Fluorescent aptamer sensor for detecting microcystin based on Zn TCPP@MOF film and its preparation method and application

Abstract

The present invention provides a fluorescent aptamer sensor for detecting microcystin based on Zn TCPP@MOF film, a preparation method and an application thereof. The operation process comprises: (1) preparing a metal organic framework (Zn TCPP@MOF) film functionalized with zinc tetraphenylporphyrin; (2) preparing a fluorescent aptamer sensor; and (3) detecting microcystin by fluorescence spectroscopy. Zn TCPP acts as a probe and also acts as a structure-directing agent to adjust the internal structure of the metal organic framework. The detection range of the method is 1.0×10 ‑12 mol / L~1.0×10 ‑ 5 mol / L, the minimum detection limit is 3.8×10 ‑13 mol / L. The fluorescent sensor based on the electrodeposition technology of the present invention is simple to operate and low in cost, and has the advantages of high sensitivity and strong specificity in the application of detecting microcystin.

Description

Technical Field

[0001] The invention relates to a fluorescent aptamer sensor for detecting microcystin based on a ZnTCPP@MOF film, and a preparation method and application thereof. Background Art

[0002] Microcystin (MC) is a natural toxin produced by harmful algae. It is a type of cyclic heptapeptide hepatotoxin with strong carcinogenicity. It is an important environmental factor that induces liver cancer, gastroenteritis and other diseases. MCs mainly enter the body through drinking contaminated water, eating crops and vegetables irrigated with contaminated water, fertilized with cyanobacteria mud, and food chain transmission, posing a potential threat to their life safety. Among them, microcystin LR (MC-LR) is a type of cyanobacterial toxin in freshwater that is extremely harmful to human health. MC-LR shows extraordinary vitality. Studies have shown that MC-LR can still retain some activity even at a high temperature of 300°C. The World Health Organization stipulates that the content of MC-LR in water bodies cannot exceed 1ug / L. Therefore, in the case of biological and environmental systems, selective detection of microcystins is crucial.

[0003] Currently, the methods reported for detecting MC-LR include high performance liquid chromatography, enzyme-linked immunosorbent assay, biological probes, liquid chromatography-mass spectrometry, etc. However, most of these technologies rely on large-scale equipment and instruments, which are complex to operate, costly, and have low detection sensitivity. Therefore, developing a rapid, sensitive, and simple method for detecting MC-LR is of great significance for human health and environmental monitoring. Fluorescence spectroscopy has attracted widespread attention due to its advantages such as high sensitivity, strong reaction controllability, and simple instrumentation. Aptamers are artificially screened single-stranded DNA or RNA sequences with good chemical stability and specificity, and have been widely used in the construction of biosensors. Fluorescent aptamer sensors combine the advantages of both. They can bind specifically and have high sensitivity, and have been increasingly used in the field of biochemistry.

[0004] Metal organic frameworks (MOFs), as a new type of porous crystalline material, have attracted much attention due to their unique properties, such as their well-defined crystal structure, a large number of adjustable micropores, large surface area and multifunctionality. Currently, MOFs materials have become one of the most promising applications in electrochemical sensors. However, these synthetic MOFs usually require complex steps such as alkaline deprotonation, high temperature or high pressure. At present, the electrochemical detection of functionalized MOFs alone is difficult to improve further, and they all need to be compounded with other substances to further improve the detection performance of MOFs materials. How to use only functionalized MOFs as electrode materials with excellent electrochemical detection effects requires further exploration.

[0005] Recently, there have been reports of using porphyrin or metalloporphyrin as an organic ligand to form porphyrin MOF as a sensor by electrodeposition, but a large part of them are concentrated on microporous MOF (pore size <2nm). Limited diffusion and slow mass transfer as well as low surface area and low guest molecule loading are the challenges in electrochemistry. The defects of microporous systems are the main problems. Using porphyrin as a structure-directing agent to prepare mesoporous functionalized MOFs films is a new, simple and eco-friendly method for preparing functionalized MOFs films.

