When Iodine Meets Starch: On-Demand Generation of Photothermal Hydrogels for Mild-Temperature Photothermal–Chemo Disinfection

As an emerging antibacterial strategy, photothermal disinfection attracts increasing attention due to its advantages of high efficacy, wide pertinence, and non-drug resistance. However, the unavoidable shielding of observation by photothermal components and the possible damage to normal tissue caused by hyperthermia restrict its applications. Herein, we propose a composite hydrogel with the ability of on-demand generation of photothermal components and mild-temperature photothermal disinfection by elegantly tuning the binding and release of iodine and starch. The composite hydrogel is obtained by blending iodine-adsorbed pH-responsive ZIF-8 nanoparticles (NPs) with a starch-based hydrogel matrix. Through a convenient pH response, the composite hydrogel leverages the triple functions of iodine, which serves as a disinfectant and reacts with starch to generate a photothermal agent and color indicator, allowing photothermal-chemotherapy combined disinfection on demand. In vitro antibacterial experiments show that the composite hydrogel can respond to the acidification of the microenvironment caused by bacterial metabolism and produce corresponding color changes, realizing naked-eye observation. Meanwhile, under the combined treatment of heating/I₂/Zn²⁺, the composite hydrogel can completely kill Escherichia coli and Staphylococcus aureus at a mild temperature of ∼41 °C. This study represents a breakthrough in on-demand generation of photothermal hydrogels for mild-temperature photothermal disinfection.