The influence of Zn on the deposition of HA on sol-gel derived bioactive glass

To evaluate the influence of Zn on the formation of hydroxyapatite (HA), zinc-containing glass 58S4Z was prepared by substitution of CaO with 4 wt% ZnO in 58S bioactive glass, and Zn-containing simulated body fluid (ZnSBF) was prepared as soaking fluid. During the soaking, all samples could induce the deposition of HA, but 58S4Z in SBF and 58S in ZnSBF showed lower formation rate of HA than 58S in SBF, which suggests that both the Zn in glass and the Zn2+ in soaking fluid retarded the deposition of HA. The ICP and EDS analysis results indicated that the main factor was the preferential reaction of Zn2+ with PO43-, which resulted in a decrease of the PO43- concentration in soaking fluid and the nucleation of HA. Besides the inhibitory effect of Zn2+ in the soaking fluid, Zn in 58S4Z glass caused a lower release rate of Ca2+ in the initial soaking periods because of the lower CaO content as compared with 58S, and resulted in a lower nucleation rate of HA. The results suggested that small amount of Zn in bioactive glass retarded the nucleation of HA, but with the exhaustion of Zn2+ by PO43-, it did not affect the long-term deposition of HA in SBF.