Area-Specific Cell Stimulation via Surface-Mediated Gene Transfer Using Apatite-Based Composite Layers

Surface-mediated gene transfer systems using biocompatible calcium phosphate (CaP)-based composite layers have attracted attention as a tool for controlling cell behaviors. In the present study we aimed to demonstrate the potential of CaP-based composite layers to mediate area-specific dual gene transfer and to stimulate cells on an area-by-area basis in the same well. For this purpose we prepared two pairs of DNA–fibronectin–apatite composite (DF-Ap) layers using a pair of reporter genes and pair of differentiation factor genes. The results of the area-specific dual gene transfer successfully demonstrated that the cells cultured on a pair of DF-Ap layers that were adjacently placed in the same well showed specific gene expression patterns depending on the gene that was immobilized in theunderlying layer. Moreover, preliminary real-time PCR results indicated that multipotential C3H10T1/2 cells may have a potential to change into different types of cells depending on the differentiation factor gene that was immobilized in the underlying layer, even in the same well. Because DF-Ap layers have a potential to mediate area-specific cell stimulation on their surfaces, they could be useful in tissue engineering applications.     

Encapsulation of Hydroxyapatite Microspheres with Fluorapatite Using a Diffusion Process

Modification of hydroxyapatite surfaces can improve the properties of biomedical devices. The objective of this work was to encapsulate hydroxyapatite particles with a fluorapatite layer. A suspension of hydroxyapatite microspheres was prepared in a solution at different pH and treated with ammonium fluoride. pH, calcium, and fluoride were monitored in real time and particles subjected to fluoride analysis. After addition of fluoride, it was found that more material is released from the particle surface at low pH conditions, but leads to a high fluoride uptake from solution. Low solution fluoride levels produce a fluorapatite layer, but higher fluoride levels produce calcium fluoride.     

Mechanochemical Synthesis of Hydroxyapatite from Calcium Oxide and Brushite

Fine hydroxyapatite (HA) powders were prepared by mechanically activating a mixture of calcium oxide and brushite powders in a high-energy shaker mill. A defective HA phase was formed when the starting powder mixture was activated for ≤20 h. When the mixture was calcined at 800°C, it was converted to β-tricalcium phosphate. In contrast, a nanocrystalline HA phase was formed when the mechanical activation was extended to 30 h. The material was transformed to a HA compound (Ca₁₀(PO₄)₆(OH)₂) of high crystallinity when it was calcined at 800°C.     

Chemical Processing of CaHPO4·2H2O:

The aim of this paper is to develop a robust chemical process to synthesize Na- and K-doped brushite (DCPD: dicalcium phosphate dihydrate, CaHPO₄·2H₂O), a potential starting material for bone substitutes. The powders were synthesized by using sodium phosphate and potassium phosphate and aqueous solutions containing calcium chloride at room temperature, followed by drying at 37°C. DCPD powders thus formed were found to contain 460 ppm K and 945 ppm Na. On calcination in air, these powders readily transformed into monetite (DCPA: dicalcium phosphate anhydrous, CaHPO₄) first, and then into Ca₂P₂O₇ (calcium pyrophosphate). Na- and K-doped DCPD powders were shown to completely transform, in less than 1 week, into poorly crystalline carbonated apatite on immersion in an acellular simulated/synthetic body fluid (SBF) solution at 37°C. The Tris (i.e., tris(hydroxymethyl)aminomethane) buffered SBF solution used in this study had a carbonate ion concentration of 27 m M equal to that of human plasma. DCPD powders of this study displayed a notable apatite-inducing ability. This finding suggests the use of these DCPD powders as the starting materials for potential bone substitutes, which can be easily manufactured in aqueous solutions friendly to living tissues, at temperatures between room temperature and 37°C.     

磷酸钙骨水泥水化过程中浆体pH值变化的研究

为避免磷酸钙骨水泥(CPC)浆体固化过程中的pH值变化对人体的不良影响,着重研究了pH值相关影响因素.研究表明:水化过程中CPC的pH值随Ca与P的摩尔比减小而降低,加入晶种,同期pH值变化值降低.颗粒大小不同匹配可调节CPC浆体pH值变化,较大粒径TTCP和较小粒径DCPA匹配有利于得到近中性的pH变化值,适于临床应用.     

纳米羟基磷灰石的溶胶-凝胶制备及其特性研究

采用溶胶-凝胶法制备羟基磷灰石的前体物--无定形磷酸钙(ACP),并进行晶化处理得到纳米羟基磷灰石(HAP).在Ca/P＝1.67的条件下,Ca(OEt)2和H3PO4在乙醇溶液中发生反应,合成ACP凝胶体.采用化学滴定法、透射电镜(TEM),X射线衍射法(XRD),BET,傅立叶红外吸收光谱分析法(FTIR)对晶化处理前后的ACP粉料进行的性能测试表明:溶胶-凝胶法制备的HAP粉料具有粒度小、晶化处理活性高、相纯度和结晶度优良的特点.     

