An asymmetric janus hydrogel dressing and its preparation method and application

Abstract

The application provides an asymmetric Janus hydrogel dressing and a preparation method and application thereof, and belongs to the technical field of biomedical materials.The carboxymethyl cellulose, borax, acrylic acid and N-isopropyl acrylamide are mixed to prepare a nascent hydrogel; and then the nascent hydrogel is immersed in a chlorobenzalkonium chloride solution to obtain the asymmetric Janus hydrogel dressing.Through special component design and post-treatment process, the application constructs a double-sided structure with a dense hydrophobic barrier layer and a porous hydrophilic adhesive layer, realizes one-way moisture conduction, active antibiosis, high toughness and excellent anti-swelling stability.

Description

Technical Field

[0001] This invention belongs to the field of biomedical materials technology, and particularly relates to an asymmetric Janus hydrogel dressing, its preparation method, and its application. Background Technology

[0002] In wound healing management, traditional single-component hydrogel dressings, while providing a moist environment, often have significant limitations. Traditional hydrogels lack anisotropic fluid management capabilities, easily leading to the accumulation of wound exudate and causing overhydration (maceration) of the wound surface. This not only delays healing but also provides a breeding ground for bacteria (e.g., a) JP Gong, T. Kurokawa, T. Narita, G. Kagata, Y. Osada, G. Nishimura, M. Kinjo, J. Am. Chem. Soc. 2001, 123, 5582; b) F. Yang, J. Zhao, WJ Koshut, J. Watt, JCRiboh, K. Gall, BJ Wiley, Adv. Funct. Mater. 2020, 30, 2003451, etc.). Many hydrogels experience a significant decrease in mechanical strength after swelling, making them unable to accommodate large movements at joints and prone to brittle fracture. Ordinary hydrogels typically lack contact bactericidal capabilities and are ineffective against common wound infection bacteria such as Staphylococcus aureus, leading to prolonged inflammation. During repeated water absorption and dehydration cycles, traditional hydrogels are prone to structural collapse or over-expansion, losing their protective function.

[0003] Therefore, developing an asymmetric hydrogel dressing that integrates controlled moisture management (active exudate drainage), high mechanical toughness, excellent tissue adhesion, and broad-spectrum antibacterial properties is an urgent need in current clinical nursing. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes an asymmetric Janus hydrogel dressing (JPAC-NI / BC), its preparation method, and its application. Through special component design and post-processing, a double-sided structure with a dense hydrophobic barrier layer and a porous hydrophilic adhesive layer is constructed, achieving unidirectional moisture conduction, active antibacterial properties, high strength and toughness, and excellent anti-swelling stability.

[0005] To achieve the above objectives, the present invention provides the following technical solution: This invention proposes a method for preparing an asymmetric Janus hydrogel dressing, comprising the following steps: (1) Carboxymethyl cellulose (CMC), borax, acrylic acid (AA) and N-isopropylacrylamide (NIPAM) were mixed to prepare a nascent hydrogel (JPAC-NI). (2) The nascent hydrogel was immersed in chlorobenzal chloride (BC) solution to obtain an asymmetric Janus hydrogel dressing (JPAC-NI / BC). The molar ratio of AA to NIPAM is 3:1.

[0006] Furthermore, step (1) specifically involves: CMC and borax were added to water to prepare the first solution; Prepare a second solution by mixing AA and NIPAM; The first solution and the second solution are mixed to obtain a mixed solution. Then, a photoinitiator and a crosslinking agent are added, and a primary hydrogel with a composition gradient is prepared by free radical polymerization and physical crosslinking.

[0007] Furthermore, the mass ratio of CMC to borax is 4:1.

[0008] Furthermore, the volume ratio of the first solution to the second solution is 3:1.

[0009] Furthermore, the photoinitiator is 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone, and the amount added accounts for 0.01% of the volume of the mixed solution.

[0010] Furthermore, the crosslinking agent is N,N'-methylenebisacrylamide, and the amount added accounts for 5% of the mass of the AA.

[0011] Furthermore, the free radical polymerization reaction is initiated by ultraviolet light with a wavelength of 365 nm, a power of 1800 W, and an initiation time of 12 minutes.

