Role of strontium substitution in spray drying of hydroxyapatite: A comparative study on physical properties

Abstract

Spray drying (SD) has the ability to tailor granule size and morphology, thus, it is used for producing hydroxyapatite (HA) granules. Recently, Sr functionalized HA (SrHA) has been recommended owing to its improved biological properties. The aim of this article was to produce SrHA granules with the combination of nanoparticle synthesis and spray-drying. The effects of substitution on the physical properties of SrHA nanoparticles and spray-dried granules were investigated. TEM analyzes revealed that Sr substitution reduced the mean size of HA nanoparticles from 4.59 nm to 2.31 nm. Besides, Sr substitution increased the viscosity of the prepared slurry for spray drying, which may be attributed to the smaller nanoparticle sizes. The reduced nanoparticle size caused to the agglomeration of the SrHA more than the pure HA nanoparticles. Moreover the 16 mol % Sr substituted HA (16SrHA) slurry were quickly hardened, which hampered the feeding of the slurry to the SD system; eventually the atomizer was blocked. The increase in the viscosity increased the mean granule size of HA from 41.53 mu m to 49.18 mu m. HA and 8SrHA granules presented HA phase dominantly after the heat treatment at 1000 degrees C, while, 16SrHA decomposed to TCP according to RAMAN and XRD investigations.