在动态模拟体液中致密CaP陶瓷表面形貌对类骨磷灰石层形成的影响研究

磷酸钙陶瓷植入体内后其表面类骨磷灰石层的形成是诱导成骨的先决条件。本实验在模拟体液 (Simu-lated body fluid,SBF)以人体骨骼肌组织的正常生理流率 (2 ml/ 10 0 m l· min)下 ,研究在动态 SBF中致密磷酸钙陶瓷表面形貌对类骨磷灰石层形成的影响。结果表明 :在生理流速条件下 ,材料的粗糙表面有利于类骨磷灰石层的形成 ,加大 SBF中 Ca2 +、HPO4 2 -离子浓度 ,类骨磷灰石层的形成速度加快。本研究进一步证实了材料的几何形貌对类骨磷灰石形成的影响 ,加深了对磷酸钙陶瓷在体内诱导成骨机理的理解     

在不同动物肌肉中磷酸钙陶瓷表面类骨磷灰石的形成研究

磷酸钙陶瓷材料植入动物体内后其表面类骨磷灰石层的形成对骨的形成有非常重要的作用，并被认为是骨诱导发生的先决条件。我们将相同大小的孔壁有微孔的多孔材料和致密磷酸钙陶瓷材料植入猪，狗、兔和鼠的背肌或腿肌内，研究陶瓷表面类骨磷灰石的形成，以了解类骨磷灰石层的形成与骨诱导的联系。结果表明：磷酸钙陶瓷材料植入动物的肌肉内14d后，狗，兔和鼠体内的多孔材料孔隙内表面（包括陶瓷表面较深孔隙）有一层类骨磷灰石层形成；植入猪体内的多孔材料内外表面都形成了一层类骨磷灰石，致密材料在几种动物体内都未观察到类骨磷灰石层形成，类骨磷灰石层形成的快慢次序与动物组织学观察到的在不同动物的肌内骨诱导性高低的次序不一致。证实了类骨磷灰石层的形成的确是骨诱导的先决条件。但还有其它因素影响骨诱导的发生。     

炎性历程模拟体液对多孔HA/β-TCP生物陶瓷类骨磷灰石形成的影响

通过对多孔 HA/β- TCP生物陶瓷在炎性历程模拟体液 (Sim ulated body fluid,SBF)中动态浸泡 (即先在模拟炎性体液 p H6 .5的 SBF中动态浸泡 2 d,再在正常体液 p H7.4的 SBF中动态浸泡 12 d)的类骨磷灰石形成情况的研究后发现 ,模拟炎性历程的微酸性会溶解材料表面颗粒较细或曲率半径较小的部分 ,使材料表面变得光滑和溶解性能下降 ,在随后正常体液的 p H值下类骨磷灰石的形成量明显减少 ,这为理解钙磷生物陶瓷植入体内的诱导成骨机理和在体外筛选骨诱导性较好的钙磷材料提供了更可靠的方法。另外 ,实验结果还显示 ,用微波等离子体烧结的多孔 HA/β- TCP生物陶瓷 ,在正常 SBF和模拟了炎性历程的 SBF的动态实验中 ,其类骨磷灰石形成情况都好于用常规马弗炉烧结的样品 ,这预示用微波等离子体烧结的多孔 HA/β- TCP生物陶瓷可能具有更好的骨诱导活性。     

模拟体液中生物大分子对类骨磷灰石矿化的影响

为考察体内生物大分子对羟基磷灰石（hydroxyapatite,HA）基底表面矿化物形成的影响,将牛血清白蛋白（bovine serum albumin,BSA）和硫酸软骨素（chondroitin sulfate,CS）大分子分别浸入模拟体液（SBF）中制备成2种矿化介质,再将HA浸入上述矿化介质中3d观察类骨磷灰石形成过程.结果 发现HA基底表面均沉积有Na＋和CO2-3取代的类骨磷灰石（Ca3.78Na0.02）（Ca5.22Na0.48）（CO3）1.5（OH）.BSA在2SBF中的存在促进了类骨磷灰石晶体在基材表面沉积,有利于其沿（300）晶面择优取向生长.CS对类骨磷灰石晶体的生长呈阻碍作用,获得的晶粒尺寸较小.模拟体液中BSA和CS大分子对类骨磷灰石晶体生长和形貌等均有一定的作用.     

