Easy Tailorable Alginate Film Gaining Super‐Efficient Photothermal Conversion From Closed‐System Design for Antibacterial and Wound Healing Applications

Photothermal therapy plays an important role in biomedical applications. Photoswitches‐based solar thermal materials could achieve super‐high photothermal conversion efficiency, while it remains a great challenge to apply such materials in biomedical treatments. Herein, a photothermal conversion film with good mechanical strength is designed through electrostatically complexing Ca 2+ ‐cross‐linked alginate with azobenzene‐containing ammonium surfactant. The non‐covalent framework provides sufficient free volume for the trans–cis isomerization of azobenzene in film state, and thereby this film gains merits of easy energy charging, energy density up to 481.0 J/g, and controlled heat release by forming a closed system with efficient photothermal conversion. The film could on‐demand rise the environmental temperature at a range from room temperature to 75°C by regulating the film layers. This film exhibits characteristics of light weight, tailorability and good biocompatibility that are suitable for wound healing treatment. In animal studies, attractive wound healing promoting effect is achieved from the photothermal therapy with this film as dressing biomaterial, which is attributed to the created “hot spring” condition for reducing inflammation and enhancing tissue remodeling. This study realizes the biomedical application of molecular solar thermal materials by combining the photoswitches‐based closed‐system and biomacromolecules‐based film together in a non‐covalent designing strategy.