A dual cross-linked biocompatible hydrogel with adhesion disparity and its preparation method and application

Abstract

This invention discloses a bi-crosslinked biocompatible hydrogel with adhesion differences, its preparation method, and its application. The method includes the following steps: preparing a chitosan precursor solution, preparing an acrylic acid and polyethylene glycol dimethacrylate precursor solution, preparing a chitosan / acrylic acid hydrogel, preparing a bridging polymer solution, and preparing a chitosan / acrylic acid-chitosan hydrogel. Compared with the prior art, its advantages are: (1) the method can easily prepare chitosan / acrylic acid-chitosan hydrogel, which has the advantages of high efficiency, simplicity, and low energy consumption; (2) the chitosan / acrylic acid-chitosan hydrogel prepared by the method has the ability to improve the antibacterial and healing properties of wound dressings; (3) the chitosan / acrylic acid-chitosan hydrogel prepared by the method can achieve adhesion differences on both sides of the same hydrogel material.

Description

Technical Field

[0001] This invention belongs to the field of hydrogel materials, specifically relating to a double cross-linked biocompatible hydrogel with adhesion differences, its preparation method, and its application. Background Technology

[0002] Wound healing is a highly complex physiological response of living systems to physical, chemical, mechanical, or thermal damage. This process involves cellular-level interactions, the synergistic effects of matrix components and other biological factors to promote healing and restore tissue integrity. During wound healing, infection and tissue adhesions can occur, which can slow the healing process and lead to serious complications.

[0003] Wound dressings are materials used to cover wounds, designed to protect them from further damage and promote the healing process. The main goals of wound dressings are to create a favorable environment for wound healing, reduce the risk of infection, keep the wound clean and dry, and promote the healing of skin lesions. To date, various wound dressings have been developed to meet the needs of different types of wound treatment. Compared to traditional dressings such as gauze, bandages, membranes, and sponges, hydrogels have attracted much attention due to their superior properties such as high water absorption, flexibility, biocompatibility, and three-dimensional network structure. Furthermore, the swelling rate, degradation rate, porosity, biocompatibility, and mechanical strength of hydrogels can be controlled by using physical or chemical cross-linking methods, different polymer types, and the addition of different molecules to achieve personalized customization.

[0004] Currently, hydrogel dressings widely used in the medical field have a number of problems, including high cost, susceptibility to infection, low mechanical strength, and insufficient adhesion. Furthermore, because hydrogels have consistent adhesion on both sides, while repairing wound tissue, the other side of the dressing can easily adhere to surrounding tissue, requiring secondary surgery for removal, increasing patient suffering and treatment risks. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention aims to provide a bi-crosslinked biocompatible hydrogel with adhesive differences, its preparation method, and its applications. A method involving simultaneous heating at 37°C at the bottom and irradiation with 365nm ultraviolet light at the top induces a Schiff base reaction between chitosan and glutaraldehyde, while simultaneously promoting C=C radical polymerization between acrylic acid and polyethylene glycol dimethacrylate. This successfully synthesizes a bi-crosslinked biocompatible hydrogel with adhesive differences. Furthermore, chitosan is grafted onto the carboxyl groups on the hydrogel surface using a coupling agent to enhance the adhesive differences between the two sides of the hydrogel.

[0006] Another object of the present invention is to provide a double cross-linked biocompatible hydrogel with adhesion differences prepared by the above preparation method, the main components of which include chitosan, glutaraldehyde, acrylic acid, polyethylene glycol dimethacrylate, photoinitiator and coupling agent.

[0007] Another object of the present invention is to provide the application of the above-mentioned double cross-linked biocompatible hydrogel with adhesion differences in medical wound dressings.

[0008] To address the problems in the existing technology, the technical solution adopted by this invention is as follows:

[0009] A method for preparing a bi-crosslinked biocompatible hydrogel with adhesion differences includes the following steps:

[0010] S1. Dissolve chitosan in acetic acid solution to obtain the first solution;

[0011] S2. Dissolve acrylic acid and polyethylene glycol dimethacrylate in deionized water to obtain a second solution;

[0012] S3. Mix the first and second solutions, add a photoinitiator and a crosslinking agent to obtain a dual-network hydrogel precursor solution; place the dual-network hydrogel precursor solution in a glass container, heat it at 37°C for 20 minutes at the bottom of the container, and simultaneously irradiate it with a 365nm UV lamp for 10 minutes at the top of the container. Obtain a dual-network chitosan / acrylic hydrogel through Schiff base reaction and C=C free radical polymerization, named CS / AA hydrogel. The light-illuminated surface of CS / AA hydrogel is named CS / AA-LIS, and the heated surface is named CS / AA-HIS.

