[0011] Step 2: Deposit bismuth vanadate on a conductive glass to obtain a working electrode modified with bismuth vanadate. Using the metal-organic framework precursor solution prepared in Step 1 as the electrolyte, electrochemical deposition is carried out under a three-electrode system to prepare an electrode with a metal-organic framework / bismuth vanadate composite material deposited on a conductive substrate

[0012] Preferably, the organic solvent in Step 1 is a mixed solvent of ethanol and N,N-dimethylformamide

[0013] and / or; the conductive glass in Step 2 is FTO conductive glass or ITO conductive glass

[0014] Preferably, the metal nitrate salt in step 1 is selected from at least one of copper nitrate, gadolinium nitrate, zinc nitrate and their hydrates;

[0015] And / or, in the three-electrode system of step 2, a platinum electrode is used as the counter electrode, and a silver / silver chloride electrode is used as the reference electrode.

[0016] Preferably, the molar ratio of the metal nitrate salt, tetrakis(4-carboxyphenyl)porphyrin and tetrabutylammonium perchlorate in step 1 is 3-4:1:50-70;

[0017] And / or, the preparation method of the bismuth vanadate modified working electrode in step 2 includes: electrochemically depositing bismuth oxyiodide (BiOI) on the conductive glass to obtain a bismuth oxyiodide electrode, dropping a solution of vanadyl acetylacetonate, then taking out the electrode and calcining it for annealing treatment. Finally, the obtained electrode is washed and dried to obtain the bismuth vanadate modified working electrode.

[0018] Preferably, the electrochemical deposition of bismuth oxyiodide uses a three-electrode system: an FTO electrode is used as the working electrode, a platinum sheet is used as the counter electrode, and a silver / silver chloride electrode is used as the reference electrode; the preparation method of the working electrolyte used is: weighing bismuth nitrate or its hydrate, and potassium iodide are dissolved in deionized water, the pH value is adjusted to acidic, and then an ethanol solution containing p-benzoquinone is added and stirred evenly to obtain.

[0019] Preferably, the washing includes: first washing the excess divanadium oxide on the electrode surface with an alkali solution and then washing with pure water.

[0020] Preferably, the conditions for the annealing treatment are: heating at a heating rate of 1-3 °C min -1 to 400-500 °C for annealing treatment for 1-3 hours.

[0021] The present invention also provides the application of the metal-organic framework / bismuth vanadate composite material prepared by the above method in detecting biomarkers.

[0022] Preferably, the biomarker is a nucleic acid biomarker, including miRNA.

[0023] The present invention also provides a method for detecting biomarkers. This method is based on the metal-organic framework / bismuth vanadate composite material prepared by the method as described above being modified with aldehyde groups and combined with a capture probe modified with amino groups, and different biomarkers are detected by using the specific hybridization binding of the capture probe and the biomarker. Specifically, it includes the following steps:

[0024] S21. Drop the chitosan solution on the surface of the metal-organic framework / bismuth vanadate / FTO electrode, soak it with glutaraldehyde after drying to modify aldehyde groups;

[0025] S22. After rinsing with PBS buffer solution, an aqueous solution of the capture probe is added, and the capture probe is fixed by the binding of aldehyde groups and amino groups, and incubated;

[0026] S23. An albumin bovine solution is added to block the unbound active sites;

[0027] S24. The biomarker with the corresponding concentration is dropped onto the electrode;

[0028] S25. Using PBS as the electrolyte, the photocurrent or electrochemical performance of each step is tested, and the quantitative or qualitative detection of the biomarker is achieved by detecting the change in the current signal intensity before and after hybridization.

[0029] Preferably, in step S25, the photocurrent is tested using a xenon lamp as the light source.

[0030] Preferably, the quantitative detection further includes: fitting the linear fitting curve between the change ratio of the photocurrent signal intensity (ΔI / I 0 ) in the photoelectrochemical mode and different concentrations of the biomarker, or fitting the linear fitting curve between the change ratio of the current signal intensity (ΔI / I 0 ) in the electrochemical mode and different concentrations of the biomarker.

