Nanopore membrane with MOFs growing on outer surface and preparation method and application thereof

Abstract

The invention discloses a nanopore membrane with MOFs grown on the outer surface and a preparation method and application of the nanopore membrane. According to the nanopore membrane, PDA is used for adhering a copper nanowire solution, MOFs evenly grow on the outer surface of the nanopore membrane through a hydrothermal method, and surface modification of the nanopore membrane is achieved; the MOFs are controlled to only grow on the outer surface and double-sided modification is performed on the specific probe, so that the risk of internal blockage of a pore channel is avoided, the anti-interference capability is greatly enhanced, double-sided modification is performed, the probe density is increased, more binding sites exist, the response time is shortened, charge or volume disturbance after target molecules are bound is enhanced, and the detection sensitivity is improved. The specificity and the detection stability are greatly improved, and through system comparison, MC-LR and MC-RR can be synchronously detected through change analysis of electric signals.

Description

Technical Field

[0001] This invention belongs to the field of biosensor technology, specifically relating to a nanoporous membrane with MOFs grown on its outer surface, its preparation method, and its application. Background Technology

[0002] Traditional methods for detecting microcystin-LR (MC-LR) include high-performance liquid chromatography (HPLC), indirect competitive enzyme-linked immunosorbent assay (ELISA), and liquid chromatography-tandem mass spectrometry (LC-MS / MS). These methods offer high accuracy and stability, but their ability to simultaneously detect multiple toxins is weak, and they typically require complex pretreatment and experienced personnel. Existing solid-state nanopore sensors cannot precisely modify probes, potentially leading to clogging and weak anti-interference capabilities, especially in complex environmental samples (such as lake water). The structural similarity between MC-LR and other microcystin analogs (such as MC-LA, MC-RR, and MC-YR) can cause cross-reactions, limiting the ability to recognize only MC-LR and not multiple analogs simultaneously. Traditional voltage-driven nanopore sensors rely on steric hindrance changes (such as conformational rearrangements) induced by aptamer-target binding to influence transmembrane ion currents. However, the detectable signals generated by the aptamers after cumbersome structural optimization cannot simultaneously identify target analogs, limiting the method's universality and sensitivity. Therefore, it is of great significance to develop novel nanopore sensing strategies that can simultaneously identify target analogues and achieve high sensitivity and specificity. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of existing technologies by proposing a nanoporous membrane with MOFs grown on its outer surface, its preparation method, and its application. By controlling the growth of MOFs only on the outer surface of the nanoporous membrane and modifying specific probes on both sides, the risk of blockage inside the pores is avoided, greatly enhancing the anti-interference ability. At the same time, the double-sided modification increases the probe density, provides more binding sites, shortens the response time, and enhances the charge or volume perturbation after the target molecule binds, greatly improving specificity and detection stability.

[0004] The primary objective of this invention is to provide a method for preparing a nanoporous membrane with MOFs grown on its outer surface, comprising the following steps: Dopamine hydrochloride is dissolved in a buffer solution to obtain a dopamine hydrochloride solution; Anodized aluminum oxide film was placed in a prepared dopamine hydrochloride solution for self-assembly to obtain a PDA-AAO film. A copper nanowire solution was uniformly dropped onto the outer surface of the PDA-AAO film, and after drying, a Cu-PDA-AAO film was obtained; the concentration of the copper nanowire solution was 4~6 mg / mL, and the thickness of the film formed by the copper nanowire solution was 100~200 nm. Meso-tetra(4-carboxyphenyl)porphyrin was dispersed in DMF solution, and a dried Cu-PDA-AAO membrane was added. The mixture was then subjected to a hydrothermal reaction at 90℃~110℃ for 2h~3h to obtain the nanoporous membrane with MOFs grown on the outer surface.

[0005] Furthermore, the mass concentration of the dopamine hydrochloride solution is 4~6 mg / mL, and the buffer solution is a Tris-HCl solution with pH=8.5~9.0.

[0006] Furthermore, the pore diameter on the anodic aluminum oxide film is 20~30 nm, and the pore density is 6.1 × 10⁻⁶. 9 ~1.4 × 10 10 pcs / cm 2 .

[0007] Furthermore, the concentration of meso-tetra(4-carboxyphenyl)porphyrin dispersed in DMF solution is 1.0~2.0 mmol / L.

