Evaluation of the in vivo biocompatibility of hydroxyapatite granules incorporated with zinc ions

The incorporation of zinc onto biomaterials may improve their biological properties, since it is an essential trace element, involved on important steps of bone remodeling. The aim of this work was to evaluate the in vivo biocompatibility of previously characterized hydroxyapatite granules incorporated with 5% zinc (ZnHA), through a subcutaneous grafting test. Granules produced from powders of ZnHA or stoichiometric HA were subcutaneously grafted onto Balb/c mice, and histomorphometrical analysis was performed at 7, 14, 21, 28 or 60 days after grafting. HA and ZnHA induced a similar foreign body reaction, with formation of granulome and the presence of a fibrous capsule. Granulocytes were virtually absent, and agranulocytes decreased with time. ZnHA treated samples presented faster reduction on multinucleated giant cells and increase on observed angiogenesis, as compared to HA. It could be concluded that ZnHA granules are biocompatible. Further study should better address its potential use for bone therapy.