Design and Synthesis of Metalloporphyrin Nanoconjugates for Dual Light-Responsive Antimicrobial Photodynamic Therapy

Antimicrobial photodynamic therapy (APDT) utilizes photosensitizers
(PSs) that eradicate a broad spectrum of bacteria in the presence
of light and molecular oxygen. On the other hand, some light sources
such as ultraviolet (UVB and UVC) have poor penetration and high cytotoxicity,
leading to undesired PDT of the PSs. Herein, we have synthesized conjugatable
mesosubstituted porphyrins and extensively characterized them. Time-dependent
density functional theory (TD-DFT) calculations revealed that metalloporphyrin EP (5) is a suitable candidate for further applications. Subsequently,
the metalloporphyrin was conjugated with lignin-based zinc oxide nanocomposites
(ZnOAL and ZnOKL) to develop hydrophilic nanoconjugates (ZnOAL@EP
and ZnOKL@EP). Upon dual light (UV + green light) exposure, nanoconjugates
showed enhanced singlet oxygen generation ability and also demonstrated
pH responsiveness. These nanoconjugates displayed significantly improved
APDT efficiency (4–7 fold increase) to treat bacterial infection
under dual light irradiation.