[0008] The second objective of this invention is to provide a nanoporous membrane with MOFs grown on its outer surface, prepared by the above-described method.

[0009] A third objective of this invention is to provide the application of the nanoporous membrane with MOFs grown on the outer surface provided by this invention in the preparation of products for qualitative and quantitative detection of target molecules.

[0010] Furthermore, the target molecule includes microcystin-LR. The CAS number of microcystin-LR is 101043-37-2.

[0011] Furthermore, the product includes a detection chip or a detection kit.

[0012] A fourth objective of this invention is to provide a method for detecting microcystin-LR, comprising the following steps: S1. After washing the above nanoporous membrane with DMF and deionized water, dry it for later use. Place the dried nanoporous membrane in PBS buffer containing NHS and EDC, activate it, and then rinse it with PBS buffer. S2. Add a solution of microcystin-LR aptamer to the cleaned nanoporous membrane surface and let it soak for a period of time to successfully graft the microcystin-LR aptamer onto the nanoporous membrane surface. S3. After immersing the grafted nanoporous membrane in the test solution containing microcystin, the transmembrane current of the nanoporous membrane is measured using a picoammeter.

[0013] Furthermore, the nucleotide sequence of the aptamer of the microcystin-LR includes a DNA sequence or an SSW sequence, wherein the DNA sequence is shown in SEQ ID NO:1 and the SSW sequence is shown in SEQ ID NO:2~SEQ ID NO:4.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention provides a nanoporous membrane with MOFs grown on its outer surface, which can be used to detect Microcystis-LR. In order to control the growth of MOFs on the outer surface of the membrane, PDA was used to adhere copper nanowire solution, and then a hydrothermal method was used to make MOFs grow uniformly on the outer surface of the nanoporous membrane, thereby achieving modification of the nanoporous membrane surface; the activation of the membrane by EDC and NHS can enable the carboxyl groups on the MOFs to be linked with amino-modified DNA or SSW, so that DNA or SSW can be regionally modified on the surface of the nanoporous membrane. This achieves the controllability of nanoporous membrane functionalization and the specificity of the nanoporous membrane; because it is grafted with DNA or SSW aptamers, it can be used to detect analytes that bind to DNA or SSW aptamers. By utilizing the change in the binding of DNA to the analyte, the effective pore size of the nanoporous membrane is changed, thereby achieving specific detection of the analyte and amplifying its detection signal.

[0015] (2) By controlling MOFs to grow only on the outer surface and modifying specific probes on both sides, the present invention avoids the risk of blockage inside the pores and greatly enhances the anti-interference ability. At the same time, the double-sided modification increases the probe density, provides more binding sites, shortens the response time, and enhances the charge or volume perturbation after the target molecule binds, which greatly improves the specificity and detection stability. Through system comparison, after adding MC-LR and MC-RR, the surface charge of the first interface changes, so MC-LR and MC-RR can be detected simultaneously by analyzing the change in electrical signal. Attached Figure Description

