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Octacalcium phosphate (OCP) has received considerable attention in the field of ceramic biomaterials as an advanced functional material. It exhibits a layered structure composed of apatitic and hydrated layers and can incorporate various dicarboxylate ions into the hydrated layer. Saturated dicarboxylic acids (HOOC(CH2)nCOOH) with an odd number of methylene groups (–CH2–) exhibit lower incorporation fractions than those with an even number of methylene groups, possibly owing to a compositional dependence on the synthetic method. In this study, calcium carbonate, phosphoric acid, and various amounts of glutaric acid were used to produce glutarate-ion-incorporated OCP by a wet chemical method, which is different from the conventional synthetic strategy. While utilising 1–20 mmol of glutaric acid during synthesis did not produce the desired product, using 25 mmol of glutaric acid resulted in the formation of single-phase glutarate-ion-incorporated OCP with a Ca/P molar ratio of 1.57 and a 90% incorporation fraction of glutarate ions. This glutarate-ion-incorporation fraction is significantly higher than that reported in the previous studies (35%). Thus, the synthetic procedure proposed herein was able to produce single-phase OCP containing glutarate ions with a high incorporation fraction. Our findings can contribute to development of novel functional ceramic biomaterials in the future. [ABSTRACT FROM AUTHOR]

Zinc whitlockite (Zn-WH, Ca18Zn2(HPO4)2(PO4)12) is a new synthetic analog of the second most abundant biomineral – magnesium whitlockite (Mg-WH, Ca18Mg2(HPO4)2(PO4)12), which is considered as a potential material for bone regeneration. In the present work, the formation of Zn-WH via a dissolution–precipitation process under hydrothermal conditions was investigated in detail. The influence of medium pH, reaction time, temperature and concentration of precursors on the formation of the single-phase material was studied. It was demonstrated that the phase-pure material can be obtained in the pH range from 5.6 to 6.2 in a very short period of time – 1 h. Variation of chemical composition in terms of the Ca-to-Zn ratio was determined to be possible in a narrow range. The structural properties of the synthesized Zn-WH were investigated by powder X-ray diffraction analysis along with 1H and 31P solid-state NMR spectroscopy, FTIR spectroscopy, Raman spectroscopy and XPS. Rietveld refinement confirmed that the synthesized material has a rhombohedral structure with the R3c space group. The NMR study confirmed the presence of three inequivalent phosphorus atoms in the crystal structure, whereas only one PO43− tetrahedron was determined to be protonated. The size and shape of the particles can be controlled by the concentration of the precursors as well as by the initial Ca-to-Zn ratio in the reaction mixture. [ABSTRACT FROM AUTHOR]