Bio-adhesive cationic carbon dots enable photodynamic reactive oxygen species generation for cariogenic biofilm suppression.

Bacterial infections remain a major threat to human health and are often difficult to eradicate once bacteria establish structured communities. In the oral cavity, this challenge is exemplified by dental caries, a highly prevalent chronic infectious disease driven by cariogenic biofilms dominated by Streptococcus mutans (S. mutans). To develop an efficient antimicrobial strategy for cariogenic biofilms, we synthesized D-lysine-derived cationic carbon dots (Lys-CDs) through a facile hydrothermal method and investigated their photodynamic antibacterial activity. The resulting Lys-CDs are water-dispersible and exhibit favorable cytocompatibility under the tested conditions. Their positive surface charge enhanced association with biofilm-associated bacterial communities. Under blue-light irradiation (450 nm), Lys-CDs generate abundant reactive oxygen species (ROS), inducing membrane destabilization and causing substantial structural alterations of mature biofilms. In mature S. mutans biofilms, Lys-CDs + light achieved over 99% bacterial killing, reduced biofilm thickness by about 70%, and increased ROS production. Mechanistic assays and transcriptomic profiling collectively suggested a ROS-driven multi-hit mode involving membrane permeabilization, oxidative stress amplification, and broad suppression of pathways associated with energy metabolism, envelope biogenesis, and stress regulation. In a rat caries model, topical Lys-CDs + light effectively inhibited caries progression. Collectively, this work provides experimental evidence supporting that biophilic cationic Lys-CDs can acts as a simple photodynamic strategy for cariogenic biofilms control and attenuate caries development under the investigated experimental conditions.