Octacalcium Phosphate Fiber Synthesized by Homogeneous Precipitation Method

Calcium phosphate fiber was synthesized by homogeneous precipitation method using urea as precipitation agent. Effects of the reactant concentration and hydrothermal temperature on the calcium phosphate morphology and composition were studied using SEM, FTIR and XRD. It is found that fine octacalcium phosphate（OCP）fiber can be synthesized when the reactant concentrations are 0.167 mol/L for Ca（NO3）2, 0.1 mol/L for （NH4）2HPO4, and 0.6-0.7 mol/L for （NH2）2CO, respectively, with the initial reactant solution pH value around 2.2, hydrothermal temperature 90 ℃ and termination reaction at pH value around 5.0. At very low urea concentration, the product size distribution is highly inhomogeneous, however, at an excessively high concentration the product becomes larger and shorter and a mixture of OCP and hydroxyapatite （HA）. Increasing the hydrothermal temperature is favorable to the fast precipitation of OCP, higher productivity and finer product.

A thermostability perspective on enhancing physicochemical and cytological characteristics of octacalcium phosphate by doping iron and strontium

Investigation of thermostability will lead the groundbreaking of unraveling the mechanism of influence of ion-doping on the properties of calcium phosphates.In this work,octacalcium phosphate(OCP),a metastable precursor of biological apatite,was used as a stability model for doping ions(Fe^(3+)and Sr^(2+))with different ionic charges and radii.After treated under hot air at different temperatures(110-200◦C),the phase,morphology,structure,physicochemical properties,protein affinity,ions release,and cytological responses of the ion-doped OCPs were investigated comparatively.The results showed that the collapse of OCP crystals gradually occurred,accompanying with the dehydration of hydrated layers and the disintegration of plate-like crystals as the temperature increased.The collapsed crystals still retained the typical properties of OCP and the potential of conversion into hydroxyapatite.Compared to the undoped OCP,Fe-OCP,and Sr-OCP had lower and higher thermostability respectively,leading to different material surface properties and ions release.The adjusted thermostability of Fe-OCP and Sr-OCP significantly enhanced the adsorption of proteins(BSA and LSZ)and the cytological behavior(adhesion,spreading,proliferation,and osteogenic differentiation)of bone marrow mesenchymal stem cells to a varying extent under the synergistic effects of corresponding surface characteristics and early active ions release.This work paves the way for understanding the modification mechanism of calcium phosphates utilizing ion doping strategy and developing bioactive OCP-based materials for tissue repair.

Lanthanum doped octacalcium phosphate/polylactic acid scaffold fabricated by 3D printing for bone tissue engineering

Lanthanum(La)has tremendous potential in the treatment and prevention of bone diseases especially osteoporosis and metabolic disorders.However,controlling its distribution and keeping the release of La^(3+)ions sustained and steady in the body is still a big challenge.In this study,we prepared La-OCP powders via co-precipitation method,and further prepared La-OCP/PLA porous scaffolds by 3 D printing.La^(3+)was successfully introduced into the OCP crystal structure and substituted Ca^(2+)at the Ca-5 and Ca-8 sites.In particular,some La^(3+)ions were deposited on the crystal surface in the form of nanoparticles.Both octacalcium phosphate(OCP,Ca_(8)H_(2)(PO_(4))_6·5 H_(2)O)crystals and nanoparticles played as the carriers for La^(3+)ions.The La-OCP/PLA scaffolds displayed obvious mineralization effects and sustained release of La^(3+).The scaffolds contained a uniform structure with rough micro surface topography which acted as a suitable pathway for BMSCs cells to adhere,grow and proliferation.At a certain La^(3+)concentration,the extracts from La-OCP/PLA scaffolds increased the expression of osteogenesis-related genes,thus promoting the osteogenic differentiation of BMSCs.Moreover,the extracts regulated the immune responses.The experiment in vivo proved that La-OCP/PLA porous scaffolds were safe and could enhance bone defect regeneration in vivo.These findings suggest that 3 D printed La-OCP/PLA porous scaffolds have promising potentials in bone tissue engineering.

Structural modification of titanium surface by octacalcium phosphate via Pulsed Laser Deposition and chemical treatment

In the present study, the Pulsed Laser Deposition (PLD) technique was applied to coat titanium for orthopaedicand dental implant applications. Calcium carbonate (CC) was used as starting coating material.The deposited CC films were transformed into octacalcium phosphate (OCP) by chemical treatments. Theresults of X-ray diffraction (XRD), Raman, Fourier Transform Infrared Spectroscopy (FTIR) and scanningelectron microscopy (SEM) studies revealed that the final OCP thin films are formed on the titaniumsurface. Human myofibroblasts from peripheral vessels and the primary bone marrow mesenchymalstromal cells (BMMSs) were cultured on the investigated materials. It was shown that all the investigatedsamples had no short-term toxic effects on cells. The rate of division of myofibroblast cells growing onthe surface and saturated BMMSs concentration for the OCP coating were about two times faster than ofcells growing on the CC films.

Pathogenic Mineralization of Calcium Phosphate on Human Heart Valves

When calcium phosphate forms in soft tissues such as blood vessels and heart valves, it causes disease. The abnormal formation of calcium phosphate is called pathogenic mineralization or pathogenic calcification. Cases of rheumatic heart disease （RHD） always occur with fibrotic and calcified tissue of heart valve. In this article, samples taken from calcified human heart wdves were studied. The characterization was performend by scanning electronic microscope, X-ray Diffraction and transmission electron microscopy with selective diffraction patterns. It is found for the first time that calcium phosphate grains existing in the calcified human heart valves contain octacalcium phosphate （ OCP ）.