[0016] Figure 1 SEM images of MOFs prepared under different conditions are shown. In the figure, a is MOFs prepared in Example 2, b is MOFs prepared in Example 3, c is MOFs prepared in Example 4, d is MOFs prepared in Example 1, e is MOFs prepared in Example 5, f is MOFs prepared in Example 6, g is MOFs prepared in Example 5, h is MOFs prepared in Example 3, and i is MOFs prepared in Example 7. Figure 2 The figures are SEM images of the longitudinal cross-sections of nanoporous membranes with MOFs grown on the outer surface prepared under different conditions. In the figures, a is Example 1, b is Example 7, c is Example 8, and d is Example 9. Figure 3This is an XPS diagram from an embodiment of the present invention, where a represents N1s and b represents P2p. Figure 4 Electrochemical signal variation curves of nanoporous membranes with MOFs grown on the outer surface prepared under different conditions; Figure 5 This is a specificity detection diagram of the nanoporous membrane in the comparative example of the present invention after being inoculated with a target of 100 ng / mL; Figure 6 This is a specificity detection diagram of the nanoporous membrane in this embodiment of the invention after incorporation with a target of 100 ng / mL; Figure 7 This is a comparison graph showing the rate of change of current of the nanoporous membrane in the comparative example of the present invention to different concentrations of microcystin-LR and microcystin-RR. Figure 8 This is a comparison graph showing the rate of change of current of the nanoporous membrane in the comparative example of the present invention to different concentrations of microcystin-LR and microcystin-RR. Figure 9 This is a regression linear fit graph of the current change rate of the nanoporous membrane to different concentrations of microcystin-LR and microcystin-RR in the comparative example of this invention. Figure 10 This is a regression linear fitting graph based on the current change rate of the nanoporous membrane for different concentrations of microcystin-LR and microcystin-RR in an embodiment of the present invention. Figure 11 This refers to the surface charge density of the nanoporous membrane surface in the comparative examples and embodiments of the present invention. Figure 12 The zeta potential values ​​of the aptamers, microcystin-RR and microcystin-LR used in the comparative examples and embodiments of this invention were measured in 0.1 M potassium chloride solution. Figure 13 This is a comparison graph showing the changes in electrochemical impedance after the aptamers used in the comparative examples and embodiments of the present invention bind to different concentrations of microcystin-LR. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the specific embodiments and accompanying drawings are described in further detail below. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0018] This invention provides a method for preparing a nanoporous membrane with MOFs grown on its outer surface, comprising the following steps: Dopamine hydrochloride is dissolved in a buffer solution to obtain a dopamine hydrochloride solution; Anodized aluminum oxide film was placed in a prepared dopamine hydrochloride solution for self-assembly to obtain a PDA-AAO film. A copper nanowire solution was uniformly dropped onto the outer surface of the PDA-AAO film, and after drying, a Cu-PDA-AAO film was obtained. Meso-tetra(4-carboxyphenyl)porphyrin was dispersed in DMF solution, and a dried Cu-PDA-AAO membrane was added. The mixture was then subjected to a hydrothermal reaction at 90-110°C for 2-3 hours to obtain the nanoporous membrane with MOFs grown on the outer surface.

[0019] In some embodiments, the mass concentration of the dopamine hydrochloride solution can be 4-6 mg / mL, and the buffer solution can be selected to have good buffering capacity in the pH range of 7.0-9.0, preferably a Tris-HCl solution with a pH of 8.5-9.0; the anodic aluminum oxide film has a pore size between 20-30 nm and is a cylinder with a diameter of 25 mm and a thickness of 60 μm. In some embodiments, the mass concentration of the copper nanowire solution can be 4~6 mg / mL, and 50 μL is added dropwise, resulting in a film thickness of 100~200 nm.

[0020] In some embodiments, the concentration of meso-tetra(4-carboxyphenyl)porphyrin dispersed in DMF solution is 1.0~2.0 mmol / L.

[0021] The embodiments of the present invention have achieved some positive results during the research and development or use process, and have indeed great advantages compared with the prior art. The following content describes them in conjunction with the data, charts and other information of the experimental process.

[0022] The anodic aluminum oxide film used in this invention was purchased from Hefei Puyuan Nanotechnology Co., Ltd.

[0023] Example 1 This embodiment provides a method for preparing a nanoporous membrane with MOFs grown on its outer surface, as detailed below: (1) Take a circular anodic aluminum oxide film (AAO) with a diameter of 25 mm, and the film on the film... The pore diameter is 20–30 nm; the pore density is 6.1 × 10⁻⁶. 9 ~ 1.4 × 10 10 pores / cm² 2 It is a cylinder with a diameter of 25 mm and a thickness of 60 μm. (2) Carefully place the anodic aluminum oxide film into a clean petri dish, and then add an appropriate amount of deionized water to the petri dish so that the anodic aluminum oxide film is completely immersed in the deionized water for more than 5 hours. After that, dry the film and set it aside. (3) Weigh 20 mg of dopamine hydrochloride (PDA) into a centrifuge tube, add Tris-HCl (pH=8.5) to prepare a 4 mg / mL solution, shake well, and add to a dried culture dish to allow it to self-assemble on the membrane. After 24 h, a PDA-AAO membrane is formed. Rinse thoroughly with deionized water and set aside. Use a pipette to take 50 μL of copper nanowire solution (5 mg / mL) and drop it evenly onto the PDA-AAO surface. After it dries, repeat the same process on the other side. After the addition is complete, weigh 15.8 mg of racemic tetra(4-carboxyphenyl) into a centrifuge tube, add a mixture of N,N-dimethylformamide (DMF) and deionized water (V DMF :V water A total of 20 mL of a 3:1 solution was ultrasonically treated at room temperature for 10 minutes to disperse the membrane evenly. The membrane was then placed in the inner liner of a reaction vessel, the prepared solution was added, and the reaction vessel was tightened. The reaction vessel was then placed in a constant temperature oven at 100℃ for 2 h. After the reaction, MOF-modified AAO nanochannels were obtained. The prepared membrane was washed with DMF and deionized water, and then dried in a vacuum oven at room temperature.

