Bactericidal laser ablation of carbon dots: An in vitro study on wild-type and antibiotic-resistant Staphylococcus aureus.

Suspensions of Staphylococcus aureus (S. aureus) and methicillin-resistant S. aureus (MRSA) were irradiated with a 808-nm diode laser in the presence of different concentrations of carbon dots (C-dots). The effects of laser irradiation and C-dots on the bactericidal activity were separately investigated. The results indicated that without laser irradiation, C-dots caused to a significant cease in the colony formation of both wild and methicillin-resistance types of S. aureus in a concentration-dependent manner. On the other hand, the bactericidal effect of C-dots was accelerated upon laser irradiation. Mechanistic studies revealed that formation of reactive oxygen species and protein leakage, which occurred in the presence of C-dots, were greatly accelerated by laser irradiation. Moreover, field emission scanning electron microscopy (FESEM) images showed morphological changes in the bacterial surfaces in the presence of C-dots upon laser irradiations, while almost no changes in the bacteria morphology were observed in the presence of C-dots alone. Outer membrane damage was a synergism result of laser irradiation and presence of C-dots.