沉淀法制备硅酸钙及其体外生物活性的研究

采用沉淀法制备的硅酸钙粉体经成型,在1200℃下常压烧结,制备出高纯的硅酸钙陶瓷,通过模拟体液浸泡对其体外生物活性进行了研究。X射线衍射(XRD)和扫描电镜(SEM)的结果表明:在1200℃下烧结制得的硅酸钙陶瓷主晶相为β型硅酸钙(-βCS);在模拟体液中浸泡14d后其表面可见类骨羟基磷灰石生成,28d后生成大量羟基磷灰石。因此,沉淀法合成的硅酸钙具有良好的诱导类骨羟基磷灰石形成能力和体外生物活性。     

溶胶-凝胶法制备羟基磷灰石粉体

前言 羟基磷灰石[Ca10（PO4）6（OH）2]（简称HA）化学组成接近生物体骨质的矿物成分，具有良好的生物活性及生物相容性，可以用来修复损坏或者病变的硬组织，在整形外科及口腔修复方面得到了广泛的应用。人们探索了多种方法合成羟基磷灰石粉体，如固相反应法、化学沉淀法、水热合成法以及溶胶-凝胶（sol—gel）法等。     

硼对模拟体液中生物活性玻璃矿化速度的影响

本文采用溶胶-凝胶法合成了生物活性玻璃试样BG-B(含B)和BG-0(不含B),BET比表面积分析仪测试显示,BG-B具有比BG-0较高的比表面积及孔体积.模拟体液中浸泡一定时间后,两试样表面均有羟基磷灰石层矿化层形成.采用原子吸收光谱仪(AAS)测试浸泡不同时间后两试样钙离子溶出情况;X射线衍射仪(XRD)及扫描电子显微镜(SEM)对矿化产物进行了物相组成、结构分析及表面形貌的观察.结果显示,试样BG-B具有较高的Ca2+的溶出及Ca2+、PO43-的沉积速率,其表面优先沉积出矿化层HA.     

溶胶-凝胶法CaO-P2O5-SiO2系生物玻璃的制备及机理探讨

以正硅酸乙酯[Si(OC2H5)4]、四水硝酸钙[Ca(NO3)2*4H2O]等作为前驱体,采用溶胶-凝胶工艺制备CaO-P2O5-SiO2系生物活性玻璃,把制备的样品放在模拟体液中浸泡一段时间后取出,以X-射线衍射、红外光谱等手段对其作物相分析,确定在玻璃的表面有羟基磷灰石相生成,同时对其形成机理做了进一步探讨.     

Mg/HA复合生物材料的制备及表面生物活性评价

用纯镁做基体,以化学沉淀法制备的类球状纳米羟基磷灰石(HA)粉体为增强体,采用粉末冶金法制备了含HA40%的HA/Mg复合材料。对所制备复合材料的组织、物相以及在模拟体液(simulated body fluid,简称SBF)中的生物活性进行了研究。结果表明:HA相均匀分布于镁基体中,形成理想的网状组织结构;复合材料在烧结后内部相组成以HA和Mg为主,烧结过程中没有发生化学反应;随着浸泡时间的延长,表面沉积物质增多,对其进行能谱分析发现沉积物质富含Ca、P和C元素,分析认为生成物为含碳酸根的羟基磷灰石,说明复合材料具有较好的生物活性。     

纳米含氟磷灰石涂层及其在模拟溶液中的行为

以Ca(NO3)2×4H2O和P2O5乙醇溶液为先驱体，六氟磷酸(HPF6)为氟引入剂，采用溶胶-凝胶法在钛合金基板上制备含氟羟基磷灰石涂层. 获得的涂层晶粒尺寸为120~150 nm. 实验结果表明，加入HPF6后形成的含氟磷灰石涂层在模拟体液中有良好的生物活性特性，在柠檬酸改性的磷酸缓冲溶液中表现出较好的稳定性.     

