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Surface modification of calcium hydroxyapatite with pyrophosphoric acid
Hidekazu Tanaka1, Masakazu Futaoka, Ryozi Hino
1Department of Material Science, Faculty of Science and Engineering, Shimane University, 1060 Nishikawatsu, Matsue, 690-8504, Shimane, Japan. hidekazu@riko.shimane-u.ac.jp
Journal of Colloid and Interface Science
|December 5, 2003
Summary
Synthetic colloidal calcium hydroxyapatite (CaHap) treated with pyrophosphoric acid (PP) showed increased phosphate content and a decreased Ca/P ratio. Modified CaHap transformed into beta-tricalcium phosphate at high temperatures.
Area of Science:
- Materials Science
- Inorganic Chemistry
- Biomaterials Science
Background:
- Calcium hydroxyapatite (CaHap) is a crucial biomaterial.
- Surface modification of CaHap can alter its properties.
- Pyrophosphoric acid (PP) is a potential surface modifying agent.
Purpose of the Study:
- To investigate the surface modification of synthetic CaHap using pyrophosphoric acid (PP).
- To characterize the changes in CaHap composition and structure after PP treatment.
- To determine the thermal transformation products of modified CaHap.
Main Methods:
- Surface treatment of CaHap with varying concentrations of PP in acetone.
- Characterization using X-ray Diffraction (XRD), thermal analysis, N2 adsorption, Transmission Electron Microscopy (TEM), and Fourier-Transform Infrared Spectroscopy (FTIR).
- Analysis of Ca/P molar ratios and thermal transformation behavior.
Main Results:
- No significant changes in XRD patterns or particle morphology were observed.
- Increased PO4 content and decreased Ca/P molar ratio (from 1.62 to 1.35) with increasing PP concentration.
- FTIR indicated reaction between PP and surface P-OH groups of CaHap.
- CaHap modified to a Ca/P ratio < 1.50 transformed into beta-Ca3(PO4)2 upon heating to 850°C.
Conclusions:
- Pyrophosphoric acid effectively modifies the surface chemistry of CaHap by increasing its phosphate content.
- The Ca/P ratio of CaHap can be controllably reduced via PP treatment.
- Modified CaHap exhibits a phase transformation to beta-tricalcium phosphate at elevated temperatures, suggesting potential applications in ceramic processing.