CN114146052A

CN114146052A - Preparation method of hydrogel capable of loading various molecules and used for healing infected wounds

Info

Publication number: CN114146052A
Application number: CN202111405340.9A
Authority: CN
Inventors: 高长有; 邓利文
Original assignee: Zhejiang University ZJU
Current assignee: Shanxi Zhejiang University Institute Of New Materials And Chemical Industry; Zhejiang University ZJU
Priority date: 2021-11-24
Filing date: 2021-11-24
Publication date: 2022-03-08

Abstract

The invention discloses a preparation method of hydrogel capable of loading various molecules and used for healing infected wounds. The invention prepares the poly (acrylamide-co-acrylic acid) hydrogel (PAM-AA) by simple one-pot method thermal initiation. Acrylamide (AM) and Acrylic Acid (AA) are used as raw materials, ammonium persulfate/tetramethylethylenediamine (APS/TEMED) is used as an initiating system, N' -Methylene Bisacrylamide (MBA) is used as a cross-linking agent, and PAM-AA is formed by initiating polymerization under the heating condition. The polymerization reaction conditions are optimized, and the hydrogel with the lowest monomer residual rate is obtained. The prepared hydrogel can load and release various molecules through hydrogen bonds and electrostatic interaction. The doxycycline-loaded hydrogel has good in-vitro and in-vivo antibacterial activity on gram-positive bacteria and gram-negative bacteria. In a rat full-thickness skin defect wound model infected by methicillin-resistant staphylococcus aureus, the doxycycline-loaded hydrogel shows a good treatment effect and can remarkably promote wound healing. The invention has simple process flow, low production cost and good biological safety, and is expected to play a role in the field of medical antibacterial dressings.

Description

Preparation method of hydrogel capable of loading various molecules and used for healing infected wounds

Technical Field

The invention belongs to the field of medical antibacterial dressings, and particularly relates to a preparation method of hydrogel capable of loading various molecules and used for healing infected wounds.

Background

The sustained release system of the drug generally refers to a system in which a drug molecule and a drug delivery system are combined by different methods (physical or chemical methods), and then the drug molecule is released continuously and stably at an appropriate concentration by diffusion or permeation, etc. to achieve the therapeutic purpose of the drug. Currently, the drug can be loaded on the carrier through physical dispersion, hydrogen bonding, electrostatic adsorption, chemical bonding and the like. However, the difficulty is that covalent binding often results in a reduction in the biological activity potential of the molecule due to poor stability of the adsorbed molecule when physically dispersed. The drug molecules loaded through hydrogen bond action and electrostatic adsorption have better stability, and the biological activity of the drug is not reduced. Therefore, it is necessary to develop an antibacterial drug delivery system that can effectively and accurately deliver antibacterial drugs to the wound site and control the release behavior of active healing of the wound.

Thus, many types of modern wound dressings have been developed, including semi-permeable membranes, semi-permeable foams, hydrocolloids, and hydrogels with sustained drug release properties. Not only do attempts to avoid infection of the defect wound, but also attempt to promote the wound repair process. In these dressings, due to the hydrophilic nature of the hydrogel, the risk of wound infection may be reduced by absorbing wound exudate and maintaining a moist environment, which features provide a good tissue microenvironment for repair of the damaged site. Hydrogels of materials commonly used in drug delivery systems may be derived from natural polymers, synthetic polymers, or a combination of both. Superabsorbent hydrogels based on acrylic acid and acrylamide are synthetic polymers that have been used in various aspects of biomedical and tissue engineering. However, the hydrogel formed by polymerizing the monomer is often not sufficiently polymerized due to the problem of the process conditions of the previous reaction, and thus the residual amount of the monomer is large, which leads to the problem of cytotoxicity. The toxicity problem of the material is often the problem which is solved by the biomedical material, and is one of the problems to be solved by the invention.

Furthermore, although nanometals have been found to have highly effective antibacterial properties, antibiotics remain the most common and effective antibacterial agents and are also the primary strategy for clinical treatment of infections. However, the release of the antibiotic is difficult to control, and if the antibiotic can be released through hydrogen bonds and charge adsorption, a good slow release effect can be achieved, which is another problem to be solved by the invention.

Disclosure of Invention

The invention aims to provide a preparation method of hydrogel which can be loaded with various molecules and is used for healing infected wounds. It changes the traditional drug carrier to drug loading mode, provides a drug carrier which can adsorb and release various drugs through hydrogen bond action and electrostatic action. The preparation method optimizes polymerization conditions and minimizes the residual amount of unreacted monomers. The wide application prospect of the nano-particles in the biomedical field is shown through the loading and slow release of different types of molecules.

