羟基磷灰石及其复合多孔支架材料的研究概况

本文综合论述了羟基磷灰石及其多孔材料的性质,以及Ca—P“溶解－沉淀”机制对羟基磷灰石的骨传导特性的解释,概括了应用于医学骨组织领域的多孔高生物活性羟基磷灰石材料所要求具备的性能要求,并分析了羟基磷灰石复合材料的优点以及研究进展。     

微波辅助合成羟基磷灰石研究

羟基磷灰石由于具有良好的生物相容性和生物活性而应用广泛.本文分别以Ca(NO3)2·4H2O、(NH4)2 HPO4·3H2O为Ca源和P源,采用微波辅助加热的方式合成羟基磷灰石.使用傅里叶红外光谱(FT-IR)、X-射线衍射(XRD)和扫描电镜(SEM)对获得的产物进行了表征.分别研究了微波反应时间、反应功率和原料Ca/P比对合成羟基磷灰石形貌和结晶度的影响.结果表明,不同条件下,产物的形貌与结晶度均有不同.当合成时间为5 min,微波功率为400W,Ca/P比为2.0时,产物为具有结晶良好的羟基磷灰石.     

共沉淀法制备羟基磷灰石影响因素的研究

论述了共沉淀法制备羟基磷灰石粉体的过程,以Ca(OH)2和H3PO4为原料,控制适当Ca/P的比、H3PO4的滴加速率、溶液的pH值、反应温度和时间以及煅烧温度等条件,采用电子显微镜、X射线衍射仪和红外光谱仪对目标产物的结构和粒度进行了分析。结果表明,溶液在40℃下反应6 h,煅烧温度为900℃,产物用无水乙醇洗涤可获得纯度、结晶度、颗粒度和分散性均较好的羟基磷灰石粉体。     

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。     

有机磷化物制备羟基磷灰石工艺条件的探讨

探索用有机磷化物制备羟基磷灰石的工艺条件：采用硝酸钙、氨水、磷酸三丁酯为原料进行正交对比研究，优化得到了制备较佳羟基磷灰石的工艺条件。优化的工艺条件为：原料中Ca／P（molar ratio）1．67；Ca（NO3）2、4H2O／NH3H2O（g／g）为0.99；烧结温度为850℃：恒温时间为5h，并对合成的样品进行了化学和红外光谱的分析。     

等离子喷涂-水热处理制备二氧化钛-羟基磷灰石复合涂层

为克服等离子喷涂羟基磷灰石生物涂层在结合强度和成分上的缺点，通过在钛合金基体上等离子喷涂二水磷酸氢钙和二氧化钻(锐钛矿型)复合粉末，并后续水热处理，制备了二氧化钛—羟基磷灰石复合涂层。结果表明：二水磷酸氢钙和二氧化钛复合粉末的等离子喷涂涂层由CaHPO4,Ca2P2O7,Ca3(PO4)2，非晶磷酸钙和二氧化钛组成。水热处理涂层由羟基磷灰石和二氧化钛组成，升高水热处理温度可提高涂层中羟基磷灰石的结晶性。随着原始粉中二氧化钛加入量的增加，喷涂涂层中磷酸钙的含量和水热处理涂层中羟基磷灰石的含量减少，羟基磷灰石的晶体形貌从细针状变为小颗粒状，喷涂涂层和水热处理涂层的结合强度也随之升高。当二氧化钛的质量分数为60％，水热处理涂层的结合强度可达17MPa。     

碳/碳复合材料表面软复合磷酸钙层

为改进碳／碳复合材料的生物活性，发展了表面软复合磷酸钙层的制备工艺。首先在碳／碳复合材料表面通过离子束辅助沉积技术形成的钛镀层，然后经浓碱液处理后呈多孔网状，该网状结构可在模拟体液（SBF）中诱导沉积出生理磷灰石层，从而在碳／碳复合材料表面形成软复合磷酸钙层。所获得的软复合磷酸钙层厚度约为8μm ，结晶结构为羟基磷灰石，但其Ca,P摩尔比n(Ca)/n(P)低于1．67。     

钙磷比对溶—凝法合成羟基磷灰石特征的影响

讨论了溶液中Ca／P比对溶－凝法合成的羟磷灰石特征的影响。X射线粉末衍射、红外光谱、热分析和比表面积测定结果表明：提高Ca／P比有利于结构碳酸根进入磷灰石晶体结构，使结构畸变加大，结晶度下降，比表面积增大，等效粒径减小。     

