CN111714285B - Layer-by-layer self-assembled film and preparation method thereof - Google Patents

Abstract

A layer-by-layer self-assembled film and a preparation method thereof relate to the field of dressings. The preparation method of the layer-by-layer self-assembled film includes: sequentially soaking the base film in a weakly acidic polyvinylpyrrolidone aqueous solution and a weakly acidic tannic acid aqueous solution as an assembly cycle, and drying after completing a preset number of assembly cycles. The preparation method is simple in operation, easy to obtain materials, and high in utilization rate, and the loading amount can be adjusted by changing the concentration of the tannic acid aqueous solution and the preset number of assembly cycles; It can be stored and used for a long time, and at the same time, it can release tannins slowly in the wound environment to promote wound healing.

Description

Layer-by-layer self-assembled film and preparation method thereof

technical field

The present application relates to the field of dressings, in particular, to a layer-by-layer self-assembled film and a preparation method thereof.

Background technique

Antimicrobial wound dressings have grown in popularity in recent years, and most commercial suppliers now offer silver-coated or silver nanoparticle-impregnated dressings. Although the broad-spectrum antimicrobial effect of this dressing has been demonstrated, silver cytotoxicity to mammalian cells and negative effects on the wound healing process have also been reported. Therefore, we focused on finding an alternative antimicrobial agent.

Tannin (TA) is a weakly acidic polyphenolic compound that exists widely in nature. TA is considered to be an antioxidant, antibacterial and anti-inflammatory, etc., and it has good biocompatibility. However, when TA solution is used directly on the wound surface, the TA solution is easy to be lost and the antibacterial effect is not good.

With this in mind, the present application is hereby made.

SUMMARY OF THE INVENTION

The present application provides a layer-by-layer self-assembled film and a preparation method thereof provided in the embodiments of the present application, so as to improve or alleviate the above-mentioned technical problems.

According to the preparation method of the layer-by-layer self-assembled film according to the embodiment of the first aspect of the present application, it includes:

The base film is immersed in a weakly acidic polyvinylpyrrolidone aqueous solution and a weakly acidic tannic acid aqueous solution in sequence as an assembly cycle, and dried after completing a preset number of assembly cycles.

According to the method for preparing the layer-by-layer self-assembled film of the embodiment of the present application, the base film is immersed in the weakly acidic polyvinylpyrrolidone aqueous solution and the weakly acidic tannic acid aqueous solution in turn to form alternating weakly acidic polyvinylpyrrolidone on the surface of the basement film Layer and weakly acidic tannic acid layer, the tannic acid layer is stably loaded on the basement membrane through the polyvinylpyrrolidone layer, and the weakly acidic condition is more conducive to bacteriostasis.

Since the connection between polyvinylpyrrolidone and tannic acid mainly relies on hydrogen bonding, and hydrogen bonding is reversible in nature, in aqueous solution, the layer-by-layer self-assembled film will gradually decompose, so that the tannic acid self-assembles from layer to layer. The film is released into the medium. When the layers of self-assembled films are applied to the wound as wound dressings (the basement membrane is located on the side away from the wound), the wound is actually a humid microenvironment, so the layers of self-assembled films will gradually disintegrate to prevent damage. Achieve sustained release of tannins. And polyvinylpyrrolidone has high biocompatibility and has no adverse effect on the wound surface.

The preparation method of the layer-by-layer self-assembled film is simple to operate, and the raw materials polyvinylpyrrolidone and tannic acid are readily available. The long-acting sustained release of tannic acid can be achieved by changing the preset number of assembly cycles, and by changing the tannic acid aqueous solution The tannin loading can be adjusted by the concentration and preset times, and the finally obtained layer-by-layer self-assembled film exhibits good antibacterial activity and good cell behavior, which can promote better wound healing.

In addition, the method for preparing the layer-by-layer self-assembled film according to the embodiment of the present application also has the following additional technical features:

In a possible embodiment, soaking in the weakly acidic polyvinylpyrrolidone aqueous solution and the weakly acidic tannic acid aqueous solution in sequence includes: first soaking in the weakly acidic polyvinylpyrrolidone aqueous solution for 5-10 minutes, washing, and then Soak in weakly acidic tannic acid aqueous solution for 5 to 10 minutes and wash.

In the above realization process, the excess polyvinylpyrrolidone and tannin on the surface are respectively removed by washing after each soaking, so as to ensure the stability of the connection between the finally formed tannic acid layer and the polyvinylpyrrolidone layer, so as to achieve long-term retardation. release effect.

