Antibacterial film, preparation method and application thereof

Abstract

The application discloses a bacteriostatic film, a preparation method and application thereof. The preparation method of the bacteriostatic film comprises the following steps: a) preparing alcohol-soluble protein modified MOF nanoparticles; b) preparing a honeycomb-shaped polylactic acid-alcohol-soluble protein-MOF film; and c) preparing the bacteriostatic film. The alcohol-soluble protein is used to modify the MOF first, then the obtained alcohol-soluble protein modified MOF nanoparticles are blended with a PLA solution to form a film to obtain the honeycomb-shaped polylactic acid-alcohol-soluble protein-MOF film, then the honeycomb-shaped polylactic acid-alcohol-soluble protein-MOF film is subjected to charge modification to obtain the charge-modified polylactic acid-alcohol-soluble protein-MOF film, and finally the natural bacteriostatic agent is adsorbed and fixed on the polylactic acid-alcohol-soluble protein-MOF film in the presence of a cationic crosslinking agent, so that the prepared bacteriostatic film has good bacteriostasis and stability and can be applied to the fields of food packaging, medical dressings and air purification.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of bacteriostatic film, preparation method and its application, belong to functional polymer composite material field technical field. BACKGROUND

[0002] Polylactic acid (PLA) film is a kind of biobased degradable film, is currently widely used in food packaging, medical dressing, air purification and other fields.

[0003] Although polylactic acid film has biodegradability, it lacks bacteriostasis, and at present, it mainly has bacteriostasis performance by adding bacteriostatic substances, but polylactic acid film has release defects, cannot realize the slow release function of bacteriostatic substances, resulting in insufficient long-acting bacteriostasis. Metal organic framework (MOF) is a kind of porous crystalline material formed by metal ions / clusters and organic ligands through coordination bond self-assembly, can slowly release metal ions or antibacterial ligand, therefore, PLA-MOF composite film obtained by blending and compounding MOF and PLA can effectively improve the bacteriostasis and slow release of polylactic acid film, for example: in patent 202310588559.X, Ag@MOF carrier is loaded with natural antibacterial agent, then mixed with polylactic acid, and then polylactic acid active packaging film is prepared by melt extrusion blow molding. The polylactic acid active packaging film is used for packaging Clitocybe, realizes the active packaging of Clitocybe, can inhibit the growth of microorganisms, and prolongs the shelf life of Clitocybe.

[0004] However, polylactic acid is a hydrophobic organic polymer, and metal organic framework is usually a polar or hydrophilic inorganic-organic hybrid crystal, resulting in poor interfacial compatibility of PLA and MOF, and MOF is difficult to disperse uniformly in PLA matrix, and is easy to form large aggregates, thereby affecting the stability and bacteriostasis of PLA-MOF composite film. SUMMARY

[0005] In view of the above problems existing in the prior art, the purpose of the present application is to provide a kind of bacteriostatic film, preparation method and its application.

[0006] To achieve the above-mentioned purpose of the present application, the technical solutions adopted by the present application are as follows:

[0007] A preparation method of a bacteriostatic film, comprising the following steps:

[0008] a) preparation of alcohol-soluble protein modified MOF nanoparticles:

[0009] The alcohol-soluble protein is dissolved in alcohol solvent to form an alcohol solution of alcohol-soluble protein, MOF is added, and the mixture is uniformly mixed, the obtained mixed solution is added with acid to adjust pH=2~3, stirred at room temperature for 10~20 hours, to obtain a colloidal solution, freeze-dried to obtain alcohol-soluble protein modified MOF nanoparticles;

[0010] b) Preparation of the honeycomb-shaped polylactic acid-zein-MOF film:

[0011] The zein-modified MOF nanoparticles are uniformly dispersed in the PLA solution to obtain a uniform and stable PLA-zein-MOF dispersion, and the obtained dispersion is formed into a film to obtain a honeycomb-shaped polylactic acid-zein-MOF film.

[0012] c) Preparation of the antibacterial film:

[0013] The polylactic acid-zein-MOF film is subjected to charge modification to make the surface of the polylactic acid-zein-MOF film negatively charged, thereby obtaining a charge-modified polylactic acid-zein-MOF film.

[0014] The cationic crosslinking agent and the natural antibacterial agent are dissolved in an alcohol solvent, a buffer solution is added, the pH is adjusted to 4-6, and a colloidal solution is formed by ultrasonic emulsification to obtain a crosslinking agent-modified antibacterial agent dispersion.