仿生浸泡对碳酸根掺杂的钙磷生物陶瓷表面的影响

钙磷生物陶瓷表面类骨磷灰石层的形成对其诱导新骨生成起非常重要的作用。为了研究碳酸根掺杂的钙磷生物陶瓷其表面类骨磷灰石层形成的能力,利用体外模拟装置首次研究了碳酸根掺杂的钙磷生物陶瓷材料在仿生浸泡的过程其表面的类骨磷灰石层形成的变化。结果表明,钙磷生物陶瓷因有CO3^2-的存在,导致该材料形成类骨磷灰石晶体的时间大大提前。并且在-βTCP含量较低的相组成下（HA/-βTCP之比为9/1）,该陶瓷在与模拟体液（SBF）作用较短的时间内（约9d）就能形成类骨磷灰石晶体。而不含CO3^2-的钙磷生物陶瓷却只能与SBF液作用较长时间（约14d）才开始形成类骨磷灰石晶体。在相同的作用时间内,含CO3^2-的钙磷生物陶瓷所形成的类骨磷灰石晶体的情况远远优于不含CO3^2-的钙磷生物陶瓷。此外,还有部分的缺钙羟基磷灰石晶体的形成。钙磷生物陶瓷中CO3^2-的掺杂引入,有利于该材料生物活性的提高,进而有利于骨缺损的快速修复。     

原位法制备羟基磷灰石/聚乳酸纳米复合材料的体外生物学研究

通过羟基磷灰石/聚乳酸(HA/PLLA)纳米复合材料在模拟体液(SBF)中的浸泡实验评价该材料的生物学性能。测试发现HA/PLLA纳米复合材料在浸泡过程中SBF的pH值呈现下降趋势,HA的存在缓冲了PLLA的酸性;复合材料表面有类骨磷灰石层沉积,并有"蚕茧状"类骨磷灰石颗粒和夹有短棒状晶体的片状晶体簇生成;同时复合材料的降解导致表面形成大量蜂巢状多孔。因此原位法制备的HA/PLLA纳米复合材料具有较好的生物活性和可降解性。     

改性玻璃陶瓷在模拟体液中类骨磷灰石层形成的研究

研究用等离子体活化改性玻璃陶瓷(BGC)，并用模拟体液(SBF)中类骨磷灰石的形成、体外成骨细胞培养、SEM、XPS、XRD等对其进行表征。结果表明：与活化改性前相比较，等离子体活化改性后的BGC更有利于类骨磷灰石的形成，并能促进成骨细胞增殖。等离子体中丰富的高能、高活性的粒子轰击BGC，使其被刻蚀和粗化，增加了表面的溶解性和提供了更多的活性位点，易使局域的钙、磷离子浓度达到过饱和，更利于类骨磷灰石的成核和生长。表明等离子体改性提高了BGC的生物活性。     

多孔结构对碳酸化羟基磷灰石骨水泥溶解度的影响

目的探讨碳酸化羟基磷灰石骨水泥中多孔结构存在的意义及其对溶解性能的影响.方法合成能原位固化形成多孔结构的碳酸化羟基磷灰石骨水泥,并通过扫描电镜和模拟体液浸泡实验,观察其孔隙结构和失重率变化.结果多孔碳酸化羟基磷灰石骨水泥固化后的孔隙率为42%,平均孔径为153μm,孔之间以90μm左右的连通孔互相贯通,孔隙结构与松质骨相似.碳酸化羟基磷灰石的多孔结构增加了其比表面积,利于体液循环.经模拟体液浸泡后,其失重率的改变比普通型碳酸化羟基磷灰石骨水泥明显增加,二者差异显著.结论碳酸化羟基磷灰石骨水泥内部的多孔结构能促进其体外溶解.     

新型羟基磷灰石多孔支架的制备与性状

背景：目前几种钙羟磷灰石作为骨的替代品已经在临床上使用,但是由于缺少内部交互的连通孔,使得骨形成过程中经常发生病理性的骨折。 目的：采用改良的技术制备互联多孔羟磷灰石陶瓷支架材料,并对其物理化学特征进行检测。 方法：将羟基磷灰石(质量分数60%)与聚乙烯亚胺质量分数40%混合,采用改良的泡沫凝胶技术技术(聚氧乙烯十二烷基醚质量分数1%)制备多孔羟磷灰石陶瓷。扫面电镜检测材料内部结构,将制备的材料移植动物体骨缺损区观察成骨情况。 结果与结论：多孔羟磷灰石陶瓷具有三维结构,内部充满大小较均一的球形孔隙,直径平均为150 μm,孔隙率75%,孔隙上充满窗孔样相互交通的小洞,平均40 μm, 具有足够的抗压度(10~12 MPa)。动物实验表明,多孔羟磷灰石陶瓷表现出较好的成骨诱导性,可见孔隙里形成了新生骨。结果提示改良的羟基磷灰石支架能够在骨组织工程上应用,有望成为新型的改良品。     