[0024] Example 2 The experiment was basically the same as in Example 1, except that the copper nanowire solution was 3 mg / mL and the hydrothermal reaction temperature was 110°C.

[0025] Example 3 It is basically the same as Example 1, except that the hydrothermal reaction temperature is 110°C.

[0026] Example 4 The reaction was basically the same as in Example 1, except that the copper nanowire solution was 7 mg / mL and the hydrothermal reaction temperature was 110°C.

[0027] Example 5 The reaction was basically the same as in Example 1, except that the concentration of the dopamine hydrochloride solution was 2 mg / mL and the hydrothermal reaction temperature was 110°C.

[0028] Example 6 The reaction was basically the same as in Example 1, except that the concentration of the dopamine hydrochloride solution was 6 mg / mL and the hydrothermal reaction temperature was 110°C.

[0029] Example 7 It is basically the same as Example 1, except that the hydrothermal reaction temperature is 90°C.

[0030] Example 8 The reaction was basically the same as in Example 1, except that the copper nanowire solution was 4 mg / mL and the hydrothermal reaction temperature was 90°C.

[0031] Example 9 The experiment was basically the same as in Example 1, except that the copper nanowire solution was 6 mg / mL and the hydrothermal reaction temperature was 110°C.

[0032] The performance of the nanoporous membranes with MOFs grown on their outer surface prepared in Examples 1-9 was characterized, and the specific details are as follows: refer to Figure 1 Figures 1, 2, and 3 show SEM images of MOFs synthesized under different conditions. Figures a, b, and c are SEM images at different copper nanowire concentrations (Examples 2-4). Figures d, e, and f are SEM images at different PDA concentrations (Examples 1, 5-6). When the PDA concentration is low, for example, compared to d, e has a slightly higher PDA concentration, resulting in a thicker PDA layer coated on the anodic aluminum oxide film with higher coverage, better covering surface defects and improving surface smoothness. For f, the PDA concentration is too high; excessively high PDA concentration may form a thicker coating during coating, leading to uneven coating thickness, local accumulation or flow phenomena, and affecting the surface smoothness of the film. Figures g, h, and i are SEM images under the same PDA concentration but different temperature conditions (Examples 1, 3, and 7). As shown in figure g, low temperature usually leads to a slower crystallization rate of MOFs, potentially forming smaller crystals or nanoscale particles with irregular morphology and lower crystallinity. As shown in Figure h, medium temperatures typically result in regular and uniform crystal morphologies with high crystallinity and intact porosity. As shown in Figure i, high temperatures may cause significant changes in the morphology of MOFs, leading to the formation of large-sized crystals, or may cause partial structural collapse or decomposition, resulting in irregular morphologies.

[0033] refer to Figure 2 The diagram shows a cross-sectional view of the MOFs structure on the outer surface of the nanoporous membrane obtained in Examples 1, 7-9. It can be seen that the MOFs are uniformly distributed on the outer surface of the nanoporous membrane. It can also be seen that there are no MOFs inside the pores of the membrane, indicating that the MOFs have been successfully grown on the outer surface of the AAO membrane.

[0034] Example 8 This embodiment provides a method for detecting microcystin-LR.

[0035] The nanoporous membrane with MOFs grown on its outer surface was prepared using Example 1, and the specific steps are as follows: First, the nanoporous membrane was activated for 2 h with a PBS solution containing 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (100 mg / mL) and N-hydroxysulfosuccinimide (50 mg / mL). After activating the carboxyl groups on the surface of MOFs, 100-300 μL of SSW was dropped onto the activated membrane surface. The reaction was carried out on both sides for 12 h, thereby fixing the SSW on the outer surface of the membrane, and finally obtaining the SSW-modified nanoporous membrane.

[0036] Microcystin-LR and microcystin-RR solutions with different concentrations (0.01 nM, 0.1 nM, 1 nM, 10 nM, 100 nM) were detected using nanoporous membranes with pure outer surface MOFs grafted with microcystin-LR aptamers.