[0031] Preferably, in step S25, the photoelectrochemical signal amplification is achieved through the light-nanozyme amplification technology, that is, using PBS and hydrogen peroxide as the electrolyte, adopting a three-electrode system, testing the photocurrent signal, and achieving the quantitative or qualitative detection of the biomarker by calculating the change ratio of the photocurrent signal intensity (ΔI / I 0 ) before and after hybridization.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] (1) In the present invention, the metal-organic framework material is modified on the surface of bismuth vanadate by the electrochemical deposition method. The composite material prepared by this method has a large specific surface area, high porosity and excellent structural adjustment ability, significantly improving the optoelectronic and electrochemical properties, and can realize the optoelectrochemical and electrochemical dual-mode sensing detection of nucleic acid biomarkers, and the detection sensitivity is significantly improved, solving the problems that traditional biosensors are usually single-mode detection, with too high detection limits and insufficient sensitivity for low-concentration detection;

[0034] (2) The present invention can achieve the detection of different biomarkers by regulating the capture probe molecules; in addition, the use of the light-nanozyme technology can further improve its detection performance. Description of the Drawings

[0035] Figure 1:Scanning electron microscope images of bismuth vanadate and copper-based metal-organic framework / bismuth vanadate composites; (a-b) are the scanning electron microscope images of 1 μm of bismuth vanadate (a) and copper-based metal-organic framework / bismuth vanadate (b), respectively; (c-d) are the scanning electron microscope images of 3 μm of bismuth vanadate (c) and copper-based metal-organic framework / bismuth vanadate (d), respectively.

[0036] Figure 2 :Comparison chart of transient photocurrent density measured for bismuth vanadate and copper-based metal-organic framework / bismuth vanadate composites under chopped light illumination (light on / off cycle: 3 s) and at a potential of 0.1 V (vs. Ag / AgCl).

[0037] Figure 3 :Electrochemical comparison chart of bismuth vanadate and copper-based metal-organic framework / bismuth vanadate composites at a potential of 0 - 0.5 V (vs. Ag / AgCl).

[0038] Figure 4 :Photocurrent response during electrode assembly.

[0039] Figure 5 :DPV current response during electrode assembly.

[0040] Figure 6 :Linear fitting curve of copper-based metal-organic framework / bismuth vanadate composites for detecting different concentrations of miRNA-133a in photoelectrochemical mode; the ordinate ΔI represents the surface photocurrent difference before (I 0 ) and after (I) hybridization of bovine serum albumin / capture probe / glutaraldehyde / chitosan / copper-based metal-organic framework / bismuth vanadate with miRNA-133a.

[0041] Figure 7 :Linear fitting curve of copper-based metal-organic framework / bismuth vanadate composites for detecting different concentrations of miRNA-133a in electrochemical mode; the ordinate ΔI is the DPV current difference before (I 0 ) and after (I) hybridization of bovine serum albumin / capture probe / glutaraldehyde / chitosan / copper-based metal-organic framework / bismuth vanadate with miRNA-133a.

[0042] Figure 8 :Comparison chart of current changes of copper-based metal-organic framework / bismuth vanadate composites after adding different interferents in photoelectrochemical mode; the ordinate ΔI represents the surface photocurrent difference before (I 0 ) and after (I) hybridization of bovine serum albumin / capture probe / glutaraldehyde / chitosan / copper-based metal-organic framework / bismuth vanadate with miRNA-133a.

[0043] Figure 9: The change value of DPV current after adding different interfering substances to the copper-based metal-organic framework / bismuth vanadate composite material in the electrochemical mode; the vertical coordinate ΔI is the difference in DPV current between before (I 0 ) and after (I) hybridization of bovine serum albumin / capture probe / glutaraldehyde / chitosan / copper-based metal-organic framework / bismuth vanadate with miRNA-133a.

[0044] Figure 10 : Comparative plot of transient photocurrent density of bismuth vanadate and copper-based metal-organic framework / bismuth vanadate composite material under chopped light irradiation (light on / off cycle: 3 s) in the presence of hydrogen peroxide and at a potential of 0.1 V (vs. Ag / AgCl).