[0013] S4. Dissolve the bridging polymer 2% chitosan in acetic acid and adjust the pH to 6. Add coupling reagents 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS) to obtain a third solution. Immerse CS / AA-LIS in the third solution for 24 hours to obtain chitosan / acrylic acid-chitosan hydrogel, named CS / AA-CS hydrogel.

[0014] Preferably, the degree of deacetylation of chitosan in S1 is 70-90%, the mass fraction is 2%, and the volume fraction of acetic acid solution is 2%.

[0015] Preferably, the volume fraction of acrylic acid in S2 is 5%, and the mass fraction of polyethylene glycol dimethacrylate is 5%.

[0016] Preferably, the photoinitiator used in S3 is 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone, and the mass fraction of 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone is 0.1%.

[0017] Preferably, the crosslinking agent used in S3 is glutaraldehyde, and the volume fraction of glutaraldehyde is 0.85%.

[0018] Preferably, the concentration of the acetic acid solution in S4 is 2%, the mass fraction of chitosan is 2%, and the pH adjuster is 1M NaOH.

[0019] Preferably, the concentrations of the coupling agents 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide in S4 are 12 mg / mL.

[0020] Preferably, the concentration of the coupling agent N-hydroxysuccinimide in S4 is 12 mg / mL.

[0021] Chitosan / acrylic acid-chitosan hydrogels prepared by any of the above methods.

[0022] The above-mentioned chitosan / acrylic acid-chitosan hydrogel is used in the preparation of wound dressing materials.

[0023] The present invention has the following beneficial effects:

[0024] Compared with existing technologies, this invention provides a double-crosslinked biocompatible hydrogel with adhesion differences, its preparation method, and its application. Using chitosan and glutaraldehyde as the first network layer and acrylic acid and polyethylene glycol dimethacrylate as the second network layer, a double-network hydrogel CS / AA is formed. Chitosan is grafted onto CS / AA-LIS to prepare the desired hydrogel wound dressing. The hydrogel wound dressing prepared by this method, through the formation of a double-network hydrogel, can improve the wound dressing's antibacterial and healing properties while achieving adhesion differences between the two sides of the same hydrogel material. It has the following advantages:

[0025] (1) The present invention provides a two-step method for preparing a double cross-linked biocompatible hydrogel with adhesion differences, which has the advantages of high efficiency, simplicity and low energy consumption.

[0026] (2) The double cross-linked biocompatible hydrogel of the present invention has excellent antibacterial effects against Escherichia coli and Staphylococcus aureus. The inhibition zone of CS / AA-CS hydrogel against Escherichia coli is 26.5±1.24 mm; the inhibition zone against Staphylococcus aureus is 37.5±2.18 mm.

[0027] (3) The double-crosslinked biocompatible hydrogel of this invention exhibits significant differences in adhesion between its two surfaces. The adhesion energy of the CS / AA-CS hydrogel graft surface (CS / AA-CS4) to pigskin is 235.39±7.26 J / cm. 2 The adhesion energy of the CS / AA-CS hydrogel heating surface (CS / AA-HIS) to pigskin is 38.23±3.71 J / cm.2 . Attached Figure Description

[0028] Figure 1 A schematic diagram illustrating the preparation of a double-crosslinked biocompatible hydrogel with adhesive differences;

[0029] Figure 2 The figure shows the test results of the compressibility of the prepared hydrogel;

[0030] Figure 3 Figure 1 shows the results of the inhibition zone size test of the prepared hydrogel against Escherichia coli (E. coli);

[0031] Figure 4 A quantitative diagram showing the size of the inhibition zone against Escherichia coli (E. coli) using the prepared hydrogel;

[0032] Figure 5 Figure 1 shows the test results of the antibacterial properties of the prepared hydrogel against Staphylococcus aureus.