The invention is realized by the following technical scheme:

preparing a poly (acrylamide-co-acrylic acid) hydrogel (PAM-AA) comprising the steps of: preparing PAM-AA hydrogel by taking Acrylamide (AM) and Acrylic Acid (AA) as raw materials, ammonium persulfate/tetramethylethylenediamine (APS/TEMED) as an initiating system, N' -Methylene Bisacrylamide (MBA) as a cross-linking agent and reacting for 5 hours at 60 ℃; the residual amount of AM monomer prepared under these conditions was 0.25% and the residual amount of AA monomer was 0.12%.

After the hydrogel matrix material is prepared, the hydrogel matrix material is freeze-dried and stored. When molecules need to be loaded, the hydrogel is soaked in the PBS solution to achieve swelling balance, and the hydrogel after swelling balance is soaked in the solution of the molecules to be loaded with a certain concentration to carry out physical adsorption loading. Then soaking in PBS solution for releasing.

A preparation method of hydrogel capable of loading various molecules and used for healing infected wounds comprises the following steps:

step 1: sequentially adding AM, AA, MBA, APS and TEMED required by an experiment into a certain amount of water, magnetically stirring to completely dissolve the materials, obtaining a hydrogel product through a certain temperature gradient and a certain time gradient, and freeze-drying the prepared hydrogel;

step 2: the lyophilized hydrogel was ground into a powder and then soaked in water for 5 hours, and the liquid was subjected to HPLC to measure the residual amount of the monomer.

And step 3: preparing a solution of molecules to be loaded (such as Doxycycline (DOX), Methylene Blue (MB), Rhodamine B (RB), Coomassie Brilliant Blue (CBB) and Toluidine Blue (TB)) at a certain concentration, and soaking the hydrogel after swelling equilibrium in the solution to carry out loading and releasing experiments.

Further, in step 1, the total monomer solid content of AM and AA is 25 wt%, and the mass ratio of AM and AA is 13: 2, 0.1 wt% MBA/monomer, 0.9 wt% APS/monomer and 0.6 wt% TEMED/monomer.

Further, before the HPLC test described in step 2, the hydrogel was freeze-dried and ground into a fine powder, and 0.1g of a dried hydrogel block was added to 10mL of water and soaked for 5 hours to extract residual monomers.

Furthermore, in step 3, the hydrogel formed by 100. mu.L of the solution was swollen and equilibrated, and then placed in 10mL of a 100. mu.g/mL DOX solution, 10mL of a 100. mu.g/mL MB solution, 10mL of a 100. mu.g/mL RB solution, 10mL of a 100. mu.g/mL CBB solution and 10mL of a 100. mu.g/mL TB solution, respectively, to carry out the loading experiment. After reaching load balance, the samples were transferred to PBS solution for release test. Doxycycline is a natural broad-spectrum antibacterial agent, belongs to semisynthetic tetracycline antibiotics, and has an antibacterial mechanism that tRNA is prevented from entering ribosome to block the synthesis of protein in bacteria, so that the chromosome of the bacteria is cracked, and the antibacterial and anti-inflammatory effects are achieved. The hydrogel loaded with doxycycline can achieve a good slow release effect, so that the hydrogel has good in vitro and in vivo antibacterial activity on gram-positive bacteria and gram-negative bacteria.

The invention takes PAM-AA hydrogel as a matrix material, determines the reaction at 60 ℃ for 5 hours as a polymerization reaction condition through groping, and reduces the residual amount of monomers as much as possible, thereby ensuring that the hydrogel matrix material has no cytotoxicity basically. And various molecules are adsorbed and loaded through hydrogen bond action and charge action, so that the effect of separating and storing the medicament and the hydrogel matrix material before use can be realized. Particularly, the doxycycline-loaded hydrogel is applied to healing of infected skin wounds, has a good antibacterial effect in vivo and in vitro, and promotes the healing process of the infected skin wounds.

Compared with the prior art, the invention has the following advantages:

1. reaction conditions are optimized, the monomer residual amount of the hydrogel is reduced, the hydrogel matrix material basically has no cytotoxicity, and the problem of removing the monomer residual amount of the hydrogel through soaking is solved.

2. The drug is loaded and released through hydrogen bond action and electrostatic action, so that the separation and storage of the drug and the matrix material can be realized, and the purpose of dry storage of the hydrogel can be realized. The dry hydrogel is easier to store, and the problem that the wet hydrogel is easy to grow mould can be avoided.