羟基磷灰石粉体的制备及生物活性研究

以磷酸氢二铵、硝酸钙和氢氧化钠为起始原料,采用溶胶-凝胶法制备了羟基磷灰石。采用XRD、红外光谱(FTIR)、紫外吸收光谱等测试技术研究了所得样品的物相组成和生物相容性。结果表明,在pH值为10、Ca/P(摩尔比)为1.7、烧结温度为1100℃、烧结时间为2 h时可获得纯度高、纳米尺寸的纯六方晶系结构的羟基磷灰石粉体。吸附实验表明,羟基磷灰石对不同氨基酸的吸附强度不同,供试的两种氨基酸中,羟基磷灰石对L-谷氨酸有显著吸附作用,表明所得羟基磷灰石有较好的生物相容性,是一种良好的骨替代材料。     

锶羟基磷灰石的荧光性能及药物缓释性能

为探索具有荧光性能的锶羟基磷灰石作为骨疾病治疗用药物载体材料的应用前景,以Ca(NO3)2.4H2O)、Sr(NO3)2、(NH4)2HPO4、柠檬酸三钠、十六烷基三甲基溴化铵为原料,在180℃水热处理24h,制得了不同掺锶量的羟基磷灰石。表征了锶羟基磷灰石微球的晶相、形貌、组成、比表面积和荧光性能;研究了以锶羟基磷灰石作为载体,溶菌酶为模型药物的缓释效果。结果表明:合成的产物为花束状羟基磷灰石微球,随着掺锶量的增大,锶羟基磷灰石单球形貌由短棒状变为片状再变为长棒状,而比表面积和荧光强度则先增大后减小。此外,锶羟基磷灰石作为药物载体的缓释速率和释放量,随着锶含量的增大,呈现先减小后增大的趋势。     

Physicochemical and cytological properties of poorly crystalline calcium-deficient hydroxyapatite with different Ca/P ratios

Compared to highly crystalline hydroxyapatite (HA), poorly crystalline hydroxyapatite has been proved to have better bioactivity and degradability, owing to its similar crystallographic structure to natural bone. However, there are few systematic comparative studies on poorly crystalline HA with different Ca/P ratios. In this work, poorly crystalline HA with different Ca/P molar ratios (1.50, 1.55, 1.60 and 1.67) was prepared by chemical precipitation method. The effects of Ca/P ratio on its structure, composition, morphology, surface properties, protein adsorption behaviors, ion adsorption and release abilities, cytological properties were systematically investigated. Results showed that the prepared HA was poorly crystalline, nano-sized and with the gradient change of Ca/P ratios. Protein adsorption capacity and P release of calcium deficient HA (CDHA) were effectively improved by reducing the Ca/P ratio, but CDHA with lower Ca/P ratio would also adsorb more Ca ions in the culture medium, which jointly affected the cytological properties of CDHA. In vitro cell experiments indicated that when mouse bone mesenchymal stem cells were co-cultured with CDHA with a Ca/P ratio of 1.55, their proliferation, ALP activity and osteogenesis-related genes expression were the strongest. This study provides a theoretical support and potential for further improving the biological performance of poorly crystalline CDHA materials.     

Influence of Synthesis Conditions on the Characteristics of Biphasic Calcium Phosphate Powders

Mixtures of hydroxyapatite (HAp) and tricalcium phosphate (TCP) powders with different Ca/P ratios were prepared by a wet chemical precipitation synthesis of calcium-deficient hydroxy apatite (CDHA) and subsequent calcination. The influence of precipitation method and calcination temperature on the chemical and physical properties of the resulting powders were evaluated. Different ratios between HAp and TCP were obtained by variation of the velocity of orthophosphoric acid addition into calcium hydroxide suspension. Slow addition (1 mL/min, S-powder) of H₃PO₄ into Ca(OH)₂ suspension lead to a higher amount of CO₃ groups substituting PO₄ in the apatite lattice compared to powders synthesized by fast addition (200 mL/min, F-powder). Consequently, the Ca/P molar ratio of S-powder (1.55) was higher than that of F-powder (1.52), leading to a higher amount of HAp in the resulting calcinated powders. Both powders show significant differences in their calcinations behavior. Whereas for F-powders a temperature of 750°C was adequate for a complete transformation of CDHA to TCP and HAp, 950°C were required for S-powders.     

