Screen-printed electrode-based enrofloxacin aptamer sensor and rapid detection method

Abstract

The invention belongs to the technical field of electrochemical detection, and particularly relates to an enrofloxacin aptamer sensor based on a screen-printed electrode and a rapid detection method. The preparation method comprises the following steps: firstly preparing a Fe / Co two-dimensional MOF nanosheet with a lamellar structure by using a room temperature stirring method, then incubating with an enrofloxacin aptamer to prepare a nanosheet / aptamer probe, further incubating with enrofloxacin, mixing with an acetic acid-sodium acetate buffer solution, o-phenylenediamine and H2O2 to form a catalytic reaction system, and by combining with a screen-printed electrode-differential pulse voltammetry, detecting the content of the enrofloxacin. The enrofloxacin concentration of a sample to be detected is rapidly tested by drawing a quantitative analysis standard working curve, and rapid, simple and high-sensitivity detection of enrofloxacin is realized. The method is simple and rapid to operate, does not need expensive reagents, large-scale instruments and professional operators, is high in sensitivity, and can realize on-site, rapid and high-sensitivity quantitative detection of enrofloxacin in aquatic products such as grass-roots fish and shrimps in combination with a portable electrochemical detector.

Description

Technical Field

[0001] The invention belongs to the technical field of electrochemical detection, and in particular relates to an enrofloxacin aptamer sensor based on screen-printed electrodes and a rapid detection method. Background Art

[0002] Enrofloxacin (ENR) is a synthetic quinolone antibacterial drug. It has good bactericidal effects on a variety of Gram-negative bacteria and is inexpensive, making it one of the commonly used antibiotics in aquaculture. However, due to the frequent occurrence of uncontrolled and irrational use of drugs, the problem of enrofloxacin residues in aquatic products has become increasingly prominent in recent years. These contaminated aquatic products enter the human body through the food chain, causing human poisoning, allergies, and even serious consequences such as carcinogenesis, teratogenesis, and mutagenesis, posing a huge threat to human health and environmental hygiene. In view of this, governments of various countries attach great importance to and have established strict limit standards for enrofloxacin residues. The European Commission stipulates that the maximum residue limit of ENR and its active metabolite ciprofloxacin in animal muscle tissue is 100 ppb, while the United States explicitly prohibits its use in aquaculture. At present, the detection methods of quinolone residues mainly include instrumental analysis methods such as high performance liquid chromatography-mass spectrometry, turbulent chromatography-mass spectrometry, and immunoassay methods such as fluorescence and colorimetry. Although these methods can meet the requirements of sensitivity and specificity, they have certain limitations in practical application. For example, chromatography can be used for qualitative and quantitative detection, and the test results are relatively accurate, reliable, sensitive and reproducible, but the instruments and equipment used are expensive, the operation is complicated, professional technicians are required, and it cannot be used for rapid screening of a large number of samples; immunoassay has the advantages of high throughput, high sensitivity and high selectivity, but enrofloxacin has a small molecular weight, many structural analogs, and antibodies are difficult to prepare, the cost is high and the cycle is long, which limits its application. Therefore, there is an urgent need to develop a new, simple, low-cost, high-sensitivity and grassroots-friendly rapid detection technology for enrofloxacin drug residues.