3. The hydrogel capable of loading various molecules can adsorb and release drug molecules through hydrogen bonds and electrostatic action, can achieve a good slow release effect, and has the advantage of potential application to skin wound dressings.

Drawings

FIG. 1 is a graph of the monomer residues of AM and AA as a function of the reaction time at a reaction temperature of 60 ℃;

FIG. 2 is a graph showing the variation of the monomer residual amounts of AM and AA with the reaction temperature at a reaction time of 5 hours;

FIG. 3 is a graph of the loading of DOX, MB, RB, CBB, TB in the corresponding PBS solutions, respectively, as a function of incubation time.

FIG. 4 is a graph of DOX, MB, RB, CBB and TB release rates in PBS solution as a function of incubation time.

FIG. 5 in vitro viability assessment of L929 cells co-cultured with PAM-AA25 and PAM-AA25@ DOX hydrogel for 24 hours.

Fig. 6 in vitro antibacterial experiments, the left 3 samples are CFU photographs of methicillin-resistant staphylococcus aureus (MRSA) and escherichia coli (e.coli) after 24 hours contact or non-contact with PAM-AA25 and PAM-AA25@ DOX hydrogel, and the rightmost side is the inhibition zone of hydrogel to MRSA and e.coli. The circles of red and blue indicate the range of hydrogel and inhibition circles.

The wound surface photographs were taken on

days

0, 3, 6, 9, and 12 for Model group (Model), Bactroban group (Bactroban), PAM-AA25 group, and PAM-AA25@ DOX group in fig. 7.

FIG. 8 CFU photographs of MRSA of the in vivo antibacterial experiments, 3, 6 day model, Bactroban, PAM-AA25, PAM-AA25@ DOX.

Detailed Description

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Example 1:

the preparation of the blank hydrogel PAM-AA was explored with reaction conditions and comprised the following steps:

1. the hydrogel is synthesized by taking AM and AA as raw materials, APS/TEMED as an initiating system and MBA as a cross-linking agent. First, AM and AA were dissolved in a certain amount of water under magnetic stirring to give 15%, 20% and 25% by weight solutions, respectively. The mass ratio of AA to AM was kept at 2: 13. Then MBA, APS and TEMED were added in sequence to obtain a homogeneous solution under magnetic stirring. The mass ratios of MBA, APS and TEMED to monomer were 0.1%, 0.9% and 0.6 wt%, respectively. Finally, polymerization was carried out at 60 ℃ for 5 hours to obtain a hydrogel. The hydrogels with solids contents of 15%, 20% and 25% by weight were named PAM-AA15, PAM-AA20 and PAM-AA25, respectively. The parameters of the three hydrogel formulations are shown in table 1.

TABLE 1 PAM-AA hydrogel formulation parameters

2. The polymerization conditions were optimized with PAM-AA15 hydrogel to obtain hydrogel with low toxicity and good biocompatibility with minimal unreacted monomers. HPLC is used as a high-sensitivity measurement method, and two main parameters, namely reaction time at a fixed temperature and reaction temperature at the fixed time, are researched. The prepared PAM-AA15 hydrogel was freeze-dried and then ground into a fine powder. 0.1g of dried PAM-AA15 hydrogel powder was soaked in 10mL of water for 5 hours to extract residual monomers. And finally, detecting the supernatant by using HPLC to obtain a corresponding peak area value. And calculating the residual rate of the monomer according to the calculated monomer concentration. FIG. 1 is a graph of the residual monomer content of AM and AA as a function of the reaction time at a reaction temperature of 60 ℃; FIG. 2 is a graph showing the change of the monomer residual amounts of AM and AA with the reaction temperature at a reaction time of 5 hours.

In vitro load and Release experiments

A mass of PAM-AA25 hydrogel after swelling equilibrium was soaked in 10mL of PBS (pH 7.4) solution (containing 100 μ g/mL of DOX, MB, RB, CBB and TB, respectively) at 37 ℃. At predetermined time intervals, 100. mu.L of the buffer was taken, absorbance was measured with a spectrophotometric microplate reader to analyze the drug concentration, and 100. mu.L of fresh buffer was added to the tube to keep the volume constant. And obtaining corresponding medicine concentration according to the absorbance value. Similar studies were performed on the release of the drug in the same way. The DOX-loaded hydrogel was used for in vivo experiments in wound healing and was named PAM-AA25@ DOX. FIG. 3 is a graph of the loading of DOX, MB, RB, CBB, TB in the corresponding PBS solutions, respectively, as a function of incubation time. FIG. 4 is a graph of DOX, MB, RB, CBB and TB release rates in PBS solution as a function of incubation time.