[0045] Figure 11 : Photocurrent response during the electrode assembly process in the presence of hydrogen peroxide.

[0046] Figure 12 : Linear fitting curve for detecting different concentrations of miRNA-133a in the photoelectrochemical mode of the copper-based metal-organic framework / bismuth vanadate composite material in the presence of hydrogen peroxide; the vertical coordinate ΔI represents the difference in surface photocurrent between before (I 0 ) and after (I) hybridization of bovine serum albumin / capture probe / glutaraldehyde / chitosan / copper porphyrin-based metal-organic framework / bismuth vanadate with miRNA-133a.

[0047] Figure 13 : Comparative plot of photocurrent change after adding different interfering substances to the copper-based metal-organic framework / bismuth vanadate composite material in the photoelectrochemical mode in the presence of hydrogen peroxide; the vertical coordinate ΔI represents the difference in surface photocurrent between before (I 0 ) and after (I) hybridization of bovine serum albumin / capture probe / glutaraldehyde / chitosan / copper porphyrin-based metal-organic framework / bismuth vanadate with miRNA-133a. Detailed implementation manners

[0048] To make the present invention more obvious and understandable, preferred embodiments are described in detail below in conjunction with the accompanying drawings.

[0049] Example 1

[0050] Prepare MOF materials by electrodeposition method, deposit metal-organic framework (MOF) materials on bismuth vanadate to obtain excellent photoelectrochemical performance and electrochemical performance:

[0051] (1) Preparation of bismuth vanadate / FTO electrode: The FTO glass sheet was ultrasonically cleaned for 20 minutes using pure water, acetone and ethanol solutions before electrodeposition, and then dried with nitrogen for subsequent use. Weigh 0.97g of bismuth nitrate pentahydrate and 3.32g of potassium iodide and dissolve them in 50mL of deionized water, stir for 20 minutes, and then adjust the pH value to about 1.7. Then add ethanol solution containing 0.49g of p-benzoquinone and stir for 20 minutes. The constant potential deposition of bismuth iodide is carried out at room temperature using a three-electrode system with FTO as the working electrode, platinum sheet as the counter electrode, and silver / silver chloride as the reference electrode. The deposition was carried out at a potential of -0.1V (vs.Ag / AgCl) and the deposition time was 5min. The prepared bismuth iodide pre-electrode was rinsed with pure water several times to remove the excess plating solution attached to the electrode surface and dried at room temperature. In order to convert bismuth iodide into bismuth vanadate, 100 μL of a dimethyl sulfoxide solution containing 0.4 M vanadium oxide diacetylacetonate was evenly added to the surface of the bismuth iodide electrode, and then the electrode was placed in a muffle furnace and heated at 2 °C min -1 The heating rate was raised to 450°C and then annealed for 2 hours. Finally, the obtained bismuth vanadate electrode was immersed in 1M NaOH solution for 20 minutes to remove the excess vanadium pentoxide on the surface. The bismuth vanadate electrode was rinsed with pure water and dried at room temperature for subsequent experiments.

[0052] (2) Preparation of electrolyte: 10.845 mg of copper nitrate, 11.9 mg of tetrakis(4-carboxyphenyl)porphyrin and 308 mg of tetrabutylammonium perchlorate were weighed and uniformly dispersed in a mixed solution of 10 ml of ethanol and N,N-dimethylformamide by ultrasonication for 10 min to prepare an electrolyte, wherein the volume ratio of ethanol to N,N-dimethylformamide was 7 mL:3 mL.

[0053] (3) Electrodepositing a copper-based metal organic framework using a three-electrode system: using bismuth vanadate / FTO as a working electrode, a platinum sheet as a counter electrode, and silver / silver chloride as a reference electrode, the solution prepared in the above steps as an electrolyte, and depositing at a potential of -0.7 V (vs. Ag / AgCl) for 10 minutes to obtain a copper-based metal organic framework / bismuth vanadate / FTO.

