Antibacterial film as well as preparation method and application thereof

Abstract

The invention discloses an antibacterial film as well as a preparation method and application thereof. The preparation method of the antibacterial film comprises the following steps: a) preparing the prolamin modified MOF nanoparticles; b) preparing a honeycomb-shaped polylactic acid-prolamin-MOF (Metal Organic Framework) thin film; and c) preparing the antibacterial film. The preparation method comprises the following steps: firstly, modifying MOF by adopting prolamin, then blending the obtained prolamin modified MOF nanoparticles with a PLA solution to form a film, so as to obtain a honeycomb polylactic acid-prolamin-MOF film, then carrying out charge modification on the honeycomb polylactic acid-prolamin-MOF film, so as to obtain a charge modified polylactic acid-prolamin-MOF film, and finally, carrying out electrostatic modification on the charge modified polylactic acid-prolamin-MOF film, so as to obtain the charge modified polylactic acid-prolamin-MOF film. Finally, in the presence of a cationic cross-linking agent, a natural bacteriostatic agent is adsorbed and fixed to the polylactic acid-prolamin-MOF film, and the prepared bacteriostatic film is good in bacteriostatic activity and stability and can be applied to the fields of food packaging, medical dressing and air purification.

Description

Technical Field

[0001] The invention relates to an antibacterial film, a preparation method and application thereof, and belongs to the technical field of functional polymer composite materials. Background Art

[0002] Polylactic acid (PLA) film is a bio-based degradable film that is currently widely used in food packaging, medical dressings, air purification and other fields.

[0003] Although polylactic acid (PLA) films are biodegradable, they lack antibacterial properties. Currently, antibacterial properties are primarily achieved by adding antibacterial substances. However, PLA films suffer from release defects, preventing the sustained release of antibacterial substances, resulting in insufficient long-term antibacterial properties. Metal-organic frameworks (MOFs) are porous crystalline materials formed by the self-assembly of metal ions / clusters and organic ligands through coordination bonds. They can slowly release metal ions or antimicrobial ligands. Therefore, blending MOFs with PLA to create PLA-MOF composite films can effectively improve the antibacterial and sustained-release properties of PLA films. For example, in Patent 202310588559.X, a natural antimicrobial agent is loaded onto an Ag@MOF carrier and then thoroughly mixed with PLA. The resulting PLA active packaging film is then produced by melt extrusion blow molding. This film is used to package Bacillus subtilis, achieving active packaging for the fungus, inhibiting microbial growth and extending its shelf life.

[0004] However, polylactic acid is a hydrophobic organic polymer, and metal-organic frameworks are usually polar or hydrophilic inorganic-organic hybrid crystals, resulting in poor interfacial compatibility between PLA and MOF. MOF is difficult to disperse evenly in the PLA matrix and easily agglomerates to form large aggregates, which in turn affects the stability and antibacterial properties of the PLA-MOF composite film. Summary of the Invention

[0005] In view of the above problems existing in the prior art, the purpose of the present invention is to provide an antibacterial film, a preparation method and application thereof.

[0006] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is as follows: A method for preparing an antibacterial film comprises the following steps: a) Preparation of prolamin-modified MOF nanoparticles: The alcohol-soluble protein is dissolved in an alcohol solvent to form an alcohol solution of the alcohol-soluble protein, MOF is added, and the mixture is mixed evenly. Acid is added to the resulting mixture to adjust the pH to 2-3, and the mixture is stirred at room temperature for 10-20 hours to obtain a colloidal solution, which is freeze-dried to obtain alcohol-soluble protein-modified MOF nanoparticles; b) Preparation of honeycomb-shaped polylactic acid-prolamin-MOF film: The prolamin-modified MOF nanoparticles are uniformly dispersed in a PLA solution to obtain a uniform and stable PLA-prolamin-MOF dispersion, and the resulting dispersion is formed into a film to obtain a honeycomb-shaped polylactic acid-prolamin-MOF film; c) Preparation of antibacterial film: performing charge modification on the polylactic acid-gliadin-MOF film so that the surface of the polylactic acid-gliadin-MOF film is negatively charged, thereby obtaining a charge-modified polylactic acid-gliadin-MOF film; The cationic crosslinker and the natural antibacterial agent are dissolved in an alcohol solvent, a buffer solution is added, the pH is adjusted to 4-6, and ultrasonic emulsification is performed to form a colloidal solution to obtain a crosslinker-modified antibacterial agent dispersion. The charge-modified polylactic acid-gliadin-MOF film was immersed in a cross-linker-modified antibacterial agent dispersion and reacted for 10 to 30 minutes under ultrasound assistance to obtain an antibacterial film.

