Fluorescence sensor 4-MU (at) ZIF-8 (at) PLA-PEG as well as preparation method and application thereof

Abstract

The invention provides a fluorescence sensor 4-MU (at) ZIF-8 (at) PLA-PEG as well as a preparation method and application thereof, and belongs to the technical field of visual food safety monitoring materials. The fluorescence sensor comprises a zeolite imidazate framework ZIF-8, an organic dye molecule 4-MU and a polymeric macromolecule PLA-PEG (Polylactic Acid-Polyethylene Glycol), the organic dye molecule 4-MU is coated with the zeolite imidazate framework ZIF-8 to form 4-MU (ZIF-8 nano particles with a core-shell structure, and the 4-MU (ZIF-8 nano particles with the core-shell structure are doped into a polymeric macromolecule PLA-PEG (Polylactic Acid-Polyethylene Glycol). The ZIF-8, 4-MU and PLA-PEG in the fluorescence sensor provided by the invention can cooperate with each other, can visually detect TCs with high response speed and low detection limit, and has certain mechanical properties and antibacterial properties, thereby providing a new thought for the field of intelligent packaging for detecting TCs in food at present.

Description

Technical Field

[0001] The present application belongs to the technical field of visual food safety monitoring materials, and in particular relates to a fluorescent sensor 4-MU@ZIF-8@PLA-PEG and its preparation method and application. Background Art

[0002] Tetracycline antibiotics (TCs) are currently widely used in veterinary medicine for the treatment and prevention of foodborne animal diseases due to their low cost and broad-spectrum antimicrobial activity against Gram-positive and Gram-negative bacteria. However, excessive and inappropriate use of TCs has led to the contamination of animal-derived foods (such as meat, milk, and honey), which can cause gastrointestinal problems, allergic reactions, liver damage, tooth discoloration, and the growth of antibiotic-resistant bacteria. Pregnant women and infants are particularly susceptible to the negative effects of TCs. To protect the public from the potential harmful effects of TCs, regulatory agencies have established acceptable daily intakes (ADIs) and maximum residue limits (MRLs) for TCs in animal-derived foods.

[0003] Currently, the main methods for detecting TCs include high-performance liquid chromatography (HPLC), thin-layer chromatography (TLC), capillary electrophoresis (CE), and mass spectrometry (MS). Although these traditional techniques can achieve sufficiently low detection limits, the detection process usually requires complex sample pretreatment procedures, including separation and enrichment, which increases the cost and complexity of the detection. Therefore, it is necessary to develop a TCs sensor that can directly detect, has a fast response speed, and is visual. Summary of the Invention

[0004] The present invention provides a fluorescent sensor 4-MU@ZIF-8@PLA-PEG, a preparation method, and an application thereof. The fluorescent sensor has the advantages of low detection limit, fast response, high sensitivity, and visualization for the detection of TCs.

[0005] The present invention first provides a fluorescent sensor 4-MU@ZIF-8@PLA-PEG, which includes a zeolite imidazolate skeleton ZIF-8, an organic dye molecule 4-MU and a polymer PLA-PEG;

[0006] The zeolite imidazolate framework ZIF-8 coats the organic dye molecule 4-MU to form 4-MU@ZIF-8 nanoparticles with a core-shell structure. The 4-MU@ZIF-8 nanoparticles with a core-shell structure are doped into a polymer polymer PLA-PEG.

[0007] The present invention also provides a method for preparing a fluorescent sensor 4-MU@ZIF-8@PLA-PEG, comprising the steps of:

[0008] Step S1, dissolving zinc salt and organic dye 4-MU in a solvent and stirring to obtain a metal chalcogenide open framework 4-MU / zinc salt mixed solution;

[0009] Step S2, adding the 2-methylimidazole solution to the 4-MU / zinc salt mixed solution obtained in step S1 and stirring to obtain 4-MU@ZIF-8 particles;

[0010] Step S3: adding the 4-MU@ZIF-8 particles obtained in step S2 to a mixed solution of PLA and PEG to obtain a fluorescent sensor.

[0011] Preferably, in step S1, the stirring temperature is room temperature and the stirring time is 1 to 8 hours.

[0012] Preferably, in step S1, the mass ratio of zinc salt to organic dye 4-MU is (25-30): (1-5).

[0013] Preferably, in step S2, the stirring temperature is room temperature and the stirring time is 1 to 8 hours.

[0014] Preferably, in step S3, the stirring temperature is room temperature and the stirring time is 2 hours.