[0054] Bismuth vanadate / FTO

[0055] from Figure 1 ab and Figure 1 cd are 1μm and 3μm scanning electron microscope images of bismuth vanadate and copper-based metal organic framework / bismuth vanadate, respectively. It can be seen that bismuth vanadate presents a typical one-dimensional nanoworm-like, hollow structure. The two-dimensional copper-based metal organic framework is loaded on the surface of bismuth vanadate, presenting a two-dimensional film structure with a relatively thin thickness. The two-dimensional copper-based metal organic framework is evenly distributed on the surface of the bismuth vanadate substrate with good flatness.

[0056] In a three - electrode system, using PBS as the electrolyte, a xenon lamp as the light source, a copper - based metal - organic framework / bismuth vanadate as the working electrode, a platinum sheet as the counter electrode, and a silver / silver chloride as the reference electrode, the potential was set to 0.1 V (vs. Ag / AgCl). The transient photocurrent density was measured under chopped light irradiation (light on / off cycle: 3 s) and at a potential of 0.1 V (vs. Ag / AgCl).

[0057] From Figure 2 it can be seen that the transient photocurrent density of bismuth vanadate measured under chopped light irradiation (light on / off cycle: 3 s) and at a potential of 0.1 V (vs. Ag / AgCl) is about 36 μA cm -2 . The transient photocurrent density of the copper - based metal - organic framework / bismuth vanadate composite measured under chopped light irradiation (light on / off cycle: 3 s) and at a potential of 0.1 V (vs. Ag / AgCl) is about 52 μA cm -2 . The transient photocurrent density of the copper - based metal - organic framework / bismuth vanadate composite is significantly increased compared to that of bismuth vanadate measured under chopped light irradiation (light on / off cycle: 3 s) and at a potential of 0.1 V (vs. Ag / AgCl).

[0058] In a three - electrode system, using PBS as the electrolyte, a copper - based metal - organic framework / bismuth vanadate as the working electrode, a platinum sheet as the counter electrode, and a silver / silver chloride as the reference electrode, the potential was set to 0 - 0.5 V (vs. Ag / AgCl), and its electrochemical performance was tested using differential pulse voltammetry (DPV).

[0059] From Figure 3 it can be seen that the DPV current response of bismuth vanadate is 20 μA cm -2 . The DPV current response of the copper - based metal - organic framework / bismuth vanadate is 50 μA cm -2 . The DPV current response of the copper - based metal - organic framework / bismuth vanadate has a significant improvement compared to the DPV current response of bismuth vanadate.

[0060] Example 2

[0061] Based on the metal - organic framework / bismuth vanadate composite to modify groups and regulate the capture probe molecules, realizing dual - mode detection of different biomarkers by photoelectrochemistry (PEC) and electrochemistry (EC):

[0062] On the basis of the copper - based metal - organic framework / bismuth vanadate / FTO electrode prepared in Example 1, 43 μL of 0.5% chitosan solution was dropped onto the surface of the copper - based metal - organic framework / bismuth vanadate electrode. After drying, it was soaked in 5% glutaraldehyde for 2 hours. After rinsing with PBS buffer, the capture probe (NH 250 μL of a 10 nM aqueous solution of -CAGCUGGUUGAAGGGGACCAAA) was incubated at 4 °C for 6 hours. After another PBS rinse, a 2% bovine serum albumin solution was added. Finally, different concentrations of miRNA-133a were dropped onto the electrode surface. The photocurrent and DPV current were measured using a three-electrode system at each step.

[0063] From Figure 4 and Figure 5 It can be seen that the photocurrent and DPV current decreased at each step during the electrode assembly process, demonstrating the successful assembly of the electrode.

