Preparation method of molecularly imprinted paper-based microfluidic chip based on metal-organic framework

Abstract

The present invention discloses a method for preparing a molecularly imprinted paper-based microfluidic chip based on a metal-organic framework, which comprises the following steps: constructing a zeolite imidazole framework (ZIF-8) on a filter paper surface by a seed polymerization method and a secondary growth method; performing silanization and amination modification on the paper base in step S1; performing silicon coating and amination treatment on the paper base material in step S1; surface imprinting construction; and assembling a paper-based microfluidic colorimetric sensor. The present invention uses the above-mentioned preparation method as an enrichment and color development platform to establish a rapid colorimetric detection test strip that can be used for kanamycin in milk, thereby achieving rapid detection and analysis of kanamycin by integrating selective enrichment and color development, with simple operation and high sensitivity. At the same time, multiple characterization methods are used to explore its physical and chemical structure. The high porosity, high specific surface area and adjustable pore size of the metal-organic framework are used as advantages, and combined with molecular imprinting technology, not only the defects of the raw materials are overcome, but also its selectivity is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of food detection and analysis, and in particular to a method for preparing a molecularly imprinted paper-based microfluidic chip based on a metal organic framework. Background Art

[0002] The rapid detection of veterinary drug residues in animal-derived foods has always been an important topic. Among them, aminoglycoside antibiotics (AGs) are cis-dihydroxy compounds with stable chemical properties, broad-spectrum antibacterial properties and strong antibacterial ability. Because they contain amino groups, they are alkaline and have a static bactericidal effect. They have a good inhibitory and killing effect on Staphylococcus aureus, aerobic Gram-negative bacilli and Mycobacterium tuberculosis. However, AGs have serious side effects, including nephrotoxicity, ototoxicity, neuromuscular blockade, hematopoietic system toxicity and allergic reactions. Although its application in human clinical treatment has been reduced, it is frequently used in animal husbandry because of its low price and good effect. It is very easy to remain in dairy products, endangering human health, especially the greatest threat to the health of infants and young children. Therefore, many countries or regions strictly control the residues of kanamycin in dairy products. Currently, the main analytical methods for detecting AGs residues include liquid chromatography, electrochemical analysis, and immunoassays. While these methods can accurately detect kanamycin residues in dairy products, they are complex and require expensive and sophisticated instruments and specialized operators, limiting their application in the field of rapid, on-site kanamycin detection. Therefore, the development of a paper-based microfluidic chip for rapid, visual detection of antibiotics is crucial for ensuring consumer health.

[0003] Metal-organic frameworks (MOFs) have garnered significant attention in catalysis, separation, and biochemical sensing due to their high porosity, high surface area, tunable pore size, and customizability. However, MOFs bind to their targets through interactions between ligands and unsaturated metal sites, such as π-π conjugation, electrostatic adsorption, hydrogen bonding, or van der Waals forces. This results in MOFs' weak selectivity and susceptibility to interference from structurally similar compounds, limiting their application in sensing and analysis. In recent years, researchers have combined MOFs with other functional nanomaterials, such as surface molecularly imprinted polymers (MIPs). The resulting nanocomposites not only retain the advantages of MOFs and MIPs, overcome the limitations of the raw materials, but also further enhance their selectivity.

[0004] Boron affinity molecular imprinting technology, first proposed by Liu Zhen's research group at Nanjing University, utilizes the ability of boronic acid groups to bind to cis-dihydroxy target analytes under alkaline conditions, forming a five- or six-membered alicyclic ring. However, under acidic conditions, the cyclic ester formed between the boronic acid and the cis-dihydroxy compound is disrupted, allowing the cis-dihydroxy target compound to be released. This allows for a reversible reaction between the boronic acid group and the cis-dihydroxy compound. Combining this unique binding mechanism with surface molecular imprinting technology enables dual-specific adsorption, significantly improving selectivity. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing a molecularly imprinted paper-based microfluidic chip based on a metal-organic framework, using it as an enrichment and color development platform to establish a rapid colorimetric detection test strip that can be used for kanamycin in milk. This achieves rapid detection and analysis of kanamycin by integrating selective enrichment and color development, overcoming the problems of cumbersome operation and low sensitivity of traditional detection methods. In addition, multiple characterization methods are used to explore its physical and chemical structure and systematically examine its adsorption capacity and specific recognition performance.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] The preparation method of molecularly imprinted paper-based microfluidic chip based on metal organic framework is as follows:

[0008] S1, filter paper modification, using seed polymerization and secondary growth methods to construct ZIF-8 on the paper surface;

[0009] S2, siliconizing and amino treating the paper-based material;

[0010] S3, preparing boron affinity molecularly imprinted polymer, weighing a certain amount of 4-carboxyphenylboronic acid and dissolving it in an appropriate amount of methanol, ultrasonically mixing, then adding carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS), respectively, mixing thoroughly, and shaking the mixture at room temperature for 4 h to obtain a mixed solution A;

[0011] S4, surface imprint construction;

[0012] S5, assembly of paper-based microfluidic colorimetric sensor. The upper end of the paper-based microfluidic chip contacts the absorbent pad to provide a strong capillary force for a period of time during the adsorption and enrichment stage, and the lower end contacts the upper section of the NC membrane to ensure the flow of the target analyte solution, thus assembling a paper-based microfluidic colorimetric sensor that can be directly used.

[0013] As a preferred technical solution, the filter paper modification in step S1 further includes placing the modified filter paper in a poly(sodium styrene sulfonate) solution and vacuum drying after ultrasonic treatment, wherein the concentration of the poly(sodium styrene sulfonate) solution is 0.3%-0.5%.

[0014] As a preferred technical solution, the seed polymerization method and the secondary growth method in step S1 are mixed into the solution twice, wherein the seed solution required for the first polymerization is a mixed solution of zinc nitrate hexahydrate and 2-methylimidazole configured with 80% methanol, and the solution required for the secondary growth is a mixed aqueous solution of zinc nitrate hexahydrate and 2-methylimidazole configured in a certain proportion.

[0015] As a preferred technical solution, the reagents required for the silanization and amination modifications in step S2 are tetraethyl orthosilicate (TEOS) and 3-aminopropyltriethoxysiloxane (ATPES), respectively, and the solvent is an anhydrous ethanol solution.

[0016] As a preferred technical solution, the mixed solution A obtained in step S3 is slowly added to 1 mL of methanol solution containing amino test paper while adding dropwise while shaking. After the addition is completed, the mixture is reacted at room temperature for 16 hours.

[0017] As a preferred technical solution, the specific construction method of step S4 includes: after the template is fixed, directional surface imprinting is performed, and it needs to be immersed in a certain amount of ethanol, ammonia water and prepolymerization liquid are added, and the reaction reagents are removed after polymerization for a certain period of time, and it is washed with anhydrous ethanol and ultrapure water three times, and finally the template molecules are eluted with 0.1M acetic acid, 30 minutes each time, and repeated three times.

[0018] As a preferred technical solution, the paper-based microfluidic colorimetric sensor includes a substrate and a paper-based microfluidic chip, the paper-based microfluidic chip contains the above-mentioned boron-affinity molecularly imprinted polymer, the paper-based substrate is a PVC-backed board with an NC membrane attached, the surface stationary phase of which is Whatman filter paper, and the zeolite-like imidazole skeleton and the boron-affinity molecularly imprinted polymer are constructed on the surface of the paper base. The paper-based substrate is a PVC-backed board with an NC membrane attached, the surface stationary phase of which is Whatman filter paper, and the zeolite-like imidazole skeleton and the boron-affinity molecularly imprinted polymer are constructed on the surface of the paper base.

[0019] As a preferred technical solution, the paper-based microfluidic chip molding includes the following steps: sticking a water-absorbing pad to the other end of the adhesive backing plate, ensuring that a 5mm×6mm rectangular area is left between the water-absorbing pad and the NC membrane for sticking the stationary phase.

[0020] As a preferred technical solution, the paper-based detection solution is a color support solution required to complete the detection, and the color support solution is a ninhydrin ethanol solution with a pH range of 4.0-5.0.