And evaluating the cell viability of different hydrogel sample extracts by adopting a CCk-8 detection kit. In short,soaking 20mg/mL hydrogel in cell culture medium for 24 hr to obtain extract. Adding 100 μ L of the solution containing 5X 10 to each well of a 96-well plate³A cell suspension of cells. The cells were cultured in normal medium for 24 hours to allow the cells to adhere. The medium is then changed to a pre-prepared extract. After 24 hours of incubation with normal medium as a control, the cells were gently washed with PBS 3 times, and then 150. mu.L of fresh medium containing 10 vol% CCK-8 was added. After 1-2 hours of incubation, the Optical Density (OD) of 100. mu.L of medium per well was measured at 450nm using a microplate reader.

FIG. 5 is an in vitro viability assessment of L929 cells co-cultured with PAM-AA25 and PAM-AA25@ DOX hydrogel for 24 hours.

Coli and MRSA were used as model bacteria of gram-negative bacteria and gram-positive bacteria, respectively. MRSA is the most common cause of skin infections. Before use, both bacteria were cultured in LB medium at 220r/min at 37 ℃ with constant shaking.

And (3) detecting the bacteriostatic activity of different samples on E.coli and MRSA by adopting a plate colony counting method. Firstly, taking out a certain volume of frozen bacterium liquid, adding the frozen bacterium liquid into an LB liquid culture medium centrifuge tube, and incubating overnight in a shaking table at 37 ℃ and 220 r/min. The incubated solution was diluted into a 96-well plate, and the Optical Density (OD) of 100. mu.L of the solution per well was measured by 600nm microplate spectrophotometry. Coli and MRSA had OD values of 0.35 and 0.58, respectively, and the bacterial concentration was 10⁹CFU/mL. The bacterial solution was diluted to a concentration of 10⁷CFU/mL, each hydrogel sample was incubated with 500mL of the bacterial solution in a 37 ℃ bacterial incubator for 24 hours. The bacterial solution incubated with the hydrogel was then diluted 10^-41mL of the suspension was applied to an agar plate and incubated at 37 ℃ for 24 hours in a bacterial incubator. Agar plates were photographed and Colony Forming Units (CFU) were counted.

Fig. 6 is a photograph of CFU of MRSA and e.coli in the left 3 samples with and without contact with PAM-AA25 and PAM-AA25@ DOX hydrogels for 24 hours in vitro antibacterial experiments.

And evaluating the bacteriostatic effect of the antibacterial ring test. Briefly, 1mL of 10⁵CFU/mL e.coli and MRSA were each spread evenly on agar plates. Subsequently subjecting PAM-AA25 and PAM-AA25@ DOX to hydro-settingThe gel was placed on agar plates coated with bacterial solution and incubated at 37 ℃ for 24 hours, respectively. The inhibition zone of the hydrogel on the agar was observed and determined.

The rightmost panel of fig. 6 is the inhibition zone of the hydrogel for MRSA and e. The circles of red and blue indicate the range of hydrogel and inhibition circles.

Evaluation of wound healing Process in vivo with full-thickness skin Defect model of infection

Male SD rats (200g, 6-8 weeks) are selected to establish a full-thickness skin defect infection model for in vivo wound healing experiments. The groups are divided into Model, Bactroban, PAM-AA25 and PAM-AA25@ DOX groups. All rats were acclimated for 1 week before surgery. All procedures were performed under sterile conditions. Rats were then anesthetized with isoflurane gas and shaved and depilated on the back between the tail and neck. Each rat made 4 full-thickness circular skin wounds of 10 mm diameter on the back. These wounds were distributed symmetrically on the back of the rats. Then adding 10 per skin wound⁷MASA of CFU, to allow penetration of the bacterial solution into the wound surface. Model group was left without dressing. In the Bactroban group, 40. mu.L of a commercial Bactroban dressing was added to the wound surface. The hydrogel group adopts PAM-AA25 hydrogel and PAM-AA25@ DOX hydrogel to cover the wound surface. All wounds were photographed on

days

0, 3, 6, 9, and 12, wound boundaries were drawn using Image J software, and wound areas were calculated.

FIG. 7 is a photograph of wound surface taken in Model group, Bactroban group, PAM-AA25 group, PAM-AA25@ DOX group at 0, 3, 6, 9 and 12 days, respectively.

