Non-phase change arylazopyrazole-containing alginate dressings with controlled heat release providing "hot spring" effect for wound healing.

Mild heat condition could promote tissue repair by enhancing angiogenesis and accelerating regeneration. Photon energy is a bio-friendly natural energy capable of creating mild heat, while, it remains a challenge to fabricate the photothermal biomaterial with merits of high energy storage density, easy-controlled heat release and stable physical state. Here, a type of alginate complexes is designed by electrostatically complexing alginate and arylazopyrazole-containing surfactants, which could gain good photothermal effect in solid state. Taking advantage of arylazopyrazole isomerization, the ionic complexes address gravimetric energy density as high as 264.0 J/g upon UV-charging, and the stored photon energy could be released out as heat for increasing environmental temperature 3-8 °C with 3.0 mg of sample through a controlled Vis-discharging way. The high photothermal efficiency and consistent physical state make such ionic alginate complexes good biomedical dressing materials for wound healing treatment. In vitro experiments demonstrate that the ionic alginate complexes can effectively enhance cell proliferation and migration by providing mild heat stimulation, and in vivo wound healing studies confirm their ability to accelerate tissue regeneration. This study would widen the application scenarios of photoswitches-based solar thermal fuels, especially in biomedical area.