[0021] In summary, due to the adoption of the above technology, the beneficial effects of the present invention are:

[0022] 1. The filter paper used in the present invention is Whatman No. 1 qualitative filter paper, which not only provides a high specific surface area but also has a porous structure, facilitating the construction and fixation of sensing materials and the circulation of target analytical reagents;

[0023] 2. This invention leverages the high porosity, high specific surface area, and adjustable pore size of the metal-organic framework, combined with molecular imprinting technology, to not only overcome the defects of the raw materials but also further improve its selectivity.

[0024] 3. The present invention uses boron affinity molecularly imprinted polymer as an adsorption carrier, which has high selectivity for target analytes containing cis-dihydroxy structures;

[0025] 4. The present invention coats the surface of the metal organic framework with a layer of SiO2 and performs amino modification, which not only makes the surface easier to graft boric acid groups but also increases its thermal and chemical stability;

[0026] 5. Due to the extremely high specific surface area of ​​the nanomaterials in the present invention, the sensitivity of color development is improved while the time required for color development is greatly reduced;

[0027] 6. The colorimetric sensor developed in this invention takes only 30 minutes to complete and does not require complex instruments, making it easy to apply to on-site rapid detection of kanamycin.

[0028] 7. The present invention not only overcomes the problems of complicated preparation and high cost of antibodies and aptamers used in general detection methods of aminoglycosides, but also realizes a dual-mode recognition mechanism through the ninhydrin-aminoglycoside antibiotic color development strategy, further improving the selectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Build process and visual inspection flow charts for FZS@CPBA@MIP;

[0030] Figure 2 The X-ray diffraction pattern and transmission electron microscopy image of the zeolite-like imidazole metal-organic framework constructed on the surface of paper-based cellulose;

[0031] Figure 3 This is the infrared spectrum of the molecularly imprinted paper-based microfluidic chip after amino functionalization and preparation of boron affinity molecularly imprinted polymer;

[0032] Figure 4 The colorimetric sensor reacts with different concentrations of kanamycin (0-25 mg L -1 ) visual detection. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention for which protection is sought, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0034] like Figure 1-4 As shown, the present invention provides a method for preparing a molecularly imprinted paper-based microfluidic chip based on a metal organic framework, and the specific steps are as follows:

[0035] S1, filter paper modification, using seed polymerization and secondary growth methods to construct ZIF-8 on the paper surface;

[0036] S2, siliconizing and amino treating the paper-based material;

[0037] S3, preparing boron affinity molecularly imprinted polymer, weighing a certain amount of 4-carboxyphenylboronic acid and dissolving it in an appropriate amount of methanol, ultrasonically mixing, then adding carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS), respectively, mixing thoroughly, and shaking the mixture at room temperature for 4 h to obtain a mixed solution A;

[0038] S4, surface imprint construction;

[0039] S5, assembly of paper-based microfluidic colorimetric sensor. The upper end of the paper-based microfluidic chip contacts the absorbent pad to provide a strong capillary force for a period of time during the adsorption and enrichment stage, and the lower end contacts the upper section of the NC membrane to ensure the flow of the target analyte solution, thus assembling a paper-based microfluidic colorimetric sensor that can be directly used.

[0040] Specifically, the filter paper modification in step S1 further comprises placing the modified filter paper into a poly(sodium styrene sulfonate) solution, ultrasonically treating the solution, and then vacuum drying the solution, wherein the concentration of the poly(sodium styrene sulfonate) solution is 0.3%-0.5%.

[0041] Specifically, the seed polymerization method and the secondary growth method in step S1 are mixed into the solution twice, wherein the seed solution required for the first polymerization is a mixed solution of zinc nitrate hexahydrate and 2-methylimidazole configured with 80% methanol, and the solution required for the secondary growth is a mixed aqueous solution of zinc nitrate hexahydrate and 2-methylimidazole configured in a certain proportion.

[0042] Specifically, the reagents required for the silanization and amination modifications in step S2 are tetraethyl orthosilicate (TEOS) and 3-aminopropyltriethoxysiloxane (ATPES), respectively, and the solvent is an anhydrous ethanol solution.

[0043] Specifically, the mixed solution A obtained in step S3 is slowly added to 1 mL of methanol solution containing the amino test paper while adding dropwise while shaking. After the addition is completed, the mixture is reacted at room temperature for 16 hours.