[0003] Nanozymes have similar activities to natural enzymes. Compared with natural enzymes, they have higher stability, more flexible structure and composition design, and adjustable catalytic activity. They have attracted the keen attention of researchers in recent years. Among them, two-dimensional metal organic framework (MOF) nanosheets have huge surface area and ultra-thin lateral dimensions. They can effectively increase the adsorption amount of substrate molecules in the color reaction system, shorten their diffusion distance, and accelerate their catalytic response to substrate molecules. They are very ideal nanozyme materials. At the same time, nanozymes have a sheet structure similar to graphene. Through hydrogen bonding, π-π interaction, electrostatic interaction, etc., they can effectively load single-stranded DNA, aptamers, etc., giving more possibilities for analytical sensing. In addition, electrochemical detection based on screen-printed electrodes is simple to operate, has low technical barriers, and high sensitivity. If it can be combined with the above-mentioned aptamer probe, it is expected to meet the existing grassroots demand for rapid screening of enrofloxacin. Summary of the invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the present invention proposes a method for rapid detection of enrofloxacin based on screen-printed electrodes and aptamer sensors. The method is based on the sealing effect of enrofloxacin aptamers on the active sites of Fe / Co two-dimensional MOF nanosheets, and utilizes the target induction method to make the aptamer fall off the surface of the nanosheet, releasing the catalytic active sites of the nanosheet, thereby making the color development reaction more sufficient. Finally, combined with screen-printed electrode-differential pulse voltammetry, on-site, rapid, simple and highly sensitive detection of enrofloxacin is achieved.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] The present invention provides a method for rapidly detecting enrofloxacin based on a screen-printed electrode and an aptamer sensor, the method comprising the following steps:

[0007] S1. First, dissolve the cobalt salt and the iron salt in N,N-dimethylformamide solvent, then add terephthalic acid, and after fully dissolving, add water, ethanol and triethylamine in sequence under stirring at room temperature, continue stirring for 6-24 hours, and finally wash and resuspend to obtain Fe / Co two-dimensional MOF nanosheets;

[0008] S2, mixing the Fe / Co two-dimensional MOF nanosheet obtained in step S1 with the enrofloxacin aptamer, and obtaining a two-dimensional MOF nanosheet / aptamer probe after incubation;

[0009] S3, mixing the two-dimensional MOF nanosheet / aptamer probe obtained in step S2 with enrofloxacin standard solutions of different concentrations, and obtaining a two-dimensional MOF nanosheet / aptamer / enrofloxacin complex solution after incubation;

[0010] S4, the two-dimensional MOF nanosheet / aptamer / enrofloxacin complex solution obtained in S3 was mixed with acetic acid-sodium acetate buffer, o-phenylenediamine solution, and H2O2 to prepare a catalytic reaction system. After the reaction, the screen-printed electrode was used as the base electrode, and the current signal of the o-phenylenediamine oxidation product in the catalytic reaction system at -0.54V was tested by differential pulse voltammetry, and the quantitative analysis standard working curve was drawn with the logarithm of the enrofloxacin concentration as the horizontal axis and the current change value at -0.54V as the vertical axis;

[0011] S5. Incubate the sample containing enrofloxacin with the two-dimensional MOF nanosheet / aptamer probe obtained in step S2 to prepare a two-dimensional MOF nanosheet / aptamer / enrofloxacin complex solution, and further prepare a catalytic reaction system. After the reaction, detect the change value of the current signal at -0.54 V, and calculate the concentration of enrofloxacin in the sample according to the quantitative analysis standard working curve drawn in step S3.

[0012] The invention firstly adopts a room temperature stirring method to prepare a Fe / Co bimetallic two-dimensional MOF nanosheet with excellent peroxidase activity, and modifies an enrofloxacin aptamer on the surface of the nanosheet by hydrogen bonding, π-π interaction, electrostatic interaction, etc., so as to block the catalytic active sites of the nanosheet; then, the nanosheet is co-incubated with a solution containing different concentrations of enrofloxacin, and the aptamer will fall off from the surface of the nanosheet due to the interaction between enrofloxacin and the aptamer, thereby releasing the catalytic active sites of the nanosheet, so that the catalytic activity is restored; then, the solution is mixed with an acetic acid-sodium acetate buffer solution, an o-phenylenediamine solution, and H2O2 for reaction, and a screen-printed electrode is used as a three-electrode system, and a differential pulse voltammetry method is used to test the current signal of the o-phenylenediamine oxidation product in the above process; finally, the concentration of enrofloxacin in the water product is quickly tested by drawing a quantitative analysis standard working curve. The method for rapid detection of enrofloxacin based on screen-printed electrodes is simple and rapid to operate, does not require expensive reagents, large instruments, and professional operators, has high sensitivity, and can be combined with a portable electrochemical detector to achieve on-site, rapid, and highly sensitive quantitative detection of enrofloxacin in aquatic products such as fish and shrimp at the grassroots level.