[0006] The present invention provides a new strategy for in-situ preparation of tetraphenylporphyrin zinc functionalized metal organic framework (ZnTCPP@MOF) thin film by one-step electrochemical assisted deposition technology. In this method, water is used as a green solvent, Zn TCPP is used as a fluorescent signal probe and structure directing agent, H3BTC is used as an organic ligand, and Zn(NO3)2·6H2O is used as a cation source. The Zn TCPP@MOF thin film is synthesized on the FTO surface by a one-step electrochemical driven synergistic reaction method and an in-situ electrochemical synthesis method. This Zn TCPP@MOF thin film has a large number of Zn TCPP molecules encapsulated in the cavity of the framework, so it exhibits excellent fluorescence response performance as a sensing platform. Due to the specific binding of the aptamer to microcystin, the fluorescence of the modified electrode is quenched, and the fluorescence intensity has a linear relationship with the concentration of the microcystin. The present invention not only has the advantages of high sensitivity, strong specificity, wide linear range and simple instrumentation of fluorescence analysis, but also has important practical significance for the detection of microcystin in fish pond water. Summary of the invention

[0007] The present invention provides a fluorescent aptamer sensor based on Zn TCPP@MOF film, and a preparation method and application thereof. Through an electrochemically driven synergistic reaction, a Zn TCPP@MOF film is electrochemically synthesized in situ on FTO. The positively charged ZnTCPP and the negatively charged organic ligand attract each other through electrostatic action, resulting in the formation of an intermediate phase structure on the electrode surface, which provides faster electron transfer kinetics and a larger specific surface area, is more suitable for sensing, and the specific binding of the aptamer to the target detection object greatly improves the selectivity of the target detection object. The preparation method provided by the present invention has the advantages of simple process, short time and low preparation cost. The preparation size can be flexibly adjusted by adjusting the deposition time, deposition voltage, etc., does not require special equipment and conditions, has a low preparation cost, can achieve rapid detection of microcystin content, and has high practical value.

[0008] The preparation method of the fluorescent aptamer sensor based on the Zn TCPP@MOF film comprises the following steps:

[0009] (1) Preparation of Zn TCPP@MOF thin film:

[0010] Weigh Zn(NO3)2·6H2O (cation source) and NaNO3 (supporting electrolyte) and dissolve them in deionized water as solution A. At the same time, weigh H3BTC and Zn TCPP and dissolve them in ethanol as solution B. Solutions A and B are ultrasonicated and stirred respectively, and then solution B is added to solution A under vigorous stirring to form a mixed solution. The pH of the solution is adjusted to 2.1 with HCl and stirred to form a uniform plating solution.

[0011] Using a three-electrode system, the conductive substrate FTO (1×1cm 2 ) as the working electrode, and a platinum sheet electrode (1× 1cm 2 ) as the auxiliary electrode and calomel electrode (SCE) as the reference electrode were placed in the above plating solution, and a constant voltage of -1.0V to -1.6V was applied for 1800s to 4200s. The working electrode was taken out and immediately rinsed with water and ethanol, and soaked in distilled water overnight to obtain a Zn TCPP@MOF thin film on a conductive substrate, namely, a Zn TCPP@MOF / FTO electrode.

[0012] Changes in deposition time and deposition voltage will affect the morphology of the formed ZnTCPP@MOF film, and thus affect the fluorescence properties of the film. If the deposition time is too short or the deposition voltage is too low, the organic ligands produced are too few to react with Zn 2+ If the deposition time is too long or the deposition voltage is too high, the film thickness will be too thick, which will hinder the electron transfer. If the voltage is too high, the ZnTCPP@MOF film will be too thick, which will also cause the Zn 2+ The deposition of zinc on the electrode surface will affect the fluorescence performance of the film, which will affect the detection sensitivity of the sensor. The applied voltage after further optimization is -1.3V and the deposition time is 3600s.

[0013] (2) Preparation of fluorescent aptamer sensor for detecting microcystin based on ZnTCPP@MOF film:

[0014] The Tris-HCl solution containing aptamer is drop-coated on the ZnTCPP@MOF / FTO electrode prepared in step (1) to obtain an apt / ZnTCPP@MOF / FTO electrode as a fluorescent aptamer sensor.

[0015] Furthermore, in the mixed solution in step (1), the mass ratio of Zn(NO3)2·6H2O:NaNO3:H3BTC:Zn TCPP is 1.33:0.127:0.525:0.0005-0.0035; the further preferred mass ratio is 1.33:0.127:0.525:0.001, and the volume ratio of water:ethanol is 1:1.

[0016] Furthermore, in step (2), the amount of the Tris-HCl solution containing aptamer is 20.0 μL, the concentration is 1 to 3 μmol / L, and the reaction time is 4 to 5 h.

[0017] Further, the nucleotide sequence of the microcystin aptamer is as follows:

[0018] Adaptor: 5'-GGC GCC AAA CAG GAC CAC CAT GAC AAT TAC CCATAC CAC CTC ATTATG CCC CAT CTC CGC-3'.