Day 3 and day 6 healed tissue specimens were soaked in PBS, ground to a uniform tissue fluid, and groups were evaluated for antimicrobial activity against MRSA. Diluting the tissue fluid 10^-5After doubling, 1mL of the suspension was spread on agar plates and incubated in a bacterial incubator at 37 ℃ for 24 hours. Agar plates were photographed and Colony Forming Units (CFU) were counted.

FIG. 8 is a photograph of CFUs from MRSAs of the in vivo antibacterial assay, model at

days

3 and 6, Bactroban, PAM-AA25, PAM-AA25@ DOX.

Evaluation of effects

While most hydrogels are highly biocompatible, their precursor monomers are toxic. However, this important problem is often overlooked. As can be seen from FIG. 1, using PAM-AA15 hydrogel as an example, residual AM and AA monomers were first measured. At a fixed polymerization temperature of 60 ℃, the residual amounts of AM and AA both tended to decrease with the increase of the polymerization time, and at 5 hours of polymerization, the residual amounts of AM and AA were 1.33% and 0.33%, respectively. Further extension of the polymerization time does not significantly reduce the monomer content. As is clear from FIG. 2, when the polymerization time was fixed at 5 hours and the effect of the polymerization temperature was examined, the residual monomer content was the lowest at the highest polymerization temperature.

To demonstrate the versatility of PAM-AA25 hydrogels for loading and release as a delivery system, we incubated 5 different types of molecules, namely neutral DOX, positively charged MB, RB, TB and negatively charged CBB, with the hydrogel after swelling equilibrium, as shown in fig. 3 and 4. Thus, the loading is more likely driven by the thermodynamics of the interaction between the molecule and the hydrogel. Using DOX as an example, swelling-equilibrated PAM-AA25 hydrogel was soaked in 100. mu.g/mL DOX/PBS solution and incubated at 37 ℃ for 24 hours, and then DOX-loaded hydrogel was soaked in PBS at 37 ℃ to monitor release. The loading and release of these drugs is relatively fast at the beginning and tends to plateau after 10 hours of loading and 2 hours of release. The drug loading of DOX, MB, TB, RB and CBB was 8.92, 8.47, 6.67, 5.08 and 3.06. mu.g/mg, respectively, with release rates of 12%, 52%, 100%, 22% and 2%, respectively. These results indicate that they achieve loading well regardless of the charge nature of the water-soluble molecules, although neutral and positively charged molecules are more easily loaded. On the other hand, both the strength of the intermolecular interaction and the size of the molecules may be responsible for the influence on the release. In general, hydrogen bonding between hydrogels and molecules (e.g., DOX and CBB) may better sustain the payload, while electrostatic interactions may be shielded by salts in PBS, resulting in faster and larger release of positively charged molecules (MB, TB, RB).

Good cell compatibility is a prerequisite for the design of materials in the biomedical field. The cytotoxicity of the hydrogel was evaluated by the CCK-8 method. As can be seen from FIG. 5, there was no difference in the viability of L929 among the PAM-AA25, PAM-AA25@ DOX and Medium groups, indicating that neither hydrogel group had detectable cytotoxicity.

Tetracycline is a widely-used broad-spectrum antibiotic, and the skin wound repair performance of tetracycline is well proved clinically. The loaded DOX hydrogel, as a clinically well-known "second generation" tetracycline, is believed to have good antibacterial properties, which are critical for preventing bacterial infection of wounds. The bacteriostatic activity of PAM-AA25@ DOX hydrogel against E.coli (gram negative bacteria) and MRSA (gram positive bacteria) was evaluated by plate method using bacteria cultured in PBS solution as blank control, as shown in the left three panels of FIG. 6. Coli and MRSA colonies were clearly observed on agar plates. However, the survival of e.coli and MRSA exposed to PAM-AA25@ DOX hydrogel was significantly reduced, while exposure to PAM-AA25 hydrogel alone was not. The inhibition rates of PAM-AA25@ DOX hydrogel on E.coli and MRSA are 81.0% and 94.2%, respectively.

The antimicrobial properties of PAM-AA25@ DOX were further verified by an in vitro zone test (hydrogel diameter 17mm) as shown at the far right of figure 6. And the PAM-AA25 has no obvious bacteriostatic ability, and the PAM-AA25@ DOX group can form an obvious bacteriostatic zone. Inhibition zone diameters for MRSA and e.coli for PAM-AA25@ DOX set were 47 and 29mm, respectively.

