Towards the controlled release of metal nanoparticles from biomaterials: Physico-chemical, morphological and bioactivity features of Cu-containing sol–gel glasses

Two Cu-containing bioactive glasses were prepared and characterized in order to obtain a detailed description of chemical, morphological and bioactivity proprieties of potential Cu releasing systems. The characterization has demonstrated that by varying the synthesis procedure is possible to obtain two systems with Cu species in two different oxidation states and aggregation: (i) SGCu(ox) – oxidated Cu – (Cu oxidation state +2) homogeneously dispersed in the glass network matrix and (ii) SGCu(red) – metallic Cu – (Cu oxidation state 0) containing nano-particles (5–130 nm range) mainly present on the glass surface. The introduction of Cu maintains the bioactivity of the Cu-containing glasses almost unchanged, inducing a partial delay in the hydroxyapatite/hydroxy-carbonate apatite (HA/HCA) formation on the glass surface with respect to the reference glass (free Cu glass). During the bioactivity test, Cu is released from both Cu-containing glasses, in particular in the case of the SGCu(red) the presence of Cu nanoparticles (CuNPs) of diameter in the range 5–10 nm has been detected in solution.