A Natural Bone Cement—A Laboratory Novelty Led to the Development of Revolutionary New Biomaterials

Research on calcium phosphate chemistry at NIST led to the discovery of the worlds first self-hardening calcium phosphate cements (CPC) in 1987. Laboratory, animal, and clinical studies were conducted to develop CPC into clinically useful biomaterials. The combination of self-hardening capability and high biocompatibility makes CPC a unique material for repairing bone defects. Near perfect adaptation of the cement to the tissue surfaces in a defect, and a gradual resorption followed by new bone formation are some of the other distinctive advantages of this biomaterial. In 1996 a CPC, consisting of tetracalcium phosphate and dicalcium phosphate anhydrous, was approved by the Food and Drug Administration (FDA) for repairing cranial defects in humans, thus becoming the first material of its kind available for clinical use. This paper will review the course of the development, the physical and chemical properties, and clinical applications of CPC.     

In Vivo Characteristics of Premixed Calcium Phosphate Cements When Implanted in Subcutaneous Tissues and Periodontal Bone Defects

Previous studies showed that water-free, premixed calcium phosphate cements (Pre-CPCs) exhibited longer hardening times and lower strengths than conventional CPCs, but were stable in the package. The materials hardened only after being delivered to a wet environment and formed hydroxyapatite as the only product. Pre-CPCs also demonstrated good washout resistance and excellent biocompatibility when implanted in subcutaneous tissues in rats. The present study evaluated characteristics of Pre-CPCs when implanted in subcutaneous tissues (Study I) and used for repairing surgically created two-wall periodontal defects (Study II). Pre-CPC pastes were prepared by combining CPC powders that consisted of CPC-1: Ca(4)(PO(4))(2)O and CaHPO(4), CPC-2: α-Ca(3)(PO(4))(2) and CaCO(3) or CPC-3: DCPA and Ca(OH)(2) with a glycerol at powder-to-liquid mass ratios of 3.5, 2.5, and 2.5, respectively. In each cement mixture, the Ca to P molar ratio was 1.67. The glycerol contained Na(2)HPO(4) (30 mass %) and hydroxypropyl methylcellulose (0.55 %) to accelerate cement hardening and improve washout resistance, respectively. In Study I, the test materials were implanted subcutaneously in rats. Four weeks after the operation, the animals were sacrificed and histopathological observations were performed. The results showed that all of the implanted materials exhibited very slight or negligible inflammatory reactions in tissues contacted with the implants. In Study II, the mandibular premolar teeth of mature beagle dogs were extracted. One month later, two-wall periodontal bone defects were surgically created adjacent to the teeth of the mandibular bone. The defects were filled with the Pre-CPC pastes and the flaps replaced in the preoperative position. The dogs were sacrificed at 1, 3 and 6 months after surgery and sections of filled defects resected. Results showed that one month after surgery, the implanted Pre-CPC-1 paste was partially replaced by bone and was converted to bone at 6 months. The pockets filled with Pre-CPC-2 were completely covered by newly formed bone in 1 month. The Pre-CPC-2 was partially replaced by trabecular bone in 1 month and was completely replaced by bone in 6 months. Examination of 1 month and 3 month samples indicated that Pre-CPC-2 resorbed and was replaced by bone more rapidly than Pre-CPC 1. Both Pre-CPC pastes were highly osteoconductive. When implanted in periodontal defects, Pre-CPC-2 was replaced by bone more rapidly than Pre-CPC-1.     