Acidic fibroblast growth factor (aFGF) can effectively promote cell proliferation and tissue regeneration, thereby promoting wound repair and improving the quality of wound healing. At the same time, the weakly acidic polyvinylpyrrolidone aqueous solution is a kind of polymer solution with good biocompatibility. The applicant found that aFGF can be well encapsulated by the PVP polymer chain, and it can maintain its activity to the greatest extent. The PVP wrapped with aFGF then self-assembled with TA through hydrogen bonding to form a layer-by-layer self-assembled film.

Therefore, in a possible embodiment, the weakly acidic polyvinylpyrrolidone aqueous solution contains acidic fibroblast growth factor, and the concentration of the acidic fibroblast growth factor in the weakly acidic polyvinylpyrrolidone aqueous solution is 0.5-100 ug/ml .

In the above realization process, the continuous release of TA and aFGF is achieved through the above settings, so that TA and aFGF can achieve the purpose of sterilization and cell proliferation in different stages of wound healing, so that the layers of self-assembled films show good antibacterial activity and Good cell behavior, promotes angiogenesis and tissue regeneration, and promotes better wound healing.

In one possible embodiment, each assembly cycle is performed at a temperature of 2-8°C.

In the above realization process, through appropriate temperature selection, the activities of TA and aFGF are kept in a better range, so that the layer-by-layer self-assembled films have good antibacterial activity and good cell behavior, which can promote better wound healing.

In a possible embodiment, the pH value of the weakly acidic polyvinylpyrrolidone aqueous solution is 5-6.

In the above realization process, because the optimum pH of aFGF is between 5 and 6, the above pH can keep aFGF with better activity, and can also improve the wound environment and the antibacterial effect of the layer-by-layer self-assembled film.

Optionally, the concentration of polyvinylpyrrolidone in the weakly acidic polyvinylpyrrolidone aqueous solution is 0.5-10 mg/mL.

In a possible embodiment, the pH value of the weakly acidic tannic acid aqueous solution is 5-6.

In the above realization process, because the optimum pH of aFGF is between 5 and 6, the above pH can keep aFGF with better activity, and can also improve the wound environment and the antibacterial effect of the layer-by-layer self-assembled film.

Optionally, the concentration of tannic acid in the weakly acidic tannic acid aqueous solution is 0.5-10 mg/mL.

Since the surface of the base film that has completed the preset number of assembly cycles is a weakly acidic polyvinylpyrrolidone layer and a tannic acid layer, in order to avoid affecting the uniformity of the distribution of the polyvinylpyrrolidone layer and the tannic acid layer, and to ensure the tannic acid layer The activity is better, and in a possible embodiment, it is hang-dried at 2-8° C. after completing a preset number of assembly cycles.

In the above realization process, the drying effect is good, the structural integrity of the layer-by-layer self-assembled film is ensured, and the effect of promoting wound healing is good.

Optionally, the basement membrane is a hydrophobic membrane.

In the above implementation process, the outside water is prevented from being adsorbed to the wound and the wound is infected, and at the same time, the sustained release effect of TA is ensured. After use, the basement membrane is easily torn off and does not adhere to the wound.

The layer-by-layer self-assembled film according to the embodiment of the second aspect of the present application is prepared by the method for preparing the layer-by-layer self-assembled film of the embodiment of the first aspect of the present application.

The layer-by-layer self-assembled film according to the embodiment of the present application has simple structure, low cost, good antibacterial activity and good cell behavior, and effectively promotes wound healing.

The layer-by-layer self-assembled film according to the embodiment of the third aspect of the present application includes a base film and at least one functional layer formed on the base film.

Each functional layer includes a weakly acidic polyvinylpyrrolidone layer, and a weakly acidic tannic acid layer connected with the side of the polyvinylpyrrolidone layer away from the base film through hydrogen bonds.

The layer-by-layer self-assembled film according to the embodiment of the present application has simple structure, low cost, good antibacterial activity and good cell behavior, and effectively promotes wound healing.

Description of drawings

In order to illustrate the technical solutions of the embodiments of the present application more clearly, the following drawings will briefly introduce the drawings that need to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore do not It should be regarded as a limitation of the scope, and for those of ordinary skill in the art, other related drawings can also be obtained according to these drawings without any creative effort.

