This study aimed at preparing and studying the properties of nanoparticles of calcium phosphate (nCaP) with Ca/P ratios ranging from 1.0 to 1.67 using a spray-drying technique. Micro-structural analyses results suggested that the nCaPs with Ca/P ratios of 1.67 to 1.33 were nano-sized amorphous calcium phosphates (ACP) containing varying amounts of acid phosphate and carbonate. The nCaP with Ca/P ratio of 1 contained only nano-sized low crystalline dicalcium phosphate (DCP). BET measurements of the nCaPs showed specific surface areas of (12 to 50) m2/g, corresponding to estimated equivalent spherical diameters of (38 to 172) nm. However, dynamic light scattering measurements revealed much larger particles of (380 to 768) nm, owing to agglomeration of the smaller nano particles. Thermodynamic solubility measurement results showed that the nCaPs with Ca/P ratio of 1.33-1.67 all have similar solubility behavior. The materials were more soluble than the crystalline hydroxyapatite (HA) at pH greater than about 4.7, and more soluble than -tricalcium phosphate (-TCP), octacalcium phosphate (OCP) and DCP at pH above 5.5. Their solubility approached that of -tricalcium phosphate (-TCP) at about pH 7. These nCaPs, which cannot be readily prepared by other currently available methods for nanoparticle preparation, have a range of potential biomedical applications.
Pub Type: Journals
Fluoride, Plaque, Fluoride-binding, Calcium