可注射磷酸钙骨水泥的研究进展

可注射磷酸钙骨水泥以其良好的生物相容性、骨传导性和可降解性等优点被广泛应用于临床的骨替换和修复等领域。综述了磷酸钙骨水泥(CPC)注射性能的评价指标,提出了评价CPC注射性能的有效方法,讨论了骨水泥的注射体系、制备方法和组成等对CPC注射性能的改进措施,并在此基础上探讨了CPC存在的问题及对策。     

可注射镁基磷酸钙骨水泥的研究

采用MgO、KH₂PO₄、β-TCP、葡萄糖作为骨水泥的固相, 磷酸溶液作为液相, 制备可注射镁基磷酸钙骨水泥(IMPC)。考察液固比(LPR)、MgO含量、葡萄糖含量变化对IMPC胶凝性能和力学性能的影响。实验结果显示: 液固比和缓凝剂葡萄糖含量增大均会导致凝结时间变长和抗压强度下降, 但有益于可注射性; 随MgO含量增大, 凝结时间缩短, 可注射率降低, 但抗压强度提高。采用正交实验法确定MgO含量26wt%, 液固比0.30 mL/g, 葡萄糖含量6wt%时得到的IMPC综合性能良好, 水化过程缓和, 放热量低。该IMPC有望成为一种新型骨粘结材料。     

可注射磷酸钙骨水泥的流变性能研究

采用高级流变扩展系统研究了添加剂种类及其含量对可注射磷酸钙骨水泥(ICPC)流变特性的影响。采用稳态流动实验表征浆体的静态粘度,用触变环面积、应力降低率和屈服应力表征ICPC浆体的触变性,并进行动态频率扫描和动态时间扫描实验动态监测ICPC的粘、弹、塑性变化规律以及水化反应过程流变参数的依时性。结果表明:添加剂并不改变ICPC的粘弹性。水溶性高分子化合物的加入提高了ICPC的粘度和触变性,利于整个体系的稳定;添加剂不同程度上提高了ICPC剪切后的网络结构恢复能力和稳定性,尤其以黄原胶和几丁糖最为明显。在此基础上,评估了加入黄原胶后ICPC形成凝胶的时间,约为2 563～2 600 s。此外,随着黄原胶含量的增加,ICPC触变环面积增加,但形成的网络结构在高剪切状态下并不稳定。     

磷酸钙骨水泥理化性能改进的研究进展

磷酸钙骨水泥(CPC)作为骨修复材料近年来已在临床广泛应用,但因材料特性使其在应用时存在某些缺陷,需要加以改进。在本文中,我们综合评述了目前对CPC在调整固化时间,增加机械强度,提高生物降解性三方面所作出的理化性能改进的研究,并且阐述了以CPC为载体与药物、生长因子等构建复合物,以更好修复骨缺损的实验研究进展。     

In Vitro and in Vivo Characteristics of Fluorapatite-Forming Calcium Phosphate Cements

This study reports for the first time in vitro and in vivo properties of fluorapatite (FA)-forming calcium phosphate cements (CPCs). The experimental cements contained from (0 to 3.1) mass % of F, corresponding to presence of FA at levels of approximately (0 to 87) mass %. The crystallinity of the apatitic cement product increased greatly with the FA content. When implanted subcutaneously in rats, the in vivo resorption rate decreased significantly with increasing FA content. The cement with the highest FA content was not resorbed in soft tissue, making it the first known biocompatible and bioinert CPC. These bioinert CPCs might be useful for applications where slow or no resorption of the implant is required to achieve the desired clinical outcome.     

Properties of Fujicalin®, a New Modified Anhydrous Dibasic Calcium Phosphate for Direct Compression: Comparison with Dicalcium Phosphate Dihydrate

The novel, commercially available, free-flowing spherically granulated dicalcium phosphate anhydrous (SGDCPA) Fujicalin for direct tableting was compared with directly compressible dicalcium phosphate dihydrate (DCPD), the properties of which are well known. The two excipients were investigated and compared with regard to their physical and powder properties, compressibility, and compactibility. As a consequence of the spherical shape of its particles, SGDCPA shows the same good flowability and even better compactibility. In contrast to DCPD, SGDCPA shows significant uptake of moisture when exposed to relative humidities (RHs) exceeding 70%. For both excipients, the main deformation mechanism is fragmentation, with SGDCPA yielding significantly stronger tablets.     

