Nanocomposites of Polyoxometalates and Chitosan-Based Polymers as Tuneable Anticancer Agents

Representative polyoxometalates with proven bio-active properties, namely {Sb9W21}, {P2W18} and {Mo7O24}, were encapsulated into chitosan and carboxymethyl chitosan (CMC) to afford nanoscale composites. The pristine POMs were characterized with a wide range of analytical techniques, including powder X-ray diffraction as well as FT-IR and P-31 NMR spectroscopy. Size and morphology of their nanocomposites were determined within the 100-200 nm size range by dynamic light scattering (DLS) methods in combination with scanning and transmission electron microscopy. Their stability was monitored by UV/Vis and DLS measurements over several days. The cytotoxicity of pristine and encapsulated POMs was investigated on HeLa and MRC-5 cell lines, representing cancer and normal cell lines, respectively. Our results suggest that CMC encapsulation enhances the specificity towards cancer cells, especially in treatment approaches where a lower drug dose would be required. The anticancer activity of POMs emerged as a dynamic property that depends on manifold parameters, such as the POM structure, the polymeric drug carrier type, and the investigated cell line.