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Targeted photodynamic therapy in visible light by BODIPY-appended copper(II) complexes of vitamin B6 Schiff base

Abstract

Copper(II) complexes [Cu(L1/L2/L3)(A)] (1-3), where H2A.HCl is a vitamin B6 Schiff base, viz. 3-hydroxy-5-(hydroxymethyl)-4-(((2-hydroxyphenyl)imino)methyl)-2-methylpyridin-1-ium chloride, L1 and L2 are 2-(2-pyridyl)benzimidazole based borondipyrromethene (BODIPY) ligands and L3 is 2-(2-pyridyl)benzimidazole, were prepared, characterized and their visible light-induced anti-cancer activity was studied. Complex 3, characterized by X-ray crystallography, exhibits a distorted square-pyramidal geometry for copper (τ = 0.33). Complexes 1 and 2 showed absorption bands at 500 and 535 nm, respectively, in 20% DMSO/Dulbecco’s phosphate buffered saline (DPBS) medium. Complex 1 exhibited emission at ~510 nm (λexc = 480 nm) (F = 0.1) in 20% DMSO/DPBS, while the non-emissive diiodo-BODIPY complex 2 is an efficient photosensitizer. The green fluorescent complex 1 enabled us to study its cellular uptake and localization. It showed selective uptake in proliferating cancer cells and significant mitochondrial localization (Pearson’s coefficient = 0.7). Complex 2 showed excellent photocytotoxicity (400-700 nm, 10 J cm-2) in HeLa, MCF-7 and HepG2 cancer cells with IC50 values within 0.4-0.6 μM, while remaining less toxic in the dark and in non-cancerous HPL1D cells (Photocytotoxic Index ~50). Complex 2, remarkable in targeting cancer cells over non-cancerous cells, showed photoinduced generation of singlet oxygen, causing apoptotic cell death, thus satisfying the major requirements of targeted photodynamic therapy.

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Publication details

The article was received on 23 Oct 2017, accepted on 03 Dec 2017 and first published on 04 Dec 2017


Article type: Paper
DOI: 10.1039/C7DT03976J
Citation: Dalton Trans., 2017, Accepted Manuscript
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    Targeted photodynamic therapy in visible light by BODIPY-appended copper(II) complexes of vitamin B6 Schiff base

    A. R. Chakravarty, N. Mukherjee, S. Podder, K. Mitra, S. Majumdar and D. Nandi, Dalton Trans., 2017, Accepted Manuscript , DOI: 10.1039/C7DT03976J

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