[0033] Figure 6 A quantitative diagram showing the size of the inhibition zone against Staphylococcus aureus using the prepared hydrogel;

[0034] Figure 7 The figure shows the adhesion energy test results of the prepared hydrogel;

[0035] Figures 3-6 i: CS, ii: AA, iii: CS / AA-LIS, iv: CS / AA-HIS, v: CS / AA-CS. Detailed Implementation

[0036] The following embodiments further illustrate the content of the present invention, but should not be construed as limiting the present invention. Modifications and substitutions made to the methods, steps, or conditions of the present invention without departing from the spirit and essence of the invention are all within the scope of the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0037] This invention provides a bi-crosslinked biocompatible hydrogel with adhesive differences. It introduces chitosan (CS), a natural organic polymer compound with antibacterial, hemostatic, and wound-healing properties, to enhance the hydrogel's biological performance as a wound dressing. Simultaneously, a second network structure is formed by C=C radical polymerization between acrylic acid and polyethylene glycol dimethacrylate, which adsorb and release growth factors. The resulting bi-crosslinked hydrogel (CS / AA) can improve the wound dressing's antibacterial and wound-healing properties while achieving adhesive differences on both sides of the same hydrogel material. The amino groups of chitosan are condensed with the carboxyl groups on the surface of the CS / AA hydrogel using the coupling agent EDC / NHS, grafting chitosan onto the CS / AA hydrogel surface to increase the adhesive differences between the two sides, forming a CS / AA-CS hydrogel. The preparation diagram of the CS / AA-CS hydrogel is shown below. Figure 1 As shown.

[0038] The following is the reaction formula of the present invention:

[0039]

[0040] Comparative Example 1

[0041] The preparation method of chitosan hydrogel (CS hydrogel) includes the following steps:

[0042] (1) Add 0.2g of chitosan powder (Mw=150000) to 6.96ml of deionized water, stir and disperse evenly, add 2.4ml of acetic acid solution to dissolve the chitosan and prepare a 2% (w / w) CS solution;

[0043] (2) Add 0.64 ml of 0.85% glutaraldehyde solution to the CS solution obtained in step (1) and stir until homogeneous;

[0044] (3) Heat the mixed solution obtained in step (2) at 37°C for 20 min to form CS hydrogel.

[0045] Comparative Example 2

[0046] The preparation method of acrylic hydrogel (AA hydrogel) includes the following steps:

[0047] (1) Dissolve 1g of acrylic acid (AA) in 4ml of deionized water and stir well to prepare a 5% (w / w) AA solution;

[0048] (2) Dissolve 1g of polyethylene glycol dimethacrylate (PEGDMA) in 4ml of deionized water and stir well to prepare a 5% (w / w) PEGDMA solution.

[0049] (3) Mix the AA solution and PEGDMA solution prepared in the above steps, add 0.1% (w / w) of the photoinitiator 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone, stir evenly, and then add 10 ml of deionized water and stir evenly.

[0050] (4) Irradiate the mixed solution obtained in step (3) with a 365nm ultraviolet light for 10 minutes to form an AA hydrogel.

[0051] Example 1

[0052] A method for preparing chitosan / acrylic acid hydrogel (CS / AA hydrogel) includes the following steps:

[0053] (1) Add 0.2g of chitosan powder (Mw=150000) to 6.96ml of deionized water, stir and disperse evenly, add 2.4ml of acetic acid solution to dissolve the chitosan and prepare a 2% (w / w) CS solution;

[0054] (2) Dissolve 1g of acrylic acid (AA) in 4ml of deionized water and stir well to prepare a 5% (w / w) AA solution.

[0055] (3) Dissolve 1g of polyethylene glycol dimethacrylate (PEGDMA) in 4ml of deionized water and stir well to prepare a 5% (w / w) PEGDMA solution.

[0056] (4) Mix the CS solution, AA solution and PEGDMA solution prepared in the above steps, add 0.1% (w / w) of photoinitiator 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone and 0.64 ml of 0.85% glutaraldehyde solution, stir evenly to obtain the precursor solution of CS / AA hydrogel;

[0057] (5) Pour the precursor solution into the mold, heat it at 37°C for 20 min at the bottom of the mold, and irradiate it with 365 nm ultraviolet light for 10 min at the top of the container to obtain CA / AA hydrogel. Name the heated surface of CA / AA hydrogel CA / AA-HIS and the light-irradiated surface of CA / AA hydrogel CA / AA-LIS.

