BODIPY appended copper(ii) complexes of curcumin showing mitochondria targeted remarkable photocytotoxicity in visible light

Abstract

Copper(II) complexes of BODIPY (borondipyrromethene) derivatives (L¹, L²) and curcumin (Hcur), viz. [Cu(L¹)(cur)]Cl (1) and [Cu(L²)(cur)]Cl (2), where L¹ and L² are the non-iodinated and diiodinated BODIPY appended dipicolylamine ligands, are prepared and characterized and their photocytotoxic activity in visible light studied. Binding to copper(II) has rendered stability to curcumin from its hydrolytic degradation in buffer medium. The complexes show mitochondrial localization in HeLa cells emphasizing the findings that both 1 and 2 are mitochondria-targeting complexes and induce cancer cell death. Complex 1 with a fluorophoric BODIPY moiety in L¹ gave IC₅₀ values of 7.9(±0.3) μM in visible light (400–700 nm) and 29.1(±0.5) μM in the dark. Complex 2 having a diiodo BODIPY moiety in L² as a photosensitizer gave IC₅₀ values of 3.8(±0.2) μM in visible light and 32.1(±0.4) μM in the dark. The PDT effect of 2 is comparable to that of Photofrin®, an FDA approved PDTdrug. Cell death follows an apoptotic pathway with the formation of reactive oxygen species (ROS).