Potent drug candidature of an ONS donor tethered copper (II) complex: Anticancer activity, cytotoxicity and spectroscopically approached BSA binding studies.

In our continued efforts to develop metal based therapeutic agents, we have synthesized a novel copper(II) complex, [{Cu(hpdbal-sbdt)}2] (2) tethered with a biocompatible ONS2- donor backbone [H2hpdbal-sbdt] (1) [H2hpdbal-sbdt is a tridentate ligand derived from S-benzyldithiocarbazate (Hsbdt) and 2-hydroxy-5-(phenyldiazenyl)benzaldehyde (Hhpdbal)]. The metal complex (2) was characterized using attenuated total reflection-infrared (ATR-IR) spectroscopy, electron paramagnetic resonance (EPR) spectroscopy, thermogravimetry and differential scanning calorimetric (TG-DSC) analysis, field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS) and elemental (CHNS) analysis. The antineoplastic ability of copper complex was evaluated in vitro against human cervical cancer (HeLa) cells. MTT assay results showed that the copper complex exhibited significant growth inhibition of HeLa cells with an IC50 value of 4.46 μM and this value was compared with reported standards. Cytotoxicity of the copper complex towards human embryonic kidney cells (HEK-293) was also evaluated. The potentially active copper complex was studied for its solution state stability at a pH range of 3-9. Following this, the interactive behaviour of the bioactive copper complex with a drug transporter protein (BSA) was deciphered through multi-spectrosopic investigations like steady-state fluorescence, three-dimensional fluorescence, deconvoluted-IR and UV-Visible techniques.