Potentiation of Antimicrobial Photodynamic Therapy by Curcumin-loaded Graphene Quantum Dots

Increasing resistance to existing antibiotics by microbes is currently the biggest dilemma. Antimicrobial photodynamic therapy is a promising alternative for the treatment of multidrug-resistant infections. The aim of the current study was to fabricate graphene quantum dots loaded with curcumin as photosensitizer for improved antimicrobial photodynamic therapy. The study involved fabrication of blank and curcumin-loaded graphene quantum dots, their characterizations (TEM, UV-visible and fluorescence emission spectra), cytotoxicity assay, ROS assay and investigation of enhanced antimicrobial photodynamic effect against resistant microbes. The fabrication of blank and loaded graphene quantum dots was confirmed by the observation of peak shift and changes in peak intensity of blank graphene quantum dots, curcumin alone compared with curcumin-loaded graphene quantum dots in UV-visible and fluoresce emission spectra. Cytotoxicity assay showed that 100 µm concentration was not toxic to NIH/3t3 fibroblasts. In ROS assay, the curcumin-loaded formulation showed three-fold increase in ROS production. Blue-light (405 nm) irradiance of 30 J cm^-2 and photosensitizer concentration of 100 µm showed ~3.5 log₁₀ enhanced CUF reduction against Pseudomonas aeruginosa, MRSA, Escherichia coli and Candida albicans. In conclusion, curcumin-loaded graphene quantum dots shoed enhanced antimicrobial photodynamic effects and can be used as an alternative effective treatment for resistant infections.