Multifunctional Oxidized Dextran as a Matrix for Stabilization of Octahedral Molybdenum and Tungsten Iodide Clusters in Aqueous Media.

Due to their high abundance, polymeric character, and chemical tunability, polysaccharides are perfect candidates for the stabilization of photoactive nanoscale objects, which are of great interest in modern science but can be unstable in aqueous media. In this work, we have demonstrated the relevance of oxidized dextran polysaccharide, obtained via a simple reaction with H2O2, towards the stabilization of photoactive octahedral molybdenum and tungsten iodide cluster complexes [M6I8}(DMSO)6](NO3)4 in aqueous and culture media. The cluster-containing materials were obtained by co-precipitation of the starting reagents in DMSO solution. According to the data obtained, the amount and ratio of functional carbonyl and carboxylic groups as well as the molecular weight of oxidized dextran strongly affect the extent of stabilization, i.e., high loading of aldehyde groups and high molecular weight increase the stability, while acidic groups have some negative impact on the stability. The most stable material based on the tungsten cluster complex exhibited low dark and moderate photoinduced cytotoxicity, which together with high cellular uptake makes these polymers promising for the fields of bioimaging and PDT.

The role of hydrolysis in biological effects of molybdenum cluster with DMSO ligands.

Biological applications of octahedral molybdenum cluster complexes are complicated by their hydrolytic instability, since hydrolysis leads to irreversible changes in the structure and properties of these compounds. On the other hand, if such changes are thoroughly investigated and understood, the hydrolysis process can become an important tool for regulating specific biological effects of the clusters. In this work, we demonstrate how the luminescence and biological properties (cellular uptake, cytotoxicity in the dark and photodynamic effect) of highly unstable cluster complex [{Mo6I8}(DMSO)6](NO3)4 change along with the degree of hydrolysis. Particularly, cluster solution preliminarily aged in water demonstrated lower dark and higher photoinduced cytotoxicity and higher cellular uptake in comparison with fresh solution.