title: Crystallized nano-sized alpha-tricalcium phosphate from amorphous calcium phosphate: microstructure, cementation and cell response.
abstract: New insight on the conversion of amorphous calcium phosphate (ACP) to nano-sized alpha tricalcium phosphate (α-TCP) provides a faster pathway to calcium phosphate bone cements. In this work, synthesized ACP powders were treated with either water or ethanol, dried, crystallized between 700 and 800 °C, and then cooled at different cooling rates. Particle size was measured in a scanning electron microscope, but crystallite size calculated by Rietveld analysis. Phase composition and bonding in the crystallized powder was assessed by x-ray diffraction and Fourier-transform infrared spectroscopy. Results showed that 50 nm sized α-TCP formed after crystallization of lyophilized powders. Water treated ACP retained an unstable state that may allow ordering to nanoapatite, and further transition to β-TCP after crystallization and subsequent decomposition. Powders treated with ethanol, favoured the formation of pure α-TCP. Faster cooling limited the growth of β-TCP. Both the initial contact with water and the cooling rate after crystallization dictated β-TCP formation. Nano-sized α-TCP reacted faster with water to an apatite bone cement than conventionally prepared α-TCP. Water treated and freeze-dried powders showed faster apatite cement formation compared to ethanol treated powders. Good biocompatibility was found in pure α-TCP nanoparticles made from ethanol treatment and with a larger crystallite size. This is the first report of pure α-TCP nanoparticles with a reactivity that has not required additional milling to cause cementation.
authors.affiliation: Biomaterials Research Laboratory, Riga Technical University, 3/7 Paula Valdena St., LV-1048 Riga, Latvia.
authors.forename: Linda
authors.initials: L
authors.lastname: Vecbiskena
authors.forename: Karlis Agris
authors.initials: KA
authors.lastname: Gross
authors.forename: Una
authors.initials: U
authors.lastname: Riekstina
authors.forename: Thomas Chung-Kuang
authors.initials: TC
authors.lastname: Yang
mesh_terms: D001031:Apatites / Q000737:chemistry; D001843:Bone Cements / Q000737:chemistry* / Q000633:toxicity; D002130:Calcium Phosphates / Q000737:chemistry* / Q000633:toxicity; D002478:Cells, Cultured; D003460:Crystallization; D006358:Hot Temperature; D006801:Humans; D008422:Materials Testing; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000187:drug effects; D008855:Microscopy, Electron, Scanning; D053758:Nanoparticles / Q000737:chemistry* / Q000633:toxicity / Q000648:ultrastructure; D010316:Particle Size; D033362:Powder Diffraction; D011208:Powders; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D001031:Apatites; D001843:Bone Cements; D002130:Calcium Phosphates; D011208:Powders; C485828:alpha-tricalcium phosphate; C485817:beta-tricalcium phosphate