[0015] Preferably, in step S3, the mass ratio of PLA to PEG in the PLA and PEG mixed solution is (800-1000): (800-1000).

[0016] The present invention also provides application of the fluorescent sensor 4-MU@ZIF-8@PLA-PEG in the field of visual food safety monitoring.

[0017] Preferably, the application includes: using the fluorescent sensor to detect TCs in an environment of deionized water, tap water and milk.

[0018] The present invention also provides application of the fluorescent sensor 4-MU@ZIF-8@PLA-PEG in the field of food antibacterial packaging.

[0019] Beneficial effects of the present invention

[0020] The present application provides a fluorescent sensor 4-MU@ZIF-8@PLA-PEG, a preparation method, and an application. The fluorescent sensor provided in the present application is a core-shell structure 4-MU@ZIF-8 particle formed by coating an organic fluorescent dye 4-MU with a zeolite imidazolate skeleton ZIF-8 and being coated in a high molecular polymer PLA-PEG base film to prepare the fluorescent sensor 4-MU@ZIF-8@PLA-PEG. The organic fluorescent dye molecule 4-MU undergoes obvious fluorescence quenching in a solution of TCs, and the high porosity and framework of the zeolite imidazolate skeleton ZIF-8 serve to isolate the organic dye molecule 4-MU and hinder its aggregation fluorescence quenching effect. At the same time, the high specific surface area can enrich the analyte TCs, so that the fluorescent sensor 4-MU@ZIF-8@PLA-PEG has the advantages of low detection limit, fast response speed, high sensitivity, and visualization for the detection of TCs. The presence of the PLA-PEG basement membrane gives the fluorescent sensor excellent mechanical properties and thermal stability. PLA releases lactic acid in specific environments, creating an acidic environment, which gives the fluorescent sensor 4-MU@ZIF-8@PLA-PEG excellent antibacterial properties. Therefore, the ZIF-8, 4-MU, and PLA-PEG in the fluorescent sensor provided by this application work together to achieve fast response, low detection limits, and visual detection of TCs. Furthermore, it possesses certain mechanical and antibacterial properties, providing new insights into the current field of smart packaging for detecting TCs in food. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the specific implementation methods or the description of the prior art. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0022] Figure 1 Schematic diagram of the overlap of the emission spectrum of 4-MU@ZIF-8@PLA-PEG and the absorption spectrum of TCs;

[0023] Figure 2 This is the fluorescence lifetime spectrum of 4-MU@ZIF-8@PLA-PEG described in Example 1 of the present application;

[0024] Figure 3 This is the fluorescence lifetime spectrum of 4-MU@ZIF-8@PLA-PEG described in Example 1 of the present application after being soaked in TC;

[0025] Figure 4This is the fluorescence lifetime spectrum of 4-MU@ZIF-8@PLA-PEG described in Example 1 of the present application after soaking in OTC;

[0026] Figure 5 Schematic diagram of the photoelectron induction mechanism of 4-MU@ZIF-8@PLA-PEG described in Example 1 of the present application;

[0027] Figure 6 This is a scanning electron microscope image of 4-MU@ZIF-8 provided in Test Example 1 of this application;

[0028] Figure 7 This is a scanning electron micrograph of the PLA-PEG provided in Test Example 1 of this application;

[0029] Figure 8 This is a scanning electron micrograph of 4-MU@ZIF-8@PLA-PEG provided in Test Example 1 of this application;

[0030] Figure 9 X-ray diffraction spectra of 4-MU@ZIF-8, PLA-PEG, and 4-MU@ZIF-8@PLA-PEG provided in Test Example 1 of this application;

[0031] Figure 10 This is a graph of the elongation at break of 4-MU@ZIF-8@PLA-PEG with different doping concentrations in Test Example 2 of this application;

[0032] Figure 11 This is a graph of the Young's modulus of 4-MU@ZIF-8@PLA-PEG with different doping concentrations in Test Example 2 of this application;

[0033] Figure 12 This is a graph showing the tensile strength of 4-MU@ZIF-8@PLA-PEG with different doping concentrations in Test Example 2 of this application;

[0034] Figure 13 This is the emission spectrum of 4-MU@ZIF-8@PLA-PEG to different pesticides in Experimental Example 1 of this application;

[0035] Figure 14 The I of 4-MU@ZIF-8@PLA-PEG on different pesticides in Experimental Example 1 of this application 382 / I 540 Histogram of fluorescence intensity change efficiency;

