Multifunctional photothermal hydrogels: Design principles, various functions, and promising biological applications

Photothermal hydrogels with excellent photo responsive and thermal conversion ability had attract a great deal of attention from researchers to explore their biological applications. This review aimed to provide a comprehensive overview of photothermal hydrogels, focusing on their design principles, various functions, and biological applications. Firstly, several classifications of photothermal hydrogels were given according to different photothermal agents (metal, metal sulfide/oxide, Mxene, carbon-based, dyes, black phosphorus, and polymer) utilized in hydrogel construction. The photothermal conversion mechanism and hydrogel fabrication were also discussed in detail. Then, the relationship between their photothermal conversion property and functions, together with some indispensable property such as biocompatibility, adhesion, mechanical properties, and self-healing properties was fully introduced. Furthermore, the applications of photothermal hydrogels in the biomedical (i.e., wound healing, antibacterial treatments, controlled drug release, bone repair, and tumor treatment) was summarized. Finally, the future opportunities and challenges of photothermal hydrogels were proposed. We believe that this review could provide a new horizon for further preparation of photothermal hydrogels, and could promote their applications in wider fields.