Properties of Calcium Phosphate Cements With Different Tetracalcium Phosphate and Dicalcium Phosphate Anhydrous Molar Ratios

Calcium phosphate cements (CPCs) were prepared using mixtures of tetracalcium phosphate (TTCP) and dicalcium phosphate anhydrous (DCPA), with TTCP/DCPA molar ratios of 1/1, 1/2, or 1/3, with the powder and water as the liquid. Diametral tensile strength (DTS), porosity, and phase composition (powder x-ray diffraction) were determined after the set specimens have been immersed in a physiological-like solution (PLS) for 1 d, 5 d, and 10 d. Cement dissolution rates in an acidified PLS were measured using a dual constant composition method. Setting times ((30 ± 1) min) were the same for all cements. DTS decreased with decreasing TTCP/DCPA ratio and, in some cases, also decreased with PLS immersion time. Porosity and hydroxyapatite (HA) formation increased with PLS immersion time. Cements with TTCP/DCPA ratios of 1/2 and 1/3, which formed calcium-deficient HA, dissolved more rapidly than the cement with a ratio of 1/1. In conclusion, cements may be prepared with a range of TTCP/DCPA ratios, and those with lower ratio had lower strengths but dissolved more rapidly in acidified PLS.     

磷酸钙骨水泥的生物学性能

寻求修复各种原因引起的骨组织缺损、畸形的新型材料和技术一直是生命科学和生物材料科学领域的一个重要课题.磷酸钙骨水泥具有良好的生物相容性、骨引导活性和生物降解性,具有一定的抗压强度,是一种较理想的骨移植替代材料.     

On the development of an apatitic calcium phosphate bone cement

Development of an apatitic calcium phosphate bone cement is reported. 100 μ Particles of tetracalcium phosphate (TTCP) and dicalcium phosphate dihydrate (DCPD) were mixed in equimolar ratio to form the cement powder. The wetting medium used was distilled water with Na₂HPO₄ as accelerator to manipulate the setting time. The cement powder, on wetting with the medium, formed a workable putty. The setting times of the putty were measured using a Vicat type apparatus and the compressive strength was determined with a Universal Testing Machine. The nature of the precipitated cement was analyzed through X-ray diffraction (XRD), fourier transform infrared spectrometry (FTIR) and energy dispersive electron microprobe (EDAX). The results showed the phase to be apatitic with a calcium-to-phosphorous ratio close to that of hydroxyapatite. The microstructure analysis using scanning electron microscopy (SEM) showed hydroxyapatite nano-crystallite growth over particulate matrix surface. The structure has an apparent porosity of ∼ 52%. There were no appreciable dimensional or thermal changes during setting. The cement passed the in vitro toxicological screening (cytotoxicity and haemolysis) tests. Optimization of the cement was done by manipulating the accelerator concentration so that the setting time, hardening time and the compressive strength had clinically relevant values.     

Injectable Bone Cement Reinforced with Gold Nanodots Decorated rGO-Hydroxyapatite Nanocomposites,Augment Bone Regeneration

Interest in the development of new generation injectable bone cements having appropriate mechanical properties, biodegradability, and bioactivity has been rekindled with the advent of nanoscience. Injectable bone cements made with calcium sulfate (CS) are of significant interest, owing to its compatibility and optimal self-setting property. Its rapid resorption rate, lack of bioactivity, and poor mechanical strength serve as a deterrent for its wide application. Herein, a significantly improved CS-based injectable bone cement (modified calcium sulfate termed as CS_mod), reinforced with various concentrations (0–15%) of a conductive nanocomposite containing gold nanodots and nanohydroxyapatite decorated reduced graphene oxide (rGO) sheets (AuHp@rGO), and functionalized with vancomycin, is presented. The piezo-responsive cement exhibits favorable injectability and setting times, along with improved mechanical properties. The antimicrobial, osteoinductive, and osteoconductive properties of the CS_mod cement are confirmed using appropriate in vitro studies. There is an upregulation of the paracrine signaling mediated crosstalk between mesenchymal stem cells and human umbilical vein endothelial cells seeded on these cements. The ability of CS_mod to induce endothelial cell recruitment and augment bone regeneration is evidenced in relevant rat models. The results imply that the multipronged activity exhibited by the novel-CS_mod cement would be beneficial for bone repair.     

