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 31P 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.