title: Importance of nucleation in transformation of octacalcium phosphate to hydroxyapatite.
abstract: Octacalcium phosphate (OCP) is regarded as an in vivo precursor of hydroxyapatite (HA). It is important to understand the mechanism of transformation of OCP to HA in order to reveal the mechanism of mineralization and help in the development of artificial bone-repairing materials. Herein, we have examined the behavior of OCP in a simulated body fluid (SBF) and pure water. The OCP particles immersed in the SBF at 37 °C did not transform to HA even after 720 h of immersion, though the particles showed crystal growth. In distilled water at 60 °C, the OCP particles transformed to HA but the unreactive period was observed. Although the immersed solution became supersaturated with HA within 12h of immersion, the OCP was not transformed in the first 36 h of immersion. These results indicate that the nucleation of HA is the rate-determining step in the transformation of OCP to HA.
authors.affiliation: Graduate School of Environmental Studies, Tohoku University, 6-6-20, Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan.
authors.forename: Natsuko
authors.initials: N
authors.lastname: Ito
authors.affiliation: Graduate School of Environmental Studies, Tohoku University, 6-6-20, Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan. Electronic address: kamitaka@mail.kankyo.tohoku.ac.jp.
authors.forename: Masanobu
authors.initials: M
authors.lastname: Kamitakahara
authors.affiliation: Department of Materials Science and Engineering, National Cheng Kung University, No. 1, University Road, Tainan 70101, Taiwan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yoshimura
authors.affiliation: Faculty of Economics, Keio University, Building #2-101B, 4-1-1, Hiyoshi, Kohoku-ku, Yokohama 223-8521, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Ioku
mesh_terms: D001826:Body Fluids / Q000737:chemistry; D002130:Calcium Phosphates / Q000737:chemistry*; D017886:Durapatite / Q000737:chemistry*; D006801:Humans; D013696:Temperature; D013997:Time Factors; D014867:Water / Q000737:chemistry
chemical_list: D002130:Calcium Phosphates; D014867:Water; C022045:octacalcium phosphate; D017886:Durapatite
keywords: Hydroxyapatite; Octacalcium phosphate; Transformation