[0064] From Figure 6 It can be seen that as the miRNA concentration gradually increased, the photocurrent signal decreased; after adding the miRNA-133a solution, the photocurrent density decreased. There was an excellent correlation between the miRNA-133a concentration and the photocurrent signal, and the photocurrent signal was linearly correlated with the logarithm (lgCmiRNA) of the miRNA-133a concentration. The linear equation was y = 24.5136 - 7.67687*lgCmiRNA, R 2 was 0.987 (N = 5), Y was ΔI / I 0 , ΔI represented the difference in surface photocurrent before (I 0 ) and after hybridization (I) of bovine serum albumin / capture probe / glutaraldehyde / chitosan / copper-based metal-organic framework / bismuth vanadate with miRNA-133a; the detection limit was 0.052 pM (S / N = 3).

[0065] From Figure 7 It can be seen that as the miRNA concentration gradually increased, the DPV current signal decreased; after adding the miRNA-133a solution, the DPV current density decreased. There was an excellent correlation between the miRNA-133a concentration and the DPV current signal, and the DPV current signal was linearly correlated with the logarithm (lgCmiRNA) of the miRNA-133a concentration. The linear equation was y = 26.77711 - 5.20398*lgCmiRNA, R 2 was 0.976 (N = 5), Y was ΔI / I 0 , ΔI represented the difference in surface DPV current before (I 0 ) and after hybridization (I) of bovine serum albumin / capture probe / glutaraldehyde / chitosan / copper-based metal-organic framework / bismuth vanadate with miRNA-133a; the detection limit was 0.078 pM (S / N = 3).

[0066] From Figure 8 and Figure 9It can be seen that the photocurrent and DPV current change when different concentrations of biomarkers are dropped on the electrode surface, proving that the electrode has excellent selectivity for detecting miRNA-133a.

[0067] Example 3: Implementing a photo-nanozyme amplification technology strategy to improve the sensor detection performance:

[0068] On the basis of the copper-based metal-organic framework / bismuth vanadate / FTO electrode prepared in Example 1, when testing the photocurrent using a three-electrode system, 30 mM hydrogen peroxide was added. 43 μL of 0.5% chitosan solution was dropped onto the surface of the copper-based metal-organic framework / bismuth vanadate electrode, and after drying, it was soaked in 5% glutaraldehyde for 2 hours. After rinsing with PBS buffer, 50 μL of a 10 nM aqueous solution of the capture probe (NH 2 -CAGCUGGUUGAAGGGGACCAAA) was added and incubated at 4 °C for 6 hours. After another PBS rinse, 2% bovine serum albumin solution was added. Finally, different concentrations of miRNA-133a were dropped onto the electrode surface. The photocurrent in each step was measured using a three-electrode system.

[0069] From Figure 10 it can be seen that the transient photocurrent density of bismuth vanadate irradiated by chopped light (light on / off cycle: 3 s) in the presence of hydrogen peroxide and at a potential of 0.1 V (vs. Ag / AgCl) is 32 μA cm -2 , and the transient photocurrent density of the copper-based metal-organic framework / bismuth vanadate composite in the presence of hydrogen peroxide irradiated by chopped light (light on / off cycle: 3 s) and at a potential of 0.1 V (vs. Ag / AgCl) is 80 μA cm -2 , and the photo-nanozyme amplification technology strategy realizes the amplification of the photocurrent.

[0070] From Figure 11 it can be seen that the photocurrent decreases in each step during the electrode assembly process, proving the successful assembly of the electrode.

[0071] From Figure 12 it can be seen that as the miRNA concentration gradually increases, the photocurrent signal decreases; after adding the miRNA-133a solution, the photocurrent density decreases. There is an excellent correlation between the miRNA-133a concentration and the photocurrent signal, and the photocurrent signal is linearly correlated with the logarithm (lgCmiRNA) of the miRNA-133a concentration. The linear equation is y = 68740 - 1260*lgCmiRNA, and R 2 is 0.99 (N = 5). The detection limit is 0.003 fM (S / N = 3).

[0072] From Figure 13It can be seen that the photocurrent changes when biomarkers with different concentrations are dropped on the electrode surface, proving that the electrode combined with the specific capture probe has excellent selectivity for detecting miRNA-133a.

