Effect of Acid Treated Hydroxyapatite on Osteoblast Maturation

Surfaces of sintered hydroxyapatite (HAp) were treated with four kinds of acids, hydrochloric acid (HCl), nitric acid (HNO3), sulfuric acid (H2SO4) and hydrogen peroxide (H2O2). On these acid-treated HAp surfaces, osteoblast-like MC3T3-E1 cells were cultured for 20 days. The matrix mineralization was observed in HCl-treated HAp and HNO3-treated HAp, but not in non-treated HAp, H2SO4-treated HAp and H2O2-treated HAp. Gene expressions of Bglap2 encoding osteocalcin and Akp2 encoding alkaline phosphatase were higher in HCl-treated HAp and HNO3-treated HAp than those in the others. These results indicate that not only hydrochloric acid but also nitric acid improves performance of HAp to mature osteoblast.