[0013] Preferably, in S1, the cobalt salt includes cobalt chloride, cobalt oxalate, cobalt carbonate, cobalt sulfate, cobalt nitrate, and cobalt acetate; and the iron salt includes ferric chloride, ferric sulfate, ferric chloride, and ferric nitrate.

[0014] Preferably, in S1, the usage ratio of the cobalt salt, iron salt, N,N-dimethylformamide, terephthalic acid and triethylamine is 20 mg-1.5 g: 10 mg-0.35 g: 10-50 mL: 0.25-0.65 g: 2-10 mL; the volume ratio of water, ethanol and triethylamine is 5:5:0.5-6.

[0015] Preferably, in S1, the washing solution is acetone and ethanol, the resuspension solvent is water, and the concentration of the Fe / Co two-dimensional MOF nanosheets obtained after resuspension is 0.4-2 mg / mL.

[0016] Preferably, in S2, the enrofloxacin aptamer has a nucleotide sequence as shown in SEQ ID No: 1.

[0017] Preferably, in S2, the concentration of the Fe / Co two-dimensional MOF nanosheets is 0.05-1 mg / mL, the concentration of the enrofloxacin aptamer is 5-50 μM, and the volume ratio of the Fe / Co two-dimensional MOF nanosheets to the enrofloxacin aptamer is 5-20:1-5; the incubation is room temperature shaking incubation, and the incubation time is 5-60 min.

[0018] Preferably, in S3, the concentrations of the enrofloxacin standard solution are 0.1, 1, 10, 100, 10000, 100000, 100000 ppb, respectively, and the volume ratio of the two-dimensional MOF nanosheet / aptamer probe to the enrofloxacin standard solution is 4-8:1-4; the incubation is room temperature shaking incubation, and the incubation time is 5-60 min.

[0019] Preferably, in the catalytic reaction body of S4, the concentration of acetic acid-sodium acetate buffer is 0.05-0.2M, the pH is 2-5, the concentration of o-phenylenediamine solution is 10-300mM, and the concentration of H2O2 is 0.5-2M; the volume ratio of the two-dimensional MOF nanosheet / aptamer / enrofloxacin complex solution, acetic acid-sodium acetate buffer, o-phenylenediamine solution and H2O2 is 5-20:985-940:5-20:5-20.

[0020] Preferably, in S4, the reaction time of the catalytic reaction system is 2-10 min, the potential range of the differential pulse voltammetry scan is 0 to -0.85 V, each concentration is tested 3-5 times, and the average value is taken.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The invention discloses a method for rapidly detecting enrofloxacin based on a screen-printed electrode and an aptamer sensor. The method comprises the following steps: firstly, a Fe / Co two-dimensional MOF nanosheet material with a lamellar structure is prepared by a room temperature stirring method, and then the nanosheet / aptamer probe is prepared by incubating the nanosheet / aptamer probe with an enrofloxacin aptamer. After further incubation with enrofloxacin, the nanosheet / aptamer probe is mixed with an acetic acid-sodium acetate buffer solution, o-phenylenediamine (OPD) and H2O2 to form a catalytic reaction system. The system is combined with a screen-printed electrode-differential pulse voltammetry method, and the enrofloxacin concentration of a sample to be tested is rapidly tested by drawing a quantitative analysis standard working curve, thereby realizing rapid, simple and highly sensitive detection of enrofloxacin. Among them, the Fe / Co two-dimensional bimetallic MOF nanosheets provided by the present invention have a simple synthesis process, mild conditions, can be synthesized in batches (up to g level), and have good stability and strong catalytic activity, ensuring the sensitivity of the reaction and the stability of the detection; at the same time, the aptamer used in the present invention does not require functional group labeling, has low cost, and a simple modification process; in addition, the catalytic reaction in the present invention is carried out in the solution phase, and there is no need to modify the surface of the screen-printed electrode, so the operation is simple and the repeatability is good; finally, the method of the present invention does not need to rely on large instruments and professional operators during use, and the screen-printed electrode is easy to operate, disposable, and has a low technical threshold.