激光气体氮化改性NiTi形状记忆合金

为了提高生物医用材料NiTi形状记忆合金的生物活性，采用高功率连续波Nd：YAG激光辐照，在置于N，反应室中的NiTi形状记忆合金表面制备TiN激光改性层，考察改性层在37℃模拟人体体液SBF溶液中类骨磷灰石的形成能力。采用扫描电子显微镜、X射线能量损失谱仪、傅立叶转换红外光谱仪研究和分析样品表面沉积层的组织形貌、成分及沉积物的结构随沉积时间的变化规律，进而探讨激光改性层表面类骨磷灰石沉积层的形成过程。实验结果表明，激光气体氮化可显著改善NiTi形状记忆合金在体外模拟环境条件下诱导类骨磷灰石沉积的能力，其在37℃SBF溶液中沉积物成分与人体内磷灰石成分接近，Ca、P摩尔比为1．57。     

Mechanism of apatite formation on pure titanium treated with alkaline solution

The mechanism of bone-like apatite formation on the surface of pure titanium pretreated with NaOH solution is still being investigated. The apatite formation may depend on the solution that is used. In the present study, several types of solutions such as simulated body fluid (SBF), calcium aqueous solution (CAS), and phosphate aqueous solution (PAS) were used to investigate bone-like apatite formation on alkali-treated titanium. In order to observe the effect of hydrolysis on the apatite formation, experiments of pretreated titanium immersed in distilled water before the immersion in SBF were also conducted. The results showed that the mechanism of apatite formation was the hydrolysis reaction of sodium titanate which induced the apatite formation. The pre-precipitation of either calcium or phosphate could prevent the apatite formation on the surface of alkaline treated titanium.     

Formation of bone-like apatite enhanced by hydrolysis of octacalcium phosphate crystals deposited in collagen matrix

It has been shown that granules of synthetic octacalcium phosphate (OCP) or the composites with collagen are capable of enhancing bone regeneration, accompanied by a gradual conversion from OCP to apatite with time. The present study was designed to investigate whether formation of bone-like apatite can be accelerated by OCP deposited throughout collagen matrix (OCP collagen complex, OCC) immersed in simulated body fluid (SBF). The formation of bone-like apatite has been suggested to be essential to induce osteoconductivity of various substrates. The formation of OCP in collagen solution was investigated in calcium or phosphate ions in the range between 22.5 and 142.5 mM and pH 6.26 and 8.56. X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy (SEM) showed that condition to nucleate OCP was limited to that of a solution with Ca/P 0.43 around pH 7.16 in the presence of collagen. OCP was shown to be formed throughout the collagen matrix by SEM observation. The immersion of OCC in SBF up to 10 days enhanced apatite crystal deposition, probably through OCP-apatite conversion: the apatite formation in OCC took place within only 1 day. The present study indicated that the existence of OCP deposited throughout the collagen matrix promotes bone-like apatite formation under physiological condition.     

TEM study of calcium phosphate precipitation on HA/TCP ceramics

This study focuses on phase identification of precipitation on bioactive calcium phosphate (BCP) surfaces in vitro and in vivo. The BCP used in this study consisted of 70 wt% hydroxyapatite (HA) and 30 wt% beta-tricalcium phosphate. Single crystalline precipitates of calcium phosphates on porous BCP bioceramics obtained after immersion in dynamic simulated body fluid (SBF) and after implantation in pig muscle were examined using electron diffraction in transmission electron microscope. The crystals formed in vitro in dynamic SBF were identified as octacalcium phosphate (OCP), instead of apatite. Most of the precipitated crystals in vivo samples had an HA structure; while OCP and dicalcium phosphate dihydrate were also identified. The evidence from single diffraction patterns indicates that apatite formation on bioactive ceramics is a complicated process, particularly in physiological environments where formation might include a transient stage of intermediate phases.     

Processing and properties of porous poly(L-lactide)/bioactive glass composites

Porous poly(L-lactide)/bioactive glass (PLLA/BG) composites were prepared by phase separation of polymer solutions containing bioactive glass particles (average particle size: 1.5 microm). The composite microstructures consist of a porous PLLA matrix with glass particles distributed homogeneously throughout. Large pores (>100 microm) are present in a network of smaller (<10 microm) interconnected pores. The porous microstructure of the composites was not significantly influenced by glass content (9 or 29 vol%), but silane pretreatment of the glass resulted in better glass incorporation in the matrix. Mechanical tests showed that an increase in glass content increased the elastic modulus of the composites, but decreased their tensile strength and break strain. Silane pretreatment enhanced the increase in modulus and prevented the decrease in tensile strength with increasing glass content. Composites soaked in simulated body fluid (SBF) at body temperature formed bone-like apatite inside and on their surfaces. The silane pretreatment of glass particles delayed the in vitro apatite formation. This bone-like apatite formation demonstrates the composites' potential for integration with bone.     

