A copper-containing analog of the biomineral whitlockite: dissolution-precipitation synthesis, structural and biological properties

In the present work, copper whitlockite (Cu-WH, Ca18Cu2(HPO4)2(PO4)12) was successfully synthesized and comprehensively characterized, founding the base knowledge for its future studies in medicine, particularly for bone regeneration. This material is a copper-containing analog of the well-known biomineral magnesium whitlockite (Mg-WH, Ca18Mg2(HPO4)2(PO4)12). The synthesis of powders was performed by a dissolution-precipitation method in an aqueous medium under hydrothermal conditions. Phase conversion from brushite (CaHPO4·2H2O) to Cu-WH took place in an acidic medium in the presence of Cu2+ ions. Optimization of the synthesis conditions in terms of medium pH, temperature, time, Ca/Cu molar ratio and concentration of starting materials was performed. The crystal structure of the synthesized products was confirmed by XRD, FTIR and Raman spectroscopy, 1H and 31P solid-state NMR, and EPR. Morphological features and elemental distribution of the synthesized powders were studied by means of SEM/EDX analysis. The ion release in SBF solution was estimated using ICP-OES. Cytotoxicity experiments were performed with MC3T3-E1 cells. The study on thermal stability revealed that the synthesized material is thermally unstable and gradually decomposes upon annealing to Cu-substituted β-Ca3(PO4)2 and Ca2P2O7.

α-TCP-based Calcium Phosphate Cements: a critical review

Calcium phosphates are promising materials for applications in bone repair and substitution, particularly for their bioactivity and ability to form self-setting cements. Among them, α-tricalcium phosphate (α-TCP) stands out due to its high solubility, its hydration reaction and bioresorbability. The synthesis of α-TCP is particularly complex and the interactions between some of the synthesis parameters are still not completely understood. The variety of methods available to synthesize α-TCP has provided a substantial variance in the properties of α-TCP-based cements and the decision about which method, parameters and starting reagents will be used for the powder's synthesis is determinant of the properties of the resulting material. Therefore, this review paper focuses on α-TCP's synthesis and properties, presenting the synthesis methods currently in use as well as a discussion of how the synthesis parameters and the cement preparation affect the reactivity and mechanical properties of the material, providing a guide for the selection of the most suitable process for each α-TCP application. STATEMENT OF SIGNIFICANCE: α-TCP is a calcium phosphate and it is currently one of the most investigated bioceramics for applications that explore its bioresorbability and the hydration reaction of α-TCP-based cements. Despite the increasing number of publications on the topic, there are still aspects not well understood. This review article aims at contributing to this fascinating subject by offering an update on the state of the art of α-TCP's synthesis methods, while also addressing topics that are not often discussed about this material, such as the preparation of α-TCP-based cements and how its parameters affect the properties of the resulting cements.

Synthesis, structural and luminescent properties of Mn-doped calcium pyrophosphate (Ca2P2O7) polymorphs

In the present work, three different Mn²⁺-doped calcium pyrophosphate (CPP, Ca₂P₂O₇) polymorphs were synthesized by wet co-precipitation method followed by annealing at different temperatures. The crystal structure and purity were studied by powder X-ray diffraction (XRD), Fourier-transform infrared (FTIR), solid-state nuclear magnetic resonance (SS-NMR), and electron paramagnetic resonance (EPR) spectroscopies. Scanning electron microscopy (SEM) was used to investigate the morphological features of the synthesized products. Optical properties were investigated using photoluminescence measurements. Excitation spectra, emission spectra, and photoluminescence decay curves of the samples were studied. All Mn-doped polymorphs exhibited a broadband emission ranging from approximately 500 to 730 nm. The emission maximum was host-dependent and centered at around 580, 570, and 595 nm for γ-, β-, and α-CPP, respectively.