[0044] Specifically, the specific construction method of step S4 includes: after the template is fixed, directional surface imprinting is performed, and it needs to be immersed in a certain amount of ethanol, ammonia water and prepolymerization liquid are added, the reaction reagents are removed after polymerization for a certain period of time, and it is washed with anhydrous ethanol and ultrapure water three times, and finally the template molecules are eluted with 0.1M acetic acid, 30 minutes each time, and repeated three times.

[0045] Specifically, the paper-based microfluidic colorimetric sensor comprises a substrate and a paper-based microfluidic chip, wherein the paper-based microfluidic chip contains the boron-affinity molecularly imprinted polymer. The paper-based substrate is a PVC-backed adhesive plate with an NC membrane attached, and its surface stationary phase is Whatman filter paper. A zeolite-like imidazole skeleton and a boron-affinity molecularly imprinted polymer are constructed on the surface of the paper-based substrate. The paper-based substrate is a PVC-backed adhesive plate with an NC membrane attached, and its surface stationary phase is Whatman filter paper. A zeolite-like imidazole skeleton and a boron-affinity molecularly imprinted polymer are constructed on the surface of the paper-based microfluidic colorimetric sensor. After selectively adsorbing kanamycin, the color developer ninhydrin ethanol solution is added dropwise, and the color intensity of the paper-based microfluidic colorimetric sensor increases with the increase of kanamycin concentration, even at a concentration of 0.1 mg L -1 The color development phenomenon can also be directly observed by naked eyes. When the kanamycin concentration is 0 mg L -1 When the reagent blank is used, after normal color development, the color of the core is almost the same as that of the core without color development under naked eye observation, indicating that the background signal value generated by the matrix blank is extremely low.

[0046] Specifically, the paper-based microfluidic chip forming includes the following steps: sticking a water-absorbing pad to the other end of the adhesive backing plate, ensuring that a 5mm×6mm rectangular area is left between the water-absorbing pad and the NC membrane for sticking the stationary phase.

[0047] Specifically, the paper-based detection solution is a color development support solution that needs to be prepared to complete the detection. The color development support solution is a ninhydrin ethanol solution with a pH range of 4.0-5.0.

[0048] Specifically, the steps of preparing paper-based ZIF-8 by the seed polymerization method & secondary growth method include:

[0049] (1) Whatman No. 1 filter paper was engraved into several 6 mm diameter discs using a laser engraver. The discs were immersed in 20 mL of 0.3% poly(sodium styrene sulfonate) solution and sonicated for 30 min. The excess reagent was discarded and the discs were washed three times with ultrapure water to obtain poly(sodium styrene sulfonate)-modified filter paper, i.e., FP@PSS.

[0050] (2) Weigh 1.17 g of zinc nitrate hexahydrate and 22.7 g of 2-methylimidazole and dissolve them in 44 mL of ultrapure water, stir at room temperature for 12 h, centrifuge, and wash twice with ultrapure water and methanol respectively. Then evaporate the methanol completely, weigh it, and prepare a 0.1% ZIF-8 seed suspension with methanol. Half immerse the paper substrate treated in (1) in the seed suspension for 20 seconds, cut it parallel to the liquid surface, and dry it vertically for use;

[0051] (3) Weigh 0.11 g of zinc nitrate hexahydrate and 2.27 g of 2-methylimidazole, dissolve them in 40 mL of ultrapure water, add them to a reagent bottle, and vertically place the paper-based material in (2) in the reagent bottle, and react at 30°C for 4 h;

[0052] (4) After the reaction, the product was washed with ultrapure water and methanol three times, then immersed in 30 mL of methanol for 12 h. After the immersion, the product was dried under vacuum at room temperature for 24 h. FP@ZIF-8 was obtained, which is subsequently referred to as FZ.

[0053] The method for siliconizing and amino treating paper-based materials is as follows:

[0054] (1) Take a piece of filter paper and soak it in 2 mL of ultrapure water, then add 8 mL of anhydrous ethanol, mix well, and heat to 40°C in a water bath. Then slowly add 200 μL of TEOS and mix well by ultrasonication for 5 minutes. Then add 200 μL of ammonia water and shake in the dark at room temperature for 12 hours (120 rpm). After the reaction, wash it with anhydrous ethanol three times and dry it in a vacuum at 50°C for 1 hour to obtain FP@ZIF-8@SiO2, referred to as FZS.