[0073] The above embodiments are only the preferred embodiments of the present invention, and do not limit the present invention in any formal or substantial way. It should be noted that for those of ordinary skill in the art of this technology, without departing from the premise of the present invention, several improvements and supplements can still be made, and these improvements and supplements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a metal organic framework / bismuth vanadate composite material based on electrodeposition, characterized in that: The following steps are involved: Step 1, preparing a mixed solution of ethanol and N,N-dimethylformamide, mixing and dispersing metal nitrate, tetrakis(4-carboxyphenyl)porphyrin and tetrabutylammonium perchlorate in an organic solvent to obtain a metal organic framework precursor solution; Step 2: Using conductive glass as a substrate, prepare a bismuth vanadate-modified working electrode, use the metal organic framework precursor solution prepared in step 1 as an electrolyte, and perform electrochemical deposition in a three-electrode system to prepare an electrode having a metal organic framework / bismuth vanadate composite material deposited on a conductive substrate.

2. The method according to claim 1, characterized in that The organic solvent in step 1 is a mixed solvent of ethanol and N,N-dimethylformamide; And / or; the conductive glass in step 2 is FTO conductive glass or ITO conductive glass.

3. The method according to claim 1, characterized in that The metal nitrate in step 1 is selected from at least one of copper nitrate, gadolinium nitrate, zinc nitrate and hydrates thereof; And / or, the three-electrode system in step 2 uses platinum as the counter electrode and silver / silver chloride as the reference electrode.

4. The method according to claim 1, characterized in that The molar ratio of the metal nitrate, tetrakis(4-carboxyphenyl)porphyrin and tetrabutylammonium perchlorate in step 1 is 3-4:1:50-70; And / or, the preparation method of the bismuth vanadate modified working electrode in step 2 includes: depositing bismuth oxyiodide (BiOI) on conductive glass to obtain a bismuth oxyiodide electrode, dripping a solution of vanadium diacetylacetonate oxide, then taking out the electrode and calcining it for annealing, and finally, washing and drying the obtained electrode to obtain a bismuth vanadate modified working electrode.

5. Use of the metal organic framework / bismuth vanadate composite material prepared by the method according to any one of claims 1 to 4 in detecting biomarkers.

6. The use according to claim 5, characterized in that The biomarkers are nucleic acid markers, including miRNA.

7. A method for detecting a biomarker, characterized in that: The method is based on modifying the aldehyde group of the metal organic framework / bismuth vanadate composite material prepared by the method according to any one of claims 1 to 4, and combining it with an amino-modified capture probe, and using the specific hybridization of the capture probe and the biomarker to detect different biomarkers, specifically comprising the following steps: S21, dropping chitosan solution on the surface of metal organic framework / bismuth vanadate / FTO electrode, and soaking it in glutaraldehyde after drying to modify the aldehyde group; S22, after washing with PBS buffer, adding an aqueous solution of the capture probe, fixing the capture probe through aldehyde and amino groups, and incubating; S23, adding bovine serum albumin solution to block unbound active sites; S24, dropping a biomarker of corresponding concentration onto the electrode; S25. Using PBS as the electrolyte, the photocurrent or electrochemical performance of each step was tested, and the quantitative or qualitative detection of biomarkers was achieved by calculating the change in current signal intensity before and after hybridization.

8. The method according to claim 7, characterized in that The photocurrent is tested in step S25 using a xenon lamp as the light source.

9. The method according to claim 7, characterized in that The quantitative detection also includes: fitting a linear fitting curve between the photocurrent signal intensity change ratio in the photoelectrochemical mode and different concentrations of biomarkers, or fitting a linear fitting curve between the current signal intensity change ratio in the electrochemical mode and different concentrations of biomarkers.

10. The method according to claim 7, characterized in that In step S25, photoelectrochemical signal amplification is achieved by light-nanozyme amplification technology, that is, PBS and hydrogen peroxide are used as electrolytes, a three-electrode system is adopted, the photocurrent signal is tested, and the quantitative or qualitative detection of biomarkers is achieved by calculating the change ratio of the photocurrent signal intensity before and after hybridization.

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