Structural and in vitro study of cerium, gallium and zinc containing sol-gel bioactive glasses

Sol-gel derived glasses comprised of bioactive materials exhibit a high in vitro response, i.e., the capability to form a hydroxycarbonate apatite (HCA) layer that is claimed to be responsible for the bonding between the glass and the host bone. In this paper, the sol-gel bioactive glass 80% SiO 2-15% CaO-5% P 2O 5 (B-BG) was modified by adding the biologically relevant elements cerium, gallium and zinc. Structural characterization of the glasses was performed by 29Si MAS NMR and their in vitro response was investigated by soaking them in simulated body fluid (SBF) for up to 15 days at 37 °C. The HCA formation was monitored by XRD, FTIR, SEM-EDS and ICP measurements. Ce 3+, Ga 3+, and Zn 2+ can be classified as "intermediate ions". However, 29Si NMR revealed that Ce 3+ ions have a more marked role of "modifier ions" than Ga 3+ ions, while the behavior of Zn 2+ lies between those of Ce 3+ and Ga 3+. On the other hand, in spite of the decrease in the in vitro response of B-BG by substitution, the glasses show HCA formation after 15 days of soaking. In addition, an increase in substitution of zinc accelerated the formation of HCA along with the formation of the mixed phase CaZn 2(PO 4) 2·2H 2O (scholzite) acting as nucleating agent for HCA. Moreover, the therapeutic effect of optimum Zn released as an ionic dissolution product from Zn-glasses could be beneficial to stimulate osteogenesis