[0012] Furthermore, in step (2), the concentration of the BC solution is 0.25 wt.%, the soaking time is two days, and the solution is changed every four hours during the soaking time.

[0013] The present invention also proposes an asymmetric Janus hydrogel dressing, which is prepared according to the above preparation method.

[0014] The asymmetric Janus hydrogel dressing of the present invention comprises a hydrophobic layer and a hydrophilic layer, wherein: The hydrophobic layer has a dense structure with a contact angle (WCA) greater than 90°. It is formed by the electrostatic interaction and hydrophobic aggregation of the BC and polyAA segments in the polymer network to form a network collapse. The hydrophobic layer contains quaternary ammonium salt groups and has contact antibacterial properties. The hydrophilic layer has a porous structure with a contact angle of less than 55°, and is formed by electrostatic interaction between BC and carboxyl-containing polysaccharides. The hydrophobic layer and the hydrophilic layer have a gradient transition structure without a macroscopic interface.

[0015] Technical principle: This invention uses CMC, borax, AA, and NIPAM as raw materials to prepare a primary hydrogel with a compositional gradient through a combination of free radical polymerization and physical crosslinking. This matrix hydrogel naturally forms a side rich in CMC / borax (smooth, aggregated matrix) and a side rich in AA / NIPAM (porous structure). The prepared primary hydrogel is immersed in a chlorobenzalkonium chloride (BC) solution, utilizing electrostatic interactions (CMC-COO... - With BC's -N + R4) and hydrophobic interactions induce asymmetric shrinkage and densification of the hydrogel. After BC treatment, the original AA / NIPAM enriched layer collapses due to the strong electrostatic bonding and hydrophobic aggregation between BC and polyacrylic acid segments, transforming into a highly dense, hydrophobic barrier layer; while the original CMC enriched layer, although its surface becomes rough, still maintains a relatively hydrophilic and porous structure, serving as an adhesive layer. BC molecules are integrated into the dynamic borate ester network as molecular zippers, providing additional sacrificial bonds through ion pairs and hydrophobic water regions, significantly improving the mechanical modulus, elongation at break, and fatigue resistance of the hydrogel in the swollen state.

[0016] The asymmetric Janus hydrogel dressing prepared in this invention exhibits an integrated structural gradient in its cross-section, without macroscopic layering. One side is a dense, highly cross-linked hydrophobic layer (NIPAM / BC side) with a contact angle greater than 90°, acting as a protective barrier. The other side is a hydrophilic layer (CMC / BC side) maintaining an interconnected porous structure with a contact angle less than 51°, absorbing exudate and promoting tissue adhesion. In this hydrogel dressing, the top hydrophobic and dense layer prevents external moisture intrusion and controls evaporation, while the bottom hydrophilic layer rapidly absorbs exudate, pumping the liquid out of the interface using osmotic pressure difference, effectively preventing wound maceration. The CMC, AA, and BC reinforcing network endows the material with skin-like low modulus and high elongation, allowing it to adapt to joint movements without detachment or tissue damage. The quaternary ammonium salt (chlorobenzalkonium chloride, BC) integrated into the network provides contact bactericidal ability, significantly reducing bacterial load such as Staphylococcus aureus. Through borate ester bonds, hydrogen bonds, and electrostatic interlocking, strong and reversible adhesion to skin and various substrates is achieved, with no residue after peeling. BC-mediated strong electrostatic bridging limits excessive water absorption by the polymer network, ensuring that the dressing maintains its structural integrity during long-term use.

[0017] This invention also proposes the application of the aforementioned asymmetric Janus hydrogel dressing in the preparation of medical materials for the repair of infected wounds. The asymmetric Janus hydrogel dressing simultaneously achieves active moisture management, contact antibacterial properties, and biomechanical adaptation. The active moisture management prevents external moisture intrusion and controls evaporation through a hydrophobic layer, while the hydrophilic layer absorbs exudate and utilizes osmotic pressure difference to pump the liquid out from the interface, preventing wound maceration.

[0018] Compared with the prior art, the present invention has the following advantages and technical effects: (1) Excellent unidirectional moisture-wicking properties: The asymmetric Janus hydrogel dressing obtained in this invention has a hydrophobic layer contact angle greater than 90° and a hydrophilic layer contact angle less than 55°. It utilizes the osmotic pressure difference to achieve unidirectional pumping of liquid from the wound interface to the outside, effectively preventing wound maceration.

