Plasma-sprayed calcium phosphate particles with high bioactivity and their use in bioactive scaffolds

Abstract

Highly crystalline feedstock hydroxyapatite (HA) particles with irregular shapes were spheroidized by plasma spraying them onto the surface of ice blocks or into water. The spherical Ca–P particles thus produced contained various amounts of the amorphous phase which were controlled by the stand-off distance between the spray nozzle and the surface of ice blocks or water. The smooth surface morphology without cracks of spherical Ca–P particles indicated that there were very low thermal stresses in these particles. Plasma-sprayed Ca–P particles were highly bioactive due to their amorphous component and hence quickly induced the formation of bone-like apatite on their surfaces after they were immersed in an acellular simulated body fluid at 36.5°C. Bone-like apatite nucleated on dissolved surface (due to the amorphous phase) of individual Ca–P particles and grew to coalesce between neighboring Ca–P particles thus forming an integrated apatite plate. Bioactive and biodegradable composite scaffolds were produced by incorporating plasma-sprayed Ca–P particles into a degradable polymer. In vitro experiments showed that plasma-sprayed Ca–P particles enhanced the formation of bone-like apatite on the pore surface of Ca–P/PLLA composite scaffolds.