Preparation and Characterization of Mono- and Biphasic Ca(1−x)Ag(x)HPO(4)·nH(2)O Compounds for Biomedical Applications

This study aimed to explore the effects of the full-scale replacement (up to 100%) of Ca(2+) ions with Ag(1+) ions in the structure of brushite (CaHPO(4)·2H(2)O). This substitution has potential benefits for producing monophasic and biphasic Ca(1−x)Ag(x)HPO(4)·nH(2)O compounds. To prepare the starting solutions, (NH(4))(2)HPO(4), Ca(NO(3))(2)·4H(2)O, and AgNO(3) at different concentrations were used. The results showed that when the Ag/Ca molar ratio was below 0.25, partial substitution of Ca with Ag reduced the size of the unit cell of brushite. As the Ag/Ca molar ratio increased to 4, a compound with both monoclinic CaHPO(4)·2H(2)O and cubic nanostructured Ag(3)PO(4) phases formed. There was a nearly linear relationship between the Ag ion ratio in the starting solutions and the wt% precipitation of the Ag(3)PO(4) phase in the resulting compound. Moreover, when the Ag/Ca molar ratio exceeded 4, a single-phase Ag(3)PO(4) compound formed. Hence, adjusting the Ag/Ca ratio in the starting solution allows the production of biomaterials with customized properties. In summary, this study introduces a novel synthesis method for the mono- and biphasic Ca(1−x)Ag(x)HPO(4)·nH(2)O compounds brushite and silver phosphate. The preparation of these phases in a one-pot synthesis with controlled phase composition resulted in the enhancement of existing bone cement formulations by allowing better mixing of the starting ingredients.