[0019] Further, the specific detection method is as follows:

[0020] Step 1: Prepare a series of microcystin standard solutions with different concentrations, ranging from 1.0×10 -12 mol / L~1.0×10 -5 mol / L;

[0021] Step 2, using the fluorescent aptamer sensor as a fluorescence test sample, soaking it in a series of standard solutions containing different concentrations of microcystin prepared in step 1 for a certain period of time, and performing fluorescence measurement to obtain a series of concentration-fluorescence intensity correspondences, establish a linear relationship between the fluorescence intensity before and after adding microcystin and the logarithm of the microcystin concentration, and obtain a corresponding linear regression equation;

[0022] Step 3, sample testing, after filtering and removing impurities from the sample, adjust the pH to 7.5, test according to the above step 2 and obtain the fluorescence intensity, and calculate the obtained fluorescence intensity using the linear regression equation obtained in step 2 to obtain the concentration of microcystin in the sample.

[0023] Preferably, the immersion time of the fluorescent aptamer sensor in step 2 is 40 minutes, the excitation wavelength is set to 310 nm, and the excitation and emission slits are set to 5 nm.

[0024] The significant advantage of the present invention is that a fluorescent aptamer sensor for detecting microcystin by electro-depositing Zn TCPP@MOF film has been developed. Compared with ordinary fluorescent sensors, the present invention has the following three significant advantages: the Zn TCPP@MOF film is a mesoporous three-dimensional structure with a vertical electrode and a good crystallinity framework, so that more ZnTCPP is encapsulated in the polyhedral MOF, promoting the generation of fluorescence intensity; the introduction of electrochemical assisted deposition technology makes the sensor have high conductivity and good chemical stability; since the prepared functionalized MOF is a three-dimensional mesoporous structure with more cavities and loading, it can fully react with apt, thereby achieving a better effect of detecting MC-LR, resulting in greater quenching of the fluorescence signal and a wider detection range. The addition of the aptamer of the present invention enables the sensor to specifically detect microcystin and has a higher sensitivity, and the minimum detection limit is 3.8×10 -13 mol / L. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a brief flow chart of the preparation of the sensor in the invention and the detection of microcystin.

[0026] Figure 2 It is the fluorescence emission spectra of different concentrations of microcystin.

[0027] The concentration of microcystin from bottom to top according to the peak value of the curve is: 1.0×10 5 mol / L(a), 1.0×10 -6 mol / L(b), 1.0×10 -7 mol / L(c), 1.0×10 -8 mol / L(d), 1.0×10 -9 mol / L(e), 1.0×10 -10 mol / L(f), 1.0×10 -11 mol / L(g), and 1.0×10 -12 mol / L(h).

[0028] Figure 3 It is the standard curve of the difference in fluorescence intensity before and after adding microcystin and the logarithm of the microcystin concentration.

[0029] Figure 4 This is a scanning electron microscope image of the ZnTCPP@MOF film.

[0030] Figure 5 is the FL performance influence diagram of ZnTCPP@MOF film;

[0031] (A) shows the effect of changing the deposition voltage on the FL performance of ZnTCPP@MOF film. (B) shows the effect of changing the deposition time on the FL performance of ZnTCPP@MOF film. (C) shows the effect of changing the amount of ZnTCPP added on the FL performance of ZnTCPP@MOF film.

[0032] Figure 6 is the FL intensity diagram of different modified electrodes;

[0033] The excitation wavelength is 314 nm (the excitation wavelength is set to 310 nm), and the slit width is 5 nm. DETAILED DESCRIPTION

[0034] The present invention is further described in detail below in conjunction with embodiments:

[0035] Embodiment 1:

[0036] (1) Preparation of ZnTCPP functionalized MOF (ZnTCPP@MOF) thin films:

[0037] First, 1.33 g of zinc nitrate hexahydrate as a cation source and 0.127 g of sodium nitrate as a supporting electrolyte were dissolved in 15 mL of deionized water and recorded as solution A. At the same time, 0.525 g of 1,3,5-benzenetricarboxylic acid (H3BTC) and 1 mg of ZnTCPP were weighed and dissolved in 15 mL of ethanol and recorded as solution B. Solutions A and B were ultrasonicated for 10 min and stirred for 15 min, respectively, and then solution B was added to solution A under vigorous stirring to form a mixed solution, and the solution pH was adjusted to 2.1 with HCl, and stirred for 2.5 h to form a uniform plating solution.

