Polyethyleneimine anchored copper(II) complexes: Synthesis, characterization, in vitro DNA binding studies and cytotoxicity studies

• Polymer–copper(II) complexes with different ‘x’ containing L-tyrosine as co-ligand synthesized.
• DNA binding interaction was done for the complexes.
• These complexes bind to DNA via electrostatic modes.

The water soluble polyethyleneimine–copper(II) complexes, [Cu(phen)(L-tyr)BPEI]ClO4 (where phen = 1,10-phenanthroline, L-tyr = L-tyrosine and BPEI = branched polyethyleneimine) with various degree of copper(II) complex units in the polymer chain were synthesized and characterized by elemental analysis and electronic, FT-IR, EPR spectroscopic techniques. The binding of these complexes with CT-DNA was studied using UV–visible absorption titration, thermal denaturation, emission, circular dichroism spectroscopy and cyclic voltammetric methods. The changes observed in the physicochemcial properties indicated that the binding between the polymer–copper complexes and DNA was mostly through electrostatic mode of binding. Among these complexes, the polymer–copper(II) complex with the highest degrees of copper(II) complex units (higher degrees of coordination) showed higher binding constant than those with lower copper(II) complex units (lower degrees of coordination) complexes. The complex with the highest number of metal centre bound strongly due to the cooperative binding effect. Therefore, anticancer study was carried out using this complex. The cytotoxic activity for this complex on MCF-7 breast cancer cell line was determined adopting MTT assay, acridine orange/ethidium bromide (AO/EB) staining and comet assay techniques, which revealed that the cells were committed to specific mode of cell death either apoptosis or necrosis.

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