[0007] In one embodiment, in step a), 0.1-0.5 g of prolamin is dissolved in 100 ml of an alcohol solvent to form an alcohol solution of prolamin.

[0008] In one embodiment, in step a), the alcohol-soluble protein is any one of zein, wheat alcohol-soluble protein, hordein, secalin, and kafirin, preferably zein; the pure solvent is ethanol; and the MOF includes silver-based MOF, zinc-based MOF (for example: ZIF-8, ZIF-67, ZIF-90, ZIF-L, etc.), and copper-based MOF.

[0009] In one embodiment, in step a), the mass ratio of prolamin:MOF is (2-3):1.

[0010] In one embodiment, in step a), the acid used is citric acid.

[0011] In one embodiment, in step b), the PLA solution is a chloroform or dichloromethane solution of PLA with a concentration of 2 to 10 wt %.

[0012] In one embodiment, in step b), the mass ratio of PLA to prolamin-modified MOF nanoparticles is (20-40): 1. In one embodiment, in step b), the obtained dispersion is formed into a film by a coating method or a casting method.

[0013] In a preferred embodiment, in step b), during the film formation process, the obtained wet film is dried under constant temperature and humidity conditions of 45-55°C and 60-80% humidity for 10-20 hours to obtain a honeycomb polylactic acid-gliadin-MOF film.

[0014] In one embodiment, in step c), the polylactic acid-gliadin-MOF film is charge-modified by any of the following methods: ① Immerse the polylactic acid-prolamin-MOF film in a 0.1~1M NaOH solution for 30-60 seconds to hydrolyze the surface of the polylactic acid-prolamin-MOF film to generate carboxylic acid groups, thereby making the surface of the polylactic acid-prolamin-MOF film negatively charged (Zeta potential ≤-25mV), thereby obtaining a charge-modified polylactic acid-prolamin-MOF film; ② Plasma treatment technology is used to surface treat the polylactic acid-alcohol-soluble protein-MOF film, introducing oxygen-containing polar groups on the surface of the polylactic acid-alcohol-soluble protein-MOF film to enhance the surface negative charge density, so that the surface of the polylactic acid-alcohol-soluble protein-MOF film is negatively charged, thereby obtaining a charge-modified polylactic acid-alcohol-soluble protein-MOF film; the plasma treatment power is 50~100W, and the time is 2~5 minutes.

[0015] In one embodiment, in step c), the cationic crosslinking agent used is polyethyleneimine (PEI).

[0016] In one embodiment, in step c), the natural antibacterial agent used is astaxanthin, curcumin, resveratrol or natural flavonoids with antioxidant and antibacterial properties (for example, quercetin, kaempferol, luteolin, baicalein, catechin, etc.), the alcohol solvent used is ethanol, and the buffer used is phosphate buffer.

[0017] In one embodiment, in step c), the mass ratio of cationic crosslinking agent to natural antibacterial agent is 1:(8-12).

[0018] In one embodiment, in step c), the concentration of the antibacterial agent in the antibacterial agent dispersion is 1-5 mg / mL.