Coating of an apatite layer on polyamide films containing sulfonic groups by a biomimetic process

Coating organic polymers with hydroxyapatite is an attractive method for the development of materials for medical applications, as it allows hydroxyapatite to show its unique biological properties such as its ability for bone bonding and protein adsorption. The biomimetic process focuses attention on fabricating such hydroxyapatite-polymer hybrids, where bone-like apatite is deposited on an organic polymer surface in solutions mimicking physiological conditions. In this process, a bone-like apatite layer can be coated onto organic substrates either by using a simulated body fluid (SBF), which has ion concentrations nearly equal to those of human extracellular fluid, or by using fluids that are supersaturated with respect to apatite at ambient conditions. We previously reported that apatite was deposited on polyamide films containing carboxyl groups in a solution mimicking body fluid, when they were incorporated with calcium salts. In the present study, to find an alternative functional group effective in apatite formation, we examined the apatite-forming ability of polyamide films containing sulfonic groups in the same solution. It was found that the polyamide film containing sulfonic groups could deposit apatite on its surface in the solution when the film was incorporated with calcium salts. These results show that the sulfonic group also acts as a functional group, and is as effective for apatite deposition in the body environment as the carboxyl group.     

Surface potential change in bioactive titanium metal during the process of apatite formation in simulated body fluid

Bioactive titanium metal can be prepared by NaOH and heat treatments that present the metal with a graded bioactive surface layer of amorphous sodium titanate. This study used laser electrophoresis together with transmission electron microscopy (TEM) and energy-dispersive X-ray microanalysis (EDX) to relate the surface potential change of the bioactive titanium metal with its surface structural change in simulated body fluid (SBF). The surface potential of the metal was highly negative immediately after immersion in SBF. With increasing soaking time, the surface potential increased, revealing a maximum positive value, and then decreased to a constant negative value. TEM-EDX showed that immediately after immersion in SBF, the metal surface formed Ti-OH groups by exchanging Na(+) ions in the surface sodium titanate with H3O(+) ions in the fluid. Thereafter, with increasing soaking time the metal surface formed an amorphous calcium titanate, then an amorphous calcium phosphate, and, finally, apatite with bone-like composition and structure. These results indicate that the process of apatite formation on bioactive titanium metal is initiated by the formation of Ti-OH groups with negative charges that interact with calcium ions with positive charges to form calcium titanate. The calcium titanate gains a positive charge and later interacts with phosphate ions with negative charges, forming amorphous calcium phosphate. The amorphous calcium phosphate eventually transforms and stabilizes into bone-like crystalline apatite with a negative charge.     

In vitro bioactivity of a biocomposite fabricated from HA and Ti powders by powder metallurgy method

Traditionally, hydroxyapatite was used as a coating material on titanium substrate by various techniques. In the present work, a biocomposite was successfully fabricated from hydroxyapatite and titanium powders by powder metallurgy method. Bioactivity of the composite in a simulated body fluid (SBF) was investigated. Main crystal phases of the as-fabricated composite are found to be Ti2O, CaTiO3, CaO, alpha-Ti and a TiP-like phase. When the composite is immersed in the simulated body fluid for a certain time, a poor-crystallized, calcium-deficient, carbonate-containing apatite film will form on the surface of the composite. The time required to induce apatite nucleation is within 2 h. In addition, the apatite is also incorporated with a little magnesium and chlorine element. It is found that Ti2O has the ability to induce the formation of bone-like apatite in the SBF. And a dissolve of the CaO phase could also provide favorable conditions for the apatite formation, by forming open pores on the surface of the composite and increasing the degree of supersaturation of the SBF with respect to the apatite.     

Hydroxyapatite formation on alkali-treated titanium with different content of Na+ in the surface layer

Titanium can form a bone-like apatite layer on its surface in SBF when it is treated in NaOH. When pre-treated titanium is exposed to SBF, the alkali ions are released from the surface into the surrounding fluid. The Na+ ions increase the degree of supersaturation of the soaking solution with respect to apatite by increasing pH. On the other hand, the released Na+ cause an increase in external alkalinity that triggers an inflammatory response and leads to cell death. Therefore, it would be beneficial to decrease the release of Na+ into the surrounding tissue. The purpose of this study was to evaluate the hydroxyapatite formation on alkali-treated titanium with different content of Na+ in the surface layer. Using SEM, gravimetric analysis and measurement of calcium and phosphate concentration, it was found that the rate of apatite formation was not significantly influenced by a lower amount of Na+ in the surface layer. Titanium with the lowest content of Na+ could be more suitable for implantation in the human body. The amount of alkali ions released in the surrounding tissue is lower and the rate of apatite formation is identical to titanium with the highest content of Na+ in the surface layer.