磁性生物活性陶瓷的制备

采用溶胶-凝胶法制备前驱体,经高温烧结制备出磁性生物活性陶瓷。利用体外实验方法,结合X射线衍射、扫描电子显微镜和红外光谱分析了材料结构、晶相和生物活性。结果显示,溶胶-凝胶法可制备出微细的非晶态前驱体粉末,经1 050℃烧结的玻璃陶瓷主晶相为β-硅灰石和铁酸钴、磷硅灰石。陶瓷粉末平均粒径为300 nm。烧结的材料在模拟人体血浆浓度的模拟体液中浸泡7 d,在材料表面可生成大量磷灰石,显示出较好的生物活性。     

纳米羟基磷灰石应用及合成方法

介绍了羟基磷灰石的结构及特性;分别从硬组织修复材料、药物载体及抗肿瘤活性等三方面综述了纳米羟基磷灰石的应用研究进展;总结了目前纳米HA的主要合成方法,如干法合成、微乳液法、沉淀法、溶胶-凝胶法、超声波合成法、水解法、自燃烧法、水热法等及其研究现状。     

医用Ti合金表面生物玻璃涂层的制备与研究

在医用Ti合金表面涂覆一层生物玻璃涂层可阻止金属离子的溶出并且提高其生物活性。本文采用溶胶-凝胶法在Ti合金基体上制备了SiO2-CaO-MgO-P2O5系生物玻璃涂层。利用差示量热扫描仪(DSC)、扫描电镜(SEM)、拉伸试验和模拟体液(SBF)浸泡等手段系统研究了涂层的表面形貌、粘附性能及生物活性。结果表明:热处理温度为800℃时涂层与基体间的粘附强度最大,涂层越薄涂层与基体间的粘附强度越大;在模拟体液中浸泡30天后,材料表面生成了大量磷灰石。用溶胶-凝胶法可在Ti合金基体上制备出SiO2-CaO-MgO-P2O5系生物活性高的生物玻璃涂层。     

A2La8(SiO4)6O2(A=Ca,Sr,Ba)的合成及其导电性能

以溶胶-凝胶法和固相反应方法分别合成了硅酸盐氧基磷灰石A2La8(SiO4)6O2(A=Ca,Sr,Ba),经XRD表征,证明所得产品为磷灰石相.和固相反应方法相比,溶胶-凝胶法合成磷灰石反应温度低,高温焙烧时问短.电化学阻抗谱研究表明:随着A(A=Ca,Sr,Ba)半径的增大,电导率也逐步加大,活化能却逐步减小.700℃时溶胶·凝胶法合成的Ba2La8(SiO4)6O2的电导率(4.42×10-6S·cm-1)要比固相反应法合成的电导率大一个数量级.离子迁移数和氧分压对电导率的研究表明,主要的电荷载体是O2-离子.     

Dissolution behavior of CaO-MgO-SiO2-based bioceramic powders in simulated physiological environments

In this study, the dissolution behavior of CaO-MgO-SiO₂-based bioceramics was investigated in vitro by using a stage-by-stage simulating physiological environment method. Preliminary dissolution rules of CaO-MgO-SiO₂-based bioceramics are presented by soaking akermanite, bredigite, and diopside powders in saline solution. Dissolved Ca and Mg ion concentrations were proportional to the chemical composition of the bioceramics, while the dissolution of Si ion was more affected by their crystal structure. The analysis of zeta potential indicated that ions (possibly including both the dissolved and intrinsic ions) would be adsorbed on the surface of bioceramic powders during soaking in saline solution. Further studies of the dissolution of akermanite powder was performed using different solid-liquid ratios in simulated body fluid (SBF) and α-MEM culture medium. It was found that hydroxyapatite was formed on the surface of akermanite in SBF and amino-containing compounds attracted to the surface of the powders in α-MEM culture medium would impede the diffusion of ions to delay ions release and weaken hydroxyapatite formation. When akermanite powders were co-cultured with BMSCs, HUVECs, or L929 cells, the concentrations of Ca, Mg and Si ions in the solution were lower than that in cell-free medium. Additionally, the pH value gradually decreased with soaking time, unlike what occurs when the materials are soaked in cell-free media, suggesting effects due to the cellular intake of related ions and the release of acidic cellular metabolites. The akermanite extracts in a certain concentration range could promote cell proliferation via cellular intake of related ions. In turn, this ion consumption would affect the dissolution behavior of bioceramics in simulated physiological environments.     

