Photoluminescence and photothermal conversion in boric acid derived carbon dots for targeted microbial theranostics

Theranostic carbon dots (CDs) have attracted widespread attention recently due to their tunable optical properties and diverse bioactivities. Beyond fluorescent imaging application, the photothermal property endows CDs with the potential for microbial inactivation. However, realization of the effective conversion between fluorescence and heat in one CD system has rarely been reported. Herein, we provide a simple strategy for targeted microbial theranostics based on 4-carboxyphenylboronic acid-derived CDs (PCBA-CDs) which possess concentration-dependent photoluminescence/photothermal features. At lower concentrations, PCBA-CDs show bright and stable fluorescent signals ranging from blue to green. The fluorescence intensity gradually decreases with increasing concentration, while on the contrary, the photothermal effect of PCBA-CDs ascends progressively due to the rearrangement of electronic transitions in aggregated CDs. PCBA-CDs also demonstrate high affinity to the polysaccharide structures on the surface of microbe which allows rapid microbial fluorescence imaging as well as specific photothermal ablation of pathogens in skin wounds using PCBA-CDs at lower and higher concentrations, respectively. This study supplies a facile nanotheranostic strategy for just-in-time microbial management using bioactive CDs.