Photo-induced anticancer activity of polypyridyl platinum(II) complexes

Polypyridyl platinum(II) complexes (1-5), viz., [Pt(pyphen)Cl]Cl (1), [Pt(pyphen)(C≡CFc)]Cl (2), [Pt(pydppz)Cl]Cl (3), [Pt(pydppz)(C≡CPh)]Cl (4) and [Pt(pydppz)(C≡CFc)]Cl (5), where pyphen is 6-(2-pyridyl)-1,10-phenanthroline, pydppz is 6-(2-pyridyl)-dipyrido-[3,2-a:2',3'-c]-phenazine, FcC≡CH is ferrocenyl acetylene and PhC≡CH is phenyl acetylene, were synthesized, characterized and their DNA binding and photocytotoxic properties studied. The complexes showed strong binding affinity to calf-thymus DNA giving K(app) of ∼10(6)-10(7) M(-1). Complexes 4 and 5 showed dual mode of binding to ct-DNA. The pydppz complexes 3-5 having a photoactive phenazine moiety showed photocytotoxicity in HeLa and MCF-7 cells in UV-A light of 365 nm with apoptotic cell death as evidenced from the acridine orange/ethidium bromide dual staining and the FACS data.