Study of the bioactivity of fluorophlogopite–whitlockite ceramics

Fluorophlogopite–whitlockite phase compositions containing ceramics were prepared using Egyptian raw materials. The in vitro studies confirmed the bioactivity of the prepared mixtures. Finely divided HA layer was formed on the surface of the ceramic samples after immersion in SBF. The morphology of finely divided HA grains was found to be needle-like crystalline aggregates. The contents of calcium cations measured in SBF increased on the seventh day, compared with the first day of immersion which is attributed to dissolution. The values of phosphorous cations were slightly reduced on the seventh day, compared with the first day of immersion that is attributed to the successive dissolution and precipitation.     

Three routes for the synthesis of the bioceramic powder of the CaO-MgO-SiO2 system

We report three routes for the synthesis of CaO-MgO-SiO₂ (CMS) bioceramic powder using different Si sources and synthesis procedures. The ceramic powders were synthesized from Na₂SiO₃ waste solution by the sol-gel process combined with co-precipitation (synthesis route I and synthesis route II), and from TEOS (tetraethyl orthosilicate) by conventional sol-gel (synthesis route III). Ceramic powders of the CMS multiphase system were obtained, including diopside, wollastonite, akermanite, monticellite and merwinite, which are suitable for application as biomaterial. These powders were sintered at 1200 °C for 2 h to obtain the CMS ceramics. The ceramics mostly contained diopside and wollastonite crystalline phases. Those ceramics when submitted to cytotoxicity tests revealed to be non-cytotoxic, according to ISO10993-5:2009. The ceramics were tested for in vitro bioactivity while soaked in simulated body fluid (SBF) solution. After 14 days, the presence of hydroxyapatite particles on the surface of ceramics was confirmed by Fourier Transform Infrared (FTIR) spectroscopy and Scanning Electron Microscopy (SEM) micrographs. The surfaces were completely covered with hydroxyapatite, after 21 days. In summary, CaO-MgO-SiO₂ (CMS) ceramic powder derived from three routes of synthesis have potential application in the biomedical area. However, further in-vitro and in-vivo studies are needed.     

Influence of Sterilization Techniques on the In Vitro Bioactivity of Pseudowollastonite

The purpose of this study was to investigate the effect of four sterilization methods (Steam autoclave, Hydrogen peroxide plasma, Ethylene oxide, and Gamma sterilization) on the surface chemistry and in vitro bioactivity of polycrystalline pseudowollastonite (psW). psW samples obtained by solid-state reaction sintering were sterilized and soaked in Kokubo et al .'s proposed simulated body fluid (SBF) up to 30 days. The sterilization procedure was found to result in no significant chemical changes in the surface of the samples. On the other hand, a Ca/P layer, of different thickness, identified as hydroxyapatite (HA) like, was developed on all the samples after soaking, although the Ethylene oxide-sterilized samples present a non-homogeneous and ∼68% thinner HA layer. The psW samples before soaking were analyzed by X-ray diffraction, raman spectroscopy, and scanning electron microscopy (SEM). The interfacial reaction product was examined by SEM fitted with an energy-dispersive X-ray analyzer. Additionally, changes in ionic concentrations at the psW/SBF interface were measured.     

Synthesis and characterization of hydroxyapatite/β-tricalcium phosphate nanocomposites using microwave irradiation

Microwave assisted synthesis method is a relatively new approach employed to decrease synthesis time and form a more homogenous structure in biphasic calcium phosphate bioceramics. In this study, nanocrystalline HA/β-TCP composites were prepared by microwave assisted synthesis method and, for comparison reason, by conventional wet chemical methods. The chemical and phase composition, morphology and particle size of powders were characterized by FTIR, XRD and SEM, respectively. The use of microwave irradiation resulted in improved crystallinity. The amount of hydroxyapatite phase in BCP ranged from 5% to 17%. The assessment of bioactivity was done by soaking of powder compacts in simulated body fluid (SBF). The decreasing pH of the solution in the presence of β-TCP indicated its biodegradable behavior. Rod-like hydroxyapatite particles were newly formed during the treatment in SBF for microwave assisted substrate synthesis. In contrast, globular particles precipitate under same conditions if BCP substrates were synthesized using conventional wet chemical methods.     

