HA/PDLLA复合材料的体内成骨过程研究

目的研究HA／PDLLA复合材料植入体内后与细胞、组织的相互作用，探讨HA／PDLLA复合材料在体内的成骨过程，为其临床应用及设计具有生物功能的人工骨替换材料和骨组织工程支架材料提供依据。方法采用液相吸附法制备了HA／PDLLA复合材料，以纯PDLLA和空白组进行对照，进行体内植入实验，通过组织学观察和四环素标记考察其成骨过程。结果HA／PDLLA复合材料植入机体后，体内的无菌性炎症轻微，新骨形成速率高于PDLLA材料。HA微粒的存在，加强了复合材料的机械强度，使之可以避免过早的丧失力学强度。第24w时，材料被组织分隔包裹，新生骨组织长入材料，骨愈合情况良好。结论HA／PDLLA复合材料具有良好的生物相容性、生物降解性能、生物学活性和骨传导性能。     

Differential osteogenic activity of osteoprogenitor cells on HA and TCP/HA scaffold of tissue engineered bone

Biomaterial, an essential component of tissue engineering, serves as a scaffold for cell attachment, proliferation, and differentiation; provides the three dimensional (3D) structure and, in some applications, the mechanical strength required for the engineered tissue. Both synthetic and naturally occurring calcium phosphate based biomaterial have been used as bone fillers or bone extenders in orthopedic and reconstructive surgeries. This study aims to evaluate two popular calcium phosphate based biomaterial i.e., hydroxyapatite (HA) and tricalcium phosphate/hydroxyapatite (TCP/HA) granules as scaffold materials in bone tissue engineering. In our strategy for constructing tissue engineered bone, human osteoprogenitor cells derived from periosteum were incorporated with human plasma-derived fibrin and seeded onto HA or TCP/HA forming 3D tissue constructs and further maintained in osteogenic medium for 4 weeks to induce osteogenic differentiation. Constructs were subsequently implanted intramuscularly in nude mice for 8 weeks after which mice were euthanized and constructs harvested for evaluation. The differential cell response to the biomaterial (HA or TCP/HA) adopted as scaffold was illustrated by the histology of undecalcified constructs and evaluation using SEM and TEM. Both HA and TCP/HA constructs showed evidence of cell proliferation, calcium deposition, and collagen bundle formation albeit lesser in the former. Our findings demonstrated that TCP/HA is superior between the two in early bone formation and hence is the scaffold material of choice in bone tissue engineering.     

Nucleation and growth of mineralized bone matrix on silk-hydroxyapatite composite scaffolds

We describe a composite hydroxyapatite (HA)-silk fibroin scaffold designed to induce and support the formation of mineralized bone matrix by human mesenchymal stem cells (hMSCs) in the absence of osteogenic growth factors. Porous three-dimensional silk scaffolds were extensively used in our previous work for bone tissue engineering and showed excellent biodegradability and biocompatibility. However, silk is not an osteogenic material and has a compressive stiffness significantly lower than that of native bone. In the present study, we explored the incorporation of silk sponge matrices with HA (bone mineral) micro-particles to generate highly osteogenic composite scaffolds capable of inducing the in vitro formation of tissue-engineered bone. Different amounts of HA were embedded in silk sponges at volume fractions of 0%, 1.6%, 3.1% and 4.6% to enhance the osteoconductive activity and mechanical properties of the scaffolds. The cultivation of hMSCs in the silk/HA composite scaffolds under perfusion conditions resulted in the formation of bone-like structures and an increase in the equilibrium Young's modulus (up to 4-fold or 8-fold over 5 or 10 weeks of cultivation, respectively) in a manner that correlated with the initial HA content. The enhancement in mechanical properties was associated with the development of the structural connectivity of engineered bone matrix. Collectively, the data suggest two mechanisms by which the incorporated HA enhanced the formation of tissue engineered bone: through osteoconductivity of the material leading to increased bone matrix production, and by providing nucleation sites for new mineral resulting in the connectivity of trabecular-like architecture.     

Mechanical and in vivo performance of hydroxyapatite implants with controlled architectures.

Internal architecture has a direct impact on the mechanical and biological behaviors of porous hydroxyapatite (HA) implant. However, traditional processing methods provide minimal control in this regard. To address the issue, we developed a new processing method combining image-based design and solid free-form fabrication. We have previously published the processing method showing fabricated HA implants and their chemical properties. This study characterized the mechanical and the in vivo performance of designed HA implants. Thirteen HA implants with orthogonal channels at 40% porosity were tested on an Instron machine. The compressive strength and compressive modulus measured were 30+/-8 MPa and 1.4+/-0.4 GPa, comparable to coralline porous HA. Twenty-four cylindrical HA implants with two architecture designs, orthogonal and radial channels, were implanted in the mandibles of four Yucatan minipigs for 5 and 9 weeks. Normal bone regeneration occurred in both groups. At 9 weeks, bone penetrated 1.4mm into both scaffold designs. The percent bone ingrowth in the penetration zone was higher in the orthogonal channel design but not statistically different due to the low number of samples. However, the overall shape of the regenerated bone tissue was significantly different. In the orthogonal design, bone and HA formed an interpenetrating matrix, while in the radial design, the regenerated bone formed an intact piece at the center of the implant. These preliminary results showed that controlling the overall geometry of the regenerated bone tissue is possible through the internal architectural design of the scaffolds.     