[0015] The charge-modified polylactic acid-zein-MOF film is immersed in the crosslinking agent-modified antibacterial agent dispersion, and reacted for 10-30 minutes under ultrasonic assistance to obtain an antibacterial film.

[0016] In one embodiment, in step a), 0.1-0.5 g of zein is dissolved in 100 ml of an alcohol solvent to form an alcohol solution of zein.

[0017] In one embodiment, in step a), the zein is any one of corn zein, wheat zein, barley zein, rye zein, and sorghum zein, and preferably corn 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.

[0018] In one embodiment, in step a), the mass ratio of zein to MOF is (2-3):1.

[0019] In one embodiment, in step a), the acid used is citric acid.

[0020] In one embodiment, in step b), the PLA solution is a chloroform or dichloromethane solution of PLA with a concentration of 2-10 wt%.

[0021] In one embodiment, in step b), the mass ratio of PLA to zein-modified MOF nanoparticles is (20-40):1. In one embodiment, in step b), the obtained dispersion is formed into a film by using a coating method or a casting method.

[0022] In a preferred embodiment, in step b), the obtained wet film is dried for 10-20 hours under constant temperature and humidity conditions of 45-55℃ and 60-80% humidity during the film forming process, to obtain a honeycomb-shaped polylactic acid-zeatin-MOF film.

[0023] In an embodiment, in step c), the polylactic acid-zeatin-MOF film is subjected to charge modification by any of the following methods:

[0024] ① The polylactic acid-zeatin-MOF film is immersed in a 0.1-1M NaOH solution for 30-60 seconds to hydrolyze carboxyl groups on the surface of the polylactic acid-zeatin-MOF film, thereby making the surface of the polylactic acid-zeatin-MOF film negatively charged (Zeta potential ≤-25mV), to obtain a charge-modified polylactic acid-zeatin-MOF film;

[0025] ② The polylactic acid-zeatin-MOF film is subjected to surface treatment by plasma treatment technology to introduce oxygen-containing polar groups on the surface of the polylactic acid-zeatin-MOF film, thereby enhancing the surface negative charge density and making the surface of the polylactic acid-zeatin-MOF film negatively charged, to obtain a charge-modified polylactic acid-zeatin-MOF film; the power of the plasma treatment is 50-100W, and the time is 2-5 minutes.

[0026] In an embodiment, in step c), the cationic crosslinking agent used is polyethyleneimine (PEI).

[0027] In an embodiment, in step c), the natural antibacterial agent used is astaxanthin, curcumin, resveratrol, or a natural substance with antioxidant and antibacterial properties (for example: quercetin, kaempferol, luteolin, baicalein, catechin, etc.), the alcohol solvent used is ethanol, and the buffer solution used is a phosphate buffer solution.

[0028] In an embodiment, in step c), the mass ratio of the cationic crosslinking agent to the natural antibacterial agent is 1:(8-12).

[0029] In an embodiment, in step c), the concentration of the antibacterial agent in the antibacterial agent dispersion solution is 1-5mg / mL.

[0030] In an embodiment, in step c), when ultrasonic assistance is used, the ultrasonic frequency is 20-60kHz, and the ultrasonic power is 50-150W.

[0031] An antibacterial film prepared by the above preparation method.

[0032] The application of an antibacterial film prepared by the above preparation method in the fields of food packaging, medical dressings, and air purification.

[0033] Compared with the prior art, the present application has the following remarkable beneficial effects:

[0034] The present application first modifies MOF with prolamine to obtain prolamine modified MOF nanoparticles, then blends the prolamine modified MOF nanoparticles with a PLA solution to form a film to obtain a honeycomb-shaped polylactic acid-prolamine-MOF film, then charges the honeycomb-shaped polylactic acid-prolamine-MOF film to obtain a charge-modified polylactic acid-prolamine-MOF film, and finally adsorbs and fixes a natural bacteriostatic agent on the polylactic acid-prolamine-MOF film in the presence of a cationic crosslinking agent to prepare a bacteriostatic film with good bacteriostatic property and stability, which can be widely applied in the fields of food packaging, medical dressings and air purification and has great potential value. In addition, the preparation method of the present application is economical and practical, the preparation process is simple, the cost is low, no special equipment and harsh conditions are needed, and the method is easy to realize large-scale production and has strong industrial application value. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 Figure 1 is a field emission scanning electron microscope image of the honeycomb-shaped polylactic acid-prolamine-MOF film prepared in Example 1 of the present application.