[0036] Figure 15 This is the emission spectrum of 4-MU@ZIF-8@PLA-PEG at different TC concentrations in Experimental Example 1 of this application;

[0037] Figure 16The fluorescence intensity ratio I of 4-MU@ZIF-8@PLA-PEG in Experimental Example 1 of this application is 382 / I 450 Relationship diagram with TC concentration;

[0038] Figure 17 This is the emission spectrum of 4-MU@ZIF-8@PLA-PEG at different OTC concentrations in Experimental Example 1 of this application;

[0039] Figure 18 The fluorescence intensity ratio I of 4-MU@ZIF-8@PLA-PEG in Experimental Example 1 of this application is 382 / I 450 Relationship graph with OTC concentration;

[0040] Figure 19 The fluorescence intensity ratio I of 4-MU@ZIF-8@PLA-PEG in tap water in Experimental Example 1 of this application is 382 / I 450 Relationship diagram with TC concentration;

[0041] Figure 20 The fluorescence intensity ratio I of 4-MU@ZIF-8@PLA-PEG in milk in Experimental Example 1 of this application is 382 / I 450 Relationship diagram with TC concentration;

[0042] Figure 21 This is a graph showing the antibacterial test results of PLA-PEG and 4-MU@ZIF-8@PLA-PEG in Experimental Example 2 of this application. DETAILED DESCRIPTION

[0043] The present invention first provides a fluorescent sensor 4-MU@ZIF-8@PLA-PEG, which includes a zeolite imidazolate skeleton ZIF-8, an organic dye molecule 4-MU (4-methylumbelliferone) and a polymer PLA-PEG;

[0044] The zeolite imidazolate framework ZIF-8 encapsulates the organic dye molecule 4-MU to form a core-shell structure 4-MU@ZIF-8 nanoparticles, which are then doped into the polymer PLA-PEG. The organic fluorescent dye molecule 4-MU undergoes significant fluorescence quenching in a TCs solution, while the high porosity and framework of the zeolite imidazolate framework ZIF-8 act to isolate the organic dye molecule 4-MU, hindering its aggregation and fluorescence quenching effect. At the same time, the high specific surface area can enrich the analyte TCs. The reaction mechanism is as follows: Figure 1 As shown in the figure, the absorption spectrum of TCs overlaps with the emission spectrum of the fluorescent sensor 4-MU@ZIF-8@PLA-PEG in a large area, so the response mechanism involves fluorescence resonance transfer (FRIT).

[0045] According to the present invention, the size of the 4-MU@ZIF-8 is 1 mm, and the basement membrane PLA-PEG presents a porous structure.

[0046] The present invention also provides a method for preparing a fluorescent sensor 4-MU@ZIF-8@PLA-PEG, comprising the steps of:

[0047] Step S1, dissolving a zinc salt and an organic dye 4-MU in a solvent and stirring, the stirring temperature is preferably room temperature, and the stirring time is preferably 1 to 8 hours, to obtain a metal chalcogenide open framework 4-MU / zinc salt mixed solution; the solvent is preferably methanol; the zinc salt is preferably zinc acetate; the mass ratio of the zinc salt to the organic dye 4-MU is preferably (25 to 30): (1 to 5);

[0048] Step S2, adding the 2-methylimidazole solution to the 4-MU / zinc salt mixed solution obtained in step S1 and stirring, the stirring temperature is preferably room temperature, the stirring speed is preferably 4000 rpm, and the stirring time is preferably 15 minutes, discarding the supernatant, washing the precipitate with methanol until the supernatant is non-fluorescent, and finally, drying the precipitate, preferably at 60° C. for 12 hours, to obtain 4-MU@ZIF-8 particles; the 2-methylimidazole solution is preferably a methanol solution of 2-methylimidazole;

[0049] Step S3: Add the 4-MU@ZIF-8 particles obtained in step S2 to a mixed solution of PLA and PEG and stir. The stirring temperature is preferably room temperature and the stirring time is preferably 2 hours to obtain a fluorescent sensor. The PLA and PEG mixed solution preferably comprises a mixed polymer film formed by adding polylactic acid and polyethylene glycol in a mass ratio of 1:1 and then adding dichloromethane solvent. The sources of the polylactic acid (PLA, Mw 80000) and polyethylene glycol (PEG, Mw 6000) are both commercially available.

[0050] According to the present invention, preferably, in step S1, 25 to 30 parts by mass of zinc salt and 1 to 5 parts by mass of organic dye 4-MU are included;

[0051] In step S2, 100 to 150 parts by mass of 2-methylimidazole is included.

