title: Characterization, physicochemical properties and biocompatibility of La-incorporated apatites.
abstract: In this study, the physicochemical properties and biocompatibilities of La-containing apatites were intensively investigated together with their characterizations in terms of composition, structure, valent state and morphology using X-ray diffraction, Fourier-transform infrared spectra, X-ray photoelectron spectroscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy, respectively. The results indicate that the La(3+) ion can be incorporated into the crystal lattice of hydroxyapatite resulting in the production of La-incorporated apatites (La(x)Ca(10-x)(PO(4))(6)(OH)(2+x-2y)O(y square y-x) (x> or =0.5, y<1+x/2) or La(x)Ca(10-x)(PO(4))(6)O(y square y-x) (0.5<x<2, y=1+x/2)) by high-temperature solid phase synthesis. For La content <20%, the product is composed of the major phase, La(x)-OAP, as well as a small amount of tricalcium phosphate, but for a La content of 20%, the product is pure La-incorporated oxyapatite with the formula La(2)Ca(8)(PO(4))(6)O(2) (La(2)-OAP, x=2, y=2). It is also found that the La content plays important roles in both the physicochemical properties and biocompatibilities of the La-incorporated apatites. In contrast to La-free apatite, La-incorporated apatites possess a series of attractive properties, including higher thermal stability, higher flexural strength, lower dissolution rate, larger alkaline phosphatase activity, preferable osteoblast morphology and comparable cytotoxicity. In particular, the sintered La-incorporated apatite block achieves a maximal flexure strength of 66.69+/-0.98 MPa at 5% La content (confidence coefficient 0.95), increased 320% in comparison with the La-free apatite. The present study suggests that the La-incorporated apatite possesses application potential in developing a new type of bioactive coating material for metal implants and also as a promising La carrier for further exploring the beneficial functions of La in the human body.
authors.affiliation: State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China. guodagang@mail.xjtu.edu.cn
authors.forename: D G
authors.initials: DG
authors.lastname: Guo
authors.forename: A H
authors.initials: AH
authors.lastname: Wang
authors.forename: Y
authors.initials: Y
authors.lastname: Han
authors.forename: K W
authors.initials: KW
authors.lastname: Xu
mesh_terms: D000818:Animals; D001031:Apatites / Q000737:chemistry*; D001672:Biocompatible Materials / Q000737:chemistry; D002118:Calcium / Q000737:chemistry; D002478:Cells, Cultured; D006801:Humans; D007811:Lanthanum / Q000737:chemistry*; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism; D056951:Photoelectron Spectroscopy; D051381:Rats; D017207:Rats, Sprague-Dawley; D017550:Spectroscopy, Fourier Transform Infrared; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength; D014961:X-Ray Diffraction
chemical_list: D001031:Apatites; D001672:Biocompatible Materials; D007811:Lanthanum; D002118:Calcium