Fig. 1 is the antibacterial effect comparison diagram of different samples of Test Example 1;

Figure 2 is a statistical chart of the wound area of the mouse wound in Test Example 2 at different periods;

FIG. 3 is a comparison diagram of the agar-plated plates of the exudate from the infected wounds of the mice in Test Example 3. FIG.

Detailed ways

Embodiments of the present application are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals refer to the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, but should not be construed as a limitation on the present application.

The application provides a layer-by-layer self-assembled film, which is prepared by the following preparation method:

S1. The basement membrane is immersed in a weakly acidic polyvinylpyrrolidone aqueous solution and a weakly acidic tannic acid aqueous solution in sequence as an assembly cycle.

Optionally, soaking in the weakly acidic polyvinylpyrrolidone aqueous solution and the weakly acidic tannin aqueous solution in turn includes: first soaking in the weakly acidic polyvinylpyrrolidone aqueous solution for 5-10 min, washing, and then soaking in the weakly acidic tannin solution for 5-10 minutes. Soak in acid aqueous solution for 5-10 minutes and wash.

Specifically, the washing is performed with a rinsing solution for 1-2 s. Among them, the rinsing liquid is, for example, water, which has a good rinsing effect and does not introduce new substances.

Among them, the basement membrane is a hydrophobic membrane, which prevents the wound from being infected, and at the same time ensures that after use, the basement membrane is easily torn off and does not adhere to the wound.

Specifically, the base film includes, but is not limited to, a polydimethylsiloxane film, and can also be made by mixing one of polylactic acid and polycaprolactone with chitosan, which is not limited herein.

Optionally, the base film is a polydimethylsiloxane film.

Optionally, the pH value of the weakly acidic polyvinylpyrrolidone aqueous solution is 5-6, for example, the pH value of the weakly acidic polyvinylpyrrolidone aqueous solution is 5, 5.5 or 6.

Optionally, the concentration of polyvinylpyrrolidone in the weakly acidic polyvinylpyrrolidone aqueous solution is 0.5 to 10 mg/mL, for example, the concentration of the front ketone of polyvinylpyrrolidone in the polyvinylpyrrolidone aqueous solution is 0.5 mg/mL, 1 mg/mL, 3 mg/mL. mL, 5 mg/mL, 7 mg/mL, 10 mg/mL, etc.

Optionally, the pH value of the weakly acidic tannic acid aqueous solution is 5-6, for example, the pH value of the weakly acidic tannic acid aqueous solution is 5, 5.5 or 6.

Optionally, the concentration of tannic acid in the weakly acidic tannic acid aqueous solution is 0.5-10 mg/mL. For example, the concentration of tannic acid in the weakly acidic tannic acid aqueous solution is 0.5 mg/mL, 1 mg/mL, 3 mg/mL, 5 mg/mL, 7 mg/mL, 10 mg/mL and the like.

It should be noted that the actual concentration of the weakly acidic polyvinylpyrrolidone aqueous solution and the weakly acidic tannic acid aqueous solution used in each assembly cycle may be the same or different, and may vary with the increase of the assembly cycle, for example It is not limited here to increase or decrease.

Optionally, the weakly acidic polyvinylpyrrolidone aqueous solution contains acidic fibroblast growth factor, and the concentration of the acidic fibroblast growth factor in the weakly acidic polyvinylpyrrolidone aqueous solution is 0.5-100ug/ml, such as 0.1ug/ml, 1ug/ml, 10ug/ml, 20ug/ml, 30ug/ml, 50ug/ml, 55ug/ml, 70ug/ml, 80ug/ml, 100ug/ml, etc.

Optionally, each assembly cycle is performed at a temperature of 2-8°C, eg, 2°C, 4°C, 5°C, 7°C, or 8°C.

S2. Dry after completion of a preset number of assembly cycles.

The preset number of times is one or more times, and those skilled in the art can select according to actual needs.

Optionally, the preset number of times is multiple times, specifically, for example, 2 times, 10 times, 30 times, 50 times, etc., which can be limited by those skilled in the art according to actual needs.

Wherein, after completing the preset number of assembly cycles, hang drying at 2 to 8 °C, for example, at 2 °C, 4 °C, 5 °C, 7 °C, or 8 °C, wherein the hanging includes: sandwiching the layers of self-assembled films At least one edge allows it to hang.

Through the above preparation method, polyvinylpyrrolidone (PVP) and tannic acid (TA) are selected to form a layer-by-layer self-assembled film through hydrogen bonding, which is not limited by the size and shape of the base film, and is easy to control the layer-by-layer self-assembled film. Thickness and loading of TA and aFGF, the drug sustained release effect is good.

