LED irradiation of halogen/nitrogen-doped polymeric graphene quantum dots triggers the photodynamic inactivation of bacteria in infected wounds

Abstract

Graphene quantum dots (GQDs) are emerging disinfectants, owing to their distinctive photodynamic and antibacterial activities. Halogen-based antimicrobial materials are also known to be effective against infectious pathogens. In this work, we have developed visible light-activatable halogen/nitrogen co-doped polymeric graphene quantum dots [X/NePGQDs, (X = Cl, Br, I)] as an antibacterial agent, prepared from spermidine and hydrohalic acid by a simple one-step heating method. We demonstrate that these high positively charged X/NePGQDs are effective antibacterial agents (minimum inhibitory concentration (MIC) less than 0.5 mg mL(-1)) for the inhibition of both Gram-positive and Gram-negative bacteria. The antibacterial activities of X/NePGQDs are enhanced upon exposure to white LED light irradiation due to the generation of reactive oxygen species (ROS) which induce oxidative stress, as well as physical disruption of the bacteria. Moreover, the MIC of X/NePGQDs with LED light irradiation is 100-fold lower than in the dark, revealing their strong photo-induced inactivation of bacteria. X/NePGQDs are effective for the eradication of multidrug-resistant bacteria in infectious wounds, even with just 1-min of irradiation. With their negligible cytotoxicity, we believe that X/NePGQDs have great potential as a visible light-activated antibacterial nanomaterial for preclinical application in wound healing. (C) 2020 Elsevier Ltd. All rights reserved.