[0023] Therefore, the enrofloxacin aptamer sensor based on screen-printed electrodes and the rapid detection method constructed in the present invention can be used for on-site, rapid and highly sensitive detection of the enrofloxacin content in aquatic products such as fish and shrimp. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 TEM (A) and SEM (B) characterization images of Fe / Co two-dimensional MOF nanosheets;

[0025] Figure 2 This is the XRD characterization diagram of Fe / Co two-dimensional MOF nanosheets;

[0026] Figure 3 SEM characterization of Fe / Co two-dimensional MOF nanosheets prepared in batches;

[0027] Figure 4 Characterization diagram of peroxidase activity of Fe / Co two-dimensional MOF nanosheets;

[0028] Figure 5 Fluorescence characterization diagram to verify that the enrofloxacin aptamer can be modified onto the surface of Fe / Co two-dimensional MOF nanosheets;

[0029] Figure 6 The sensitivity test diagram (A) and standard working curve (B) for detecting enrofloxacin;

[0030] Figure 7 This is a diagram of the selectivity experiment for detecting enrofloxacin. DETAILED DESCRIPTION

[0031] The specific embodiments of the present invention are further described below. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0032] The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used in the following examples are commercially available unless otherwise specified.

[0033] Example 1: Establishment of a method for rapid detection of enrofloxacin based on screen-printed electrodes and aptamer sensors

[0034] 1. Preparation of Fe / Co 2D MOF nanosheets

[0035] First, disperse 0.11g Co(NO3)2 and 0.045g FeCl3 in 50mL N,N-dimethylformamide solvent; then, add 250mg terephthalic acid, and after it is fully dissolved, add 10mL water, 10mL anhydrous ethanol, and 4mL triethylamine in sequence under stirring at room temperature, and continue stirring overnight; finally, wash the product three times with acetone and anhydrous ethanol by centrifugation (5000rpm, 10min), and then resuspend the resulting product in 50mL deionized water at a concentration of 0.6mg / mL, and store it in a refrigerator at 4℃ for later use.

[0036] The Fe / Co two-dimensional MOF nanosheets synthesized above were subjected to TEM and SEM tests, such as Figure 1 As shown in Figure 2, the obtained MOF material is a lamellar structure with wrinkles in some parts. Further XRD characterization ( Figure 2 ) shows that the material presents typical crystal diffraction peaks and is a typical crystalline material.

[0037] 2. Batch preparation of Fe / Co two-dimensional MOF nanosheets

[0038] First, 1.31g Co(NO3)2 and 0.305g FeCl3 were dispersed in 50mL N,N-dimethylformamide solvent; then, 625mg terephthalic acid was added and fully dissolved, and then 10mL water, 10mL anhydrous ethanol, and 5mL triethylamine were added in sequence under stirring at room temperature, and stirring was continued overnight; finally, the product was washed three times with acetone and anhydrous ethanol by centrifugation (5000rpm, 10min), and then the obtained product was vacuum dried at 45℃ overnight. The obtained product was about 0.5g. Further SEM characterization ( Figure 3) shows that the material is still in a flake structure at this time.

