Effect of laser irradiation on the dissolution kinetics of hydroxyapatite preparations.
This research investigated the effects of a laser irradiation treatment on the dissolution characteristics of hydroxyapatite (HAP), and the results provide an insight into the relationship between the effects of laser treatment and the two-site dissolution kinetics of HAP samples. The HAP samples prepared by aqueous precipitation and digestion at approximately 100 degrees C were irradiated with a CO2 laser (20-50 W) with a beam diameter of 14 mm for a total of 10-400 s. Dissolution rates of the laser-treated HAP samples were subsequently determined in acetate buffer (pH = 4.5, mu = 0.50) at various levels of partial saturation (0-24% with respect to the HAP thermodynamic solubility of pKsp = 116). The following were the important findings. The X-ray diffraction and the IR spectroscopy results suggested that the HAP crystalline structure was not changed by laser treatment. Laser treatment of HAP powder at 50 W for 400 s, however, caused an approximately 3.5-fold reduction in the specific surface area of HAP and reduced the initial dissolution rate of HAP in acetate buffer by a factor of approximately 22.9. Also, this laser treatment appeared to reduce the dissolution rate of HAP in 16 and 24% partially saturated acetate buffer from substantial levels to essentially zero. These results may be summarized as follows. Laser treatment of HAP results in a reduction in the dissolution rate and also a reduction in the specific surface area of this material. However, the dissolution rate reduction is significantly greater than the reduction in the specific surface area.(ABSTRACT TRUNCATED AT 250 WORDS)
Department of Pharmaceutics, University of Utah, Salt Lake City 84112.
J
J
Wong
M
M
Otsuka
W I
WI
Higuchi
G L
GL
Powell
J L
JL
Fox
D006882:Hydroxyapatites / Q000528:radiation effects*; D007700:Kinetics; D007834:Lasers; D010710:Phosphates / Q000032:analysis; D011208:Powders; D012995:Solubility; D012996:Solutions; D013055:Spectrophotometry, Infrared; D013816:Thermodynamics; D014961:X-Ray Diffraction
D006882:Hydroxyapatites; D010710:Phosphates; D011208:Powders; D012996:Solutions