Nanosized hydroxyapatite powders from microemulsions and emulsions stabilized by a biodegradable surfactant

Abstract

Ultrafine hydroxyapatite powders have been successfully synthesized in inverse microemulsions and emulsions consisting of petroleum ether as the oil phase, 1.0 M CaCl₂ solution as the aqueous phase and biodegradable KB6ZA as the surfactant. The titration of 0.6 M (NH₄)₂HPO₄ aqueous solution into the inverse microemulsion and emulsions containing 25.0 and 35.0 wt% aqueous phase, resulted in hydroxyapatite precursors that were nanometer sized and more or less spherical in morphology. However, they underwent a considerable degree of particle coarsening when calcined at 650 °C for 6 h. A nanocrystalline hydroxyapatite powder, which exhibited a dendritic agglomerate morphology, was synthesized in an oil-in-water emulsion containing 90.0 wt% aqueous phase. It shows an average particle size of 25 nm upon calcination at 650 °C for 6 h, as little particle coarsening and growth in crystallite size were observed at the calcination temperature. The inverse microemulsion- and emulsion-derived hydroxyapatites exhibit a degree of type B carbonate substitution, which cannot be eliminated by calcination in air at 650 °C.

References

1. K. de Groot, Bioceramics of Calcium Phosphate, CRC Press, Boca Raton, FL, 1984.
2. K. de Groot, Biomaterials, 1980, 1, 47.
3. L. L. Hench, J. Am. Ceram. Soc., 1991, 74, 1487.
4. P. Ducheyne, L. L. Hench, A. Kagan, M. Martens, A. Burssen and J. Muller, J. Biomed. Mater. Res., 1980, 14, 225.
5. T. Takaoka, M. Okumura, H. Ohgushi, K. Inone, Y. Takakura and S. Tamai, Biomaterials, 1996, 17, 1499.
6. T. Suzuki, T. Hatsushika and Y. Hayakawa, J. Chem. Soc., Faraday Trans. 1, 1982, 78, 3605.
7. J. Reichert and J. G. P. Binner, J. Mater. Sci., 1996, 31, 1231.
8. T. Kanazawa, Materials Science Monographs: Inorganic Phosphate Materials, Elsevier, Tokyo, 1989, pp. 15–76.
9. G. K. Lim, J. Wang, S. C. Ng and L. M. Gan, Mater. Lett., 1996, 28, 431.
10. G. K. Lim, J. Wang, S. C. Ng, C. H. Chew and L. M. Gan, Biomaterials, 1997, 18, 1433.
11. M. R. Porter, Handbook of Surfactants, Chapman and Hall, New York, 1991.
12. R. D. Swisher, Surfactant Biodegradation, Marcel Dekker Inc., New York, 1970.
13. J. Sanchez Leal, M. T. Garcia, I. Ribosa and F. Cornelles, in Surfactant in Solutions, ed. K. L. Mittal, Surfactant Science Series Vol. 64, Marcel Dekker, New York, 1996, p. 379.
14. J. H. Clint, Surfactant Aggregation, Chapman and Hall, New York, 1992.
15. J. C. Elliot, The Crystallographic Structure of Dental Enamel and Related Apatites, PhD Thesis, University of London, 1964.
16. W. H. Emerson and E. E. Fisher, Arch. Oral Biol., 1962, 7, 671.
17. R. Z. LeGeros, J. Dent. Res., 1990, 69, 567.
18. R. Z. LeGeros, Biological and Synthetic Apatites in Hydroxyapatite and Related Materials, ed. P. W. Brown and B. Constantz, CRC Press, Boca Raton, FL, 1994.
19. R. Z. LeGeros, Prog. Cryst. Growth Charact., 1981, 4, 1.
20. L. G. Ellies, D. G. A. Nelson and J. D. B. Featherson, J. Biomed. Mater. Res., 1988, 22, 541.