Molecularly imprinted ratio-type working electrode for detecting mitomycin C as well as preparation method and application of molecularly imprinted ratio-type working electrode

Abstract

The invention discloses a molecularly imprinted ratio-type working electrode for detecting mitomycin C as well as a preparation method and application of the molecularly imprinted ratio-type working electrode, and belongs to the technical field of analysis and detection. The invention aims to solve the problem that the content of mitomycin C (MMC) can be simply, conveniently and accurately detected. According to the preparation method, a cerium-nickel bimetal organic framework material is prepared through solvothermal reaction, a cerium-nickel bimetal organic framework / multi-walled carbon nanotube composite material is prepared through ultrasonic reaction, and the cerium-nickel bimetal organic framework / multi-walled carbon nanotube composite material and thionine are used as modification materials of an electrochemical sensing interface. And preparing the molecular imprinting ratio type electrochemical sensor with specific recognition response to the template molecule MMC on the surface of the modified electrode through an electrochemical polymerization method. The method is applied to MMC content detection, and has the advantages of simple operation, low cost, high sensitivity and good selectivity.

Description

Technical Field

[0001] The present invention belongs to the technical field of analysis and detection, and in particular relates to a molecular imprinting ratiometric working electrode for detecting mitomycin C (MMC), a preparation method thereof, and an application thereof. Background Art

[0002] Mitomycin C (MMC), a natural compound derived from Streptomyces, is a chemotherapeutic antitumor antibiotic with promising efficacy against gastric, intestinal, and liver cancers. Currently, methods for determining MMC content primarily include ultraviolet spectrophotometry, high-performance liquid chromatography, and capillary electrophoresis. Although relatively mature, these methods suffer from disadvantages such as expensive instrumentation, long experimental cycles, cumbersome procedures, and a lack of portability. Compared with other detection methods, electrochemical methods have attracted considerable attention due to their simplicity, ease of operation, low material consumption, and high sensitivity. Their primary advantage is direct detection without the need for pre-processing. While electrochemical methods for determining MMC content have been reported, their sensitivity and selectivity remain to be further improved. Therefore, the development of high-precision methods for MMC detection could provide theoretical and technical support for its production and quality control. Summary of the Invention

[0003] In order to enable simple and accurate detection of MMC content, the present invention provides a method for preparing a molecularly imprinted ratiometric working electrode for detecting mitomycin C, which is used as an electrochemical sensor working electrode for high-precision detection of MMC content.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions: This invention uses a cerium-nickel bimetallic organic framework / multi-walled carbon nanotube composite and thionine as electrode modification materials to improve the conductivity and electroactive area of ​​a bare glassy carbon electrode. Thionine also serves as a reference probe for electrochemical detection, enhancing detection accuracy. On the modified electrode surface, o-phenylenediamine (O-PD) is used as a functional monomer for preparing a molecularly imprinted membrane (MIM), creating a molecularly imprinted ratiometric electrochemical sensor that specifically responds to MMC. The electrode prepared by this method exhibits high sensitivity and good selectivity, and the introduction of a reference probe significantly improves test accuracy.

[0005] The present invention uses a solvent thermal reaction to prepare a cerium-nickel bimetallic organic framework material, an ultrasonic reaction to prepare a cerium-nickel bimetallic organic framework / multi-walled carbon nanotube composite material, and the cerium-nickel bimetallic organic framework / multi-walled carbon nanotube composite material and thionine as modification materials for the electrochemical sensing interface. A molecularly imprinted ratiometric electrochemical sensor with a specific recognition response to the template molecule MMC is prepared on the surface of the modified electrode by an electrochemical polymerization method. The present invention introduces a ratiometric detection strategy, using the electrochemical responses of polythionine and potassium ferrocyanide as reference probe signals and detection signals, respectively, and combining molecular imprinting technology to prepare a molecularly imprinted ratiometric electrochemical sensor with a specific recognition response to the MMC molecule. The sensor is then applied to the detection of MMC content, with the advantages of simple operation, low cost, high sensitivity, and good selectivity.