Bioactivity of hydroxyapatite/wollastonite composite films deposited by pulsed laser

Hydroxyapatite/wollastonite (HA/WS) composite films on titanium alloy were prepared by pulsed laser deposition, and their bioactivity was studied. The dissolution and precipitation behaviors of the films were evaluated by soaking in simulated body fluid (SBF), and the osseointegration ability was evaluated by in vivo test. In the early soaking stage, the dissolution action will dominate, thus resulting in the gradual disappearance of the smooth spherical feature of the particles. After 7 days of soaking, new precipitates were observed which indicates that reprecipitation reaction dominates, and the surface was almost completely covered by new precipitates after the film was soaked for 28 days. The in vivo test showed that the composite films have excellent osseointegration ability. When the sample was embedded in the shin bone of rabbit for 3 weeks, a good combination of bone tissue and implant was achieved, and after embedding for 6 weeks, osteoblasts were observed between the bone tissue and implant.     

In vitro apatite formation of calcium phosphate composite synthesized from fish bone

Calcium phosphate-based composite (CPC) is the main biomaterial substitute used for bone repair. Properties affecting bioactivity of this composite vary depending on the types of calcium phosphate crystalline phases. Hence, in this study, bioactivity behavior of novel CPC cement by the incorporation of calcium phosphate (CP), which was obtained from fish bones, dicalcium phosphate dehydrate, and chitosan solution, was monitored in simulated body fluid (SBF). In advance, the microstructure of CP produced by heat treatment (annealing) of fish bone was evaluated at two different temperatures 600 and 900°C. The X-ray diffraction (XRD) results showed that there was no secondary phase formation aside from natural hydroxyapatite (HA) in bones annealed; and the annealing process enhanced the crystallinity of CP phase in the bone matrix particularly when annealed at 900°C. After incubation of CPC cement in SBF, bone bonding ability and producing of biomimetic HA coat on the CPC cement surface were confirmed using XRD, fourier-transform infrared spectroscopy, and scanning electron microscopy. The analysis results show that needle-like and cauliflower apatite layer with the crystallite size about 100 nm was grown on the surface of CPC cement after 28 days incubation in SBF. Regardless of above findings, we conclude that varying the annealing temperature has tremendous effect on the production of natural HA from fish bone with required properties and the ultimate morphology of obtained CPC cements after soaking is directly depended on the degree of crystallinity of the prepared natural HA.     

Mechanical properties,in vitro and in vivo bioactivity assessment of Na2O-CaO-P2O5-B2O3-SiO2 glass-ceramics

Glasses having chemical composition based on Na₂O-CaO-P₂O₅-SiO₂ system were crystallized. Then, the resultant crystallized phases were examined by X-ray diffraction technique. Furthermore, density, microhardness and fracture toughness were measured. In order to investigate the biological responses of these glass-ceramic samples, in vitro and in vivo experiments were performed. In vitro test was performed by soaking the prepared samples in simulated body fluid (SBF) for different time intervals and then, specimens were examined by Fourier transform infrared spectroscopy. Moreover, the conversion kinetics of these samples to hydroxyapatite (HA) were determined by measuring the weight loss of glass-ceramic grains, pH values of SBF solution and recording the ionic concentrations of Si, B, P and Ca using inductive coupled plasma-atomic emission spectroscopy. The results pointed out that the prepared samples possessed fair in vitro bioactivity. However, after six weeks of implantation, the prepared glass-ceramics, on the contrary to the parent glasses, did not exhibit any bioactivity suggesting that they may need longer time. On the other hand, the crystallization process caused significant increases of microhardness and density values. From these results, we can conclude that the prepared glasses and glass-ceramics had suitable properties for bone grafts and dental applications, respectively.