Investigation on structural properties and bioactivity of nanosized biphasic calcium phosphate

Abstract

Synthetic biphasic bioceramics composed of hydroxyapatite (HA) and other calcium phosphates (CPs) can provide promising efficiency in the treatment of bone defects based on the rapid dissolution of the CPs, to allow its replacement by freshly formed bone, along with the slow resorption of the HA, to preserve the volume of the grafted area. For this purpose, the present study was conducted to prepare nanosized biphasic calcium phosphate (n-BCP) using a facile mechanochemical process. The experimental outputs were also compared to the commercial-grade HA in terms of physicochemical features. The Rietveld refinement was utilized to calculate the phase contents and crystal structures of the composites, including crystallite size, lattice parameters, and unit cell volume. Besides, the atomic arrangement of Ca1, Ca2, PO43−, and OH− groups in the hexagonal crystal structure of HA and triclinic structure of anhydrous dicalcium phosphate (DCPA) was determined. The phase fraction, crystallite size, and the powder density of the biphasic structures, which were derived by Rietveld refinement, were found to be affected by ball-milling. In addition to biphasic structures, a monolithic hexagonal HA with an isotropic crystal growth was formed after 7 h of ball-milling under an argon atmosphere. The in vitro test in a simulated body fluid (SBF) confirmed the bioactivity of the biphasic structure through the formation of a bone-like apatite layer after one week.