Graphene Quantum Dot/Silver Nanoparticle Hybrids with Oxidase Activities for Antibacterial Application

We report the first attempt of using graphene quantum dot Ag nanoparticles (GQD/AgNP hybrids) as oxidase mimics and antibacterial agents. Unlike previous silver- and graphene-based materials, the GQD/AgNP hybrids exhibit a high oxidase-like catalytic activity and possess favorable stability in neutral medium within the range from room temperature to 60 degrees C. In accordance with their prominent enzyme activities, the GQD/AgNP hybrids show excellent antibacterial properties against Gram-negative and Grampositive bacteria as well as drug resistant bacteria, with an ultralow minimal inhibitory concentration (2-4 mu g/mL) against 1 X 10(7) to 1 X 10(8) mu g/mL Escherichia coli and Staphylococcus aureus. In the presence of the GQD/AgNP hybrids, the fluorescence behavior after the introduction of 2', 7'-dichlorofluorescin diacetate demonstrated a possible role of reactive oxidative species in the GQD/AgNP hybrid-mediated antibacterial therapeutic effect. Furthermore, TEM and SEM imaging identified concomitant disruption of the bacterial cell membrane and loss of barrier function during the sterilization process. Therefore, the GQD/AgNP hybrids exhibit vast potentials for serving as highly effective, broad-spectrum antibacterial agent for sterilization use without the need of additional stimulation by laser irradiation (photosensitization) or the provision of H2O2, facilitating their relative ease of use and cost-effectiveness.