Hydroxyapatite formation under calcium-deficient concentration conditions modulated by amino acid-capped gold nanoparticles

This study investigated the effects of the surface modification of gold nanoparticles (AuNPs) with negative, positive, and polar uncharged amino acids on hydroxyapatite formation under calcium-deficient conditions. The AuNPs were prepared using a chemical reduction method and capped with eight different amino acids. The different amino acid (AA) side chains had different interactions with the AuNPs, as indicated by the different shifts in the ultraviolet–visible spectra. The calcium and phosphor sources were added at the same concentration to obtain calcium-deficient hydroxyapatite (CDHA). X-ray diffraction revealed the presence of amino acid-capped AuNPs during synthesis resulting in CDHA with low crystallinity. The calculated crystallinity index (CI) indicated that aspartic acid could promote the crystallization of biomimetic hydroxyapatite. The crystallite size decreased by 6%–62%, which is beneficial for osteoinductivity in bone substitute applications. The involvement of AA-AuNPs in the synthesized hydroxyapatite resulted in apatite with a higher Ca/P ratio than that of the control except for cysteine, lysine, and glutamine. The morphology of the samples ranged from quasi-spherical to needle-like, which can potentially be used as an osteoinductive material.     

Effect of CO32− Incorporation on the Mechanical Properties of Wet Chemically Synthesized β-Tricalcium Phosphate (TCP) Ceramics

Calcium-deficient hydroxyapatite (CDHA) powders were synthesized by a wet chemical precipitation method using Ca(OH)₂ and H₃PO₄ solutions. Single-phase β-tricalcium phosphate (β-TCP) powder with a molar (Ca+Mg)/P ratio of 1.5 was obtained after calcination of CDHA synthesized under vacuum. During synthesis in air, CO₂ can be adsorbed and HBO₄²⁻ is partly substituted by CO₃²⁻, resulting in a lower phosphorous content and consequently an increase of the molar (Ca+Mg)/P ratio to 1.53. A two-phase β-TCP powder containing 20 wt% hydroxyapatite (HA) was obtained after calcination. Samples prepared from β-TCP powders synthesized under vacuum achieved a compressive strength of 301±23 MPa at 99.6% fractional density, while TCP/HA samples prepared in air achieved a maximum compressive strength of 132±29 MPa at 91.7% fractional density. This decrease in strength can be correlated to the porosity retaining due to CO₂ release during sintering and residual tensile stresses in the TCP matrix caused by the thermal expansion mismatch of β-TCP and HA.     

Synthesis of chitin calcium phosphate composite in different growth media

This paper presents some results concerning chitin calcium phosphate composites obtained in different growth media. The synthesis of chitin calcium phosphate composite was carried out by phosphorylation, calcification, and soaking in different calcium phosphate growth media. This research is focused on studying and understanding the effect of using different growth media on composite samples. Hydroxyapatite was determined in the composite samples synthesized by using both simulated body fluid (SBF) and calcium phosphorus tris (Ca‐PTris) solution. Calcium/phosphorus (Ca:P) ratio of the composite synthesized by using SBF was found higher than that of composite synthesized by using Ca‐PTris solution as calcium phosphate growth media. The Ca:P ratio of the composite (1.72) immersed in 1.5× SBF for 35 day is similar to the theoretical value of hydroxyapatite (1.67) and closer to the theoretical value of human bone (1.75). POLYM. COMPOS., 29:84–91, 2008. © 2007 Society of Plastics Engineers     

In vitro behaviour of Nurse's Ass-phase: A new calcium silicophosphate ceramic

In the present study, a new single phase Si–Ca–P-based ceramic (called Nurse's A_ss) was obtained and its in vitro behaviour was explored for potential bone tissue regeneration. A porous Si–Ca–P single phase ceramic was obtained from high-temperature sintering of previously synthesised γ-dicalcium silicate and β-tricalcium phosphate. Apatite-mineralisation ability and the dissolution rate were systematically studied by immersing the material in simulated body fluid (SBF) for several time points. Massive new dense calcium deficient hydroxyapatite (CDHA) layer formation was observed at the SBF-sample interface. Adjacent to the dense CDHA layer, a porous structure developed parallel to the interface, formed by the pseudomorphic transformation of Si–Ca–P (Nurse's A_ss) into CDHA. The cell attachment test showed that the new material supported adult human bone marrow-derived mesenchymal stem cells (hMSCs) adhesion and spreading, and cells came into close contact with the ceramic surface during an extended 28-day culture. These findings indicate that the new calcium silicophosphate ceramic possesses good bioactivity and biocompatibility, and might be a promising bone graft substitute.     