[0038] Using a three-electrode system, the conductive substrate FTO (1×1cm 2 ) as the working electrode, and a platinum sheet electrode (1× 1cm 2 ) as the auxiliary electrode, and a calomel electrode (SCE) as the reference electrode were placed in the above plating solution, and a constant voltage of -1.3V was applied for 1h, and the stirring rate was 400rpm for deposition. After the deposition was completed, the working electrode was quickly taken out of the solution and immediately rinsed with distilled water and ethanol, and soaked in distilled water overnight to obtain a ZnTCPP@MOF film on a conductive substrate, namely a ZnTCPP@MOF / FTO electrode.

[0039] (2) Preparation of fluorescent aptamer sensor for detecting microcystin based on ZnTCPP@MOF film:

[0040] 20 μL of Tris-HCl solution (2 μM) containing aptamer was drop-coated on the ZnTCPP@MOF / FTO electrode prepared in the above step (1) to obtain an apt / ZnTCPP@MOF / FTO electrode, namely the fluorescent aptamer sensor.

[0041] (3) Drawing of standard curve

[0042] Prepare a series of microcystin standard solutions with different concentrations (1.0×10 -12 mol / L、1.0×10 -11 mol / L、1.0×10 -10 mol / L、1.0×10 -9 mol / L、1.0×10 -8 mol / L、1.0×10 -7 mol / L、1.0×10 -6 mol / L and 1.0×10 -5 mol / L); the apt / ZnTCPP@MOF / FTO fluorescent aptamer sensor was used as a fluorescence test sample and immersed in a series of standard solutions containing different concentrations of microcystin prepared above for 40 min. The excitation wavelength was set to 310 nm, and the excitation and emission slits were set to 5 nm. Fluorescence measurement was performed to obtain a series of concentration-fluorescence intensity correspondences, and a linear relationship between the fluorescence intensity before and after the addition of microcystin and the logarithmic value of the microcystin concentration was established to obtain the corresponding linear regression equation; which is: △I FL =61186.55445+4609.5029LogC(mol / L), the correlation coefficient (R) is 0.99444. The detection range of the linear regression equation is 1.0×10 -12 ~1.0×10 -5 mol / L, the minimum detection limit is 3.8×10 -13 mol / L.

[0043] (4) Sample testing

[0044] A certain amount of fish pond water after filtration and impurity removal was taken for fluorescence detection. The concentration of microcystin in the sample to be detected was calculated according to the linear regression equation corresponding to the above step (3). The results are listed in Table 1.

[0045] Comparative Example 1

[0046] (1) Preparation of apt / Zn-MOF thin film modified electrodes

[0047] 1.33 g of zinc nitrate hexahydrate as a cation source and 0.127 g of sodium nitrate as a supporting electrolyte were dissolved in 15 mL of deionized water and recorded as solution A. At the same time, 0.525 g of 1,3,5-benzenetricarboxylic acid (H3BTC) was weighed and dissolved in 15 mL of ethanol and recorded as solution B. Solutions A and B were ultrasonicated for 10 min and stirred for 15 min, respectively, and then solution B was added to solution A under vigorous stirring to form a mixed solution, and the solution pH was adjusted to 2.1 with HCl, and stirred for 2.5 h to form a uniform plating solution.

[0048] The conductive substrate (FTO) was placed in the above plating solution as the working electrode, and the platinum sheet electrode (1×1 cm 2 ) as the auxiliary electrode, calomel electrode (SCE) as the reference electrode, a constant voltage of -1.3V was applied for 1h, and the stirring rate was 400rpm for deposition. After the deposition was completed, the working electrode was quickly taken out of the solution and immediately rinsed with distilled water and ethanol, and immediately soaked in distilled water overnight. The electrodeposited film was aged at room temperature overnight to obtain a Zn-MOF film modified electrode (Zn-MOF / FTO)

[0049] 20 μL of Tris-HCl solution (2 μM) containing aptamer was drop-coated on the Zn-MOF / FTO electrode prepared in step (1) to obtain an apt / Zn-MOF / FTO electrode, which was used as a sample for subsequent fluorescence testing.

