Harnessing Multi‐Modal Exciton Migration in Hybrid Halide Perovskite for Photocatalytic Amplification of Nitric Oxide and Hydroxyl Radicals toward Bacterial Killing and Biofilm Disruption

Abstract Antimicrobial resistance is a multifaceted phenomenon and a serious threat to the prevailing global healthcare options. Photocatalytic therapy using nanotherapeutics is a promising alternative as this enables redox‐tuning of substrates inside biofilm while forming cytotoxic reactive oxygen species at hypoxic conditions. Herein, a new paradigm using the heterostructure of metal halide perovskite (PeV) nanocrystals is introduced by in situ capping with a nitric oxide (NO) releasing derivative (NTFA) and a ^•OH releasing phenothiazine ligand (BA‐PTZ) to yield NTFA@PeV@BA‐PTZ heterostructure. Material characterization, along with the mechanistic insights for the sunlight‐induced exciton formation, separation, and migration into respective molecular ligands inducing the catalytic generation of cytotoxic ^•OH/NO species are supported by in situ spectroscopic/microscopic studies. Encapsulation of NTFA@PeV@BA‐PTZ NCs with silica results NTFA@PeV@BA‐PTZ@SiO₂, ensures its physiological stability and biologically benign nature. The efficacy of heterostructure toward biofilm inactivation and bactericidal activity are established through appropriate in vitro and in vivo biocompatibility, biodistribution, and assessment of antibacterial activity. The results also confirm the minimal toxicity and effective excretion of NTFA@PeV@BA‐PTZ@SiO₂ from orally administered Balb/c mice. Together, based on manipulating the redox gradient omnipresent in bacterial/biofilm microenvironments and by catapulting the exciton‐mediated redox process, a proof‐of‐concept for an efficient multimodal photocatalytic nanotherapeutics is demonstrated.