Analytical Evaluation of Wet and Dry Mechanochemical Syntheses of Calcium-Deficient Hydroxyapatite Containing Zinc Using X-ray Diffractometry and Near-Infrared Spectroscopy

Abstract

Calcium-deficient zinc-containing calcium phosphate (ZnAP), which has sustained zinc release properties that are effective for treating osteoporosis, can be efficiently synthesized as a biomaterial through wet grinding. To elucidate the physicochemical mechanism of these mechanochemical syntheses, ground products were obtained from the starting material powder (S-CP), consisting of calcium hydrogen phosphate dihydrate (CHPD), calcium oxide (CaO), and zinc oxide (ZnO), by wet and dry grinding for 0–3 h in a centrifugal ball mill. The ground S-CP products were analyzed using powder X-ray diffraction (XRD) and near-infrared spectroscopy (NIRS); the crystal transformations and molecular interactions of the ground products were kinetically analyzed. The XRD and second-derivative NIRS results indicate that the S-CP is primarily transformed into ZnAP via amorphous solid formation in wet grinding, and the reaction follows a consecutive reaction model. In contrast, in dry grinding, the ground product of CHPD and CaO is transformed into an amorphous solid following an equilibrium reaction model; however, ZnO is predominantly not transformed and remains crystalline.

Calcium Phosphate Loaded Biopolymer Composites—A Comprehensive Review on the Most Recent Progress and Promising Trends

“…The quality of calcium precursors used also affects the morphology, and the particle size and shape [22]. Other methods applied for CaP preparation include hydrothermal [23][24][25], sol-gel [26,27], electrochemical [28], solid phase powder milling [29][30][31], and spray freeze-drying techniques [32,33]. Additionally, because the human bone contains trace elements such as Mg, Zn, Sr, etc., the mineralization of CaP particles with such bioactive ions makes them more biocompatible.…”