[0050] (2) Drawing of standard curve

[0051] The apt / Zn-MOF / FTO was placed in a series of microcystin standard solutions with different concentrations (1.0 × 10 - 12 mol / L、1.0×10 -11 mol / L、1.0×10 -10 mol / L、1.0×10 -9 mol / L、1.0×10 -8 mol / L、 1.0×10 - 7 mol / L、1.0×10 -6 mol / L and 1.0×10 -5 mol / L) for 40 min, set the excitation wavelength to 310 nm, and the excitation and emission slits to 5 nm, and perform fluorescence measurement to obtain a series of concentration-fluorescence intensity correspondences, establish a linear relationship between the fluorescence intensity before and after the addition of microcystin and the logarithmic value of the microcystin concentration, and obtain the corresponding linear regression equation.

[0052] (3) Sample testing

[0053] A certain amount of fish pond water after filtration and impurity removal was taken for fluorescence detection, and the concentration of microcystin in the sample to be detected was calculated according to the linear regression equation corresponding to the above step (2). The results are listed in Table 1. Comparative Example 2:

[0054] (1) Preparation of Apt / Zn TCPP-MOF / FTO modified electrodes

[0055] 1.33 g of zinc nitrate hexahydrate as a cation source and 0.127 g of sodium nitrate as a supporting electrolyte were dissolved in 15 mL of deionized water as solution A. At the same time, 0.525 g of Zn TCPP was dissolved in 15 mL of ethanol as solution B. Solutions A and B were ultrasonicated for 10 min and stirred for 15 min, respectively, and then solution B was added to solution A under vigorous stirring to form a mixed solution. The pH of the solution was adjusted to 2.1 with HCl and stirred for 2.5 h to form a uniform plating solution.

[0056] The conductive substrate (FTO) was placed in the above plating solution as the working electrode, and the platinum sheet electrode (1×1 cm 2 ) as the auxiliary electrode, calomel electrode (SCE) as the reference electrode, a constant voltage of -1.3V was applied for 1h, and the stirring rate was 400rpm for deposition. After the deposition, the working electrode was quickly taken out of the solution and immediately rinsed with distilled water and ethanol, and immediately soaked in distilled water overnight. The electrodeposited film was aged at room temperature overnight to obtain a ZnTCPP-MOF film modified electrode (ZnTCPP-MOF / FTO)

[0057] 20 μL of Tris-HCl solution (2 μM) containing aptamer was drop-coated on the Zn TCPP-MOF / FTO electrode prepared in step (1) to obtain an apt / Zn TCPP-MOF / FTO electrode as a subsequent fluorescence test sample.

[0058] (2) Drawing of standard curve

[0059] The apt / Zn TCPP-MOF / FTO electrode was placed in a series of microcystin standard solutions with different concentrations (1.0×10 -12 mol / L、1.0×10 -11 mol / L、1.0×10 -10 mol / L、1.0×10 -9 mol / L、1.0×10 -8 mol / L、1.0×10 -7 mol / L、1.0×10 -6 mol / L and 1.0×10 -5mol / L) for 40 min, set the excitation wavelength to 310 nm, and the excitation and emission slits to 5 nm, and perform fluorescence measurement to obtain a series of concentration-fluorescence intensity correspondences, establish a linear relationship between the fluorescence intensity before and after the addition of microcystin and the logarithmic value of the microcystin concentration, and obtain the corresponding linear regression equation.

[0060] (3) Sample testing

[0061] A certain amount of fish pond water after filtration and impurity removal was taken for fluorescence detection. The concentration of microcystin in the sample to be detected was calculated according to the linear regression equation corresponding to the above step (2). The results are listed in Table 1.

[0062] Table 1 Determination results of microcystins in fish pond water

[0063]

[0064] Note: a is the average of three measurements.

[0065] As shown in Table 1, the samples were tested three times in parallel, the relative standard deviation was less than 5%, and the spike recovery ranged from 96% to 104%. The above results show that it is impossible to detect microcystins using apt / Zn-MOF / FTO or apt / ZnTCPP-MOF / FTO electrodes alone without using apt / Zn TCPP@MOF / FTO electrodes, and the present invention is feasible for detecting microcystins in fish pond water.

[0066] from Figure 4 It can be seen that the ZnTCPP@MOF film is a mesoporous three-dimensional structure that grows vertically to the electrode and emits in all directions.

[0067] from Figure 5 It can be seen that when the deposition voltage is -1.3 V, the deposition time is 3600 s, and the ZnTCPP addition amount is 1 mg, the ZnTCPP@MOF film has the best FL performance and the best detection sensitivity.

