Biomimetic mineralisation on plasma sprayed apatite particles and coatings in different simulated physiological fluids

Abstract

In vitro mineralisation experiments in simulated physiological fluids (SPFs) are designed to mimic the in vivo mineralisation process and hence can provide vital information during materials development. There is no doubt that intrinsic properties of a material play an important role in the mineralisation process. The commonly used plasma spray technique for depositing bioceramic coatings induces changes in the structure of sprayed hydroxyapatite (HA) and hence its biological performance. Although fluorapatite (FA) has a similar crystallographic structure to that of HA, it is more stable during the plasma spray process. In this investigation, plasma spray was employed to produce HA or FA coatings and HA particles with controlled crystallinity. Post-spray heat treatment was performed to increase the crystallinity of HA coatings. These coatings and particles were immersed in different SPFs to investigate in vitro biomimetic mineralisation processes on their surfaces. It was shown that materials having the apatite structure were important for inducing the formation of calcium phosphate mineral but could display different in vitro performances as they contain different amounts of the amorphous phase. The mineralisation process proceeded differently in different SPFs with different ion concentrations.