钙磷摩尔比对新型PCCP+DCPA体系骨水泥性能的影响

用化学沉淀法合成了不同钙/磷摩尔比并含碳酸根的部分结晶磷酸钙(partially crystallized calcium phosphates,PCCP),用PCCP和无水磷酸氢钙(dicalcium phosphate anhydrous ,DCPA)配制了PCCP DCPA体系磷酸钙骨水泥,用去离子水作为骨水泥的固化液.通过相组成的X射线衍射分析、扫描电子显微镜观察、孔隙率和抗压强度测定,研究了钙磷摩尔[n(Ca)/n(P)]对PCCP DCPA磷酸钙骨水泥性能的影响.结果表明:随着部分结晶磷酸钙中n(Ca)/n(P)的提高,磷酸钙骨水泥试件的抗压强度明显下降,但磷酸钙骨水泥水化产物羟基磷灰石的结晶度提高,固化体中大于100 nm的孔隙增多、固化体的孔隙率增大,可见,n(Ca)/n(P)对磷酸钙骨水泥的性能有重要影响,在制备磷酸钙骨水泥时应选择适当的n(Ca)/n(P).     

Synthesis and microstructural characterization of nano-size calcium phosphates with different stoichiometry

Calcium phosphates with Ca/P molar ratios of 0.5, 0.75, 1.33, 1.5, 1.55, 1.67, 2.0, and 2.5 were synthesized by a wet chemistry precipitation method and sintered at 500 °C, 700 °C, 900 °C, 1100 °C and 1300 °C for 2 h. Presence of phases and microstructures of calcium phosphates were determined by X-ray diffraction and scanning electron microscopy. In all different Ca/P ratios, the precipitated phase was always hydroxyapatite with very small size and/or partial disorderness regardless of the Ca/P ratios in the starting precipitating medium. For samples with 0.5 and 0.75 Ca/P ratios in starting solution, tricalcium phosphate and calcium pyrophosphate phases were observed. In contrast, for samples with 1.0 and 1.33 Ca/P ratios, the only stable phase was tricalcium phosphate. For the samples with Ca/P ratio of 1.5, the tricalcium phosphate phase was dominant. However, small amounts of hydroxyapatite started to appear. For samples with Ca/P ratio of 1.67, the hydroxyapatite phase was dominant. Lastly, for samples with the Ca/P ratios of 2.0 and 2.5, the CaO phase started to appear in addition to the hydroxyapatite phase which was the dominant phase. Moreover, the average grain size, porosity (%) and the average pore size decreased with increasing the Ca/P ratios.     

The Effects of Calcium‐to‐Phosphorus Ratio on the Densification and Mechanical Properties of Hydroxyapatite Ceramic

In this work, hydroxyapatite (HA) powders were synthesized using calcium hydroxide Ca(OH)₂ and orthophosphoric acid H₃PO₄ via wet chemical precipitation method in aqueous medium. Calcium‐to‐phosphorus (Ca/P) ratio was set to 1.57, 1.67, 1.87 that yield calcium‐deficient HA, stoichiometric HA, and calcium‐rich HA, respectively. These synthesized HA powders (having different Ca/P ratio) were characterized in terms of particle size and microstructural examination. Then, the densification and mechanical properties of the calcium‐deficient HA, stoichiometric HA, and calcium‐rich HA were evaluated from 1000 to 1350°C. Experimental results have shown that no decomposition of hydroxyapatite phase was observed for stoichiometric HA (Ca/P = 1.67) and calcium‐deficient HA (Ca/P = 1.57) despite sintered at high temperature of 1300°C. However, calcium oxide (CaO) was detected for calcium‐rich HA (Ca/P = 1.87) when samples sintered at the same temperature. The study revealed that the highest mechanical properties were found in stoichiometric HA samples sintered at 1100–1150°C, having relative density of ~99.8%, Young's modulus of ~120 GPa, Vickers hardness of ~7.23 GPa, and fracture toughness of ~1.22 MPam^1/2.     

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.