[0019] In one embodiment, in step c), when ultrasound is used as an aid, the ultrasound frequency is 20-60 kHz and the ultrasound power is 50-150 W.

[0020] An antibacterial film prepared by the above preparation method.

[0021] The invention discloses an application of the antibacterial film prepared by the preparation method in the fields of food packaging, medical dressing and air purification.

[0022] Compared with the prior art, the present invention has the following significant beneficial effects: The present invention first uses alcohol-soluble protein to modify MOF to obtain alcohol-soluble protein-modified MOF nanoparticles, then blends the alcohol-soluble protein-modified MOF nanoparticles with a PLA solution to form a film to obtain a honeycomb polylactic acid-alcohol-soluble protein-MOF film, then charges the honeycomb polylactic acid-alcohol-soluble protein-MOF film to obtain a charge-modified polylactic acid-alcohol-soluble protein-MOF film, and finally, in the presence of a cationic cross-linking agent, adsorbs and fixes a natural antibacterial agent on the polylactic acid-alcohol-soluble protein-MOF film. The prepared antibacterial film has good antibacterial properties and stability, can be widely used in the fields of food packaging, medical dressings and air purification, and has great potential value. In addition, the preparation method of the present invention is economical and practical, has a simple preparation process, is low-cost, does not require special equipment and harsh conditions, is easy to achieve large-scale production, and has extremely strong industrial application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a field emission scanning electron micrograph of the honeycomb-shaped polylactic acid-gliadin-MOF film prepared in Example 1 of the present invention; Figure 2 This is a field emission scanning electron microscope image of the polylactic acid-MOF film prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0024] The technical scheme of the present invention is further described in detail and completely below with reference to the examples. It should be understood that these examples are intended only to illustrate the present invention and are not intended to limit the scope of the invention. The experimental methods in the following examples, for which specific conditions are not specified, are generally carried out under conventional conditions or as recommended by the manufacturer.

[0025] Example 1 a) Preparation of prolamin-modified MOF nanoparticles: 0.125 g of zein (Zein for short) was added to 50 ml of ethanol and stirred at room temperature for 30 minutes to form an ethanol solution of zein. 0.05 g of MOF (specifically ZIF-8) was then added and stirred at room temperature to mix uniformly. Citric acid was added to the resulting mixture to adjust the pH to 2-3. The mixture was stirred at room temperature overnight (approximately 12 hours) to obtain a colloidal solution, which was then freeze-dried to obtain zein-modified MOF nanoparticles, namely, Zein-MOF nanoparticles. b) Preparation of honeycomb-shaped polylactic acid-prolamin-MOF film: PLA was dissolved in dichloromethane (or chloroform) at room temperature to prepare a 5 wt% PLA solution. Zein-MOF nanoparticles were added to the PLA solution at a mass ratio of 30:1. Ultrasonic dispersion was performed for 30 minutes to uniformly disperse the Zein-MOF nanoparticles in the PLA solution to obtain a uniform and stable PLA-Zein-MOF dispersion. The resulting dispersion was coated into a film using a four-sided preparation device by a coating method. The resulting wet film was placed in a constant temperature and humidity chamber and dried for 12 hours under constant temperature and humidity conditions of 50° C. and 70% humidity to obtain a honeycomb PLA-Zein-MOF film. c) Preparation of antibacterial film: The PLA-Zein-MOF film was immersed in 0.1M NaOH solution for 50s. The surface of the film was hydrolyzed to generate carboxylic acid groups, which made the surface of the PLA-Zein-MOF film negatively charged, thus obtaining a charge-modified PLA-Zein-MOF film. Polyethyleneimine and astaxanthin were dissolved in ethanol at a mass ratio of 1:10, wherein the concentration of astaxanthin was 2.5 mg / mL, and then phosphate buffer was added, the pH was adjusted to 5, and ultrasonic emulsification was performed to form a colloidal solution to obtain a polyethyleneimine-modified astaxanthin dispersion; The charge-modified PLA-Zein-MOF film was immersed in a polyethyleneimine-modified astaxanthin dispersion and reacted for 20 minutes under ultrasonic assistance (ultrasonic frequency of 40 kHz, ultrasonic power of 100 W). The astaxanthin was evenly adsorbed on the surface of the PLA-Zein-MOF film by electrostatic attraction to obtain an antibacterial film.