[0037] The SSW-modified nanoporous membranes were immersed in solutions of different concentrations for 3–5 h. The transmembrane current of the nanoporous membranes was measured using a picoammeter with the following parameters: mode set to 1–V test, voltage range of -1.1V to 1.1V, number of cycles of 5; KCl solution was used as the electrolyte; Ag / AgCl electrode was used; and an plexiglass mold was used as the electrolytic cell.

[0038] Comparative Example 1 The difference from Example 8 is that DNA can be added to only one side.

[0039] The SSW and DNA sequences are shown in Tables 1 and 2, respectively. The SSW sequence consists of a fixed aptamer, a linker DNA, and a mobile aptamer, as shown in SEQ ID NO:2 to SEQ ID NO:4. The linker DNA sequence has two complementary pairing sequences. From the 5' to 3' 31st "G" boundary, the first segment is complementary to the fixed aptamer, and the second segment is complementary to the mobile aptamer. The SSW sequence is linked to the nanoporous membrane via the 5' modified amino group of the fixed aptamer. The DNA sequence, as shown in SEQ ID NO:1, is linked to the nanoporous membrane via the 5' modified amino group.

[0040] Table 1. SSW sequences

[0041] Table 2. DNA Sequences

[0042] refer to Figure 3 The image shown is the XPS plot of Example 8. It can be seen that, compared to bare AAO nanochannels, MOFs contain element N, which leads to the presence of the N1s peak. After SSW grafting, the intensities of the N1s and O1s peaks significantly increase, indicating an increase in the content of elements N and O. Figure 3 As shown in a. Furthermore, a new characteristic peak appears, indicating the presence of P elements in the SSW@MOF, such as... Figure 3 As shown in b. These XPS results confirm the successful grafting of SSW onto MOFs.

[0043] refer to Figure 4 IV curves of nanoporous films with MOFs grown on the outer surface prepared under different conditions. In the figure, T is the temperature, C is the PDA concentration, and P is the copper nanowire concentration.

[0044] refer to Figure 5 The diagram shows the specificity detection of microcystin-LR in Comparative Example 1 of this invention. It can be found that microcystin-LR and microcystin-RR have the smallest current change rate, and are the least specific compared to other homologues.

[0045] refer to Figure 6 The image shows the specificity detection of microcystin-LR in Example 8 of this invention. It can be found that microcystin-LR and microcystin-RR have the largest current change rate and the highest specificity compared with other homologues.

[0046] refer to Figure 7 The image shows the current signal detection graphs of microcystin-LR and microcystin-RR in Comparative Example 1 of this invention. By comparing the signal change rate, it was found that under low concentrations of microcystin, differential analysis revealed significant differences when detecting high concentrations (greater than 10 nM) of the target molecule, with a P value less than 0.001, indicated by 3 stars. When detecting medium to low concentrations (0.1 nM to 1 nM), the P value was between 0.001 and 0.01, indicated by 2 stars. When detecting a concentration of 0.01 nM, the P value was greater than 0.01, showing essentially no difference.

[0047] refer to Figure 8 The image shows the current signal detection diagrams of microcystin-LR and microcystin-RR in an embodiment of the present invention. By comparing the signal change rate, it was found that at low concentrations of microcystin, differential analysis revealed significant differences in the range of (0.01 nm to 100 nM), with a P-value less than 0.001, indicated by 3 stars. This is mainly because the SSW probe on the nanoporous membrane binds to microcystin-LR and is then peeled off layer by layer, resulting in conformational changes and steric hindrance changes, which amplifies the current signal.

[0048] refer to Figure 9 The figures show linear regression curves for different concentrations of microcystin-LR and microcystin-RR in the comparative examples of this invention. The results show that the signal response to microcystin-LR is the highest, and the signal response to MC-RR is higher than that of the other two homologues.

[0049] refer to Figure 10 Figure 1 shows the linear regression curves of microcystin-LR and microcystin-RR at different concentrations in this embodiment of the invention. The results show that the signal response to microcystin-LR is the highest, and the signal response to MC-RR is the lowest. Therefore, while achieving specific detection of MC-LR, the specific detection of MC-RR is greatly improved.

