In vitro photoinactivation of S. aureus and E. coli using 5,10,15,20-tetrakis[4-(benzyloxy) phenyl] porphyrin and its metal derivatives conjugated to pristine graphene quantum dots

Abstract

Antimicrobial resistance is a matter of concern to all biological systems. This work investigates the antimicrobial activity of porphyrins conjugated to pristine graphene quantum dots (pGQDs) through non-covalent linking. A novel In 5,10,15,20-tetrakis[4-(benzyloxy) phenyl] porphyrin (InTBnOPP) was synthesized and fully characterized. The photophysicochemical parameters of H2TBnOPP, ZnTBnOPP, InTBnOPP, and their conjugates were investigated. It was found that pGQDs improved the singlet oxygen quantum yield upon conjugation with the porphyrins. pGQDs-InTBnOPP had a higher singlet oxygen quantum yield of 0.80 when compared to all other conjugates. Porphyrins are well-known photosensitizers for photodynamic antimicrobial chemotherapy (PACT); this was also confirmed by pGQDs-ZnTBnOPP and pGQDs-InTBnOPP which completely inhibited both S. aureus and E. coli with log reduction values of 9.42 and 8.59 with an irradiated time of 5 and or 10 min, respectively. The porphyrins alone had significant antibacterial activities. In general, the obtained results demonstrate a good response of these nanoconjugates against Gram (+) and Gram (-) bacteria.