[0058] Example 2

[0059] A method for preparing chitosan-grafted chitosan / acrylic acid hydrogel (CS / AA-CS hydrogel) includes the following steps:

[0060] (1) Add 0.2g of bridging polymer chitosan powder (Mw=150000) to 6.96ml of deionized water, stir and disperse evenly, add 2.4ml of acetic acid solution to dissolve chitosan, prepare a 2% (w / w) bridging polymer solution, and adjust the pH of the solution to 6.

[0061] (2) Add coupling agents 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and sulfate or unsulfated N-hydroxysuccinimide (NHS). The final concentrations of EDC and NHS in the bridging polymer solution are both 12 mg / mL.

[0062] (3) The light-illuminated surface of the CS / AA hydrogel prepared in Example 1 was immersed in about 250 μl of bridging polymer solution for 24 hours to form CS / AA-CS hydrogel, which was named CS / AA-CS2. The heating surface was still CA / AA-HIS.

[0063] Example 3

[0064] A method for preparing chitosan-grafted chitosan / acrylic acid hydrogel (CS / AA-CS hydrogel) includes the following steps:

[0065] (1) Add 0.4g of bridging polymer chitosan powder (Mw=150000) to 6.96ml of deionized water, stir and disperse evenly, add 2.4ml of acetic acid solution to dissolve chitosan, prepare a 4% (w / w) bridging polymer solution, and adjust the pH of the solution to 6.

[0066] (2) Add coupling agents 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and sulfate or unsulfated N-hydroxysuccinimide (NHS). The final concentrations of EDC and NHS in the bridging polymer solution are both 12 mg / mL.

[0067] (3) The light-illuminated surface of the CS / AA hydrogel prepared in Example 1 was immersed in about 250 μl of bridging polymer solution for 24 hours to form CS / AA-CS hydrogel, which was named CS / AA-CS4. The heating surface was still CA / AA-HIS.

[0068] Effect verification:

[0069] The rheological properties, compressibility, and antibacterial properties of the hydrogels prepared in Comparative Examples 1-2 and Examples 1-2, and the adhesive properties of the hydrogels prepared in Examples 1-3 were tested using the following methods:

[0070] Compression performance:

[0071] The compressive properties of the hydrogels prepared in Comparative Examples 1-2 and Examples 1-2 were tested using a universal testing machine (CMT1203) at a unidirectional speed of 5 mm / min. The compressive modulus of the hydrogels prepared in Examples 1-4 is as follows: Figure 2 As shown, the compressive modulus of the dual-network CS / AA-CS hydrogel (103.05±5.63KPa) is greater than that of the single-network CS hydrogel (64.12±2.5KPa), AA hydrogel (36.8±1.51KPa), and CS / AA hydrogel before grafting (92.39±6.64KPa), proving that the CS / AA-CS hydrogel has the highest crosslinking density.

[0072] Antibacterial properties:

[0073] The surface antibacterial activity of the hydrogels prepared in Comparative Examples 1-2 and Examples 1-2 was tested using *Escherichia coli* and *Staphylococcus aureus*. The inhibition zone was assessed using an agar diffusion method similar to disc diffusion. In this assay, agar plates were inoculated with the corresponding microorganisms. Furthermore, the hydrogel samples prepared in Examples 1-4 were placed on the surface of agar plates, and then the agar plates were incubated at 37°C to allow microbial growth. The test samples were dispersed in agar, and microbial growth was controlled. The antibacterial performance of the hydrogel samples was evaluated by the size of the inhibition zone. Figure 3 and Figure 5 The size of the inhibition zones of the hydrogels prepared in Comparative Examples 1-2 and Examples 1-2 against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) are shown respectively. Figure 4 and Figure 6 Quantitative graphs of the inhibition zone sizes of the hydrogels prepared in Comparative Examples 1-2 and Examples 1-2 against *Escherichia coli* (E. coli) and *Staphylococcus aureus* (S. aureus) are shown. After incubation at 37°C for 24 h, CS / AA-CS showed the best antibacterial effect, with an inhibition zone size of 26.5 ± 1.24 mm against *E. coli* and 37.5 ± 2.18 mm against *S. aureus*.