[0039] 3. Characterization of peroxidase mimetic activity of Fe / Co 2D MOF nanosheets

[0040] First, 170 μL of acetic acid-sodium acetate buffer (pH = 4), 10 μL of Fe / Co two-dimensional MOF nanosheets (0.6 mg / mL), 10 μL of TMB solution (10 mM) and 10 μL of H2O2 solution (0.1 M) were mixed at room temperature to form a catalytic reaction system. After reacting for 5 minutes, the change in the absorbance value of the TMB oxidation product at the 652 nm absorption peak in the reaction system was tested by a UV-visible absorption spectrophotometer. Figure 4 As shown in Figure A, only when the nanosheets, TMB and H2O2 coexist, the absorbance of the system at 652nm is the maximum, indicating that the nanosheets have peroxidase mimetic activity. In addition, the catalytic performance of the nanosheets on two other common substrates, o-phenylenediamine (OPD) and 2-azino-bis(3-ethyl-benzothiazole-6-sulfonic acid) diammonium salt (ABTS), was also explored. Figure 4 As shown in Figure B, when nanosheets and H2O2 are present, OPD and ABTS are also efficiently catalyzed and oxidized, showing corresponding characteristic absorption peaks, which once again verifies the peroxidase-mimicking activity of the nanosheets.

[0041] 4. Electrochemical detection of enrofloxacin

[0042] (1) Preparation of 2D MOF nanosheets / aptamer probes

[0043] Add 50 μL of enrofloxacin aptamer (1 μM) to 1 mL of 2D MOF nanosheet (diluted 2 times) solution and gently shake at room temperature for 15 min. The sequence of the enrofloxacin aptamer is 5'-CCCATCAGG GGG CTAGGC TAACAC GGTTCG GCT CTC TGAGCC CGG GTTATT TCAGGG GGA-3' (SEQ ID No: 1).

[0044] In order to verify whether the aptamer can be modified onto the surface of the two-dimensional MOF nanosheet material in this process, the following fluorescence experiment was carried out: the unlabeled aptamer was replaced with the fluorescein (FAM)-labeled enrofloxacin aptamer, incubated with the two-dimensional MOF nanosheet for 15 minutes at room temperature, and then the mixture was tested for fluorescence. Figure 5 It can be seen that under 520nm light excitation, the incubated mixture showed an emission peak at 525nm similar to that of the FAM-labeled aptamer, indicating that the aptamer has been successfully modified to the surface of the nanosheet.

[0045] (2) Interaction between two-dimensional MOF nanosheets / aptamer probes and enrofloxacin

[0046] 60 μL of two-dimensional MOF nanosheet / aptamer probe was mixed with 15 μL of enrofloxacin standard solution of different concentrations (0, 10, 100, 1000, 10000, 100000 ppb) at room temperature and gently shaken for 30 min. The resulting complex acted as a nanomaterial for subsequent catalytic reactions.

[0047] (3) Electrochemical test

[0048] 10 μL of the solution obtained in step (2), 10 μL of o-phenylenediamine (OPD, 200 mM) and 10 μL of H2O2 (1 M) were added to an electrochemical analysis cell containing 970 μL of acetic acid-sodium acetate buffer (0.2 M, pH 4.0) in sequence, mixed and reacted at room temperature for 5 min, then inserted into a commercial screen-printed electrode (Changsha Sanjun Electronic Technology Co., Ltd., Carbon D-SPE301 type; the working electrode and counter electrode are carbon electrodes, and the reference electrode is a silver / silver chloride electrode), and connected to the electrochemical workstation. Differential pulse voltammetry was used for detection, with a potential scan range of 0 to -0.85 V, and each sample was tested 3-5 times. The results are shown in Figure 2. Figure 6 As shown in Figure A, when there is no enrofloxacin in the system, the two-dimensional MOF nanosheets catalyze the oxidation of OPD, and there is an obvious reduction peak at -0.54V; when different concentrations of enrofloxacin standard solutions are added, some catalytic active sites are released due to the interaction between enrofloxacin and the aptamer loaded on the surface of the nanosheets, and the peak current of the OPD oxidation product in the catalytic reaction system gradually increases with the increase of enrofloxacin concentration, indicating that this scheme can be used for the electrochemical detection of enrofloxacin.

[0049] Finally, the logarithm of enrofloxacin concentration was used as the horizontal axis (x), and the change of peak current at -0.54 V was used as the vertical axis (y). Figure 6 B shows the standard working curve. The curve equation is y = 0.1285x + 0.2576, R 2 The linear range of enrofloxacin detection was 0.1ppb-1ppm, and the detection limit was 0.052ppb.

