Nano-amorphous calcium phosphate doped with citrate: Fabrication, structure, and evaluation of the biological performance

Abstract

Amorphous calcium phosphate, a precursor phase of the bone mineral in vertebrates, is limited owing to its instability. A simple wet-chemical precipitation method was developed in this study to prepare stable and nanosized amorphous calcium phosphates doped with citrate using orthophosphoric acid, anhydrous critic acid, and anhydrous calcium chloride as the raw materials in an alcohol system at room temperature. The structure of the obtained nanosized amorphous calcium phosphate doped with citrate was evaluated by an X-ray diffraction analysis, Fourier transform-infrared spectroscopy, X-ray photoelectron spectrometry, high-resolution transmission electron microscopy and selected area electron diffraction. In addition, Ca and P ions release profile was investigated in the simulated bodily fluid solution for two weeks, and the biological performance was evaluated using in vitro mineralization and cell viability studies. The results demonstrated that the synthetic specimens in the presence of citrate had a similar structure, and their dimensions were in the nanoscale. Furthermore, the specimens possessed excellent apatite mineralization ability in simulated bodily fluid solution and a stimulatory effect on the cell viability of mouse bone-marrow stem cells. The S0.050 specimen displayed the maximum amount of Ca (152.5 ppm) and P (81 ppm) ions release at the third day and the best bioactivity and cell viability. Based on all of the results, it was concluded that the stability and bioactivity of nanosized amorphous calcium phosphates were improved by doping with citrate. Thus, bone graft substitutes could potentially be modified by the addition of citric acid to affect their performance in bone repair and regeneration.

Biological evaluation of the modified nano-amorphous phosphate calcium doped with citrate/poly-amino acid composite as a potential candidate for bone repair and reconstruction

“…Moreover, it is found that the n-ACP owns the higher reactivity, biological activity, and biocompatibility due to its larger specific surface area, but n-ACP is unstable. As our previous work [4], the results suggested that we successfully obtained the stable n-ACP doped with citrate (n-ACP-cit). Hence, the stable n-ACP-cit could be considered as a promising filling material owing to their biocompatible and bioactive properties in bone repair and regeneration.…”

“…The n-ACP-cit/PAA composites were synthesized using melt extrusion method. Firstly, n-ACP-cit powder was prepared according to our previous publication [4]. Secondly, PAA copolymer was obtained as followings: 6.56 g Lhydroxyproline, 8.91 g L-alanine, 36.09 g γ-aminobutyric acid, and 65.59 g 6-aminocaproic acid (Shanghai Experimental Reagents Co., Ltd., China) were added to a 250.00 ml reaction flask.…”

“…Mass loss rate (wt.%) = (M 0 -M i ) / M 0 × 100% At the same time, the degradation solutions were measured by pH meter at specific time periods (1,2,3,4,6,8,12, and 16 weeks) and each sample was in triplicate, and then took their mean values.…”

Amorphous Calcium Phosphate and Amorphous Calcium Phosphate Carboxylate: Synthesis and Characterization

“…In the scientific literature, the synthesis of ACP is usually described as a simple one-step process; on the contrary, ACPC is synthesized by a multistep process. − As shown in Figure , Scheme 1, the precursor of COO – -containing small organic molecules is either used in the acidic or basic form, which can lead to variation in pH, making the reaction tedious, expensive, and affecting the final product. Moreover, ACP/ACPC reactions are rapidly performed at alkaline pH.…”

“…Synthesis mechanism of ACPC. Scheme 1 represents the traditional synthesis approach in which citrate is used as an acid or a base. − The reaction of ACPC synthesis is rapid, and due to the triprotic nature of phosphate, fluctuation in pH disturbs the protonated forms of phosphates, which can affect the final product. Scheme 2 represents our synthesis approach in which citrate was used as a calcium salt, and pH adjustments were made before mixing of calcium and phosphate sources.…”