[0006] This invention is based on the rapid detection of MMC sample content. Factors that affect electrochemical performance mainly include the ratio of functional monomers to template molecules and elution conditions. These conditions are optimized to construct a molecularly imprinted ratiometric electrochemical sensor with specific recognition of MMC.

[0007] The object of the present invention is to provide a method for preparing a molecularly imprinted ratiometric working electrode for detecting mitomycin C (MMC), comprising the following steps: Step 1, dispersing a cerium salt and a nickel salt in N,N-dimethylformamide to obtain a solution A, dispersing an organic ligand in anhydrous ethanol to obtain a solution B, mixing solutions A and B, and performing a solvothermal reaction. After the reaction is completed, washing and vacuum drying are performed to obtain a cerium-nickel bimetallic organic framework material; Step 2: Dispersing the cerium-nickel bimetallic organic framework material and multi-walled carbon nanotubes in a solvent, and subjecting the mixture to ultrasonic reaction to obtain a cerium-nickel bimetallic organic framework material / multi-walled carbon nanotube composite material; Step 3: Add a fixing agent to the composite material obtained in step 2, mix well, and then apply it dropwise on a glassy carbon electrode, dry it to form a film, then place the modified glassy carbon electrode in a phosphate buffer solution of thionine, form a film by electrochemical polymerization, and dry it naturally to obtain a modified electrode; Step 4: placing the modified electrode in a phosphate buffer solution of O-PD and MMC, electrochemically polymerizing the modified electrode into a film, drying the film naturally, placing the modified electrode in a sulfuric acid solution for elution, and drying the modified electrode to obtain the working electrode.

[0008] In one embodiment of the present invention, in step 1, the cerium salt is Ce(NO3)3·6H2O.

[0009] In one embodiment of the present invention, in step 1, the nickel salt is Ni(NO3)2·6H2O.

[0010] In one embodiment of the present invention, in step 1, the organic ligand is 1,3,5-benzenetricarboxylic acid.

[0011] In one embodiment of the present invention, in step 1, the molar ratio of the cerium salt, the nickel salt and the organic ligand is 6:4:2.

[0012] In one embodiment of the present invention, in step 1, the solvent thermal reaction is carried out at 120° C. for 12 h.

[0013] In one embodiment of the present invention, in step 1, after solid-liquid separation by centrifugation, the solid is collected, then washed three times with N,N-dimethylformamide, and then washed with anhydrous ethanol until neutral.

[0014] In one embodiment of the present invention, in step 2, the mass ratio of the cerium-nickel bimetallic organic framework material to the multi-walled carbon nanotubes is 1:5.

[0015] In one embodiment of the present invention, in step 3, the fixing agent is a 0.5 wt.% chitosan solution, and the volume ratio of the composite material to the fixing agent is 3:1.

[0016] In one embodiment of the present invention, in step 3, the product is placed in an oven at 50° C. and dried for 8 min-14 min.

[0017] In one embodiment of the present invention, in step 3, the phosphate buffer of thionine is prepared by dissolving thionine in phosphate buffer. In one embodiment of the present invention, in step 3, the concentration of thionine in the phosphate buffer of thionine is 5 mM.

[0018] In one embodiment of the present invention, in step 3, the pH value of the phosphate buffer in the thionine solution is 6.0.

[0019] In one embodiment of the present invention, in step 3, the process parameters of electrochemical polymerization film formation are: scanning potential: -0.4V-0.4V, number of scanning cycles: 20 cycles, scanning rate: 0.04 V·s -1 .

[0020] In one embodiment of the present invention, the phosphate buffer of O-PD and MMC in step 4 is prepared by adding an anhydrous ethanol solution of O-PD and an anhydrous ethanol solution of MMC to the phosphate buffer; the concentration ratio of the anhydrous ethanol solution of O-PD to the anhydrous ethanol solution of MMC is (1-8) : 1, preferably 4:1.

[0021] In one embodiment of the present invention, in step 4, the concentration of MMC in the phosphate buffer of O-PD and MMC is 1 mM.

