In vitro antitumor activity of free and nano-encapsulated Na5[PMo10V2O40]·nH2O and its binding properties with ctDNA by using combined spectroscopic methods.

Free and nanosized starch and lipid encapsulated Na5[PMo10V2O40]·nH2O complexes (abbreviated as PMoV, SEP and LEP, respectively) have been prepared and structurally characterized by Fourier transform infrared (FT-IR) spectroscopy, inductively coupled plasma (ICP) analysis, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images. The results show that the PMoV retains its parent structure after encapsulation by starch and lipid nanoparticles. The in vitro antitumor activity of PMoV in its free and nano-encapsulated forms was investigated using the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide (MTT) assay that was carried out on two types of human cancer cells, MCF-7 (breast cancer cells) and HEK-293 (Human Embryonic Kidney). The results represent the enhancement of cell penetration and antitumor activity of PMoV due to its encapsulation in starch or lipid nanoparticles. However, this observed enhancement for the lipid relative to the starch nanocapsule can be attributed to its smaller size. In order to investigate the molecular nature of antitumor activity, the binding properties of PMoV with calf thymus DNA (ctDNA) were also comprehensively evaluated using UV-vis absorption spectroscopy, fluorescence quenching and fluorescence Scatchard plots. The results rule out the intercalating binding mode and propose the groove or outside stacking binding for PMoV. However, a biphasic binding behavior that is due to the change in the binding mode was observed by varying of [PMoV]/[ctDNA] mole ratio. The results of cell culture assay and DNA binding experiments represent that the rate of cell penetration is more important than DNA binding affinity in the antitumor activity for POM.