[0036] Figure 2 Figure 2 is a field emission scanning electron microscope image of the polylactic acid-MOF film prepared in Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0037] The technical solutions of the present application will be further described in detail below with reference to the examples. It should be understood that these examples are only used to illustrate the present application and not to limit the scope of the present application. The experimental methods not specified in the following examples are usually carried out according to the conventional conditions or according to the conditions recommended by the manufacturers.

[0038] Example 1

[0039] a) Preparation of prolamine modified MOF nanoparticles:

[0040] 0.125g of corn prolamine (abbreviation: Zein) was added to 50ml of ethanol, stirred at room temperature for 30 minutes to form an ethanol solution of corn prolamine, then 0.05g of MOF (specifically: ZIF-8) was added, stirred at room temperature to mix uniformly, citric acid was added to the obtained mixture to adjust pH=2~3, stirred at room temperature overnight (about 12 hours) to obtain a colloidal solution, and freeze-dried to obtain corn prolamine modified MOF nanoparticles, i.e. Zein-MOF nanoparticles;

[0041] b) Preparation of honeycomb-shaped polylactic acid-prolamine-MOF film:

[0042] The PLA was dissolved in dichloromethane (or chloroform) at room temperature to prepare a PLA solution with a concentration of 5wt%, and then the Zein-MOF nanoparticles were added into the PLA solution, wherein the mass ratio of PLA to Zein-MOF nanoparticles was 30:1, and the Zein-MOF nanoparticles were ultrasonically dispersed for 30 minutes to uniformly disperse the Zein-MOF nanoparticles in the PLA solution to obtain a uniform and stable PLA-Zein-MOF dispersion liquid, and then the obtained dispersion liquid was coated into a film by a coating method through a four-side coater, and the obtained wet film was placed in a constant temperature and humidity box for drying for 12 hours under a constant temperature and humidity condition of a temperature of 50℃ and a humidity of 70% to obtain a honeycomb-shaped PLA-Zein-MOF film;

[0043] c) Preparation of the antibacterial film:

[0044] The PLA-Zein-MOF film was immersed in a 0.1M NaOH solution for 50s, and the surface of the film was hydrolyzed to generate carboxyl groups, so that the surface of the PLA-Zein-MOF film was negatively charged to obtain a charge-modified PLA-Zein-MOF film;

[0045] Polyethyleneimine and astaxanthin were dissolved in ethanol according to a mass ratio of 1:10, wherein the concentration of astaxanthin was 2.5mg / mL, and then a phosphate buffer was added to adjust the pH to 5, and a colloidal solution was formed by ultrasonic emulsification to obtain a polyethyleneimine-modified astaxanthin dispersion liquid;

[0046] The charge-modified PLA-Zein-MOF film was immersed in the polyethyleneimine-modified astaxanthin dispersion liquid, and reacted under ultrasonic assistance (ultrasonic frequency of 40kHz and ultrasonic power of 100W) for 20 minutes, and the astaxanthin was uniformly adsorbed on the surface of the PLA-Zein-MOF film by electrostatic attraction to obtain an antibacterial film.

[0047] Figure 1 The field emission scanning electron microscope image of the polylactic acid-zein-MOF film (PLA-Zein-MOF film) prepared in this example is shown in FIG. 1. Figure 1 It can be seen that the PLA-Zein-MOF film prepared in this example has uniformly distributed pores with a pore size of 10-20µm, and the overall structure is obviously honeycomb-shaped. This structure not only effectively increases the surface area of the film, but also uniformly loads the MOF in the PLA, which lays a good foundation for better adsorption of antibacterial agents in the subsequent process.

[0048] Comparative Example 1

[0049] The difference between this comparative example and Example 1 is that the MOF is not modified by corn zein, and the specific preparation process of the antibacterial film is as follows:

[0050] a) Preparation of polylactic acid-MOF film:

[0051] The PLA was dissolved in dichloromethane at room temperature to prepare a PLA solution with a concentration of 5wt%, and the MOF was added to the PLA solution, wherein the mass ratio of PLA:MOF was 30:1, and the MOF was uniformly dispersed in the PLA solution by ultrasonic dispersion for 30 minutes to obtain a uniform and stable PLA-MOF dispersion. The obtained dispersion was coated into a film by a coating method using a four-side coater, and the obtained wet film was placed in a constant temperature and humidity box and dried at a temperature of 50°C and a humidity of 70% for 12 hours to obtain a PLA-MOF film.

