Multimodal Biofilm Inactivation Using a Photocatalytic Bismuth Perovskite-TiO2-Ru(II)polypyridyl-Based Multisite Heterojunction

Infectiousbacterial biofilms are recalcitrant to most antibioticscompared to their planktonic version, and the lack of appropriatetherapeutic strategies for mitigating them poses a serious threatto clinical treatment. A ternary heterojunction material derived froma Bi-based perovskite-TiO2 hybrid and a [Ru-(2,2 '-bpy)(2)(4,4 '-dicarboxy-2,2 '-bpy)](2+) (2,2 '-bpy,2,2 '-bipyridyl) as a photosensitizer (RuPS) is developed. Thishybrid material is found to be capable of generating reactive oxygenspecies (ROS)/reactive nitrogen species (RNS) upon solar light irradiation.The aligned band edges and effective exciton dynamics between multisiteheterojunctions are established by steady-state/time-resolved opticaland other spectroscopic studies. Proposed mechanistic pathways forthe photocatalytic generation of ROS/RNS are rationalized based ona cascade-redox processes arising from three catalytic centers. TheseROS/RNS are utilized to demonstrate a proof-of-concept in treatingtwo elusive bacterial biofilms while maintaining a high level of biocompatibility(IC50 > 1 mg/mL). The in situ generationof radical species (ROS/RNS) upon photoirradiation is establishedwith EPR spectroscopic measurements and colorimetric assays. Experimentalresults showed improved efficacy toward biofilm inactivation of theternary heterojunction material as compared to their individual/binarycounterparts under solar light irradiation. The multisite heterojunctionformation helped with better exciton delocalization for an efficientcatalytic biofilm inactivation. This was rationalized based on thefavorable exciton dissociation followed by the onset of multiple oxidationand reduction sites in the ternary heterojunction. This together withexceptional photoelectric features of lead-free halide perovskitesoutlines a proof-of-principle demonstration in biomedical optoelectronicsaddressing multimodal antibiofilm/antimicrobial modality.