[0026] Figure 1 This is a field emission scanning electron micrograph of the polylactic acid-zein-MOF film (PLA-Zein-MOF film) prepared in this embodiment. Figure 1 It can be seen that the PLA-Zein-MOF film prepared in this example has pores with a pore size of 10-20 μm uniformly distributed inside, and the whole has a distinct honeycomb structure. This structure can not only effectively increase the surface area of ​​the film, but also make the MOF uniformly loaded in the PLA, laying a good foundation for the subsequent better adsorption of antibacterial agents.

[0027] Comparative Example 1 The difference between this comparative example and Example 1 is that the MOF is not modified with zein. The specific preparation process of the antibacterial film is as follows: a) Preparation of polylactic acid-MOF film: PLA was dissolved in dichloromethane at room temperature to prepare a 5 wt% PLA solution, and MOF was added to the PLA solution at a PLA:MOF mass ratio of 30:1. Ultrasonic dispersion was performed for 30 minutes to uniformly disperse the MOF in the PLA solution to obtain a uniform and stable PLA-MOF dispersion. The obtained dispersion was coated into a film using a four-sided preparation device using a coating method. The obtained wet film was placed in a constant temperature and humidity chamber and dried for 12 hours under constant temperature and humidity conditions of 50°C and 70% to obtain a PLA-MOF thin film. b) Preparation of antibacterial film: The PLA-MOF film was immersed in 0.1 M NaOH solution for 50 seconds. The surface of the film was hydrolyzed to generate carboxylic acid groups, which made the surface of the PLA-MOF film negatively charged, thus obtaining a charge-modified PLA-MOF film. Polyethyleneimine and astaxanthin were dissolved in ethanol at a mass ratio of 1:10, wherein the concentration of astaxanthin was 2.5 mg / mL, and then phosphate buffer was added, the pH was adjusted to 5, and ultrasonic emulsification was performed to form a colloidal solution to obtain a polyethyleneimine-modified astaxanthin dispersion; The charge-modified PLA-MOF film was immersed in a polyethyleneimine-modified astaxanthin dispersion and reacted for 20 minutes under ultrasonic assistance (ultrasonic frequency of 40 kHz, ultrasonic power of 100 W). The astaxanthin was evenly adsorbed on the surface of the PLA-MOF film by electrostatic attraction to obtain an antibacterial film.

[0028] Figure 2 This is a field emission scanning electron micrograph of the PLA-MOF film prepared in this comparative example. Figure 2 It can be seen that the film prepared in this comparative example has very few internal pores and is unevenly distributed, and no honeycomb structure is formed as a whole. This is because the MOF without zein modification has poor compatibility with PLA and is prone to agglomeration during the preparation of the PLA-MOF film.

