Graphene quantum dots with covalently bonded gold nanoparticles winning the battle against methicillin-resistant Staphylococcus aureus under blue light

Over the last decades, bacterial resistance has become one of the emerging health threats. Particularly dangerous are bacterial strains resistant to various antibacterial drugs. Herein, we modified graphene quantum dots (GQDs) to produce efficient photo-induced antibacterial agents. GQDs were modified with (a) ethylene-diamine (EDA), (b) with EDA and gold nanoparticles (AuNPs), and (c) 3-amino-1,2,4-triazole (TA) using carbodiimide coupling. Photo-induced antibacterial activity of modified GQDs was tested against 8 bacterial strains. Treatment with modified GQDs and blue light (wavelength of 470 nm) resulted in remarkable antibacterial activity with minimal inhibitory concentrations (MIC) of 7.81 µg mL⁻¹ for K. pneumoniae and S. aureus and 3.9 µg mL⁻¹ against MRSA and E. faecalis. Planar organization of GQDs functionalized with AuNPs allowed direct access of molecular oxygen to AuNPs leading to more efficient ¹O₂ production as well as the ¹O₂ production from excited GQDs. Thus, GQDs functionalized with AuNPs showed outstanding efficiency in the battle against several bacterial strains, particularly those that lead to nosocomial infections.