Exceptional synergistic photodynamic antimicrobial chemotherapy of graphene oxide decorated with nicotinamide zinc phthalocyanine potentiated by potassium iodide

In this work, we synthesized nanoconjugates from nicotinamide substituted zinc phthalocyanine (NAM-ZnPc) by loading it onto graphene oxide to obtain NAM-ZnPc-GO. The efficiency of the nanoconjugate was screened for photodynamic effect against different bacterial species including both Gram-positive and Gram-negative strains ( S. aureus and E. coli ). Our finding reveals that the NAM-ZnPc-GO nanoconjugate exceptionally photo-inactivated S. aureus with 3-log reduction compared to NAM-ZnPc alone under 5 min red light irradiation with a light dose of 22.5 J/cm 2 . However, the nanoconjugate produced no significant photo-inactivation effect against E. coli strains under the same experimental conditions. The dark toxicity indicated no cytotoxic effect against both bacterial strains. Further, to find an efficient photodynamic effect, we combined 50 mM KI with NAM-ZnPc-GO and achieved substantial photoinactivation effect with a 5.5 log reduction in S. aureus under the same light dose. Interestingly, when E. coli was treated with the same nanoconjugate in combination with both KI, a significant photodynamic effect with 5.5 log reduction was noted from red light. Current study demonstrates that the photodynamic efficacy of NAM-ZnPc is exceptionally enhanced by conjugating with GO and potentiated by KI. • Graphene oxide decorated with nicotinamide zinc phthalocyanine was successfully synthesized. • The synthesized samples were characterized by advanced analytical techniques. • Photodynamic antimicrobial chemotherapy applications were observed against different bacterial species. • Photodynamic efficacy of NAM-ZnPc was exceptionally enhanced by conjugating GO potentiated by KI.