Injectable chelate-setting hydroxyapatite cement prepared by using chitosan solution: Fabrication, material properties, biocompatibility, and osteoconductivity

An injectable chelate-setting hydroxyapatite cement (IP6-HAp), formed by chelate-bonding capability of inositol phosphate (IP6), was developed. The effects of ball-milling duration of starting HAp powder and IP6 concentration on the material properties such as injectability and mechanical strength of the cement were examined. The cement powder was prepared by ball-milling the as-synthesized HAp powder for 5 min using ZrO2 beads with a diameter of 10 mm, followed by another 60 min with ZrO2 beads with a diameter of 2 mm, and thereafter surface-modified with 5000 ppm of IP6 solution. Injectable cement was then fabricated with this HAp powder and 2.5 mass% chitosan as a mixing solution, with a setting time of 36.3 ± 4.7 min and a compressive strength of 19.0 ± 2.1 MPa. The IP6-HAp cements prepared with chitosan showed favorable biocompatibility in vitro using an osteoblast cell model, and osteoconductivity in vivo using a pig tibia model.