[0019] (2) Good mechanical compatibility: The preparation process of this invention controls the ratio of AA, NIPAM and BC to enhance the network so that the hydrogel has a low modulus and high elongation similar to skin, which can adapt to large-scale movements of joints and is not easy to fall off or damage tissue.

[0020] (3) Highly efficient contact antibacterial properties: This invention integrates BC into the hydrogel network, thereby endowing the material with contact bactericidal ability, which can significantly reduce the bacterial load of common wound infection bacteria such as Staphylococcus aureus.

[0021] (4) Strong and reversible tissue adhesion properties: The asymmetric Janus hydrogel dressing obtained by the present invention achieves excellent tissue adhesion through the synergistic effect of borate ester bonds, hydrogen bonds and electrostatic interlocking, and leaves no residue after peeling.

[0022] (5) Excellent anti-swelling stability: The strong electrostatic bridging mediated by BC in this invention limits the excessive water absorption of the polymer network, ensuring that the dressing maintains structural integrity during long-term use and avoiding the structural collapse or excessive expansion problems that are common in traditional hydrogels.

[0023] (6) Good structural integrity: The asymmetric Janus hydrogel dressing obtained by the present invention has a gradient transition structure between the hydrophobic layer and the hydrophilic layer without macroscopic interface, which avoids the interlayer separation problem common in multilayer composite dressings. Attached Figure Description

[0024] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 The contact angle test results of JPAC-NI / BC in Example 1 and JPAC-NI in Comparative Example 1 at 0s and 10s are shown. Figure 2 The results are SEM measurements of the hydrophilic side, hydrophobic side, and cross-section of JPAC-NI / BC in Example 1 and JPAC-NI in Comparative Example 1. Figure 3 The FTIR spectra of the hydrogels obtained in Example 1 and Comparative Examples 1-6 are shown below. Figure 4 The XPS O element spectrum of JPAC-NI / BC in Example 1; Figure 5 The XPS C element spectrum of JPAC-NI / BC in Example 1; Figure 6 The mechanical property test results of JPAC-NI / BC in Example 1 are shown. Figure 7 The mechanical property test results are for JPAC-NI in Comparative Example 1. Figure 8 This is a comparison of the mechanical properties of JPAC-NI in Comparative Example 1 and JPAC-NI / BC hydrogel in Example 1. Figure 9 The results of the JPAC-NI / BC in Example 1 are obtained from a continuous cyclic loading-unloading tensile test at a maximum strain of 40%. Figure 10 A schematic diagram demonstrating the tissue's adhesion and peeling properties; Figure 11 The results are the tissue adhesion performance test results of JPAC-NI / BC in Example 1; Figure 12 The results of unidirectional moisture conduction and drainage rate tests are for JPAC-NI in Comparative Example 1 and JPAC-NI / BC hydrogel in Example 1. Figure 13 Results of Staphylococcus aureus infection in the blank control, JPAC-NI (Comparative Example 1), and JPAC-NI / BC (Example 1); Figure 14 The mechanical properties of JPAC-NI hydrogels prepared under different AA to NIPAM molar ratios in Example 1 (3:1) and Comparative Examples 7-10 (2:1, 4:1, 5:1, and 6:1, respectively) are presented. Detailed Implementation

[0025] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0026] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0027] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0028] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0029] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0030] This invention provides a method for preparing an asymmetric Janus hydrogel dressing, comprising the following steps: (1) Carboxymethyl cellulose (CMC), borax, acrylic acid (AA) and N-isopropylacrylamide (NIPAM) were mixed to prepare a nascent hydrogel (JPAC-NI). (2) The nascent hydrogel was immersed in chlorobenzal chloride (BC) solution to obtain asymmetric Janus hydrogel dressing (JPAC-NI / BC). The molar ratio of AA to NIPAM is 3:1.