[0050] refer to Figure 11 , Figure 12 and Figure 13 In the DNA@MOF system, the rate of change of current of DNA+RR is dominated by the surface charge of the first interface (the part between the MOF membrane and the bulk solution), while the steric hindrance remains basically unchanged. For DNA+LR, since MC-LR is negatively charged in 0.1 M KCl and the steric hindrance of the first interface on the outer surface is not significant, the charge effect plays a major role after binding.

[0051] In the SSW@MOF system, similarly, after SSW+RR, the steric hindrance change is not significant, mainly due to the charge effect at the first interface. At the first interface, SSW is a relatively long amplification strand, with a charge and steric hindrance much higher than DNA. Therefore, after SSW binds to the negatively charged MC-LR, both surface charge and steric hindrance change simultaneously. On one hand, the charge decrease caused by SSW dissociation offsets the charge increase from LR binding. Characterization using surface Zeta potential shows that the change in SSW surface charge is less than that of DNA. On the other hand, due to SSW stripping, the steric hindrance changes dramatically. Impedance experiments demonstrate that the sensor resistance decreases significantly when bound to high concentrations of MC-LR. Therefore, the overall steric hindrance effect is greater than the charge effect, making it the dominant factor.

[0052] Example 9 This embodiment provides a spiked recovery test of tap water and lake water using the method provided in Embodiment 8. The results are shown in Table 3.

[0053] Table 3. Spike Recovery Results.

[0054]

[0055] As shown in Table 3, the detection method provided by this invention has good accuracy in detecting actual samples.

[0056] For any points not covered above, existing technologies shall apply.

[0057] Although specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the direction of the invention or exceeding the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a nanoporous membrane with MOFs grown on its outer surface, characterized in that, Includes the following steps: Dopamine hydrochloride is dissolved in a buffer solution to obtain a dopamine hydrochloride solution; Anodized aluminum oxide film was placed in a dopamine hydrochloride solution for self-assembly to obtain a PDA-AAO film; A copper nanowire solution was uniformly dropped onto the outer surface of the PDA-AAO film, and after drying, a Cu-PDA-AAO film was obtained. The concentration of the copper nanowire solution is 4~6 mg / mL, and the thickness of the film formed by the copper nanowire solution is 100~200 nm. Meso-tetra(4-carboxyphenyl)porphyrin was dispersed in DMF solution, and a dried Cu-PDA-AAO membrane was added. The mixture was then subjected to a hydrothermal reaction at 90-110°C for 2-3 hours to obtain the nanoporous membrane with MOFs grown on the outer surface.

2. The preparation method according to claim 1, characterized in that, The mass concentration of the dopamine hydrochloride solution is 4~6 mg / mL, and the buffer solution is a Tris-HCl solution with pH=8.5~9.

0.

3. The preparation method according to claim 2, characterized in that, The pore diameter on the anodic aluminum oxide film is 20~30 nm, and the pore density is 6.1 × 10⁻⁶. 9 ~ 1.4 × 10 10 pcs / cm 2 .

4. The preparation method according to claim 3, characterized in that, The concentration of meso-tetra(4-carboxyphenyl)porphyrin dispersed in DMF solution is 1.0~2.0 mmol / L.

5. A nanoporous membrane with MOFs grown on its outer surface, prepared by the method described in any one of claims 1-4.

6. The application of the nanoporous membrane with MOFs grown on the outer surface as described in claim 5 in the preparation of products for qualitative and quantitative detection of target molecules.

7. The application according to claim 6, characterized in that, The target molecule includes microcystin-LR.

8. The application according to claim 6, characterized in that, The products mentioned include detection chips or detection kits.

9. A method for detecting microcystin-LR, characterized in that, Includes the following steps: S1. The nanoporous membrane described in claim 5 is washed with DMF and deionized water, dried and set aside. The dried nanoporous membrane is placed in PBS buffer containing NHS and EDC, activated, and then rinsed with PBS buffer. S2. Add a solution of microcystin-LR aptamer to the cleaned nanoporous membrane surface and let it soak for a period of time to graft the microcystin-LR aptamer onto the nanoporous membrane surface. S3. After immersing the grafted nanoporous membrane in the test solution containing microcystin, the transmembrane current of the nanoporous membrane is measured using a picoammeter.

10. The method according to claim 9, characterized in that, The nucleotide sequence of the aptamer of the microcystin-LR includes a DNA sequence or an SSW sequence, wherein the DNA sequence is shown in SEQ ID NO:1 and the SSW sequence is shown in SEQ ID NO:2~SEQ ID NO:4.

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