[0029] Comparative Example 2 The difference between this comparative example and Example 1 is that a traditional silane coupling agent is used to replace zein to modify MOF. The specific preparation process of the antibacterial film is as follows: a) Preparation of silane coupling agent modified MOF nanoparticles: 0.125 g of a silane coupling agent (specifically, KH-550) was added to 50 ml of ethanol and stirred at room temperature for 30 minutes to form an ethanol solution of the silane coupling agent. 0.05 g of MOF (specifically, ZIF-8) was then added and stirred at room temperature to mix uniformly. Citric acid was added to the resulting mixture to adjust the pH to 2-3, and the mixture was stirred at room temperature overnight (about 12 hours) to obtain a colloidal solution. The solution was freeze-dried to obtain silane coupling agent-modified MOF nanoparticles, i.e., silane coupling agent-MOF nanoparticles. b) Preparation of polylactic acid-silane coupling agent-MOF film: PLA was dissolved in dichloromethane at room temperature to prepare a PLA solution with a concentration of 5 wt %, silane coupling agent-MOF nanoparticles were added to the PLA solution, wherein the mass ratio of PLA:silane coupling agent-MOF was 30:1, ultrasonic dispersion was performed for 30 minutes to uniformly disperse the silane coupling agent-MOF nanoparticles in the PLA solution, thereby obtaining a uniform and stable PLA-silane coupling agent-MOF dispersion, the obtained dispersion was coated into a film using a four-sided preparation device by a coating method, and the obtained wet film was placed in a constant temperature and humidity chamber and dried for 12 hours under constant temperature and humidity conditions of 50° C. and 70% humidity to obtain a PLA-silane coupling agent-MOF thin film; c) Preparation of antibacterial film: The PLA-silane coupling agent-MOF film was immersed in 0.1M NaOH solution for 50s, and the surface of the film was hydrolyzed to generate carboxylic acid groups, which made the surface of the PLA-silane coupling agent-MOF film negatively charged, thus obtaining a charge-modified PLA-silane coupling agent-MOF film; Polyethyleneimine and astaxanthin were dissolved in ethanol at a mass ratio of 1:10, wherein the concentration of astaxanthin was 2.5 mg / mL, and then phosphate buffer was added, the pH was adjusted to 5, and ultrasonic emulsification was performed to form a colloidal solution to obtain a polyethyleneimine-modified astaxanthin dispersion; The charge-modified PLA-silane coupling agent-MOF film was immersed in a polyethyleneimine-modified astaxanthin dispersion and reacted for 20 minutes under ultrasonic assistance (ultrasonic frequency of 40 kHz, ultrasonic power of 100 W). Astaxanthin was adsorbed on the surface of the PLA-silane coupling agent-MOF film by electrostatic attraction to obtain an antibacterial film.

[0030] Comparative Example 3 The difference between this comparative example and Example 1 is that the conventional preparation process of "first improving MOF, then loading the antibacterial agent on the modified MOF to prepare MOF@antibacterial agent, and finally blending the MOF@antibacterial agent with PLA solution to prepare an antibacterial film" is adopted. The specific preparation process of the antibacterial film is as follows: a) Preparation of prolamin-modified MOF nanoparticles: 0.125 g of zein (Zein for short) was added to 50 ml of ethanol and stirred at room temperature for 30 minutes to form an ethanol solution of zein. 0.05 g of MOF (specifically ZIF-8) was then added and stirred at room temperature to mix uniformly. Citric acid was added to the resulting mixture to adjust the pH to 2-3. The mixture was stirred at room temperature overnight (approximately 12 hours) to obtain a colloidal solution, which was then freeze-dried to obtain zein-modified MOF nanoparticles, namely, Zein-MOF nanoparticles. b) Preparation of prolamin-modified MOF@astaxanthin nanoparticles: Astaxanthin was dissolved in ethanol to obtain a 2.5 mg / mL astaxanthin solution. Zein-MOF nanoparticles were added to the astaxanthin solution and ultrasonically dispersed for 30 minutes. The mixture was filtered, washed, and dried to obtain Zein-MOF@astaxanthin nanoparticles. c) Preparation of antibacterial film: PLA was dissolved in dichloromethane at room temperature to prepare a PLA solution with a concentration of 5 wt%, and Zein-MOF@astaxanthin nanoparticles were uniformly dispersed in a small amount of dichloromethane to form a Zein-MOF@astaxanthin dispersion. The Zein-MOF@astaxanthin dispersion was added to the PLA solution, wherein the mass ratio of PLA:Zein-MOF@astaxanthin was 30:1, and ultrasonic dispersion was performed for 30 minutes to form a uniform composite dispersion. The composite dispersion was coated into a film using a four-sided preparation device by a coating method. The obtained wet film was placed in a constant temperature and humidity chamber and dried for 12 hours under constant temperature and humidity conditions of 50°C and 70% to obtain an antibacterial film.

