Poliossometallati in domini ibridi organici-inorganici per il disegno di nanostrutture catalitiche

The polyoxometalate (POM) complex {Ru4(µ-OH)2(µ-O)4(H2O)4[γ-SiW10O36]}10- displays interesting biomimetic activity as oxygen evolving catalysts, since it is able to (i) oxidize water molecules to dioxygen, in the presence of a suitable electron acceptor (CeIV, RuIII(bipy)3, as the Photosystem II) and (II) decompose hydrogen peroxide to a mixture of water and dioxygen (as the catalase enzymes). The preparation of nanostructured materials, containing this POM, may be of interest, on one hand, for the preparation of artificial photosynthetic devices and, on the other hand, for the design of carriers to be used for the delivery of the POM in a oxidatively stressed biological environment. For these purposes, different biogenic scaffold were used. The Tobacco Mosaic Virus (TMV) has been used as nanostructured platform, because of his 1D morphology, arising from the assembly of 3140 proteins around a RNA chain, resulting in nanorods with 300 nm length and 18 nm diameter. The non covalent assembly of POMs on TMV could be exploited to prepare nanoelectronic devices featuring aligned arrays of catalytic units. Due to the negative charge of TMV, positive layer of cations/polycations ( H+, Zn2+, amorphous cationic polymers) have been successfully used to build-up suitable layers with opposite charges, so to enhance the binding affinity of the two components. The other biogenic scaffolds used for the POM, are Dextran and Chitosan. These polysaccharides have been used to encapsulate the POM in the presence of CaCO3, as sacrificial filler. In the conditions employed, microparticles with 1-5 micron have been isolated and covered with polycharged polymers, through Layer-by-Layer strategy. The microparticles have been optimized in terms of composition (presence of fluorescent labels) and sequence (core/shell confinement) of the active molecules. Their oxygenic activity in the presence of hydrogen peroxide and the delivery potential have been demonstrated.