[0052] b) Preparation of the antibacterial film:

[0053] The PLA-MOF film was immersed in a 0.1M NaOH solution for 50s, and the surface of the film was hydrolyzed to generate carboxyl groups, so that the surface of the PLA-MOF film was negatively charged to obtain a charge-modified PLA-MOF film.

[0054] Polyethyleneimine and astaxanthin were dissolved in ethanol according to a mass ratio of 1:10, wherein the concentration of astaxanthin was 2.5mg / mL, and then phosphate buffer was added to adjust the pH to 5, and a colloidal solution was formed by ultrasonic emulsification to obtain a polyethyleneimine-modified astaxanthin dispersion.

[0055] The charge-modified PLA-MOF film was immersed in the polyethyleneimine-modified astaxanthin dispersion, and reacted under ultrasonic assistance (ultrasonic frequency of 40kHz and ultrasonic power of 100W) for 20 minutes, and the astaxanthin was uniformly adsorbed on the surface of the PLA-MOF film by electrostatic attraction to obtain an antibacterial film.

[0056] Figure 2 The field emission scanning electron microscope image of the PLA-MOF film prepared in the present comparative example, from which Figure 2 It can be seen that the film prepared in the present comparative example has few internal pores and uneven distribution, and the overall honeycomb structure is not formed, because the compatibility of the MOF not modified by zein with PLA is poor, and the MOF is prone to agglomeration during the preparation of the PLA-MOF film.

[0057] Comparative Example 2

[0058] The difference between the present comparative example and Example 1 is that the MOF is modified by a traditional silane coupling agent instead of zein, and the specific preparation process of the antibacterial film is as follows:

[0059] a) Preparation of MOF nanoparticles modified by a silane coupling agent:

[0060] 0.125g silane coupling agent (specifically: KH-550) was added to 50ml ethanol, stirred at room temperature for 30 minutes to form an ethanol solution of silane coupling agent, then 0.05g MOF (specifically: ZIF-8) was added, stirred at room temperature to mix uniformly, citric acid was added to the obtained mixed solution to adjust pH=2~3, stirred at room temperature overnight (about 12 hours), a colloidal solution was obtained, and freeze-drying was performed to obtain silane coupling agent modified MOF nanoparticles, i.e. silane coupling agent-MOF nanoparticles;

[0061] b) Preparation of polylactic acid-silane coupling agent-MOF film:

[0062] PLA was dissolved in dichloromethane at room temperature to prepare a PLA solution with a concentration of 5wt%, and the silane coupling agent-MOF nanoparticles were added to the PLA solution, wherein the mass ratio of PLA to silane coupling agent-MOF was 30:1, and the silane coupling agent-MOF nanoparticles were ultrasonically dispersed for 30 minutes to uniformly disperse the silane coupling agent-MOF nanoparticles in the PLA solution to obtain a uniform and stable PLA-silane coupling agent-MOF dispersion liquid, and the obtained dispersion liquid was coated into a film by a four-side coater using a coating method, and the obtained wet film was placed in a constant temperature and humidity box and dried at a temperature of 50℃ and a humidity of 70% for 12 hours to obtain a PLA-silane coupling agent-MOF film;

[0063] c) Preparation of antibacterial film:

[0064] The PLA-silane coupling agent-MOF film was immersed in a 0.1M NaOH solution for 50s, and the surface of the film was hydrolyzed to generate carboxylic acid groups, so that the surface of the PLA-silane coupling agent-MOF film was negatively charged, and a charge-modified PLA-silane coupling agent-MOF film was obtained.

[0065] Polyethyleneimine and astaxanthin were dissolved in ethanol according to a mass ratio of 1:10, wherein the concentration of astaxanthin was 2.5mg / mL, then phosphate buffer was added to adjust pH=5, and ultrasonic emulsification was performed to form a colloidal solution, thereby obtaining a polyethyleneimine-modified astaxanthin dispersion liquid;

[0066] The charge-modified PLA-silane coupling agent-MOF film was immersed in the polyethyleneimine-modified astaxanthin dispersion liquid, and reacted under ultrasonic assistance (ultrasonic frequency was 40kHz, and ultrasonic power was 100W) for 20 minutes, and the astaxanthin was adsorbed on the surface of the PLA-silane coupling agent-MOF film by electrostatic attraction, thereby obtaining an antibacterial film.