[0052] In step S3, 800 to 1000 parts by mass of PLA and 800 to 1000 parts by mass of PEG are included.

[0053] The present invention also provides application of the fluorescent sensor 4-MU@ZIF-8@PLA-PEG in the field of visual food safety monitoring.

[0054] Preferably, the application includes: using the fluorescent sensor to detect TCs in an environment of deionized water, tap water and milk.

[0055] The present invention also provides application of the fluorescent sensor 4-MU@ZIF-8@PLA-PEG in the field of food antibacterial packaging.

[0056] The following will clearly and completely describe the technical solution of this application in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of this application.

[0057] Example 1

[0058] A preparation method of a fluorescent sensor 4-MU@ZIF-8@PLA-PEG, comprising preparing 4-MU@ZIF-8 particles and preparing the fluorescent sensor 4-MU@ZIF-8@PLA-PEG.

[0059] To prepare 4-MU@ZIF-8 particles, 1.835 g of zinc acetate and 362 mg of 4-methylumbelliferone (4-MU) were dissolved in 60 mL of methanol to obtain a methanol solution of 4-MU / zinc salt.

[0060] Dissolve 3.248 g of 2-methylimidazole (2-MI) in 60 mL of methanol to obtain a methanol solution of 2-methylimidazole;

[0061] After mixing the two solutions, centrifuge at 4000 rpm for 15 minutes. Discard the supernatant and wash the pellet with methanol until the supernatant is free of fluorescence. Finally, dry the pellet at 60°C for 12 hours and grind it into a fine powder.

[0062] The steps for preparing the fluorescent sensor 4-MU@ZIF-8@PLA-PEG include dissolving 500 mg of PLA, 500 mg of PEG, and the aforementioned 4-MU@ZIF-8 powder in 10 mL of dichloromethane and stirring for 2 hours until completely dissolved. The solution was then poured into a 6 mm diameter Petri dish and dried at room temperature for 48 hours. After drying, the material was cut into 1 cm × 0.5 cm rectangles.

[0063] Figure 2 This is the fluorescence lifetime spectrum of 4-MU@ZIF-8@PLA-PEG described in Example 1 of the present application; Figure 3 This is the fluorescence lifetime spectrum of 4-MU@ZIF-8@PLA-PEG described in Example 1 of the present application after being soaked in TC; Figure 4This is the fluorescence lifetime spectrum of 4-MU@ZIF-8@PLA-PEG described in Example 1 of the present application after soaking in OTC; Figure 2-4 It can be seen that the fluorescence lifetime is significantly reduced, which means the existence of photoinduced electron transfer (PET). The electrons in the highest occupied orbital of the organic dye molecule 4-MU are transferred to the lowest unoccupied orbital of TCs under photoinduction, resulting in fluorescence quenching. The reaction mechanism is as follows Figure 5 shown.

[0064] Test Example 1

[0065] In this test example 1, the structures of 4-MU@ZIF-8, PLA-PEG and 4-MU@ZIF-8@PLA-PEG described in Example 1 were analyzed. The electron microscopy analysis results of 4-MU@ZIF-8 were as follows: Figure 6 The rhombic dodecahedron still retains the characteristics of ZIF-8 itself, indicating that the 4-MU particles are coated by ZIF-8 without changing their structure, forming a shell-core structure. Figure 7 、 8 As shown in the figure, the cross-section of the base membrane PLA-PEG presents a porous structure, and spheres appear in the pores of 4-MU@ZIF-8@PLA-PEG, which indicates that 4-MU@ZIF-8 is successfully doped into the composite membrane.

[0066] The fluorescence sensor 4-MU@ZIF-8@PLA-PEG was further analyzed by X-ray diffraction. Figure 9 As shown in the XRD pattern of 4-MU@ZIF-8, the diffraction peaks at 2q = 7.271°, 10.320°, 12.673°, 14.658°, 16.398°, and 17.994° correspond to the crystal planes (001), (002), (112), (022), (013), and (222), which are consistent with the characteristic peaks of single crystal simulated ZIF-8. In the XRD pattern of PLA-PEG, the diffraction peaks at 2q = 16.746° and 19.201° correspond to the crystal planes (200 / 110) and (203), which may come from PLA. The strong diffraction peaks at 2q = 19.201° and 23.335° correspond to crystal planes (120) and (112). The presence of these peaks is attributed to PEG, indicating that the crystal structures of PLA and PEG remain unchanged, confirming the successful preparation of the PLA-PEG blend film. It can be seen that the XRD pattern of the composite material is consistent with that of PLA-PEG, indicating that 4-MU@ZIF-8 is embedded in the matrix rather than adsorbed on the surface of the matrix. The sample structure is consistent with expectations, and the dye molecules are encapsulated in ZIF-8, forming 4-MU@ZIF-8@PLA-PEG.