[0022] In one embodiment of the present invention, in step 4, the concentration of O-PD in the phosphate buffer of O-PD and MMC is 1 mM-8 mM.

[0023] In one embodiment of the present invention, in step 4, the pH value of the phosphate buffer in the phosphate buffer of O-PD and MMC is 7.0.

[0024] In one embodiment of the present invention, in step 4, the process parameters of electrochemical polymerization film formation are: scanning potential: 0V-0.8V, number of scanning cycles: 40 cycles, scanning rate: 0.05 V·s -1 .

[0025] In one embodiment of the present invention, in step 4, the process of eluting the template molecules is to place the electrode in a 0.1 MH2SO4 solution for elution.

[0026] Another object of the present invention is to provide a working electrode prepared by any of the above methods.

[0027] Another object of the present invention is to provide an electrochemical sensor comprising a working electrode prepared by any of the above methods.

[0028] Another object of the present invention is to provide the molecularly imprinted ratiometric working electrode as a working electrode of an electrochemical sensor for electrochemical detection of MMC content; in particular, for electrochemical detection of MMC content in production and environmental samples.

[0029] The present invention also provides a method for electrochemically detecting MMC content, which comprises the following steps: A series of MMC samples with known concentrations were prepared. The above molecularly imprinted ratiometric electrochemical sensor was used as the working electrode. The electrochemical signals of the MMC samples were detected by square wave voltammetry (SWV). At the same time, potassium ferricyanide (I Fe ) and polythiophene (I Thi ) current signal; using the current ratio I Fe / I Thi A linear relationship was established with the corresponding MMC concentration to obtain the MMC detection model.

[0030] In the method of the present invention, the concentration of a series of MMC samples ranges from 0.1 nM to 100 nM.

[0031] In the method of the present invention, the content of MMC is determined by preparing a molecularly imprinted ratiometric electrochemical sensor. In order to evaluate the electrochemical performance of the prepared cerium-nickel bimetallic organic framework / multi-walled carbon nanotube composite, the cyclic voltammetric behavior of a bare glassy carbon electrode, an electrode modified with a cerium-nickel bimetallic organic framework / multi-walled carbon nanotube composite, an electrode modified with thionine and a cerium-nickel bimetallic organic framework / multi-walled carbon nanotube composite, an electrode after electropolymerization of molecularly imprinted polymer, and an imprinted electrode after elution of MMC molecules in potassium ferrocyanide was used to verify the electrochemical performance (see Figure 1 ). The ratio of functional monomer to template molecule was further optimized, and it was found that when the concentration ratio of functional monomer to template molecule was 4:1, the prepared molecularly imprinted ratiometric electrochemical sensor had better detection performance for MMC (see Figure 2 ).

[0032] The molecularly imprinted ratiometric electrochemical sensor prepared by the present invention is based on a cerium-nickel bimetallic organic framework and multi-walled carbon nanotubes, and is used for highly sensitive recognition of MMC. Figure 3 ), and better selectivity (see Figure 4 ). It can be used to detect the content of MMC in production and environmental samples.

[0033] Compared with the prior art, the present invention has the following beneficial effects: The molecularly imprinted ratiometric electrochemical sensor prepared in the present invention is used for the specific identification and analysis of MMC. Traditional detection methods for MMC are long and cumbersome. Therefore, a molecularly imprinted ratiometric electrochemical sensor is developed to provide highly sensitive identification and specific response to MMC in the environment. In the present invention, the materials for the modified electrode are simple to prepare and inexpensive. The proposed detection method is SWV, which can quickly detect the concentration of MMC with high sensitivity (see the attached example). Figure 3 ), the current ratio is linearly related to the logarithm of MMC concentration in the concentration range of 0.1 nM-100 nM, and the detection limit is calculated to be 0.03 nM, which is about 1 times lower than the detection limit of non-ratio electrochemical sensors; and it has good selectivity (see Figure 4 ).

