Highly effective inhibition of Pseudomonas aeruginosa biofilm formation by sublethal methylene blue-photodynamic inactivation augmented by graphene oxide quantum dot

The pathogenesis of chronic Pseudomonas aeruginosa infections is mainly due to its capacity to form biofilms. Antimicrobial photodynamic inactivation (APDI) is a promising novel strategy for targeting biofilm-related infections. Nanoplatform-based photosensitizer systems can improve the efficiency of APDI. The objective of this study was to evaluate whether graphene oxide quantum dots (GOQDs) could enhance the efficiency of sublethal methylene blue (MB)-induced PDI in preventing the formation of P. aeruginosa biofilm.At first, methylene blue (MB) was immobilized on to the negatively-charged GOQDs. The planktonic cell growth of P. aeruginosa was exposed to lethal and sublethal PDI by using MB alone and MB-GOQD conjugate (at the same MB concentration) combined with a red laser (۶۵۰ nm). Then, biofilm formation ability of P. aeruginosa strain exposed to sublethal PDI (sPDI) was evaluated using crystal violet (CV) assay and scanning electron microscopy (SEM).Sublethal MB/GOQD-mediated PDI (at the final concentration of ۲۵ µM MB) significantly reduced biofilm formation up to >۹۵% while sublethal MB-mediated PDI (at the final concentration of ۲۵ µM MB) slightly reduced biofilm formation. Electron scanning microscopy images confirmed the potent ability of GOQDs to augment inhibition of P. aeruginosa biofilm formation by sublethal MB-mediated PDI.In summary, the results of this study demonstrated that sublethal APDI using hybrid GOQD-MB nano-photosensitizer is a promising approach to combat P. aeruginosa infections.

Keywords:

antibiotic resistance , nanomedicine , photodynamic therapy