Synthesis of highly regular dandelion-like hydroxyapatite particles-a Taguchi experimental design approach

Many studies have been performed on the synthesis of hydroxyapatite (HA) particles. The geometry or morphology of HA reinforcing particles theoretically affects both the specific surface area and the manner and amount of stress transfer from the polymer matrix to the filler in a typical composite-based biomaterial. Accordingly, the purpose of this study is to provide a method for the synthesis of HA having a highly regular three-dimensional complex morphology. For this aim, we have performed a design of experiment approach for the production of dandelion-like HA (DHA) structures under hydrothermal conditions, and evaluated the effect of some of the most relevant process factors (i.e., EDTA/Ca ratio, pH, amount of urea, process time and temperature) with four levels on the morphological and chemical properties of the prepared powder. Analysis of signal-to-noise ratios revealed the great influence of pH and amount of urea on the characteristic of HA particles. The DHA prepared under optimal conditions showed a highly regular dandelion-like morphology, a crystallite size of around 95 nm and a degree of crystallinity of 88%. Moreover, the SEM images of the bioactivity analysis indicated the accumulation of a new apatite-like phase on the surface of the powder along with an interesting morphological change, demonstrating a promising bioactivity of the as-synthesized powder. Finally, in vitro cell assays indicated that 3T3 cells had high cell viability and cell spreading in the presence of DHA particles, suggesting the high biocompatibility of the synthesized particles and hence their suitability for application in tissue regeneration.