[0031] Antibacterial film performance test: 1. Antibacterial test: The antibacterial properties of the antibacterial films prepared in Example 1 and Comparative Examples 1-3 were tested according to ISO 22196:2011: Gram-positive Staphylococcus aureus (ATCC 6538) and Gram-negative Escherichia coli (ATCC 8739) were selected as the test bacteria, a pure PLA film was used as a control group, and the antibacterial films prepared in Example 1 and Comparative Examples 1-3 were used as test groups. During the test: the test sample size was 50 mm × 50 mm; the test sample was sterilized by ultraviolet light; the concentration of the inoculated bacterial solution was 10 5 CFU / mL, 0.4 mL of bacterial solution was inoculated in the center of the film and covered with a sterile polyethylene film; the culture conditions were 37°C and >90% RH for 24 hours; PBS containing 0.5% Tween 80 + 0.07% lecithin was used as the eluent for elution counting; each group was tested three times, and the average value was taken according to the formula A=log 10 (C)-log 10 (T) Calculate the antibacterial activity value A, where C is the average number of viable bacteria in the control group and T is the average number of viable bacteria in the test group; and use the formula R (%) = (1-10 -A )*100 to calculate the inhibition rate R. The test results are shown in Table 1.

[0032] Table 1 Antibacterial performance test data of the antibacterial films prepared in Example 1 and Comparative Examples 1-3

[0033] As can be seen from Table 1, the films prepared by compounding PLA, MOF and astaxanthin in Example 1 and Comparative Examples 1-3 have antibacterial activity against Staphylococcus aureus and Escherichia coli. However, the antibacterial film prepared in Example 1 has the best antibacterial performance. This may be because the antibacterial film prepared in Example 1 has the best internal pore structure, which can load more and better MOF and astaxanthin with antibacterial function, so that the antibacterial film of Example 1 has the best antibacterial activity.

[0034] 2. Stability test The antibacterial films prepared in Example 1 and Comparative Examples 1-3 were placed in an environment of 50°C / 90% RH for 28 days to accelerate the aging of the antibacterial films. The antibacterial properties were then tested again according to the method of ISO 22196:2011. The inhibition rate R after aging was compared with the inhibition rate measured in Table 1 before aging, and the inhibition rate decay rate was calculated. The stability of the antibacterial films was evaluated by the inhibition rate decay rate. The test results are shown in Table 2.

[0035] Table 2 Stability test data of antibacterial films prepared in Example 1 and Comparative Examples 1-3

[0036] As can be seen from Table 2, after accelerated aging, the antibacterial rate decay rate of the antibacterial film of Example 1 is less than 20%, while the antibacterial rate decay rates of the antibacterial films prepared in Comparative Examples 1-3 are all greater than 20%, indicating that the antibacterial film prepared in Example 1 has excellent antibacterial stability compared with the antibacterial films of Examples 1-3. This shows that only by adopting the preparation method of Example 1 can the MOF and antibacterial agent with antibacterial function be firmly fixed on the PLA film, so that the MOF and antibacterial agent in the antibacterial film are not easily migrated and fallen off from the PLA film, and ultimately the antibacterial film of Example 1 has excellent antibacterial stability.

[0037] From Table 1 and Table 2, it can be seen that the antibacterial film prepared by the technical solution of the present invention has good antibacterial properties and stability. Therefore, the antibacterial film can be used in the fields of food packaging (for example, food cling film, food packaging film), medical dressing (for example, base film of medical dressing) and air purification (for example: air purification filter membrane).

[0038] Finally, it should be pointed out that the above are only some preferred embodiments of the present invention and should not be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above contents of the present invention fall within the scope of protection of the present invention.