Fabrication of β‐tricalcium phosphate composite ceramic scaffolds based on spheres prepared by extrusion‐spheronization

In this study, β‐tricalcium phosphate/phosphate‐based glass (β‐TCP/PG) composite spheres were prepared by an extrusion‐spheronization method featuring high production and fine control of sphere size. Subsequently, fully interconnected β‐TCP composite ceramic sphere‐based (TCCS) scaffolds were fabricated by sintering the randomly packed β‐TCP/PG composite spheres. The results manifested that at least 20% microcrystalline cellulose (MCC) was required to obtain β‐TCP/PG composite spheres in good spherical shape. The prepared TCCS scaffolds showed hierarchical pore architecture, which consisted of interconnected macropores among the spheres, a hollow core in the sphere, plentiful medium‐sized pores in the sphere shell and micropores among the grains. The pore architecture and mechanical strength of the TCCS scaffolds could be tailored by adjusting the sintering temperature, sphere size, and amounts of PG and MCC in the β‐TCP/PG composite spheres. This work is believed to open up new paths for the design and fabrication of interconnected bioceramic scaffolds for application in bone regeneration.     

医用双相磷酸钙陶瓷的制备工艺研究

医用双相磷酸钙（BCP）陶瓷是β-磷酸三钙（β-TCP）和羟基磷灰石（HA）的复合体,其成分与骨矿物组成类似。它具有良好的生物相容性,在生物医学领域具有非常广阔的应用前景。且在生理环境下能发生不同程度的降解,被组织吸收。通过化学沉淀法制备纳米羟基磷灰石,然后通过可溶性钙盐和磷酸盐反应工艺制得β-磷酸三钙,最后将二者进行机械复合而制得双相磷酸钙,将所得样品用X射线衍射仪（XRD）进行了表征。结果显示：所得的双相磷酸钙中掺杂有β-焦磷酸钙,但是它的结晶较好,并且可以改善双相磷酸钙陶瓷的力学性能。     

自硬化磷酸钙骨水泥的微结构分析

应用SEM研究了磷酸四钙(TTCP)和无水磷酸氢钙(DCPA)组成的磷酸钙骨水泥(CPC)体系水化过程中浆体的微结构.结果表明:完全硬化的CPC由纳米级针状羟基磷灰石微晶组成,微晶与人体骨有类似的低结晶度和结构特性.CPC产物结晶形态与Ca与P摩尔比有关,Ca与P摩尔比减小,CPC水化产物的轴比增大而形态较细长.     

Three​-dimensional porous poly(ε-caprolactone)/beta-tricalcium phosphate microsphere-aggregated scaffold for bone tissue engineering

In this study, porous scaffolds made of polycaprolactone (PCL)/β-tricalcium phosphate (BTCP) biocomposite were fabricated for bone tissue engineering (BTE) applications. The microsphere-aggregated scaffolds were prepared with various BTCP concentrations (10wt%, 20wt%, 50wt%) by the freeze-drying method. The porosity of obtained microsphere-aggregated scaffolds with various pore sizes was 80–85%, where this value was about 70% for the PCL/BTCP (50) sample with no microsphere formation. The results indicated that adding BTCP has enhanced mechanical strength, and the mineralization of PCL/BTCP composite scaffolds has been increased compared to the pure PCL scaffolds in simulated body fluid (SBF). The adhesion and proliferation of mouse bone marrow mesenchymal stem cells (mMSCs) seeded onto PCL/BTCP scaffolds were enhanced compared to the PCL. In addition, in terms of differentiation, the incorporation of BTCP led to increasing the mineral deposition and alkaline phosphatase activity of mMSCs. The synergistic effect of using microsphere-aggregated scaffolds along with BTCP as a reinforcing agent in PCL biocomposite showed that these porous biocomposite scaffolds have the potential application in BTE.     

非陶瓷羟基磷灰石人工骨的研究

磷酸钙骨是一种非陶瓷的新型骨修复材料，它是由几种磷酸钙盐组成的混合物，用水调和后呈糊状物，能在人体的环境和温度下自行固化，其成分最终转化为羟基磷灰石，高的生物相容性和能根据缺损部位塑形的特性使其成为研究的热点。本文综述了磷酸钙骨水泥的组成与特性，涉及磷酸钙的制备，骨水泥自行水化硬化的化学变化过程及其生物相容性研究的等的研究进展。     

针状缺钙羟基磷灰石涂层的烧结特征及磷酸氢钙相的影响

研究了Ｔｉ６Ａｌ４Ｖ表面针状缺钙羟基磷灰石涂层在４５０－９８０℃空气中烧结后的相组成和显微主磷酸氢钙相的影响,分析了缺钙羟基磷灰石的高温分解行为。烧结过程不仅使Ｔｉ６Ａｌ４Ｖ表面形成致密的ＴｉＯ２保护膜,而且获得了对骨组织生长 有利的 式磷灰石＋β－磷酸三钙双相涂层结构。由此使涂层／基体系统的生物特性和力学性能同时得到改善。