[0050] (4) Selective experiment

[0051] Five common interferences were selected to conduct the following selectivity experiments: the final concentrations of streptomycin, tetracycline, kanamycin, and gentamicin were 1 ppm, and the final concentrations of ciprofloxacin and enrofloxacin were 100 ppb. Figure 7 It can be seen that only when enrofloxacin exists, the catalytic system has obvious current changes. It can be inferred that the method constructed by the present invention has specific selectivity for enrofloxacin and has good feasibility in actual sample detection.

[0052] Example 2: Application of the method for rapid detection of enrofloxacin based on screen-printed electrodes and aptamer sensors

[0053] Carp and shrimp samples were purchased from a local supermarket and refrigerated at 4°C for later use. The samples were pretreated as follows: 4.0 g of each sample was accurately weighed and placed in a 50 mL beaker, 20 mL of acetonitrile containing 50% hydrochloric acid was added to mix evenly, and medium speed homogenization was performed for 5 min. After the supernatant was filtered through a 0.45 μm organic filter membrane, the obtained filtrate was used as the matrix solution, and the simulated sample solutions with final concentrations of 50, 200 and 800 ppb were prepared by adding enrofloxacin standard solution, and enrofloxacin was detected according to the method of Example 1. By measuring the peak current change value of the OPD oxidation product at -0.54 V in the system before and after the sample was added, and then according to the working curve obtained in Example 1, the concentration and recovery rate of enrofloxacin in the simulated sample were calculated, and the specific test results are shown in Table 1.

[0054] As can be seen from Table 1, the recoveries of the three groups of crucian carp and three groups of shrimp simulation samples were all between 80% and 95%, and the RSDs were all less than 5%. This result shows that the method of the present invention has a good effect in actual sample detection and has good accuracy.

[0055] Table 1 Test results of enrofloxacin simulation samples

[0056]

[0057] In summary, the present invention uses the blocking effect of enrofloxacin aptamer on the catalytic active sites of Fe / Co two-dimensional MOF nanosheets, utilizes the target induction method to make the aptamer fall off the surface of the nanosheet to restore the active sites of the nanosheet, and combines the excellent peroxidase activity of the nanosheet and the simplicity and sensitivity of screen-printed electrode-differential pulse voltammetry to construct a simple, rapid, economical and highly sensitive electrochemical detection scheme for enrofloxacin, providing strong scientific and technological support for the on-site and rapid detection of enrofloxacin in aquatic products at the grassroots level.

[0058] The embodiments of the present invention are described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments are made without departing from the principles and spirit of the present invention, and still fall within the protection scope of the present invention.

Claims

1. A method for rapid detection of enrofloxacin based on screen-printed electrodes and aptamer sensors, characterized in that: The following steps are involved: S1. First, dissolve the cobalt salt and the iron salt in N,N-dimethylformamide solvent, then add terephthalic acid, and after fully dissolving, add water, ethanol and triethylamine in sequence under stirring at room temperature, continue stirring for 6-24 hours, and finally wash and resuspend to obtain Fe / Co two-dimensional MOF nanosheets; S2, mixing the Fe / Co two-dimensional MOF nanosheet obtained in step S1 with the enrofloxacin aptamer, and obtaining a two-dimensional MOF nanosheet / aptamer probe after incubation; S3, mixing the two-dimensional MOF nanosheet / aptamer probe obtained in step S2 with enrofloxacin standard solutions of different concentrations, and obtaining a two-dimensional MOF nanosheet / aptamer / enrofloxacin complex solution after incubation; S4, the two-dimensional MOF nanosheet / aptamer / enrofloxacin complex solution obtained in S3 was mixed with acetic acid-sodium acetate buffer, o-phenylenediamine solution, and H2O2 to prepare a catalytic reaction system. After the reaction, the screen-printed electrode was used as the base electrode, and the current signal of the o-phenylenediamine oxidation product in the catalytic reaction system at -0.54V was tested by differential pulse voltammetry, and the quantitative analysis standard working curve was drawn with the logarithm of the enrofloxacin concentration as the horizontal axis and the current change value at -0.54V as the vertical axis; S5. Incubate the sample containing enrofloxacin with the two-dimensional MOF nanosheet / aptamer probe obtained in step S2 to prepare a two-dimensional MOF nanosheet / aptamer / enrofloxacin complex solution, and further prepare a catalytic reaction system. After the reaction, detect the change value of the current signal at -0.54 V, and calculate the concentration of enrofloxacin in the sample according to the quantitative analysis standard working curve drawn in step S3.