[0034] In order to further understand the features and technical contents of the present invention, please refer to the following detailed description of the present invention and the accompanying drawings. However, the accompanying drawings are provided for reference and illustration only and are not intended to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1Figures of molecular imprinting ratiometric electrochemical sensors with different modified electrodes; among them, A is a bare glassy carbon electrode, B is a cerium-nickel bimetallic organic framework / multi-walled carbon nanotube composite modified electrode, C is a polysulfide pine pThi / cerium-nickel bimetallic organic framework / multi-walled carbon nanotube composite modified electrode, D is the electrode after electropolymerization molecular imprinting membrane, and E is the molecular imprinting electrochemical sensor after elution.

[0036] Figure 2 Comparison of response signals of molecularly imprinted ratiometric electrochemical sensors prepared with different concentration ratios of functional monomers and template molecules. Figure 3 (A) SWV diagram of the molecularly imprinted ratiometric electrochemical sensor of the present invention detecting different concentrations of MMC (the concentrations from a to e are 0.1, 0.5, 5, 10, and 100 nM, respectively). Figure 3 (B) is a linear relationship diagram of the molecular imprinting (MIP) and non-molecular imprinting (NIP) ratio electrochemical sensors constructed in the present invention for MMC detection.

[0037] Figure 4 Comparison of the selectivity performance of molecularly imprinted ratiometric electrochemical sensors for MMC (1 nM): (a) MMC, (b) MMC + oxytetracycline (OTC, 1 nM), (c) MMC + penicillin (PG, 1 nM), (d) MMC + roxithromycin (ROX, 1 nM). DETAILED DESCRIPTION

[0038] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art further understand the present invention and are not intended to limit the present invention in any way. It should be noted that those skilled in the art may make various modifications and improvements without departing from the scope of the present invention. These modifications and improvements are all within the scope of protection of the present invention.

[0039] Example 1: The preparation method of the molecularly imprinted ratiometric working electrode for detecting mitomycin C in this example is prepared according to the following steps: Step 1. Preparation of cerium-nickel bimetallic organic framework material: 0.6 mmol Ce(NO3)3·6H2O and 0.4 mmolNi(NO3)2·6H2O were dispersed in 18 mL N,N-dimethylformamide (DMF) to obtain solution A, and 0.2 mmol 1,3,5-benzenetricarboxylic acid was dispersed in 18 mL anhydrous ethanol to obtain solution B. Then, solutions A and B were mixed and placed in a 100 mL polytetrafluoroethylene high-pressure reactor. The solvent thermal reaction was carried out at a solvent thermal reaction temperature of 120°C for 12 h. After the solvent thermal reaction was completed, the solid was separated by centrifugation and the solid was collected. The collected solid was washed three times with N,N-dimethylformamide (DMF), then washed with anhydrous ethanol until neutral, placed in a vacuum drying oven, and dried at 60°C for 10 h to obtain a cerium-nickel bimetallic organic framework material.

[0040] Step 2. Preparation of cerium-nickel bimetallic organic framework / multi-walled carbon nanotube composite material: 2 mg of the cerium-nickel bimetallic organic framework material obtained in step 1 and 10 mg of multi-walled carbon nanotubes were placed in 10 mL of N,N-dimethylformamide, and ultrasonic reaction was carried out in an ultrasonic cleaner with an operating frequency of 40 kHz and an ultrasonic power of 600 W. The reaction time was 30 min and the reaction temperature was room temperature. After the ultrasonic reaction, a cerium-nickel bimetallic organic framework / multi-walled carbon nanotube composite material was obtained.

[0041] Step 3. Prepare a cerium-nickel bimetallic organic framework / multi-walled carbon nanotube composite modified electrode: Use the cerium-nickel bimetallic organic framework / multi-walled carbon nanotube composite material obtained in step 2 to prepare a modified electrode: Mix the above-mentioned cerium-nickel bimetallic organic framework / multi-walled carbon nanotube composite material with 0.5wt.% chitosan solution (fixative) until it is evenly dispersed. The volume ratio of the cerium-nickel bimetallic organic framework / multi-walled carbon nanotube composite material to the fixative is 3:1. Take 10 μL and drop it on the polished glassy carbon electrode. Place it in an oven at 50°C and dry it for 12 min to obtain the modified electrode.