The present application provides a layer-by-layer self-assembled film, comprising a base film and at least one functional layer formed on the base film.

Each functional layer includes a weakly acidic polyvinylpyrrolidone layer, and a weakly acidic tannic acid layer connected with the side of the polyvinylpyrrolidone layer away from the base film through hydrogen bonds. Wherein, at least one layer is, for example, two layers, five layers, or thirty layers, etc., which are not limited herein.

The layer-by-layer self-assembled film of the present application and its preparation method will be further described in detail below with reference to the examples.

Example 1

A layer-by-layer self-assembled film of slow-release TA, its preparation method comprises the steps:

Step 1: Obtain a polydimethylsiloxane (PDMS) film, wash the PDMS film with deionized water, and then dry.

Step 2: Prepare 5 mg/mL PVP (MW=8000) aqueous solution and 5 mg/mL TA aqueous solution respectively, and adjust the pH of the PVP aqueous solution and the TA aqueous solution to between 5 and 6 with 0.1 M hydrochloric acid and 0.1 M NaOH solution, respectively, to obtain Weak acid PVP water solution and weak acid TA water solution.

Step 3: Soak the dried PDMS film in step 1 in a weakly acidic PVP aqueous solution for 5 minutes, then clean it in deionized water for 1-2 seconds, then soak it in a weakly acidic TA solution for 5 minutes, take it out for cleaning for 1-2 seconds, and complete a The assembly cycle is used to form a functional layer on the PDMS film. The functional layer includes a weakly acidic polyvinylpyrrolidone layer and a weakly acidic tannic acid layer connected to the side of the polyvinylpyrrolidone layer away from the PDMS film through hydrogen bonds.

Step 4: Repeat Step 3 until 10 functional layers are obtained, and the film body is obtained. Wherein, steps 2 to 4 are all carried out at 4°C.

Step 5: Hang the film body obtained in step 4 at 4° C. until the water evaporates completely to obtain a layer-by-layer self-assembled film.

Example 2

A layer-by-layer self-assembled film of slow-release TA, its preparation method comprises the steps:

Step 1: Obtain a polydimethylsiloxane (PDMS) film, wash the PDMS film with deionized water, and then dry.

Step 2: Prepare 5 mg/mL PVP (MW=8000) aqueous solution and 5 mg/mL TA aqueous solution respectively, and adjust the pH of the PVP aqueous solution and the TA aqueous solution to between 5 and 6 with 0.1 M hydrochloric acid and 0.1 M NaOH solution, respectively, to obtain Weak acid PVP water solution and weak acid TA water solution.

Step 3: Soak the dried PDMS film in step 1 in a weakly acidic PVP aqueous solution for 5 minutes, then clean it in deionized water for 1-2 seconds, then soak it in a weakly acidic TA solution for 5 minutes, take it out for cleaning for 1-2 seconds, and complete a The assembly cycle is used to form a functional layer on the PDMS film. The functional layer includes a weakly acidic polyvinylpyrrolidone layer and a weakly acidic tannic acid layer connected to the side of the polyvinylpyrrolidone layer away from the PDMS film through hydrogen bonds.

Step 4: Repeat Step 3 until 30 functional layers are obtained, and the film body is obtained. Wherein, steps 2 to 4 are all carried out at 4°C.

Step 5: Hang the film body obtained in step 4 at 4° C. until the water evaporates completely to obtain a layer-by-layer self-assembled film.

Example 3

A layer-by-layer self-assembled film of slow-release TA, its preparation method comprises the steps:

Step 1: Obtain a polydimethylsiloxane (PDMS) film, wash the PDMS film with deionized water, and then dry.

Step 2: Prepare 5 mg/mL PVP (MW=8000) aqueous solution and 5 mg/mL TA aqueous solution respectively, and adjust the pH of the PVP aqueous solution and the TA aqueous solution to between 5 and 6 with 0.1 M hydrochloric acid and 0.1 M NaOH solution, respectively, to obtain Weak acid PVP water solution and weak acid TA water solution.

Step 3: Soak the dried PDMS film in step 1 in a weakly acidic PVP aqueous solution for 5 minutes, then clean it in deionized water for 1-2 seconds, then soak it in a weakly acidic TA solution for 5 minutes, take it out for cleaning for 1-2 seconds, and complete a The assembly cycle is used to form a functional layer on the PDMS film. The functional layer includes a weakly acidic polyvinylpyrrolidone layer and a weakly acidic tannic acid layer connected to the side of the polyvinylpyrrolidone layer away from the PDMS film through hydrogen bonds.