Claims

1. A method for preparing an antibacterial film, characterized in that: The steps include: a) Preparation of prolamin-modified MOF nanoparticles: The alcohol-soluble protein is dissolved in an alcohol solvent to form an alcohol solution of the alcohol-soluble protein, MOF is added, and the mixture is mixed evenly. Acid is added to the resulting mixture to adjust the pH to 2-3, and the mixture is stirred at room temperature for 10-20 hours to obtain a colloidal solution, which is freeze-dried to obtain alcohol-soluble protein-modified MOF nanoparticles; b) Preparation of honeycomb-shaped polylactic acid-prolamin-MOF film: The prolamin-modified MOF nanoparticles are uniformly dispersed in a PLA solution to obtain a uniform and stable PLA-prolamin-MOF dispersion, and the resulting dispersion is formed into a film to obtain a honeycomb-shaped polylactic acid-prolamin-MOF film; c) Preparation of antibacterial film: performing charge modification on the polylactic acid-gliadin-MOF film so that the surface of the polylactic acid-gliadin-MOF film is negatively charged, thereby obtaining a charge-modified polylactic acid-gliadin-MOF film; The cationic crosslinker and the natural antibacterial agent are dissolved in an alcohol solvent, a buffer solution is added, the pH is adjusted to 4-6, and ultrasonic emulsification is performed to form a colloidal solution to obtain a crosslinker-modified antibacterial agent dispersion. The charge-modified polylactic acid-gliadin-MOF film was immersed in a cross-linker-modified antibacterial agent dispersion and reacted for 10 to 30 minutes under ultrasound assistance to obtain an antibacterial film.

2. The method for preparing the antibacterial film according to claim 1, wherein: In step a), the alcohol-soluble protein is any one of zein, wheat alcohol-soluble protein, hordein, secalin, and kafirin; and the MOF includes silver-based MOF, zinc-based MOF, and copper-based MOF.

3. The method for preparing the antibacterial film according to claim 1, wherein: In step a), the mass ratio of prolamin:MOF is (2-3):

1.

4. The method for preparing the antibacterial film according to claim 1, wherein: In step b), the mass ratio of PLA to alcohol-soluble protein-modified MOF nanoparticles is (20-40):

1.

5. The method for preparing the antibacterial film according to claim 1, characterized in that: In step c), the polylactic acid-gliadin-MOF film is charge-modified by any of the following methods: ① Immerse the polylactic acid-prolamin-MOF film in a 0.1~1M NaOH solution for 30-60 seconds to hydrolyze the surface of the polylactic acid-prolamin-MOF film to generate carboxylic acid groups, thereby making the surface of the polylactic acid-prolamin-MOF film negatively charged, thereby obtaining a charge-modified polylactic acid-prolamin-MOF film; ② Plasma treatment technology is used to treat the surface of the polylactic acid-alcohol-soluble protein-MOF film, and oxygen-containing polar groups are introduced on the surface of the polylactic acid-alcohol-soluble protein-MOF film to enhance the surface negative charge density, so that the surface of the polylactic acid-alcohol-soluble protein-MOF film is negatively charged, thereby obtaining a charge-modified polylactic acid-alcohol-soluble protein-MOF film.

6. The method for preparing the antibacterial film according to claim 1, wherein: In step c), the cationic crosslinking agent used is polyethyleneimine.

7. The method for preparing the antibacterial film according to claim 1, wherein: In step c), the natural antibacterial agent used is astaxanthin, curcumin, resveratrol or flavonoids, which are natural substances with antioxidant and antibacterial properties.

8. The method for preparing the antibacterial film according to claim 1, wherein: In step c), the mass ratio of cationic crosslinking agent to natural antibacterial agent is 1:(8-12).

9. An antibacterial film prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the antibacterial film according to claim 9 in the fields of food packaging, medical dressing and air purification.

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