[0042] Step 4. Preparation of polythionine pThi cerium-nickel bimetallic organic framework / multi-walled carbon nanotube composite modified electrode: The cerium-nickel bimetallic organic framework / multi-walled carbon nanotube composite modified electrode obtained in step 3 is used to prepare a modified electrode: the above-mentioned cerium-nickel bimetallic organic framework / multi-walled carbon nanotube composite modified electrode is placed in a phosphate buffer of thionine (prepared by dissolving thionine in phosphate buffer, the concentration of thionine is 5 mM, and the pH of the phosphate buffer is 6.0), and electrochemical polymerization is performed to form a film. After that, the polymerized electrode is naturally allowed to dry to obtain a modified electrode. The electropolymerization conditions in step 4 are: scanning potential: -0.4 V-0.4 V, number of scanning cycles: 20 cycles, and scanning rate: 0.04 V·s -1 .

[0043] Step 5. Preparation of a molecularly imprinted ratiometric working electrode: The modified electrode obtained in the above step 4 is placed in a phosphate buffer solution of O-PD and MMC (prepared by adding anhydrous ethanol solution of O-PD and MMC to a phosphate buffer solution, the concentration ratio of O-PD to MMC is 1:1, the concentration of MMC is 1 mM, and the pH of the phosphate buffer solution is 7.0), and electrochemical polymerization is performed to form a film. After that, the polymerized electrode is naturally allowed to dry and then placed in a 0.1 M H2SO4 solution for elution to obtain a molecularly imprinted ratiometric working electrode, which is used as a working electrode of an electrochemical sensor for electrochemical detection of MMC content. In step 5, the electropolymerization conditions are: scanning potential: 0 V-0.8 V, number of scanning cycles: 40 cycles, and scanning rate: 0.05 V·s -1 .

[0044] Example 2: This example differs from Example 1 in that, in step 5, the modified electrode obtained in step 4 is placed in a phosphate buffer solution of O-PD and MMC (prepared by adding anhydrous ethanol solution of O-PD and MMC to a phosphate buffer solution, with a concentration ratio of O-PD to MMC of 2:1, an MMC concentration of 1 mM, and a buffer pH of 7.0), and electrochemical polymerization is performed to form a film (electropolymerization conditions: scanning potential: 0 V-0.8 V, number of scanning cycles: 40 cycles, scanning rate: 0.05 V·s -1 ), the polymerized electrode was then allowed to dry naturally and then eluted in a 0.1 M H2SO4 solution to obtain a molecularly imprinted ratiometric working electrode, which was used as an electrochemical sensor working electrode for electrochemical detection of MMC content. The other steps and parameters were the same as in Example 1.

[0045] Example 3: This example differs from Example 1 in that, in step 5, the modified electrode obtained in step 4 is placed in a phosphate buffer solution of O-PD and MMC (prepared by adding anhydrous ethanol solution of O-PD and MMC to a phosphate buffer solution, with a concentration ratio of O-PD to MMC of 4:1, an MMC concentration of 1 mM, and a buffer pH of 7.0), and electrochemical polymerization is performed to form a film (electropolymerization conditions: scanning potential: 0 V-0.8 V, number of scanning cycles: 40 cycles, scanning rate: 0.05 V·s -1 ), the polymerized electrode was then allowed to dry naturally and then eluted in a 0.1 M H2SO4 solution to obtain a molecularly imprinted ratiometric working electrode, which was used as an electrochemical sensor working electrode for electrochemical detection of MMC content. The other steps and parameters were the same as in Example 1.