[0031] It should be noted that, in the technical solution of the present invention, in addition to CMC, other polysaccharides containing carboxyl and hydroxyl groups such as sodium alginate can be used as raw materials; in addition to NIPAM, other thermosensitive or amphiphilic monomers can be used; in addition to BC, other quaternary ammonium salt compounds with long alkyl chains or other cationic hydrophobic modifiers can be used as long as they can induce network shrinkage through electrostatic and hydrophobic interactions.

[0032] In some preferred embodiments of the present invention, the preparation method of the asymmetric Janus hydrogel dressing specifically includes the following steps: (1) Prepare the first solution by adding CMC and borax in water at a mass ratio of 4:1; A second solution was prepared by mixing AA and NIPAM at a molar ratio of 3:1. The first solution and the second solution were mixed at a volume ratio of 3:1 to obtain a mixed solution. Then, a photoinitiator (2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone, added at 0.01% of the volume of the mixed solution) and a crosslinking agent (N,N'-methylenebisacrylamide, added at 5% of the mass of AA) were added. The polymerization was initiated by irradiation under a 365nm, 1800W UV lamp for 12min to prepare JPAC-NI with a compositional gradient. (2) JPAC-NI was soaked in a 0.25 wt.% BC solution, and the BC solution was changed every four hours. After soaking for two days, an asymmetric Janus hydrogel dressing (JPAC-NI / BC) was obtained.

[0033] This invention also proposes a JPAC-NI / BC, which is prepared according to the above preparation method.

[0034] The JPAC-NI / BC obtained by this invention comprises a hydrophobic layer and a hydrophilic layer, wherein: The hydrophobic layer (NIPAM / BC side) has a dense structure with a contact angle (WCA) greater than 90°. It is formed by the electrostatic interaction and hydrophobic aggregation of the BC and the polyAA segments in the polymer network to form a network collapse. The hydrophobic layer contains quaternary ammonium salt groups and has contact antibacterial properties. The hydrophilic layer (CMC / BC side) has a porous structure with a contact angle of less than 51°, and is formed by the electrostatic interaction between BC and carboxyl-containing polysaccharides. The hydrophobic layer and the hydrophilic layer have a gradient transition structure without a macroscopic interface.

[0035] The JPAC-NI / BC obtained by this invention can be used to prepare medical materials for the repair of infected wounds.

[0036] All raw materials used in the embodiments of this invention were purchased commercially.

[0037] The technical solution of the present invention will be further illustrated by the following embodiments.

[0038] Example 1 A method for preparing an asymmetric Janus hydrogel dressing specifically includes the following steps: (1) Add 2g of CMC and 0.5g of borax to 100mL of deionized water and stir well to prepare the first solution; Prepare a second solution by mixing 3 mol AA and 1 mol NIPAM in a molar ratio of 3:1; The first solution and the second solution were mixed at a volume ratio of 3:1 to obtain a mixed solution. Then, a photoinitiator (2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone, added at 0.01% of the volume of the mixed solution) and a crosslinking agent (N,N'-methylenebisacrylamide, added at 5% of the mass of AA) were added. The polymerization was initiated by irradiation under a 365nm, 1800W UV lamp for 12min to prepare JPAC-NI with a compositional gradient. (2) JPAC-NI was soaked in a 0.25 wt.% BC solution, and the BC solution was changed every four hours. After soaking for two days, an asymmetric Janus hydrogel dressing (JPAC-NI / BC) was obtained.

[0039] Comparative Example 1 Same as Example 1, except that the step of soaking in BC solution is omitted to obtain JPAC-NI.

[0040] Comparative Example 2 Same as Example 1, except that the steps of adding NIPAM and soaking in BC solution are omitted. Specifically: The first solution was prepared by mixing CMC and borax at a mass ratio of 4:1. The first solution was mixed with AA at a volume ratio of 3:1 to obtain a mixed solution. Then, a photoinitiator (2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone, added at 0.01% of the volume of the mixed solution) and a crosslinking agent (N,N'-methylenebisacrylamide, added at 5% of the mass of AA) were added. The polymerization was initiated by irradiation under a 365nm, 1800W UV lamp for 12min to prepare sodium carboxymethyl cellulose / borax / acrylic acid hydrogel.

