Iodinated BODIPY-C₆₀ systems bearing bis-phosphonate groups for antimicrobial PDT

Organic triplet photosensitizers developed for aPDT applications have gained considerable interest in recent years. In this study, 3 new iodinated-BODIPY and BODIPY-fullerene based triplet photosensitizers bearing bis phosphonate units were prepared to determine their photophysical properties and singlet oxygen generation capabilities and determine their use in aPDT applications against the bacteria E. coli and S. aureus. The chemical structures of the BODIPYs and their fullerene-C₆₀ dyads were analyzed by mass and NMR (¹H, ³¹P and ¹³C) and then their photophysical characteristics including the UV-Vis absorption spectra, fluorescence emission profiles, fluorescence quantum yields, and lifetimes were investigated. The quantitative singlet oxygen formation of the molecules was both determined by chemical trapping using 1,3-diphenylisobenzofuran (DPBF) in DMSO and 9,10-anthracenediyl-bis(methylene)dimalonic acid (ADBA) in PBS: DMSO (95: 5; v: v). BODIPY derivative 8 and BODIPY-fullerene dyad 11 eradicate E. coli by producing the singlet oxygen (¹O₂) under red LED. The molecules exhibited potent antibacterial activity which may contribute to the management of bacterial infections.