碳纤维增强α-TCP/TTCP骨水泥的研究

制备了经过氧化处理的碳纤维增强磷酸钙骨水泥(α—tricalcium phosphate cement／tetracalcium phosphate，α—TCP／TTCP)，初步探讨了碳纤维长径比、含量对硬化体抗压、抗折强度的影响．实验结果表明长径比为375，添加量为0．3wt％时，增强效果最为理想，抗压强度提高了55％(最大为63．46MPa)，抗折强度提高近100％(最大为11．95MPa)，而掺入量太大及长径比太高，碳纤维因不能均匀分散将限制其性能的发挥．生物学评价实验结果表明碳纤维增强的骨水泥具有良好的生物相容性。     

磷酸钙/BMP复合生物活性骨水泥水化性能及诱导成骨特性研究

采用微细α-磷酸三钙(α-TCP)粉料、辅助料与冻干牛骨形态发生蛋白(BMP)预先固相混合制备了新型磷酸钙(CPC)/BMP复合生物骨水泥.通过水化、凝固性能研究优化了配料成分、调和液和促凝剂组成;通过大鼠肌袋种植实验研究了骨水泥的异位成骨性能.结果表明:以α-TCP:CaHPO₄:CaO(0.95:0.025:0.025)为固相配料,以0.25mol/LNaH₂PO₄/Na₂HPO₄混合液([P]_T=0.5mol/L)作为调合液可制备性能优异的骨水泥材料,骨水泥初凝时间为6min,终凝时间为30min,固化强度达33MPa,达到临床手术的要求;α-TCP粉料粒度对骨水泥凝固性能影响显著,实验选用α-TCP粉料粒径d₅₀为1.3μm;骨水泥在Hank’s溶液中浸泡5天抗压强度可达最大值;骨水泥块经浸泡后内部生成针状羟基磷灰石晶体的网状结构.新型CPC/BMP复合骨水泥异位成骨作用明显,4周即能快速形成板层骨结构,证明该新型复合材料具有较强的诱导成骨活性.该生物活性骨水泥复合材料可望成为一类新型组织工程骨修复材料.     

骨碎补载入对磷酸钙骨水泥性能的影响及体外生物学评价

通过在湿法合成的二水磷酸氢钙膏体中加入中药骨碎补的提取物, 作为磷酸钙骨水泥(Calcium Phosphate Cement,CPC)原料之一, 分别制备0、5wt%、10wt%和15wt%的载骨碎补磷酸钙骨水泥. 采用Gilmore针、X射线衍射仪、红外光谱仪、万能材料试验机、扫描电子显微镜和紫外分光光度计研究载骨碎补CPC的理化性能和药物释放; 体外培养MC-3T3成骨细胞, 进行Alamar Blue和碱性磷酸酶检测, 研究载骨碎补CPC对成骨细胞增殖和分化的影响, 扫描电子显微镜观察细胞形貌. 结果表明: 随骨碎补浓度的增加, CPC凝结时间明显延长, 其抗压强度显著提高; 骨碎补促进初期CPC的水化, 却阻碍了α-磷酸三钙的转化, 且随骨碎补浓度增大作用愈明显, 骨碎补不影响CPC水化后的相成分; 含骨碎补CPC的微观形貌中出现片状和针状晶体, 结构较空白CPC更加致密; 药物释放分为突释和缓释两个阶段, 符合Higuchi基质扩散释放模型; 载骨碎补CPC对成骨细胞的作用呈剂量和时间依赖关系, 培养5d时浓度为5wt%和10wt%的CPC较明显地促进细胞增殖, 7d时载骨碎补CPC的细胞增殖较稳定, 细胞分化能力无显著性差异; 成骨细胞在载骨碎补CPC表面生长形态良好, 表明该材料具有较好的生物相容性.     

