Synthesis of Metallo-Chromone Porphyrin Nano-Starch Sensitizers as Photodynamic Therapeutics for the Eradication of Enterococci Dental Pathogens

Mechano-triggered eradication of dentinal tubule biofilm via in situ generation of nanoscale sonosensitizer by the tailored irrigation formulation

The efficient elimination of bacteria within the dentinal tubules has been hindered by the poor deposition and short residence of disinfecting agents. Meanwhile, the current irrigant (e.g., NaClO, 5.25 %) shows severe adverse effects on the surrounding soft tissues because of its inherent high irritancy. To address this issue, this work reports an in situ generated sonosensitizer to handle the biofilm in dentinal tubules with minimal adverse effects. The production of nanoscale sonosensitizer involves the concurrent delivery of H2O2 (0.01 %), ferrocene derivative (Fc), and indocyanine green (ICG). With ultrasound treatment, the reaction between H2O2 and Fc liberated Fe3+ that was further complexed with ICG to generate the nanoscale sonosensitizer in situ, followed by singlet oxygen production for potent disinfecting action. Because the above cascade reactions occur within the confined dentinal tubules, the generated ICG-Fe3+ nanosensitizer would show prolonged retention therein. The anti-bacterial potency of nanosensitizer was demonstrated in petrodish and ex vivo biofilm models. Meanwhile, the transmission electron microscope imaging of biofilm and cytotoxicity assay in L929 fibroblast cells proved the superiority of nanosensitizer against NaClO regarding adverse effects. The current work opens new avenues of biofilm elimination in dentinal tubules, showing a high translation potential.

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.