[0068] Figure 6It is the FL intensity diagram of different modified electrodes, where curve c is the FL intensity of Zn TCPP-MOF, where ZnTCPP-MOF is prepared by depositing MOF with ZnTCPP as an organic ligand. Curve d is the Zn TCPP@MOF prepared by the present invention using Zn TCPP as a structure directing agent and H3BTC as an organic ligand. It can be seen that the fluorescence performance of ZnTCPP-MOF (curve c) is not as good as that of ZnTCPP@MOF (curve d) prepared by using ZnTCPP as a structure directing agent without changing the organic ligand. It can also be seen that MC-LR has a good quenching effect on apt / Zn TCPP@MOF film (curve f).

[0069] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A fluorescent aptamer sensor for detecting microcystin based on Zn TCPP@MOF film, characterized in that: First, a Zn TCPP@MOF film was synthesized on the surface of a conductive substrate, and then the aptamer was modified on the Zn TCPP@MOF modified electrode to obtain the apt / ZnTCPP@MOF modified electrode, which was used as a fluorescent aptamer sensor for detecting microcystin. The preparation method of the fluorescent aptamer sensor is as follows: (1) Preparation of Zn TCPP@MOF thin film: Weigh zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and sodium nitrate (NaNO3) and dissolve them in deionized water as solution A; weigh 1,3,5-benzenetricarboxylic acid (H3BTC) and zinc tetraphenylporphyrin (Zn TCPP) and dissolve them in ethanol as solution B; sonicate and stir solutions A and B respectively, then add solution B to solution A under vigorous stirring to form a mixed solution, adjust the solution pH with HCl, and stir to form a uniform plating solution; The conductive substrate was placed in the above-mentioned plating solution, and a three-electrode system was used to apply a constant voltage of -1.0 V to -1.6 V for 1800 s to 4200 s. The working electrode was taken out and rinsed with water and ethanol, and soaked in distilled water overnight to obtain a Zn TCPP@MOF film on the conductive substrate, which was a Zn TCPP@MOF-modified electrode. (2) Preparation of fluorescent aptamer sensor for detecting microcystin based on Zn TCPP@MOF film: A Tris-HCl solution containing a microcystin aptamer is drop-coated on the Zn TCPP@MOF modified electrode prepared in step (1) to obtain an apt / Zn TCPP@MOF modified electrode, which is the fluorescent aptamer sensor; the microcystin aptamer nucleotide sequence is as follows: 5'-GGC GCC AAA CAG GAC CAC CAT GAC AAT TAC CCA TAC CAC CTC ATT ATG CCCCAT CTC CGC-3'.

2. The fluorescent aptamer sensor based on Zn TCPP@MOF film according to claim 1, characterized in that: The mass ratio of Zn(NO3)2·6H2O:NaNO3:H3BTC:Zn TCPP in the mixed solution in step (1) is 1.33:0.127:0.525:0.0005-0.0035, and the volume ratio of water:ethanol is 1:

1.

3. The fluorescent aptamer sensor based on Zn TCPP@MOF film according to claim 1, characterized in that: In step (1), the conductive substrate is FTO, and the three-electrode system is: the FTO electrode modified with apt / Zn TCPP@MOF is the working electrode, the platinum sheet electrode is the auxiliary electrode, and the calomel electrode is the reference electrode.

4. Use of the fluorescent aptasensor according to any one of claims 1 to 3 in detecting microcystin, characterized in that: The specific detection methods are as follows: Step 1: Prepare a series of microcystin standard solutions with different concentrations, ranging from 1.0×10 -12 mol / L ~1.0×10 -5 mol / L; Step 2, using the fluorescent aptamer sensor as a fluorescence test sample, soaking it in a series of standard solutions containing different concentrations of microcystin prepared in step 1 for a certain period of time, and performing fluorescence measurement to obtain a series of concentration-fluorescence intensity correspondences, establish a linear relationship between the fluorescence intensity before and after adding microcystin and the logarithm of the microcystin concentration, and obtain a corresponding linear regression equation; Step 3, sample testing, after filtering and removing impurities from the sample, adjust the pH to 7.5, test according to the above step (2) and obtain the fluorescence intensity, and calculate the obtained fluorescence intensity using the linear regression equation obtained in step 2 to obtain the concentration of microcystin in the sample.

5. The use according to claim 4, characterized in that: The immersion time of the fluorescent aptamer sensor in step (2) is 40 min, the excitation wavelength set during fluorescence measurement is 310 nm, and the excitation and emission slits are 5 nm.

6. The use according to claim 4, characterized in that: In step (2), a constant voltage of -1.3 V was applied and the deposition time was 3600 s.

Images