[0067] Test Example 2

[0068] In order to prepare the 4-MU@ZIF-8@PLA-PEG sensor with the best mechanical properties, 4-MU@ZIF-8@PLA-PEG composite materials with different 4-MU@ZIF-8 contents (1%, 3%, 5%, and 7% mass fraction relative to PLA) were prepared according to the method of Example 1, and the optimal ratio was selected according to the mechanical properties. Figure 10-12 As shown, as the 4-MU@ZIF-8 concentration increases, the elongation at break decreases, while the Young's modulus and tensile strength first increase and then decrease, reaching a peak at 3% mass fraction. This phenomenon is attributed to the fact that, at low 4-MU@ZIF-8 concentrations, its introduction enhances intermolecular interactions, promotes physical crosslinking, and improves the elastic modulus and tensile strength of the material; however, this also restricts the movement of the molecular chains, leading to a decrease in elongation at break. As the concentration increases, aggregates gradually form, becoming weak points in the material, leading to a decrease in the elastic modulus and tensile strength. This further restricts the movement of the molecular chains, resulting in stress concentration and a reduction in elongation at break. In summary, considering all the mechanical properties, 4-MU@ZIF-8@PLA-PEG-3 was selected as the optimal preparation scheme.

[0069] Experimental Example 1

[0070] In this experimental example, the TCs detection performance of the fluorescent sensor 4-MU@ZIF-8@PLA-PEG described in Example 1 was analyzed, including screening test analysis, quantitative test analysis, and practical application test analysis.

[0071] The screening analysis test process includes: in order to test the selectivity for TCs, the sensor is immersed in 10mL of various 10-3M pesticide solutions for 30 minutes and then fluorescence detection is performed. Figure 13 As shown, from Figure 13 It can be seen that after immersion in different pesticides for 30 min, the emission intensity at 382 nm decreased to varying degrees, among which TC and OTC had the largest decrease, accompanied by an emission peak at 540 nm. Figure 14 The I of 4-MU@ZIF-8@PLA-PEG to different pesticides is shown. 382 / I 540 The results show that the response of TC and OTC is significantly lower than that of blank sample and other pesticides (0.034 times and 0.086 times of blank group respectively). 382 / I 540 It can be used as a basis for the detection of TCs, indicating that 4-MU@ZIF-8@PLA-PEG has the selective detection ability for TCs.

[0072] The quantitative analysis test process includes: using deionized water as the solvent, preparing the concentration range of 10-3M to 10 -9 M TC and OTC solution. 4-MU@ZIF-8@PLA-PEG sensor was immersed in 10mL TC and OTC solution with different concentrations for 30 minutes and then fluorescence detection was performed. The results are shown in Figure 2. Figure 15-18 It shows that with the increase of TC and OTC concentrations, the fluorescence intensity at 382nm decreases, the fluorescence intensity at 450nm increases, and I 382 / I 540 The ratio also decreased. With increasing concentrations of OTC and TC, the visible color under UV light changed from light blue to cyan and then to yellow. The fitted regression equation showed excellent linearity, with detection limits of 0.192 nM and 203.032 nM, respectively. These results demonstrate that the prepared 4-MU@ZIF-8@PLA-PEG sensor can quantitatively detect TCs in water samples with excellent linearity and low detection limits, making it a highly selective, sensitive, and visual sensor for TCs detection.

[0073] The actual application analysis and testing process includes: In the actual application experiment, tap water and milk were used as solvents to prepare -3 M to 10 -7 The sensor was immersed in 10 mL of TC and OTC solution for 30 minutes and then fluorescence detection was performed. Figure 19 and 20 As shown, the sensor's I 382 / I 540 The ratio showed excellent linear relationship with the TC concentration in tap water and milk. 2 The values are 0.999 and 0.982 respectively. Under 365nm UV light, the sensor has a TC concentration range of 10 -3 M to 10 -7 M. Therefore, the 4-MU@ZIF-8@PLA-PEG sensor has a low detection limit and high sensitivity for detecting TC content in tap water and milk, intuitively demonstrating its great potential for detecting TC in food.

