Preparation of Porous Spherical Hydroxyapatite Agglomerates Interacted With Cyclodextrin

Abstract

Porous spherical hydroxyapatite (Ca10(PO4)6(OH)2: HAp) agglomerates with diameters of approximately 1 µm were prepared by: (i) the spray-pyrolysis of calcium phosphate solution containing 0.5 mol•dm-3 Ca(NO3)2, 0.3 mol•dm-3 (NH4)2HPO4, 0.1-0.4 mol•dm-3 glutaric acid and concentrated HNO3 at 600ºC, using an ultrasonic vibrator, and then (ii) the burnout of residual carbon resulting from the pyrolysis of glutaric acid upon the heat treatment of the spray-pyrolyzed powder at 900°C for 10 min. Three types of resulting HAp powders were then hydrothermally treated with 1.5 mass% β-cyclodextrin (β-CyD) solution at 120°C for 1 h. The amounts of β-CyD in the resulting HAp agglomerates were found to be in the range of 1.1 to 13.1 mass%. Transmission electron microscopy confirmed the presence of β-CyD not only on the surfaces but also inside the spherical HAp agglomerates. When the HAp powder with 13.1 mass% β-CyD addition was immersed in pure water at 90ºC for 1 h, the released amount of β-CyD was as low as 2.1 mass%, indicating the enhanced chemical bonding between β-CyD and HAp, due to the hydrothermal treatment.