Premium
Effect of Process Variables on the Microstructure of Hollow Hydroxyapatite Microspheres Prepared by a Glass Conversion Method
Author(s) -
Fu Hailuo,
Rahaman Mohamed N.,
Day Delbert E.
Publication year - 2010
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2010.03833.x
Subject(s) - microsphere , materials science , microstructure , factorial experiment , grain size , core (optical fiber) , glass microsphere , morphology (biology) , specific surface area , chemical engineering , composite material , chemistry , catalysis , organic chemistry , statistics , mathematics , biology , engineering , genetics
Solid microspheres (diameter=106–150 μm) of a Li 2 O–CaO–B 2 O 3 glass were reacted in a K 2 HPO 4 solution to form hollow hydroxyapatite (HA) microspheres. The effect of the temperature (25°–60°C), K 2 HPO 4 concentration (0.01–0.25 M ), and pH (9–12) of the solution on the diameter ( d ) of the hollow core normalized to the diameter ( D ) of the HA microspheres, the surface area, and the pore size of the microsphere wall was studied. The statistically significant process variables that influenced these microstructural characteristics were evaluated using a factorial design approach. While the pH had little effect, the concentration of the solution had a marked effect on d / D , surface area, and pore size, whereas temperature markedly influenced d / D and pore size, but not the surface area. The largest hollow core size ( d / D value ≈0.6) was obtained at the lowest temperature (25°C) or the lowest K 2 HPO 4 concentration (0.02 M ), while microspheres with the highest surface area (140 m 2 /g), with pores of size 10−12 nm were obtained at the highest concentration (0.25 M ). The consequences of these results for potential application of these hollow HA microspheres as devices for local delivery of proteins, such as drugs or growth factors, are discussed.