[0074] Adhesion properties:

[0075] Pigskin was cut into 2.5cm × 3cm pieces and soaked in PBS at 37°C for 1 hour. The hydrogels prepared in Examples 1-3 were cut into rectangular shapes, 35mm long, 1mm wide, and 1.5mm thick. A hydrogel dressing coated with a bonding liquid on one side was then bonded to the treated pigskin tissue. The other side of the hydrogel dressing was bonded to a rigid polyethylene terephthalate (PET) film using Krazy Glue. The PET film served as the backing for the hydrogel dressing. The backing and the pigskin tissue were connected to a fixture. All the work done by the machine was equivalent to the energy dissipated at the crack tip. Testing was conducted using a universal testing machine (CMT1203) with a constant loading rate of 10mm / min. The adhesion energy test results for the light-exposed and heated sides of each hydrogel are as follows: Figure 7 As shown.

[0076] The adhesion energy difference between the two sides of the CS / AA-CS hydrogel before grafting was 38.76±2.72 J / m. 2 The adhesion energies on both sides of the CS / AA-CS hydrogel grafted with 2% chitosan differed by 79.76 ± 2.72 J / m. 2 The adhesion energies on both sides of the CS / AA-CS hydrogel grafted with 4% chitosan differed by 235.39 ± 7.26 J / m. 2 This indicates that grafting chitosan onto the CS / AA hydrogel under light illumination can significantly improve the difference in adhesion energy between the two sides of the hydrogel; grafting chitosan with a larger mass fraction can significantly improve the adhesion energy of the grafted surface of the CS / AA-CS hydrogel, making the difference in adhesion between the two sides of the CS / AA-CS hydrogel more obvious.

Claims

1. A method for preparing a dual cross-linked biocompatible hydrogel having adhesion disparity, characterized in that, Includes the following steps: S1. Dissolve chitosan in acetic acid solution to obtain the first solution; S2. Dissolve acrylic acid and polyethylene glycol dimethacrylate in deionized water to obtain a second solution; S3. Mix the first and second solutions, add a photoinitiator and a crosslinking agent to obtain a dual-network hydrogel precursor solution; place the dual-network hydrogel precursor solution in a glass container, apply 37°C heating to the bottom of the container for 20 minutes, and simultaneously apply 365nm UV irradiation to the top of the container for 10 minutes. Obtain a dual-network chitosan / acrylic hydrogel through Schiff base reaction and C=C free radical polymerization, named CS / AA hydrogel. The light-illuminated surface of CS / AA hydrogel is named CS / AA-LIS, and the heated surface is named CS / AA-HIS. S4. Chitosan was dissolved in acetic acid solution to obtain a 2% chitosan solution by mass, and the pH was adjusted to 6. Coupling reagents 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide were added to obtain a third solution. CS / AA-LIS was soaked in the third solution for 24 hours to obtain chitosan / acrylic acid-chitosan hydrogel, named CS / AA-CS hydrogel.

2. The method for preparing a dual cross-linked biocompatible hydrogel with adhesion differential according to claim 1, characterized in that, In S1, the degree of deacetylation of chitosan is 70-90%, the mass fraction is 2%, and the volume fraction of acetic acid solution is 2%.

3. The method of claim 1, wherein the method further comprises the step of: S2 contains 5% acrylic acid by volume and 5% polyethylene glycol dimethacrylate by mass.

4. The method of claim 1, wherein the method further comprises the step of, The photoinitiator used in S3 is a solution of 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone, and the mass fraction of the 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone solution is 0.1%.

5. The method for preparing a double-crosslinked biocompatible hydrogel with adhesion differences according to claim 1, characterized in that, The crosslinking agent used in S3 is glutaraldehyde solution, with a volume fraction of 0.85%.

6. The method for preparing a double-crosslinked biocompatible hydrogel with adhesion differences according to claim 1, characterized in that, The volume fraction of acetic acid solution in S4 is 2%, and the pH adjuster is 1M NaOH.

7. The method for preparing a double-crosslinked biocompatible hydrogel with adhesion differences according to claim 1, characterized in that, The mass concentration of the coupling reagents 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide in S4 is 12 mg / mL.

8. Chitosan / acrylic acid-chitosan hydrogel prepared by any one of the methods of claims 1-7.

9. The use of the chitosan / acrylic acid-chitosan hydrogel according to claim 8 in the preparation of wound dressing materials.

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