[0041] Comparative Example 3 Same as Example 1, except that the steps of adding NIPAM and AA and soaking in BC solution are omitted. Specifically: A first solution was prepared by mixing CMC and borax at a mass ratio of 4:1. Then, a photoinitiator (2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone, added at 0.01% of the volume of the first solution) and a crosslinking agent (N,N'-methylenebisacrylamide, added at 5% of the mass of CMC) were added. The polymerization was initiated by irradiation under a 365nm, 1800W UV lamp for 12min to prepare sodium carboxymethyl cellulose / borax hydrogel.

[0042] Comparative Example 4 Same as Example 1, except that the steps of adding NIPAM and borax and soaking in BC solution are omitted. Specifically: A second solution was prepared by mixing AA and NIPAM at a molar ratio of 3:1. CMC and the second solution were mixed at a volume ratio of 3:1 to obtain a mixed solution. Then, a photoinitiator (2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone, added at 0.01% of the volume of the mixed solution) and a crosslinking agent (N,N'-methylenebisacrylamide, added at 5% of the mass of AA) were added. The polymerization was initiated by irradiation under a 365nm, 1800W UV lamp for 12min to prepare sodium carboxymethyl cellulose / acrylic acid hydrogel.

[0043] Comparative Example 5 Same as Example 1, except that the steps of adding NIPAM and CMC and soaking in BC solution are omitted. Specifically: Borax and AA were mixed at a volume ratio of 3:1 to obtain a mixed solution. Then, a photoinitiator (2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone, added at 0.01% of the volume of the mixed solution) and a crosslinking agent (N,N'-methylenebisacrylamide, added at 5% of the mass of AA) were added. The polymerization was initiated by irradiation under a 365nm, 1800W UV lamp for 12min to prepare an acrylic / borax hydrogel.

[0044] Comparative Example 6 Same as Example 1, except that the steps of adding NIPAM, CMC, and borax, and soaking in BC solution are omitted. Specifically: Acrylic acid hydrogel was prepared by adding a photoinitiator (2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone, with an addition amount of 0.01% of the volume of AA) and a crosslinking agent (N,N'-methylenebisacrylamide, with an addition amount of 5% of the mass of AA) to AA and irradiating it under a 365nm, 1800w UV lamp for 12min to initiate polymerization.

[0045] Comparative Example 7 Same as Example 1, except that 2 mol AA and 1 mol NIPAM are mixed in a molar ratio of 2:1 to prepare a second solution.

[0046] Comparative Example 8 Same as Example 1, except that 4 mol AA and 1 mol NIPAM are mixed in a molar ratio of 4:1 to prepare a second solution.

[0047] Comparative Example 9 Same as Example 1, except that 5 mol AA and 1 mol NIPAM are mixed in a molar ratio of 5:1 to prepare a second solution.

[0048] Comparative Example 10 Same as Example 1, except that 6 mol AA and 1 mol NIPAM are mixed in a molar ratio of 6:1 to prepare a second solution.

[0049] Performance testing 1. Wettability test (contact angle WCA) Wetting tests were performed on JPAC-NI / BC of Example 1 and JPAC-NI of Comparative Example 1. The contact angle test results at 0s and 10s are shown in the figure. Figure 1 As can be seen, the contact angle of the hydrophobic layer (NIPAM side) of JPAC-NI / BC changes from 91.7° to 84.3°, resulting in a 7.4° contact angle, demonstrating a highly efficient hydrophobic barrier function. The contact angle of the hydrophilic layer (CMC side) of JPAC-NI / BC changes from 87.4° to 50.4°, resulting in a 37.0° contact angle, enabling efficient moisture absorption. The significant difference in wettability between the two sides provides a physical basis for unidirectional moisture conduction and active moisture management. This indicates that the top layer of the hydrogel (NIPAM / BC side) after BC treatment becomes highly hydrophobic, while the bottom layer (CMC / BC side) remains hydrophilic; this difference provides a physical basis for active moisture management.