Step 4: Repeat Step 3 until 50 functional layers are obtained, and the film body is obtained. Wherein, steps 2 to 4 are all carried out at 4°C.

Step 5: Hang the film body obtained in step 4 at 4° C. until the water evaporates completely to obtain a layer-by-layer self-assembled film.

Example 4

A layer-by-layer self-assembled film of slow-release TA and aFGF, the preparation method of which comprises the following steps:

Step 1: Obtain a polydimethylsiloxane (PDMS) film, wash the PDMS film with deionized water, and then dry.

Step 2: Prepare 5 mg/mL PVP (MW=8000) aqueous solution and 5 mg/mL TA aqueous solution respectively, adjust the pH of the PVP aqueous solution and the TA aqueous solution to between 5 and 6 with 0.1M hydrochloric acid and 0.1M NaOH solution respectively. AFGF was added to the PVP aqueous solution whose pH was adjusted to between 5 and 6 to obtain a weakly acidic PVP aqueous solution and a weakly acidic TA aqueous solution containing 100 ug/ml of aFGF.

Step 3: Soak the dried PDMS film in step 1 in a weakly acidic PVP aqueous solution for 5 minutes, then clean it in deionized water for 1-2 seconds, then soak it in a weakly acidic TA solution for 5 minutes, take it out for cleaning for 1-2 seconds, and complete a Assembly cycle to form a functional layer on the PDMS film, the functional layer includes a weakly acidic polyvinylpyrrolidone layer containing aFGF, and weakly acidic tannins connected to the side of the polyvinylpyrrolidone layer away from the PDMS film through hydrogen bonds acid layer.

Step 4: Repeat Step 3 until 50 functional layers are obtained, and the film body is obtained. Wherein, steps 2 to 4 are all carried out at 4°C.

Step 5: Hang the film body obtained in step 4 at 4° C. until the water evaporates completely to obtain a layer-by-layer self-assembled film.

Test Example 1

In contrast to a 0.5 McFurney tube (1.5×10 ⁸ CFU/mL), the LB broth containing Staphylococcus aureus was diluted with physiological saline to a similar turbidity to obtain a suspension with a bacterial order of 10 ⁸ . Aspirate 100 μL of the above suspension and dilute to 1 mL to obtain a suspension of bacterial order of 10 ⁷ . To each 96-well plate, add 200 μL of the above-mentioned bacterial suspension with an order of magnitude of 10 ⁷ bacteria, and add 75 μL of the leaching solution of the corresponding PDMS film and the layer-by-layer self-assembled film of different layers to each 96-well plate (a single PDMS of uniform size). The films, as well as the layer-by-layer self-assembled films made in Examples 1, 2, and 3, were immersed in 1 mL of pH 7.4 PBS buffer solution for 4 days), and each 96-well plate was placed in a 37°C incubator 5 hours. After taking out, shake on a shaker for 20 seconds, take 20 μL of the bacterial suspension in each well plate and dilute it in 980 μL of PBS, and then take 70 μL of the above-diluted bacterial suspension dropwise onto a nutrient agar plate and spread it evenly. All agar plates were placed in a 37°C incubator for 12 hours.

The results are shown in Figure 1. Among them, the white dots in Figure 1 are Staphylococcus aureus. According to FIG. 1 , it can be seen that the layer-by-layer self-assembled film in Example 3 has obvious antibacterial effect.

Test Example 2

Four groups of wounds of the same size and number were set on mice as blank control group, control group 1, experimental group 1 and experimental group 2. The wounds of each group were infected with the same amount of Staphylococcus aureus and administered to the wounds, and the blank control The group was not treated, the control group 1 was coated with a weakly acidic TA aqueous solution containing aFGF, the test group 1 was covered with the layer-by-layer self-assembled film obtained in Example 3, and the test group 2 was covered with the layer-by-layer self-assembled film made in Example 4. The test group 1 is the same size as the layer-by-layer self-assembled film of experimental group 2, wherein the weakly acidic TA aqueous solution containing aFGF was prepared by the following method: adding aFGF to a 5 mg/mL TA aqueous solution with a pH between 5 and 6 to obtain a 100ug/ml of aFGF in weakly acidic TA aqueous solution. Among them, the amount of aFGF and TA used in control group 1 was basically the same as the amount of aFGF and TA released from the layer-by-layer self-assembled film in test group 2.

