Photoactivated antimicrobial activity of carbon dots in combination with different co-agents and mechanistic implications

Combating antibiotic-resistant bacteria has been a long-lasting challenge. This study investigated the photoactivated antibacterial function of carbon dots (CDots) in combination with antibiotics and membrane destabilizing agents as co-agents against drug resistant bacteria E. faecalis and L. monocytogenes. The results of the study demonstrated that CDots in combination with the membrane destabilizing agent poly-L-lysine as co-agent exhibited significant enhancement in the overall antibacterial activity, especially with the longer poly-L-lysine, achieving complete inactivation of cells in the samples with ~ 8 log viable cell reduction. The combination of CDots with bacterial resistant antibiotics streptomycin, erythromycin, or tetracycline, did not expectedly enhance the overall antibacterial activity of photoactive CDots to E. faecalis, in contrast, the combination with streptomycin significantly reduced the antibacterial activity of CDots. Implications of these experimental results toward the understanding of mechanistical action of photoexcited CDots were discussed. The study demonstrated that appropriately selected co-agents could effectively enhance the photoactivated antibacterial function of CDots and its potential to combat drug resistant pathogens.