Boron Cluster Renders Organic Radicals Water-Stable for Photothermal Anti-Infections.

Water-stable organic radicals are promising photothermal conversion candidates for photothermal therapy (PTT). However, organic radicals are usually unstable in biological environments, which greatly hinders their wide application. Here, we have developed a chaotropic effect-based and photoinduced water-stable supramolecular radical (MB 12 -2) for efficient antibacterial PTT. The supramolecular radical precursor MB 12 -1 was constructed by the chaotropic effect between closo -dodecaborate cluster (B 12 H 12 2- ) and N , N '-dimethylated dipyridinium thiazolo [5,4- d ] thiazole (MPT 2+ ). Subsequently, with triethanolamine (TEOA) serving as an electron donor, MB 12 -1 could transform to its radical form MB 12 -2 through photoinduced electron transfer (PET) under 435-nm laser irradiation. The N 2 adsorption-desorption analysis confirmed that MB 12 -2 was tightly packed through the introduction of B 12 H 12 2- , which effectively enhanced its stability via a spatial site-blocked effect. Moreover, the half-life of MB 12 -2 in water was calculated through ultraviolet-visible light (UV-vis) absorption spectra results for periods as long as 20 days. In addition, in the skin infection model, MB 12 -2, as a wound dressing, showed remarkable photothermal antibacterial activity (>97%) under 660-nm laser irradiation and promoted wound healing. This study presents a simple method for designing long-term water-stable supramolecular radicals, offering a novel avenue for noncontact treatments for bacterial infections.