[0055] (2) A piece of filter paper was immersed in 20 mL of 50% ethanol and aqueous solution, and 200 μL of APTES was added. The mixture was mixed and reacted at 27°C for 4 h. After the reaction, the paper was washed three times with ultrapure water and dried in a vacuum oven at 50°C for 1 h to obtain a surface-amino-modified paper-based material, namely FZS-NH2.

[0056] The preparation method of boron affinity molecularly imprinted polymer is as follows:

[0057] (1) A certain amount of 4-carboxyphenylboronic acid (4-CPBA) was weighed and dissolved in 20 mL of methanol. After ultrasonic mixing, EDC and NHS were added respectively. After thorough mixing, the mixture was shaken at room temperature for 4 h. The above solution was slowly added dropwise to 1 mL of methanol solution containing FZS-NH2 while shaking. After the addition was completed, the mixture was reacted at room temperature for 16 h. After the reaction was completed, the mixture was washed with methanol and water three times each, and finally dried in a vacuum drying oven at 50°C for 1 h to obtain a paper-based material subjected to siliconization and amino treatment of the paper-based material in step S1, namely FZS@CPBA.

[0058] (2) Weigh a certain amount of kanamycin and dissolve it in 10 mL of 0.1 mol L -1 The paper-based material treated with silicon and amino in step S1 was added to a phosphate buffer solution (pH = 7.4), and incubated at room temperature for 120 min. After the incubation, 0.01 mol L -1 The plate was washed three times with phosphate buffer solution to remove unbound kanamycin, and FZS@CPBA bound to the template molecule was obtained.

[0059] (3) The template-fixed FZS@CPBA was rinsed with ethanol and immersed in 40 mL of ethanol. 0.7 mL of ammonia and 10 mL of prepolymerization solution (23.6 μL of TEOS and 10 mL of ethanol) were added. After polymerization for a certain period of time, the reaction reagents were removed and the FZS@CPBA was washed three times with anhydrous ethanol and ultrapure water.

[0060] (4) Using 0.1 mol L -1 The template molecules were eluted with acetic acid solution for 30 min each time, repeated 3 times, and finally washed with pure water 3 times. The mixture was dried in a vacuum at 50°C for 1 h and then used to obtain FZS@CPBA@MIP.

[0061] 4. Sample pretreatment and actual sample visual detection

[0062] Take 10mL of pure milk purchased from a local supermarket, add 0.1mL of kanamycin standard solution of different concentrations, then add a certain amount of 20% acetic acid solution, adjust the pH to 4.6, and let it stand in a 45℃ oven for 10min. After standing, centrifuge and take the supernatant (10000rpm, 25min), filter through a 0.22μm filter membrane, and then use 2mol L -1 The pH value was adjusted to 7.4 by adding NaOH solution, and the supernatant was collected by centrifugation (5000 rpm, 10 min) for later use.

[0063] Take 0.3 mL of sample solution with different concentrations in a 96-well plate, insert the assembled MOF / MIP paper-based microfluidic chip into the sample solution, and let it stand at room temperature for 15 minutes (e.g. Figure 2The chip was then removed and the nonspecific adsorption pad (kanamycin) was rinsed with 5 mL of ultrapure water. The chip was then placed in a 125°C oven for 2 minutes. After removal, a color developer solution of ninhydrin (pH 4.5) was added to the chip surface and the chip was placed in the oven again for 5 minutes to develop color.

[0064] In summary, the color development detection principle of the present invention is:

[0065] Directed and controllable imprinting was achieved on the paper-based MOF surface based on the boron affinity strategy, in which the formed imprinted layer did not completely cover the kanamycin template molecules bound to the boronic acid groups under the control of imprinting time;

[0066] Secondly, kanamycin contains abundant α-amino groups. The exposed α-amino groups can react with the ketone groups of ninhydrin. The resulting reaction products can then react with ninhydrin to form a blue-purple complex.