As shown in fig. 7, the wound healing effect of the hydrogel dressing was evaluated in a rat full-thickness skin defect infection model. With the increase of time, the MRSA infected wound area gradually decreases after the Model group, Bactroban group (commercial dressing ointment), PAM-AA25 group and PAM-AA25@ DOX treatment, but the exact degree is obviously different. The PAM-AA25@ DOX group has the fastest wound healing speed in the whole treatment period, which shows that the PAM-AA25@ DOX group has higher promotion effect on wound healing. MRSA infection was observed in the Model group until day 9, and other groups were not obvious even with PAM-AA hydrogel alone.

In the process of wound healing, the wound dressing is used as an effective antibacterial agent to prevent infection and reduce inflammatory reaction of the wound, thereby promoting the healing process. Here, as shown in fig. 8, each group evaluated the healing process in vivo for the antibacterial behavior of MRSA at day 3 and day 6. The number of MRSA colonies extracted from the wound site was determined by plate method. The colony numbers in the Bactroban and PAM-AA25@ DOX groups were significantly reduced on day 6 compared to day 3, revealing their antibacterial effect over time. On day 3, the inhibition was 83% and 95% for the Bactroban group and PAM-AA25@ DOX group, respectively, and expanded to 85% and 97% on day 6 as compared to the Model group, respectively. PAM-AA25 also showed some antimicrobial action compared to the Model group. The maintenance and sustained release of DOX by PAM-AA25@ DOX is the primary reason for its best in vivo antimicrobial properties. It is worth mentioning that due to the low amount of fluid in the body, the release rate of the drug in the body is much slower than in vitro, and thus can be maintained on the wound for a considerable period of time.

The above embodiments are only intended to illustrate the technical solutions of the present invention, and those skilled in the art can make many changes or additions in form and detail according to the content and the specific embodiments of the present invention, and these changes and additions should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of hydrogel capable of loading various molecules and used for healing infected wounds is characterized in that acrylamide and acrylic acid are used as raw materials, ammonium persulfate/tetramethylethylenediamine is used as an initiation system, N' -methylene bisacrylamide is used as a cross-linking agent, and polyacrylamide-co-acrylic acid hydrogel is obtained by heating and is stored in a freeze-drying manner; before loading, the freeze-dried polyacrylamide-co-acrylic acid hydrogel is swelled and balanced, then soaked in a molecule solution to be loaded, and the hydrogel loaded with the required molecules is obtained through the hydrogen bond and charge action between the hydrogel network and the loaded molecules.

2. The method for preparing a hydrogel which can be loaded with a plurality of molecules and used for wound healing infection according to claim 1, wherein the mass ratio of acrylamide to acrylic acid is 13: 2, N, N' -methylenebisacrylamide was 0.1 wt% of acrylamide and acrylic acid, ammonium persulfate was 0.9 wt% of acrylamide and acrylic acid, and tetramethylethylenediamine was 0.6 wt% of acrylamide and acrylic acid.

3. The method for preparing a hydrogel capable of supporting a plurality of molecules and used for healing an infected wound according to claim 2, wherein the polyacrylamide-co-acrylic acid hydrogel is prepared by the following steps:

acrylamide and acrylic acid are used as raw materials, ammonium persulfate/tetramethylethylenediamine is used as an initiating system, N' -methylene bisacrylamide is used as a cross-linking agent, and the raw materials are heated in an oven at the temperature of 60 ℃ for 5 hours to obtain polyacrylamide-co-acrylic acid hydrogel; the polyacrylamide-co-acrylic acid hydrogel is freeze-dried and stored.

4. The method for preparing a hydrogel which can be loaded with various molecules and used for wound healing infection according to claim 1, wherein the step of loading the desired molecules with the polyacrylamide-co-acrylic acid hydrogel comprises the following steps:

(1) soaking the hydrogel in a phosphate solution for swelling balance;

(2) and soaking the hydrogel after the swelling balance in a molecular solution to be loaded for 10-12h to load the molecules in the hydrogel.

5. A hydrogel prepared according to any one of claims 1 to 4 and capable of carrying a plurality of molecules and being used for healing infected wounds.

6. The hydrogel capable of being loaded with a plurality of molecules and used for infectious wound healing according to claim 5, wherein the hydrogel is used for loading negatively charged, positively charged or electrically neutral molecules.

7. The hydrogel capable of being loaded with multiple molecules and used for infectious wound healing according to claim 6, wherein doxycycline is loaded to obtain a hydrogel dressing for infectious wound healing.