NIR-emitting carbon dots for discriminative imaging and photo-inactivation of pathogenic bacteria

The rapid identification of pathogens and their viability are important for the effective diagnosis and treatment of infectious diseases. In this study, real near-infrared (NIR)-emitting carbon dots (Cy7-CDs, λmax = 710 nm) were synthesized using a solvothermal reaction method, in which the optical properties of cyanine dye were partially retained, and the water solubility and fluorescence quantum yield were greatly improved. The abundant functional groups on the surface of Cy7-CDs facilitated their interactions with biomolecules within the bacteria. Cy7-CDs quickly integrated into cell wall of G+ bacteria with obvious fluorescence or outer membrane of G- bacteria with no fluorescence. As a result, Cy7-CDs can not only be used to identify bacterial species (G+ or G- bacteria), but can also be used to quickly and efficiently monitor bacterial viability using fluorescence imaging. Furthermore, within 15 min, 97.7% Escherichia coli (G-) and 95.8% Methicillin-resistant Staphylococcus aureus (G+) were killed rapidly by Cy7-CDs, due to its powerful ability to produce singlet oxygen (1O2) under single light irradiation (650 nm). Therefore, the Cy7-CDs strategy has the potential to be used for diagnosis and treatment of bacterial disease integration.