[0046] Example 4: This example differs from Example 1 in that, in step 5, the modified electrode obtained in step 4 is placed in a phosphate buffer solution of O-PD and MMC (prepared by adding anhydrous ethanol solution of O-PD and MMC to a phosphate buffer solution, with a concentration ratio of O-PD to MMC of 8:1, an MMC concentration of 1 mM, and a buffer pH of 7.0), and electrochemical polymerization is performed to form a film (electropolymerization conditions: scanning potential: 0 V-0.8 V, number of scanning cycles: 40 cycles, scanning rate: 0.05 V·s -1 ), the polymerized electrode was then allowed to dry naturally and then eluted in a 0.1 M H2SO4 solution to obtain a molecularly imprinted ratiometric working electrode, which was used as an electrochemical sensor working electrode for electrochemical detection of MMC content. The other steps and parameters were the same as in Example 1.

[0047] Study on the Detection Performance of Molecularly Imprinted Ratio-type Electrochemical Sensor for MMC The following experiments were conducted to verify the effects of the invention: Test 1: Detection of MMC In a mixture of 2.5 mM K3[Fe(CN)6] and 0.1 M KCl, the molecularly imprinted ratiometric working electrode obtained in Example 3 was used as the working electrode of the electrochemical sensor, the Ag / AgCl electrode was used as the reference electrode, and the platinum wire electrode was used as the auxiliary electrode. The electrochemical signal was detected using SWV technology, and the corresponding current ratio I was measured. Fe / I Thi ; Using the current ratio I Fe / I Thi A linear detection model was constructed with the corresponding MMC concentration, such as Figure 3 As shown in the figure, within the concentration range of 0.1 nM-100 nM, as the MMC concentration increases, the current ratio decreases, and the current ratio is linearly related to the logarithm of the MMC concentration, with a detection limit of 0.03 nM.

[0048] Experiment 2: Investigating the effects of different O-PD and MMC concentration ratios on the constructed molecularly imprinted ratiometric electrochemical sensor Preparation of molecularly imprinted ratiometric electrochemical sensor: The modified electrode obtained in step 4 of Example 1 above was placed in a phosphate buffer containing O-PD and MMC (the concentration ratio of O-PD to MMC was 8:1, the MMC concentration was 1 mM, and the buffer pH was 7.0), and electrochemical polymerization was performed to form a film (electropolymerization conditions: scanning potential: 0 V-0.8 V, number of scanning cycles: 40 cycles, scanning rate: 0.05 V·s-1). The polymerized electrode was then left to dry naturally and then placed in a 0.1 M H2SO4 solution for elution to obtain a molecularly imprinted ratiometric working electrode, which was used as the working electrode of the electrochemical sensor for electrochemical detection of MMC content.

[0049] Molecularly imprinted electrochemical sensors were constructed by using molecularly imprinted ratiometric working electrodes prepared with O-PD and MMC concentration ratios of 1:1, 2:1, 4:1, and 8:1 as working electrodes, Ag / AgCl electrodes as reference electrodes, and platinum wire electrodes as auxiliary electrodes. The molecularly imprinted electrochemical sensors were then placed in a 1 nM MMC solution for adsorption for 8 min. The electrochemical sensors were then removed and the electrochemical response signals were tested.

[0050] Electrochemical testing of sensors made with different O-PD / MMC concentration ratios: Sensors made with different O-PD / MMC concentration ratios were placed in a mixture of 2.5 mM K3[Fe(CN)6] and 0.1 M KCl, and electrochemical signal testing was performed using SWV technology. The results are shown in Figure 2. Figure 2 As shown, when the concentration ratio is 1:1, 2:1, and 8:1, the current ratio I Fe / I Thi The higher the concentration, the poorer the polymerization effect. The obtained molecular imprinting ratio electrochemical sensor cannot be used for subsequent specific content detection. When the concentration ratio is 4:1, the current ratio I Fe / I Thi The lowest, the best aggregation effect, can be constructed to obtain the high-sensitivity detection model shown in Experiment 1.

[0051] Experiment 3: Selectivity evaluation of analytical methods In a mixture of 2.5 mM K3[Fe(CN)6] and 0.1 M KCl, a molecularly imprinted electrochemical sensor was constructed using the molecularly imprinted working electrode in Experiment 2 as the working electrode, the Ag / AgCl electrode as the reference electrode, and the platinum wire electrode as the auxiliary electrode.