[0050] 2. Structural and morphological characterization (SEM) SEM tests were performed on the hydrophilic side, hydrophobic side, and cross-section of JPAC-NI / BC in Example 1 and JPAC-NI in Comparative Example 1. The results are shown in [Figure Number]. Figure 2 It can be seen that in JPAC-NI, the CMC side is a smooth aggregated matrix, and the NIPAM side is a porous interconnected structure with a compositional gradient in the cross section. However, after BC treatment, the NIPAM / BC side of JPAC-NI / BC collapses due to hydrophobic aggregation, forming a highly dense hydrophobic barrier layer; while the CMC / BC side maintains a rough porous hydrophilic structure, and the cross section is an overall gradient transition without macroscopic layering, with no risk of interlayer separation.

[0051] 3. Chemical structure characterization (FTIR, XPS) The FTIR spectra of the hydrogels obtained in Example 1 and Comparative Examples 1-6 are shown below. Figure 3 The XPSO elemental spectrum of JPAC-NI / BC in Example 1 is shown below. Figure 4 The C element spectrum can be found in [the image / data]. Figure 5 The FTIR spectrum shows 1350-1450 cm⁻¹ -1 COO - The enhanced and blue-shifted peak confirms ion interactions; the increased area of ​​the CN peak (285.9 eV) in the XPS C1s spectrum confirms successful high-density loading of BC and strong electrostatic complexation with the polymer network (-COO). - With -N+ R4).

[0052] 4. Mechanical property testing The JPAC-NI hydrogel of Comparative Example 1 and the JPAC-NI / BC hydrogel of Example 1 were swollen in 0.9% physiological saline for different times, and their mechanical properties were tested. Figure 6 The mechanical property test results of JPAC-NI / BC in Example 1 are as follows. Figure 7 The mechanical property test results are for JPAC-NI in Comparative Example 1. Figure 8 The graph shows a comparison of the mechanical properties of JPAC-NI in Comparative Example 1 and JPAC-NI / BC hydrogel in Example 1. It can be seen that the JPAC-NI hydrogel has high stiffness but is easily broken in its completely dry state. After immersion in physiological saline, the dynamic borate ester bonds and hydrogen bonds are activated as ions and water molecules penetrate, and the mechanical properties gradually recover. The JPAC-NI / BC hydrogel, due to the integration of BC molecules as molecular zippers into the dynamic borate ester network, provides additional sacrificial bonds through ion pairs and hydrophobic water regions, resulting in significantly improved mechanical modulus, elongation at break, and fatigue resistance in the swollen state.

[0053] The JPAC-NI / BC of Example 1 was subjected to a continuous cyclic loading-unloading tensile test with a maximum strain of 40%. The results are shown in [Figure Number]. Figure 9 It can be seen that stress softening occurs in the early stage, and the peak stress and hysteresis loop area decrease slightly. As the number of cycles increases, the loading-unloading curves gradually overlap, indicating that the material has excellent fatigue resistance and mechanical durability and can be adapted to repeated movement of the wound site.

[0054] 5. Tissue adhesion performance test Using a mechanical testing machine, the JPAC-NI / BC of Example 1 was tested on mouse skin using the 90° peel method. A schematic diagram of the peel demonstration is shown below. Figure 10 The test results are shown below. Figure 11 It can be seen that the JPAC-NI / BC hydrogel has a peel strength of approximately 400 N / m. It achieves strong and reversible adhesion to the skin through the synergistic effect of borate ester bonds, hydrogen bonds, and electrostatic interlocking. There is no residue after peeling, and it does not damage newly formed tissue.

[0055] 6. One-way moisture conduction and drainage rate test The test results of unidirectional moisture conduction and drainage rates of JPAC-NI in Comparative Example 1 and JPAC-NI / BC hydrogel in Example 1 are shown in the figure. Figure 12As can be seen, initially, JPAC-NI exhibits a faster water conduction rate due to its highly interconnected porous hydrophilic network (consistent with SEM observations), allowing water to rapidly permeate the entire gel via capillary action and evaporate directly. In contrast, JPAC / NI-BC is initially in an unsaturated "hydration-activated" stage. The introduction of BC causes hydrophobic collapse and high densification of the top layer, forming an initial water diffusion barrier, thus slowing down immediate water penetration. Over time, as the hydrophilic bottom layer of JPAC / NI-BC absorbs water to saturation and establishes a stable osmotic pressure and humidity gradient within the gel, its water drainage rate gradually surpasses that of JPAC / NI, demonstrating superior and sustained active water conduction capabilities.

