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BODIPY‐Appended 2‐(2‐Pyridyl)benzimidazole Platinum(II) Catecholates for Mitochondria‐Targeted Photocytotoxicity
Author(s) -
Mitra Koushambi,
Gautam Srishti,
Kondaiah Paturu,
Chakravarty Akhil R.
Publication year - 2016
Publication title -
chemmedchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.817
H-Index - 100
eISSN - 1860-7187
pISSN - 1860-7179
DOI - 10.1002/cmdc.201600320
Subject(s) - singlet oxygen , benzimidazole , chemistry , bodipy , photochemistry , fluorescence , mitochondrion , photodynamic therapy , reactive oxygen species , biophysics , oxygen , biochemistry , biology , organic chemistry , physics , quantum mechanics
Abstract Platinum(II) complexes of the type [Pt(L)(cat)] ( 1 and 2 ), in which H 2 cat is catechol and L represents two 2‐(2‐pyridyl)benzimidazole ligands with 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐ s ‐indacene (BODIPY) pendants, were synthesized to achieve mitochondria‐targeted photocytotoxicity. The complexes showed strong absorptions in the range λ =510–540 nm. Complex 1 exhibited intense emission at λ =525 nm in 1 % DMSO/water solution (fluorescence quantum yield of 0.06). Nanosecond transient absorption spectral features indicated an enhanced population of the triplet excited state in di‐iodinated complex 2 . The generation of singlet oxygen by complex 2 upon exposure to visible light, as evidenced from experiments with 1,3‐diphenylisobenzofuran, is suitable for photodynamic therapy because of the remarkable photosensitizing ability. The complexes resulted in excellent photocytotoxicity in HaCaT cells (half maximal inhibitory concentration IC 50 ≈3 μ m , λ =400–700 nm, light dose=10 J cm −2 ), but they remained non‐toxic in the dark (IC 50 >100 μ m ). Confocal microscopy images of 1 and Pt estimation from isolated mitochondria showed colocalization of the complexes in the mitochondria. Complex 2 displayed generation of reactive oxygen species induced by visible light, disruption of the mitochondrial membrane potential, and apoptosis.