等静压处理对磷酸钙骨水泥结构和性能的影响

采用冷等静压技术,在150MPa的压力下对磷酸钙骨水泥粉体进行等静压处理,然后使其在一定的条件下进行水化.采用扫描电镜(Scanning electronmicroscope,SEM)、红外光谱(Fourier transform ininfrared spectrome-try,FTIR)、X射线衍射(X-ray diffraction,XRD)和压汞仪等测试手段对其水化产物的结构和性能进行研究.结果表明,经过等静压处理,磷酸钙骨水泥粉体水化环境被改变,部分水化产物的晶体形貌由细小的短棒状变为六棱柱状,但主要物相仍为羟基磷灰石;水化固化体的孔隙率由未经等静压处理时的(46.32±2.70)%降到(24.75±1.15)%,抗压强度由(12.62±2.70)MPa提高到(43.05±2.08)MPa.     

磷酸钙骨水泥/明胶复合组织工程支架材料的制备及其结构与性能

磷酸钙骨水泥组织工程支架材料具有良好的生物相容性和骨传导性,是一种良好的骨组织工程支架材料,但是这种材料存在力学性能差的缺点,限制了它的应用.本文采用生物相容性良好的可降解明胶材料与磷酸钙骨水泥支架进行复合,制备出的明胶/磷酸钙骨水泥复合支架材料,其压缩强度可达3.7MPa,比复合前磷酸钙支架材料的强度提高了37倍,而且材料具有良好的柔韧性,适合用作为非承重部位骨组织缺损修复用组织工程支架材料.     

载不同浓度香丹注射液磷酸钙骨水泥性能研究

研究载不同浓度香丹注射液(简称香丹)磷酸钙骨水泥(CPC)的理化性能和药物释放,为优化CPC中载入香丹浓度提供理论依据.将香丹与CPC主要原料之一磷酸氢钙混合烘干代替磷酸氢钙制得一系列载不同浓度香丹的CPC,香丹浓度范围在0.05～0.5mL/g.采用Gilmore针、万能材料力学试验机、X射线衍射仪、傅立叶红外光谱仪表征载不同浓度香丹CPC的理化性能,用扫描电镜观察微观形貌,测定载不同浓度香丹CPC的药物释放.结果表明CPC凝结时间随香丹浓度的增加而延长,浓度不高于0.2mL/g的CPC样品凝结时间符合临床要求;抗压强度随香丹含量的增加而增加;香丹加入对CPC转化没有明显影响,但导致水化产物晶体形貌从颗粒状松散搭接转化为片状交织,且浓度越高片状晶体越多.在药物释放的最初4h,载入香丹浓度范围为0.1～0.5mL/g的CPC其释药量符合临床需要.因此,载入香丹浓度范围为0.1～0.2mL/g的CPC凝结时间符合临床要求,比空白CPC具有更高的抗压强度,在初阶段药物释放量符合治疗需求.     

丝素纤维强化磷酸钙骨水泥的性能

采用在磷酸钙骨水泥(CPC)中掺入丝素纤维(SFF)来强化CPC。用X射线衍射(XRD)、红外光谱(FT-IR)研究材料的结构,用ISO水泥标准维卡仪测定CPC的凝固时间,用扫描电镜(SEM)观察材料的表面形态,在Instron上测定样品的力学性能。结果表明,CPC中的磷酸三钙和磷酸氢钙在固化过程中基本上转化为羟基磷灰石,SFF的加入加快了磷酸氢钙的转化。CPC的凝固时间随着掺入SFF含量的增加而缩短;弯曲强度和弯曲断裂功均随着SFF含量的增加而增加,尤其弯曲断裂功增加显著,但当SFF含量大于1.5%,两者均随着SFF含量的增加而所下降,但均比纯CPC的高;在CPC中加入1.5%的SFF,压缩强度和压缩断裂功均明显比纯CPC的高。