Design, synthesis, and biological evaluation of a new palladium(II) complex: beta-lactoglobulin and K562 as targets

A water-soluble Pd(II) complex (2,2'-bipyridinglycinato Pd(II) nitrate) has been synthesized and characterized. The effect of synthesized complex on the carrier model protein structure and cell proliferation was investigated. Whey carrier protein beta-lactoglobulin-B (BLG-B) and chronic myelogenous leukemia cell line K562 were the targets. Fluorescence and CD instruments were used to assess effect of the complex on the protein structure at different temperatures. Growth inhibitory and apoptotic effect of the Pd(II) complex toward the cancer cells was measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and flow cytometry. This complex exhibited potent cytotoxic properties against chronic myelogenous leukemia cell line K562. The cells showed different sensitivity to complex. Cytotoxic studies shown that Pd(II) complex induced apoptosis of K562 cells in a concentration and time dependent manner. Then, it might be concluded that Pd(II) complex is a promising antiproliferative agent and should execute its biological effects by inducing apoptosis. Results of fluorescence studies revealed that Pd(II) complex can quench the intrinsic fluorescence emission of the protein at different temperatures. The far- and near-UV CD studies displayed that the Pd(II) complex induces changes in the secondary and tertiary structures of BLG-B at different temperatures. The biological significance of this work is evident since BLG serves as a carrier molecule for several antitumor compounds. Therefore, the interaction of the Pd(II) complex (with antitumor activity) can provide useful information to better design metal anticancer complexes with fewer side effects.