[0052] The structural analogs of MMC, oxytetracycline (OTC), penicillin (PEG), and roxithromycin (ROX), were used as interfering substances. The electrochemical response signals of MMC (1 nM) at the same concentration with and without the addition of interfering substances were investigated, and the I P / I A Value(I P Indicates the presence of interfering substances I Fe / I Thi , I A I represents the absence of interfering substances Fe / I Thi ), and the selection performance of the method is evaluated by the current ratio.

[0053] The results are as follows Figure 4 As shown, I P / I A The variation ranged from 97% to 105%, which was relatively small, indicating that the prepared molecularly imprinted ratiometric electrochemical sensor had a high specific recognition function for MMC. The detection method had good selectivity and could achieve specific detection of MMC.

[0054] The above describes the specific embodiments of the present invention. It should be noted that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a molecularly imprinted ratiometric working electrode for detecting mitomycin C, characterized in that: The following steps are involved: Step 1, dispersing a cerium salt and a nickel salt in N,N-dimethylformamide to obtain a solution A, dispersing an organic ligand in anhydrous ethanol to obtain a solution B, mixing solutions A and B, and performing a solvothermal reaction. After the reaction is completed, centrifuging, washing, and vacuum drying are performed to obtain a cerium-nickel bimetallic organic framework material; Step 2: dispersing the cerium-nickel bimetallic organic framework material and the multi-walled carbon nanotubes in a solvent and performing an ultrasonic reaction; Step 3: then add a fixing agent, mix evenly, and apply it dropwise on the glassy carbon electrode. After drying, place it in a phosphate buffer of thionine, electrochemically polymerize it into a film, and dry it naturally to obtain a modified electrode; Step 4: placing the modified electrode in a phosphate buffer solution of O-PD and MMC, electrochemically polymerizing the modified electrode into a film, drying the film naturally, placing the modified electrode in a sulfuric acid solution for elution, and drying the modified electrode to obtain the working electrode.

2. The method according to claim 1, characterized in that The cerium salt is Ce(NO3)3·6H2O; the nickel salt is Ni(NO3)2·6H2O; and the organic ligand is 1,3,5-benzenetricarboxylic acid.

3. The method according to claim 1, characterized in that The molar ratio of cerium salt, nickel salt and organic ligand is 6:4:2; the solvent thermal reaction is carried out at 120°C for 12 h; and the washing is carried out three times with N,N-dimethylformamide and then with anhydrous ethanol until neutral.

4. The method according to claim 1, characterized in that In step 2, the solvent is N,N-dimethylformamide, and the mass ratio of the cerium-nickel bimetallic organic framework material to the multi-walled carbon nanotubes is 1:

5.

5. The method according to claim 1, characterized in that: In step 3, the fixative was a 0.5 wt.% chitosan solution; the concentration of thionine was 5 mM, and the pH value of the phosphate buffer was 6.0; the parameters for electrochemical polymerization film formation were: scanning potential: -0.4 V to 0.4 V, number of scanning cycles: 20 cycles, and scanning rate: 0.04 V·s -1 . .

6. The method according to claim 1, characterized in that In step 4, the concentration of MMC is 1 mM, the concentration of O-PD is 1 mM-8 mM, and the pH value of the phosphate buffer is 7.

0.

7. The method according to claim 1, characterized in that: The process parameters of electrochemical polymerization film formation are: scanning potential: 0 V-0.8 V, number of scanning cycles: 40 cycles, scanning rate: 0.05 V·s -1 ; The concentration of sulfuric acid solution is 0.1 M.

8. A working electrode prepared by the method according to any one of claims 1 to 7.

9. An electrochemical sensor, characterized in that A working electrode prepared by the method according to any one of claims 1 to 7.

10. A working electrode prepared by the method according to any one of claims 1 to 7 for electrochemical detection of MMC content.

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