Crystallized nano-sized alpha-tricalcium phosphate from amorphous calcium phosphate: microstructure, cementation and cell response

• Published in: Biomedical materials (Bristol) 2015-04, Vol.10 (2), p.025009-025009
• Main Authors: Vecbiskena, Linda, Gross, Karlis Agris, Riekstina, Una, Yang, Thomas Chung-Kuang
• Format: Article
• Language: English
• Subjects: alpha tricalcium phosphate; amorphous calcium phosphate; Apatites - chemistry; Bone cements; Bone Cements - chemistry; Bone Cements - toxicity; Calcium phosphate; Calcium Phosphates - chemistry; Calcium Phosphates - toxicity; cell response; Cells, Cultured; Crystallites; Crystallization; Ethanol; Ethyl alcohol; Formations; Hot Temperature; Humans; Materials Testing; Mesenchymal Stromal Cells - cytology; Mesenchymal Stromal Cells - drug effects; Microscopy, Electron, Scanning; Nanoparticles - chemistry; Nanoparticles - toxicity; Nanoparticles - ultrastructure; Nanostructure; Particle Size; Powder Diffraction; Powders; regenerative medicine; Rietveld refinement; Spectroscopy, Fourier Transform Infrared
• ISSN: 1748-6041; 1748-605X; 1748-605X
• DOI: 10.1088/1748-6041/10/2/025009

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.