[0056] 7. Antibacterial performance test Wounds were created on the skin of mice cultured for 6-8 weeks. Cultured Staphylococcus aureus was then instilled into the wounds and cultured for one day to establish a Staphylococcus aureus infection mouse wound model. Three groups were set up: a blank control, JPAC-NI (Comparative Example 1), and JPAC-NI / BC (Example 1). Results are shown in […]. Figure 13 The results showed that the JPAC-NI / BC group had a significantly reduced bacterial load at the wound site due to the contact bactericidal effect of quaternary ammonium salt (BC) in the network, and the antibacterial effect was far superior to the blank group and the JPAC-NI group, which could effectively shorten the inflammatory period of infected wounds.

[0057] 8. Mechanical properties of hydrogels with different AA to NIPAM molar ratios The mechanical properties of JPAC-NI hydrogels prepared in Example 1 (3:1) and Comparative Examples 7-10 (2:1, 4:1, 5:1, 6:1) with different AA:NIPAM molar ratios were tested. The results are shown in [Figure number missing]. Figure 14 It can be seen that when the molar ratio is less than 3:1 (Comparative Example 7), the material has poor ductility. 3:1 (Example 1) is the optimal ratio, which balances Janus structure formation with mechanical toughness and energy dissipation. In Comparative Examples 8-10, when the AA:NIPAM ratio is 4:1, 5:1 or 6:1, the NIPAM content is even lower. The amount of NIPAM is the key to forming the hydrophobic side of the Janus structure. The more NIPAM there is, the thicker the hydrophobic layer is, which is conducive to the discharge of exudate. Therefore, a ratio with a higher amount of NIPAM should be selected while ensuring good ductility.

[0058] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing an asymmetric Janus hydrogel dressing, characterized in that, Includes the following steps: (1) Carboxymethyl cellulose, borax, acrylic acid and N-isopropylacrylamide were mixed to prepare a primary hydrogel; (2) The nascent hydrogel is immersed in chlorobenzal chloride solution to obtain an asymmetric Janus hydrogel dressing; The molar ratio of acrylic acid to N-isopropylacrylamide is 3:

1.

2. The method for preparing the asymmetric Janus hydrogel dressing according to claim 1, characterized in that, Step (1) is as follows: Carboxymethyl cellulose and borax were mixed to prepare a first solution; A second solution was prepared by reacting acrylic acid with N-isopropylacrylamide. The first solution and the second solution are mixed to obtain a mixed solution. Then, a photoinitiator and a crosslinking agent are added, and a primary hydrogel with a composition gradient is prepared by free radical polymerization and physical crosslinking.

3. The method for preparing the asymmetric Janus hydrogel dressing according to claim 2, characterized in that, The mass ratio of carboxymethyl cellulose to borax is 4:

1.

4. The method for preparing the asymmetric Janus hydrogel dressing according to claim 2, characterized in that, The volume ratio of the first solution to the second solution is 3:

1.

5. The method for preparing the asymmetric Janus hydrogel dressing according to claim 2, characterized in that, The photoinitiator is 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone, and the amount added accounts for 0.01% of the volume of the mixed solution.

6. The method for preparing the asymmetric Janus hydrogel dressing according to claim 2, characterized in that, The crosslinking agent is N,N'-methylenebisacrylamide, and the amount added accounts for 5% of the mass of the acrylic acid.

7. The method for preparing the asymmetric Janus hydrogel dressing according to claim 2, characterized in that, The free radical polymerization reaction was initiated by ultraviolet light with a wavelength of 365 nm, a power of 1800 W, and an initiation time of 12 minutes.

8. The method for preparing the asymmetric Janus hydrogel dressing according to claim 1, characterized in that, In step (2), the concentration of the chlorobenzal chloride solution is 0.25 wt.%, the soaking time is two days, and the solution is changed every four hours during the soaking time.

9. An asymmetric Janus hydrogel dressing, characterized in that, The asymmetric Janus hydrogel dressing, prepared according to any one of claims 1-8, comprises a hydrophobic layer and a hydrophilic layer.

10. The use of the asymmetric Janus hydrogel dressing as described in claim 9 in the preparation of medical materials for the repair of infected wounds.

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