Modulating the Anticancer Activity of Square-Planar Platinum (II) Complex by Its Chelated Diphosphine

This work reports the preparations and anticancer activities of a set of platinum (II) complexes. Two types of bidentate ligands, azadiphosphine (PNP) and diphosphine (PP), were applied to afford different kinds of platinum centers, the homoleptic complexes, [Pt (PNP)2]2+ (1 and 2) and [Pt (PP)2]2+ (4), and the hybrid complex, [Pt (PNP)(PP)]2+ (3). All these complexes are characterized by various analytical techniques, and their structures were validated using single-crystal X-ray diffraction analysis. Notably, the stability of the complexes 1-4 is differentiated both in phosphate-buffered saline (PBS) and in the culture media (RPMI-1640), relative to the type of coordinated diphosphine ligands, specifically, the more PNP ligands, the less stability. The bite angles of P-Pt-P bonds in 1-4 would be reliant on their stability, so that complexes 1 and 2 with small bite angles tend to be labile. A mechanistic understanding on the decomposition of 2 is proposed with the aid of mass analysis. As a result, their anticancer activities should be also associated with their stability so that the chelated ligands, with more PNP ligands, lead to more cytotoxicity. Mechanistically, the poisonous platinum (II) derivatives of complex 2 should interact with the nucleus DNA, whereas the intact complex 4 is not traceable, confirming from a gamma-H2AX-related immunofluorescence staining kit. Additionally, complex 2 exhibits severe toxicity toward several cancer cells as well as a normal cell. Furthermore, complex 2 has inhibited the formation and viability of three-dimensional T24 mammospheres, reminding it of a promising candidate for anticancer treatments. Overall, the present work provides a way for the systematic investigation to elucidate how a bidentate diphosphine ligand modulates the stability and the anticancer activities of the corresponding square-planner platinum (II) complex. Anticancer activities of platinum (II) complexes are modulated by the chelated phosphine ligands, with more azadiphosphines resulting in more cytotoxicity.image