[0067] Comparative Example 3

[0068] The difference between this comparative example and Example 1 is that the preparation process of the antibacterial film is as follows: the traditional "first modifying MOF, then loading bacteriostatic agent on the modified MOF to prepare MOF@bacteriostatic agent, and finally blending MOF@bacteriostatic agent with PLA solution to prepare antibacterial film" preparation process is adopted.

[0069] a) Preparation of alcohol-soluble protein modified MOF nanoparticles:

[0070] 0.125 g of corn alcohol-soluble protein (abbreviation: Zein) was added to 50 ml of ethanol, stirred at room temperature for 30 minutes to form an ethanol solution of corn alcohol-soluble protein, then 0.05 g of MOF (specifically: ZIF-8) was added, and stirred at room temperature to mix uniformly. Citric acid was added to the obtained mixture to adjust the pH to 2-3, and stirred overnight (about 12 hours) at room temperature to obtain a colloidal solution, which was freeze-dried to obtain Zein-MOF nanoparticles.

[0071] b) Preparation of alcohol-soluble protein modified MOF@astaxanthin nanoparticles:

[0072] Astaxanthin was dissolved in ethanol to obtain a 2.5 mg / mL astaxanthin solution, and Zein-MOF nanoparticles were added to the astaxanthin solution and ultrasonically dispersed for 30 minutes. After filtration, washing and drying, Zein-MOF@astaxanthin nanoparticles were obtained.

[0073] c) Preparation of antibacterial film:

[0074] 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, and the mass ratio of PLA to Zein-MOF@astaxanthin was 30:1. The mixture was ultrasonically dispersed for 30 minutes to form a uniform composite dispersion. The obtained composite dispersion was coated into a film by a four-side coater using a coating method. The obtained wet film was placed in a constant temperature and humidity box and dried at a temperature of 50°C and a humidity of 70% for 12 hours to obtain an antibacterial film.

[0075] Antibacterial film performance test:

[0076] 1. Test of antibacterial property:

[0077] The antibacterial properties of the antibacterial films prepared in Example 1 and Comparative Examples 1-3 were tested according to the method of ISO 22196:2011: Gram-positive Staphylococcus aureus (ATCC 6538) and Gram-negative Escherichia coli (ATCC 8739) were selected as test bacteria, and 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.

[0078] During the test: the size of the test sample was 50 mm x 50 mm; the test sample was treated by ultraviolet sterilization; the concentration of the bacterial solution for inoculation was 10 5 CFU / mL, 0.4 mL of bacterial solution was inoculated in the center of the film, and a sterile polyethylene film was covered; the culture conditions were 37°C, >90% RH for 24 hours; 0.5% Tween 80 + 0.07% lecithin in PBS was used as an eluent for elution counting; each group was tested three times, and the average value was taken, and the antibacterial activity value A was calculated according to the formula A = log 10 (C)-log 10 (T); and the antibacterial rate R was calculated according to the formula R (%) = (1-10 -A )*100, and the test results are shown in Table 1.

[0079] Table 1: Antibacterial performance test data of antibacterial films prepared in Example 1 and Comparative Examples 1-3

[0080]

[0081] 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, but the antibacterial film prepared in Example 1 has the best antibacterial performance, which may be because the antibacterial film prepared in Example 1 has the best internal pore structure, which can better load MOF and astaxanthin with antibacterial function, thereby making the antibacterial film of Example 1 have the best antibacterial activity.

[0082] 2. Stability test

[0083] 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, and then their antibacterial properties were tested again according to the method of ISO 22196:2011, the antibacterial rate R after aging was compared with the antibacterial rate measured in Table 1 before aging, the antibacterial rate decay rate was calculated, and the stability of the antibacterial film was evaluated by the antibacterial rate decay rate, and the test results are shown in Table 2.