[0067] Furthermore, adding a certain amount of acetic acid to the ninhydrin colorimetric reagent ensures a weakly acidic environment for the reaction between ninhydrin and kanamycin, which not only increases the stability of the colorimetric reaction, but also partially destroys the ester ring formed by boric acid and kanamycin in a weakly acidic environment, which may release some kanamycin α-amino binding sites, facilitating the binding of more ninhydrin and improving the colorimetric sensitivity to a certain extent.

[0068] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

[0069] It should be noted that, in this article, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements that are inherent to such process, method, article or apparatus.

Claims

1. A method for preparing a molecularly imprinted paper-based microfluidic chip based on a metal organic framework, characterized in that: The specific steps are as follows: S1, filter paper modification, using seed polymerization and secondary growth methods to construct ZIF-8 on the paper surface; S2, siliconizing and amino treating the paper-based material; S3, preparing boron affinity molecularly imprinted polymer, weighing a certain amount of 4-mercaptophenylboronic acid and dissolving it in an appropriate amount of methanol, ultrasonically mixing, then adding carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS), respectively, mixing thoroughly, and shaking the mixture at room temperature for 4 h to obtain a mixed solution A; S4, surface imprint construction; S5, assembly of the paper-based microfluidic colorimetric sensor. The upper end of the paper-based microfluidic chip contacts the absorbent pad to provide a strong capillary force for a period of time during the adsorption and enrichment stage, and the lower end contacts the upper section of the NC membrane to ensure the flow of the target analyte solution, thus assembling a paper-based microfluidic colorimetric sensor that can be directly used. The filter paper modification in step S1 further comprises placing the modified filter paper in a poly(sodium styrene sulfonate) solution, ultrasonically treating the modified filter paper, and then vacuum drying the poly(sodium styrene sulfonate) solution, wherein the concentration of the poly(sodium styrene sulfonate) solution is 0.3%-0.5%; The reagents required for the silanization and amination modifications in step S2 are tetraethyl orthosilicate (TEOS) and 3-aminopropyltriethoxysiloxane (ATPES), respectively, and the solvent is an anhydrous ethanol solution.

2. The method for preparing a molecularly imprinted paper-based microfluidic chip based on a metal organic framework according to claim 1, characterized in that: The seed polymerization method and the secondary growth method in step S1 are mixed into the solution twice, wherein the seed solution required for the first polymerization is a mixed solution of zinc nitrate hexahydrate and 2-methylimidazole configured with 80% methanol, and the solution required for the secondary growth is a mixed aqueous solution of zinc nitrate hexahydrate and 2-methylimidazole configured in a certain proportion.

3. The method for preparing a molecularly imprinted paper-based microfluidic chip based on a metal organic framework according to claim 1, characterized in that: The mixed solution A obtained in step S3 was slowly added to 1 mL of methanol solution containing the amino test paper while adding dropwise while shaking. After the addition was completed, the mixture was reacted at room temperature for 16 hours.

4. The method for preparing a molecularly imprinted paper-based microfluidic chip based on a metal organic framework according to claim 1, characterized in that: The specific construction method of step S4 includes: after the template is fixed, directional surface imprinting is performed, which requires immersion in a certain amount of ethanol, addition of ammonia water and prepolymerization liquid, removal of the reaction reagent after polymerization for a certain period of time, and washing with anhydrous ethanol and ultrapure water three times, and finally elution of the template molecule with 0.1M acetic acid, 30 minutes each time, repeated three times.

5. The method for preparing a molecularly imprinted paper-based microfluidic chip based on a metal organic framework according to claim 1, characterized in that: The paper-based microfluidic colorimetric sensor comprises a substrate and a paper-based microfluidic chip. The paper-based microfluidic chip contains the above-mentioned boron-affinity molecularly imprinted polymer. The substrate is a PVC-backed adhesive board with an NC membrane attached, and its surface fixed phase is Whatman filter paper. A zeolite-like imidazole skeleton and a boron-affinity molecularly imprinted polymer are constructed on the surface of the paper substrate.

6. The method for preparing a molecularly imprinted paper-based microfluidic chip based on a metal organic framework according to claim 1, characterized in that: The paper-based microfluidic chip molding comprises the following steps: sticking a water-absorbing pad to the other end of the adhesive backing plate, ensuring that a 5 mm×6 mm rectangular area is left between the water-absorbing pad and the NC membrane for sticking the stationary phase.

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