The 7th, 10th, 14th, and 17th days after administration of the wound surface were compared with the blank control group, and the wound surface of the mice in the control group 1, the experimental group 1, and the experimental group 2 were evaluated, and the statistics are shown in Figure 2.

According to FIG. 2 , the wound healing speed of the layer-by-layer self-assembled film prepared in Example 4 is relatively fast.

Test Example 3

The wound healing status of the mice in the control group 1, the experimental group 1 and the experimental group 2 on the 17th day after administration of the wounds in Test Example 2 is described, and the results are shown in Table 1.

Table 1 Results of wound healing

At the same time, on the 2nd, 7th, and 10th days of administration to the wounds of the mice in the blank control group, control group 1, experimental group 1, and experimental group 2, the secretions from the wounds of each group of mice were wiped with sterile cotton swabs. After dilution with saline, it was spread on agar plates, and the results are shown in Figure 3.

Combining Table 1 and Figure 3, it can be seen that the bacterial amount on the wounds of test group 1 and test group 2 has been decreasing, while the bacterial amount in the wound of control group 1 decreased greatly at the beginning, but increased again later.

In the actual operation process, the applicant tried to use a one-step method for assembly, that is, firstly mixing the weakly acidic polyvinylpyrrolidone aqueous solution and the weakly acidic tannic acid aqueous solution, or first mixing the polyvinylpyrrolidone and tannic acid and then adding water. , and then adjusted the pH, and then immersed PDMS in the above mixed solution. In practice, it was found that if the above method was used, polyvinylpyrrolidone and tannic acid were first complexed, and they could not be stably loaded on PDMS to form a layered structure.

To sum up, the preparation method provided by the present application is simple in operation, easy to obtain materials, and high in utilization rate, and the load can be adjusted by changing the concentration of TA solution and the preset number of assembly cycles; the film prepared by the above method has good stability and can be Long-term storage for use.

The layers of self-assembled films can release TA slowly in the wound environment to promote wound healing; and TA has high biocompatibility and low cytotoxicity. To achieve sterilization at different stages of wound healing, while promoting cell proliferation.

The above are only preferred embodiments of the present application, and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application shall be included within the protection scope of this application.

Claims (4)

1. a kind of preparation method of layer by layer self-assembly film, is characterized in that, comprises: The base film is immersed in the weakly acidic polyvinylpyrrolidone aqueous solution and the weakly acidic tannic acid aqueous solution in turn as an assembly cycle, and after completing the preset number of said assembly cycles, it is hung and dried at 2-8° C., and each assembly cycle is performed. The cycle is carried out at a temperature of 2 to 8 °C; The weakly acidic polyvinylpyrrolidone aqueous solution contains acidic fibroblast growth factor, and the concentration of the acidic fibroblast growth factor in the weakly acidic polyvinylpyrrolidone aqueous solution is 0.5-100ug/ml; The pH value of the weakly acidic polyvinylpyrrolidone aqueous solution is 5-6; the pH value of the weakly acidic tannic acid aqueous solution is 5-6; the base film is a hydrophobic film; the weakly acidic polyvinylpyrrolidone is The concentration of polyvinylpyrrolidone in the aqueous solution is 0.5-10 mg/mL, and the concentration of tannic acid in the weakly acidic tannic acid aqueous solution is 0.5-10 mg/mL. 2. The preparation method of the layer-by-layer self-assembled film according to claim 1, characterized in that, successively soaking in the weakly acidic polyvinylpyrrolidone aqueous solution and the weakly acidic tannic acid aqueous solution comprises: After soaking in the weakly acidic polyvinylpyrrolidone aqueous solution for 5-10 min, washing, and then soaking in the weakly acidic tannic acid aqueous solution for 5-10 min, washing. 3 . A layer-by-layer self-assembled film, characterized in that, it is prepared by the method for preparing a layer-by-layer self-assembled film according to any one of claims 1 to 2 . 4. A layer-by-layer self-assembled film is characterized in that, comprising a base film, and at least one functional layer formed on the base film, the functional layer of each layer comprises a weakly acidic polyvinylpyrrolidone layer, and a A side of the polyvinylpyrrolidone layer away from the basement membrane is a weakly acidic tannic acid layer connected by hydrogen bonds, and the polyvinylpyrrolidone layer contains an acidic fibroblast growth factor.

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