[0084] Table 2. Stability test data of the antibacterial film prepared in Example 1 and Comparative Examples 1-3

[0085]

[0086] As can be seen from Table 2, after accelerated aging, the antibacterial rate attenuation rate of the antibacterial film of Example 1 is <20%, while the antibacterial rate attenuation rate of the antibacterial films prepared in Comparative Examples 1-3 are all >20%, indicating that the antibacterial film prepared in Example 1 has excellent antibacterial stability compared to the antibacterial films of Examples 1-3, indicating that only the preparation method of Example 1 can firmly fix the MOF and antibacterial agent with antibacterial function on the PLA film, so that the MOF and antibacterial agent in the antibacterial film are not easy to migrate and fall off from the PLA film, finally making the antibacterial film of Example 1 have excellent antibacterial stability.

[0087] As can be seen from Tables 1 and 2, the antibacterial film prepared by the technical scheme of the present application has good antibacterial property and stability, and therefore, the antibacterial film can be used in the fields of food packaging (for example, food preservative film, food packaging film), medical dressing (for example, base film of medical dressing) and air purification (for example: air purification filter film).

[0088] Finally, it needs to be pointed out that: the above is only some preferred embodiments of the present application, and cannot be understood as limiting the protection scope of the present application, and some non-essential improvements and adjustments made by the person skilled in the art according to the above content of the present application all belong to the protection scope of the present application.

Claims

1. A method for preparing an antibacterial film, characterized in that, Includes the following steps: a) Preparation of prolysin-modified MOF nanoparticles: Alcohol-soluble protein was dissolved in an alcohol solvent to form an alcohol solution of alcohol-soluble protein. MOF was added and mixed evenly. Acid was added to the resulting mixture to adjust the pH to 2-3. The mixture was stirred at room temperature for 10-20 hours to obtain a colloidal solution. The solution was then freeze-dried to obtain alcohol-soluble protein modified MOF nanoparticles. b) Preparation of honeycomb-structured polylactic acid-prolyl-MOF films: Alcohol-modified MOF nanoparticles were uniformly dispersed in PLA solution to obtain a uniform and stable PLA-alcohol-MOF dispersion. The obtained dispersion was then used to form a film to obtain a honeycomb-shaped polylactic acid-alcohol-MOF film. c) Preparation of antibacterial film: Charge modification was performed on polylactic acid-prolyl protein-MOF films to make the surface of the polylactic acid-prolyl protein-MOF films negatively charged, thus obtaining charge-modified polylactic acid-prolyl protein-MOF films; The cationic crosslinking agent and the natural antibacterial agent were dissolved in an alcohol solvent, a buffer solution was added, the pH was adjusted to 4-6, and the mixture was ultrasonically emulsified to form a colloidal solution, thus obtaining a crosslinking agent modified antibacterial agent dispersion. The charge-modified polylactic acid-protein-MOF film was immersed in a crosslinking agent-modified antibacterial agent dispersion and reacted under ultrasonic assistance for 10-30 minutes to obtain the antibacterial film. In step c), the polylactic acid-prolyl-MOF film is charged using any of the following methods: ① Immerse the polylactic acid-protein-MOF film in 0.1~1M NaOH solution for 30-60 seconds to hydrolyze the surface of the polylactic acid-protein-MOF film to generate carboxylic acid groups, thereby making the surface of the polylactic acid-protein-MOF film negatively charged, and obtaining a charge-modified polylactic acid-protein-MOF film. ② The surface of polylactic acid-alcohol-MOF film is treated with plasma treatment technology to introduce oxygen-containing polar groups on the surface of polylactic acid-alcohol-MOF film, enhance the surface negative charge density, and make the surface of polylactic acid-alcohol-MOF film negatively charged, thus obtaining charge-modified polylactic acid-alcohol-MOF film. In step c), the cationic crosslinking agent used is polyethyleneimine, and the natural antibacterial agent used is astaxanthin, curcumin, resveratrol, or flavonoids, which are natural substances with antioxidant and antibacterial properties.

2. The method for preparing the antibacterial film according to claim 1, characterized in that: In step a), the prolysin is any one of zein, wheat prolysin, barley prolysin, rye prolysin, and sorghum prolysin; 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, characterized in that: In step a), the mass ratio of prolysin to MOF is (2~3):

1.

4. The method for preparing the antibacterial film according to claim 1, characterized in that: In step b), the mass ratio of PLA to prolysin-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 mass ratio of cationic crosslinking agent to natural antibacterial agent is 1:(8~12).

6. An antibacterial film prepared by any one of claims 1-5.

7. The application of the antibacterial film as described in claim 6 in the preparation of food packaging, medical dressings and air purification materials.

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