Multifunctional hydrogels acting as wound dressing have received extensive attention in soft tissue repair; however, it is still a challenge to develop a non-antibiotic-dependent antibacterial hydrogel that has tunable adhesion and deformation to achieve on-demand removal. Herein, an asymmetric adhesive hydrogel with near-infrared (NIR)-triggered tunable adhesion, self-deformation, and bacterial eradication is designed. The hydrogel is prepared by the crosslinking polymerization of N-isopropylacrylamide and acrylic acid, during the sedimentation of conductive PPy-PDA nanoparticles based on the polymerization of pyrrole (Py) and dopamine (DA). Due to the conversion capacity from NIR light into heat for PPy-PDA NPs, the formed temperature-sensitive hydrogel exhibits tissue adhesive as well as NIR-triggered tunable adhesion and self-deformation property, which can achieve an on-demand dressing refreshing. Systematically in vitro/in vivo antibacterial experiments indicate that the hydrogel shows excellent disinfection capability to both Gram-negative and Gram-positive bacteria. The in vivo experiments in a full-layer cutaneous wound model demonstrate that the hydrogel has a good treatment effect to promote wound healing. Overall, the asymmetric hydrogel with tunable adhesion, self-deformation, conductive, and photothermal antibacterial activity may be a promising candidate to fulfill the functions of adhesion on skin tissue, easy removing on-demand, and accelerating the wound healing process.
Free radical polymerization is a mature method and can be used for preparing multifunctional hydrogels by simply changing the commercial monomers, but the harsh and timeconsuming initiation conditions restrict its injectable ability, which further limits its application in the biomedical field. Though some catalysts can be used to accelerate the polymerization, their application is restrained by the biotoxicity. Hence, finding a biocompatible catalyzer for in situ free radical polymerization of hydrogels has a great prospect in biomedical application but is still challenging. In this study, we discovered that silver ions could catalyze free radical polymerization under ambient by transforming hydrone into hydroxyl radicals in the presence of ammonium persulfate, and the in situ-formed hydrogels prepared by this way showed great histocompatibility, hemocompatibility, cytocompatibility, and immunocompatibility. Benefitting from its convenience and biocompatibility, the in situ polymerization of polyacrylamide-based hydrogels for tissue adhesion, wound dressing, and conductive materials on the skin could be realized by simply blending diverse ingredients. Furthermore, this discovery may be a step toward the in situ-polymerized hydrogels for biomedical applications.
Incomplete contact between a pre-formed hydrogel and irregular wound limits the therapeutic effect of the dressing and increases the risk of infection; while great concerns have remained regarding the potential toxicity of the residual additives of chemical crosslinking for in situ forming hydrogels. Therefore, it is desirable to develop a self-adaptive hydrogel in response to skin temperature with shape adaptability and efficient antibacterial properties to prevent microbial invasion. Herein, a dually-thermoresponsive hydrogel composed of poly(N-isopropylacrylamide) (PNIPAm) and methacrylated 𝜿-carrageenan (MA-𝜿-CA) is designed with compliance at physiological temperature to realize shape adaptability for completely covering irregular wounds. Furthermore, the hydrogel with near-infrared (NIR)-responsive polypyrrole-polydopamine nanoparticles (PPy-PDA NPs) and Zn 2+ -derived zeolitic imidazolate framework (ZIF-8) can generate localized heat and gradually release Zn 2+ to realize safe, effective synergetic photothermal-chemical bactericidal capability. In addition, the release rate of Zn 2+ can be accelerated by NIR-induced heating, and thus a more efficient sterilization can be provided to severely infected wounds. Therefore, the proposed hydrogel would serve as a promising wound dressing for the full course of wound healing, with the abilities of perfectly covering the wound and adapting to regenerating tissue, and controllable photothermal-chemical antibacterial capability to reach high bactericidal efficiency and long-term release of antibacterial agents.
Developing ultra-stretchable, universally sticky, and highly conductive nanocomposite hydrogels without doping agents and nanoparticle-aggregation is still a challenge.
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