title: TEM study of calcium phosphate precipitation on HA/TCP ceramics.
abstract: This study focuses on phase identification of precipitation on bioactive calcium phosphate (BCP) surfaces in vitro and in vivo. The BCP used in this study consisted of 70 wt% hydroxyapatite (HA) and 30 wt% beta-tricalcium phosphate. Single crystalline precipitates of calcium phosphates on porous BCP bioceramics obtained after immersion in dynamic simulated body fluid (SBF) and after implantation in pig muscle were examined using electron diffraction in transmission electron microscope. The crystals formed in vitro in dynamic SBF were identified as octacalcium phosphate (OCP), instead of apatite. Most of the precipitated crystals in vivo samples had an HA structure; while OCP and dicalcium phosphate dihydrate were also identified. The evidence from single diffraction patterns indicates that apatite formation on bioactive ceramics is a complicated process, particularly in physiological environments where formation might include a transient stage of intermediate phases.
authors.affiliation: Department of Mechanical Engineering, Hong Kong University of Science and Technology, Kowloon, Hong Kong, China. meleng@ust.hk
authors.forename: Yang
authors.initials: Y
authors.lastname: Leng
authors.forename: Jiyong
authors.initials: J
authors.lastname: Chen
authors.forename: Shuxin
authors.initials: S
authors.lastname: Qu
mesh_terms: D000327:Adsorption; D000818:Animals; D001826:Body Fluids / Q000737:chemistry; D018786:Bone Substitutes / Q000737:chemistry*; D002130:Calcium Phosphates / Q000737:chemistry*; D002516:Ceramics / Q000737:chemistry*; D011232:Chemical Precipitation; D020099:Coated Materials, Biocompatible / Q000737:chemistry; D003460:Crystallization / Q000379:methods; D003461:Crystallography / Q000379:methods*; D017886:Durapatite / Q000737:chemistry*; D008422:Materials Testing / Q000379:methods*; D008854:Microscopy, Electron; D008968:Molecular Conformation; D018482:Muscle, Skeletal / Q000737:chemistry; D044367:Phase Transition; D013552:Swine
chemical_list: D018786:Bone Substitutes; D002130:Calcium Phosphates; D020099:Coated Materials, Biocompatible; C485828:alpha-tricalcium phosphate; C485817:beta-tricalcium phosphate; C485830:tetracalcium phosphate; C485838:calcium phosphate, monobasic, anhydrous; D017886:Durapatite; C020243:calcium phosphate; C018392:tricalcium phosphate; C485829:calcium phosphate, dibasic, anhydrous