[0074] Experimental Example 2

[0075] This experimental example analyzes the antibacterial properties of PLA-PEG and 4-MU@ZIF-8@PLA-PEG described in Example 1.

[0076] The antibacterial performance test process of PLA-PEG and 4-MU@ZIF-8@PLA-PEG includes the following steps: Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were used to test the antibacterial performance of PLA-PEG and 4-MU@ZIF-8@PLA-PEG. The sensor was cut into small discs with a diameter of 6 mm and then placed in a container containing 10 -5 The samples were immersed in 1 mL of bacterial suspension containing 100 CFU / mL of Escherichia coli and Staphylococcus aureus for 2 hours. Subsequently, the bacterial suspension was evenly spread on a solid agar plate and the colony count was counted after incubation at 37°C for 10 hours. E. coli and S. aureus are common bacteria found in spoiled milk and were used to test the antibacterial properties of 4-MU@ZIF-8@PLA-PEG in this project. The results are shown in Figure 2. Figure 21 As shown, both PLA-PEG and 4-MU@ZIF-8@PLA-PEG exhibited excellent antibacterial effects, with inhibition rates of 81.92% and 87.17% against Escherichia coli, and 69.57% and 71.74% against Staphylococcus aureus, respectively. This indicates that the presence of PLA-PEG plays a significant role in the antibacterial activity, as PLA degrades under specific conditions and releases lactic acid molecules. These lactic acid molecules lower the pH of the environment, thereby inhibiting bacterial growth. Furthermore, the added 4-MU@ZIF-8 may interact with lipids on the bacterial cell membrane, impairing their function and further increasing the inhibition rate. Therefore, the 4-MU@ZIF-8@PLA-PEG sensor exhibits excellent antibacterial properties and can effectively inhibit bacterial growth in milk, demonstrating great potential for application in milk packaging.

[0077] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A fluorescent sensor 4-MU@ZIF-8@PLA-PEG, characterized in that It includes zeolite imidazolate framework ZIF-8, organic dye molecule 4-MU and polymer polymer PLA-PEG; The zeolite imidazolate framework ZIF-8 coats the organic dye molecule 4-MU to form 4-MU@ZIF-8 nanoparticles with a core-shell structure. The 4-MU@ZIF-8 nanoparticles with a core-shell structure are doped into a polymer polymer PLA-PEG.

2. The preparation method of a fluorescent sensor 4-MU@ZIF-8@PLA-PEG according to claim 1, characterized in that: Including steps: Step S1, dissolving zinc salt and organic dye 4-MU in a solvent and stirring to obtain a metal chalcogenide open framework 4-MU / zinc salt mixed solution; Step S2, adding the 2-methylimidazole solution to the 4-MU / zinc salt mixed solution obtained in step S1 and stirring to obtain 4-MU@ZIF-8 particles; Step S3: adding the 4-MU@ZIF-8 particles obtained in step S2 to a mixed solution of PLA and PEG to obtain a fluorescent sensor.

3. The preparation method of a fluorescent sensor 4-MU@ZIF-8@PLA-PEG according to claim 2, characterized in that: In the step S1, the stirring temperature is room temperature and the stirring time is 1 to 8 hours.

4. The preparation method of a fluorescent sensor 4-MU@ZIF-8@PLA-PEG according to claim 2, characterized in that: In the step S1, the mass ratio of zinc salt to organic dye 4-MU is (25-30): (1-5).

5. The preparation method of a fluorescent sensor 4-MU@ZIF-8@PLA-PEG according to claim 2, characterized in that: In the step S2, the stirring temperature is room temperature and the stirring time is 1 to 8 hours.

6. The preparation method of a fluorescent sensor 4-MU@ZIF-8@PLA-PEG according to claim 2, characterized in that: In the step S3, the stirring temperature is room temperature and the stirring time is 2 hours.

7. The method for preparing a fluorescent sensor 4-MU@ZIF-8@PLA-PEG according to claim 2, characterized in that: In step S3, the mass ratio of PLA to PEG in the PLA and PEG mixed solution is (800-1000): (800-1000).

8. Use of the fluorescent sensor 4-MU@ZIF-8@PLA-PEG according to claim 1 in the field of visual food safety monitoring.

9. The use according to claim 8, characterized in that The application includes: using the fluorescent sensor to detect TCs in deionized water, tap water and milk environments.

10. Use of the fluorescent sensor 4-MU@ZIF-8@PLA-PEG according to claim 1 in the field of food antibacterial packaging.

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