2. The method for rapid detection of enrofloxacin based on screen-printed electrodes and aptamer sensors according to claim 1, characterized in that: In S1, the cobalt salt includes cobalt chloride, cobalt oxalate, cobalt carbonate, cobalt sulfate, cobalt nitrate, and cobalt acetate; the iron salt includes ferric chloride, ferric sulfate, ferric chloride, and ferric nitrate.

3. The method for rapid detection of enrofloxacin based on screen-printed electrodes and aptamer sensors according to claim 1, characterized in that: In S1, the dosage ratio of the cobalt salt, iron salt, N,N-dimethylformamide, terephthalic acid and triethylamine is 20mg-1.5g:10mg-0.35g:10-50mL:0.25-0.65g:2-10mL; the volume ratio of water, ethanol and triethylamine is 5:5:0.5-6.

4. The method for rapid detection of enrofloxacin based on screen-printed electrodes and aptamer sensors according to claim 1, characterized in that: In S1, the washing solution is acetone and ethanol, the resuspension solvent is water, and the concentration of the Fe / Co two-dimensional MOF nanosheets obtained after resuspension is 0.4-2 mg / mL.

5. The method for rapid detection of enrofloxacin based on screen-printed electrodes and aptamer sensors according to claim 1, characterized in that: In S2, the enrofloxacin aptamer has a nucleotide sequence as shown in SEQ ID No:

1.

6. The method for rapid detection of enrofloxacin based on screen-printed electrodes and aptamer sensors according to claim 1, characterized in that: In S2, the concentration of Fe / Co two-dimensional MOF nanosheets is 0.05-1 mg / mL, the concentration of enrofloxacin aptamer is 5-50 μM, and the volume ratio of Fe / Co two-dimensional MOF nanosheets to enrofloxacin aptamer is 5-20:1-5; the incubation is room temperature shaking incubation, and the incubation time is 5-60 min.

7. The method for rapid detection of enrofloxacin based on screen-printed electrodes and aptamer sensors according to claim 1, characterized in that: In S3, the concentrations of the enrofloxacin standard solution are 0.1, 1, 10, 100, 1000, 10000, 100000, and 1000000 ppb, respectively, and the volume ratio of the two-dimensional MOF nanosheet / aptamer probe to the enrofloxacin standard solution is 4-8:1-4; the incubation is room temperature shaking incubation, and the incubation time is 5-60 min.

8. The method for rapid detection of enrofloxacin based on screen-printed electrodes and aptamer sensors according to claim 1, characterized in that: In the catalytic reaction body of S4, the concentration of acetic acid-sodium acetate buffer is 0.05-0.2M, the pH is 2-5, the concentration of o-phenylenediamine solution is 10-300mM, and the concentration of H2O2 is 0.5-2M; the volume ratio of the two-dimensional MOF nanosheet / aptamer / enrofloxacin complex solution, acetic acid-sodium acetate buffer, o-phenylenediamine solution and H2O2 is 5-20:985-940:5-20:5-20.

9. The method for rapid detection of enrofloxacin based on screen-printed electrodes and aptamer sensors according to claim 1, characterized in that: In S4, the reaction time of the catalytic reaction system is 2-10 min, the potential range of the differential pulse voltammetry scan is 0 to -0.85 V, each concentration is tested 3-5 times, and the average value is taken.

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