No effect of hydroxyapatite particles in phagocytosable sizes on implant fixation: an experimental study in dogs

The influence of wear debris on bone healing around orthopedic implants is debated. Hydroxyapatite (HA) particles and polyethylene (PE) particles have been shown to have a negative effect on osteoblast cultures in vitro. The present study investigated the in vivo effects of HA and PE particles on the mechanical fixation and gap healing around experimental HA implants. Nonloaded implants (n = 30) were inserted bilaterally into the proximal tibia of 15 dogs with a 2-mm gap to the bone. The peri-implant gap was either (1) empty (n = 6) or filled with (2) hyaluronic acid (n = 8), (3) hyaluronic acid and HA particles (n = 8), or (4) hyaluronic acid and PE particles (n = 8). After 4 weeks, the animals were killed. The implant interface was evaluated by pushout testing until failure and by histomorphometry. Both HA and PE particles were found to be phagocytosed by macrophage-like cells in the interfacial tissue. HA particles were also integrated in newly formed bone. We found no negative effect of the particulate material on mechanical fixation of the implants or on bone formation around the implants.     

Simultaneous electrospin–electrosprayed biocomposite nanofibrous scaffolds for bone tissue regeneration

Currently, the application of nanotechnology in bone tissue regeneration is a challenge for the fabrication of novel bioartificial bone grafts. These nanostructures are capable of mimicking natural extracellular matrix with effective mineralization for successful regeneration of damaged tissues. The simultaneous electrospraying of nanohydroxyapatite (HA) on electrospun polymeric nanofibrous scaffolds might be more promising for bone tissue regeneration. In the current study, nanofibrous scaffolds of gelatin (Gel), Gel/HA (4:1 blend), Gel/HA (2:1 blend) and Gel/HA (electrospin–electrospray) were fabricated for this purpose. The morphology, chemical and mechanical stability of nanofibres were evaluated by means of field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy and with a universal tensile machine, respectively. The in vitro biocompatibility of different nanofibrous scaffolds was determined by culturing human foetal osteoblasts and investigating the proliferation, alkaline phosphatase (ALP) activity and mineralization of cells. The results of cell proliferation, ALP activity and FESEM studies revealed that the combination of electrospinning of gelatin and electrospraying of HA yielded biocomposite nanofibrous scaffolds with enhanced performances in terms of better cell proliferation, increased ALP activity and enhanced mineralization, making them potential substrates for bone tissue regeneration.     

骨髓间充质干细胞在淫羊藿苷/羟基磷灰石/聚乳酸-羟基乙酸共聚物支架上的成骨

文题释义：纳米结构：是尺寸介于分子和微米尺度间的物体结构。当纳米羟基磷灰石与高分子材料物理混合后,羟基磷灰石会发生自聚,从而在材料表面产生纳米结构。这种纳米结构有利于细胞(如骨髓充间质干细胞)的黏附,是骨修复材料表面细胞增殖和后期成骨分化的基础。成骨分化：当干细胞接受诱导时可以向成骨细胞转变。淫羊藿苷高分子复合支架与间充质干细胞共培养一段时间后,其骨分化标志物碱性磷酸酶和骨钙素的活性增高,同时成骨相关基因和蛋白(Runx-2、COLⅠ)表达水平上升,即细胞在淫羊藿苷诱导下发生了成骨分化。  摘要背景：近年来,骨组织工程技术为临床治疗骨缺损提供了全新的思路和模式。该研究首次将传统中药与组织工程支架的纳米结构结合,以期探索并构建一种可用于骨缺损治疗的新型骨组织替代材料。目的：研究淫羊藿苷(icariin,ICA)/羟基磷灰石(hydroxyapatite,HA)/聚乳酸-羟基乙酸共聚物(poly(lactic-co-glycolic acid),PLGA)复合支架的成骨活性。方法：将HA与PLGA通过物理共混的方式制成HA/PLGA复合支架,然后将其浸泡于不同浓度的ICA溶液中,从而得到ICA/HA/PLGA支架。利用兔骨髓间充质干细胞分别对复合支架的细胞黏附、增殖、成骨作用和细胞毒性进行评价。细胞黏附、细胞增殖和细胞毒性采用MTT法进行检测,碱性磷酸酶活性和骨钙素活性采用ELISA法进行检测,成骨相关基因和蛋白表达水平分别用荧光定量PCR和Western blot法进行检测。结果与结论：①PLGA中加入适量HA可以提高支架的力学强度,且在HA含量为10%时效果最佳,拉伸强度为(1.67±0.37) MPa;压缩模量为(4.17±1.62) MPa,且会在支架表面形成纳米结构;该微结构可以促进骨髓间充质干细胞在支架表面的黏附;②ICA不会影响骨髓间充质干细胞在复合支架上的增殖,且1.00 µmol/L ICA水溶液浸泡后的ICA/HA/PLGA复合支架具有最优的成骨分化功能,其碱性磷酸酶活性、骨钙素活性、成骨相关基因和蛋白(Runx-2和COLⅠ)的表达水平均最高;③ICA/HA/PLGA复合支架无细胞毒性;④结果表明,HA(10%)/ICA(1.00 µmol/L)/PLGA支架具有良好的机械性能、成骨作用和生物相容性,是一种具有良好应用潜力的骨组织工程支架。ORCID: 0000-0002-9770-9109(王德欣) 中国组织工程研究杂志出版内容重点：干细胞;骨髓干细胞;造血干细胞;脂肪干细胞;肿瘤干细胞;胚胎干细胞;脐带脐血干细胞;干细胞诱导;干细胞分化;组织工程     

Long-term durability of porous hydroxyapatite with low-pressure system to support osteogenesis of mesenchymal stem cells

In this study, we hypothesize that loading more marrow-derived mesenchymal stem cells (MSCs) into porous material by using a low-pressure system during subculture, creating a composite which combines MSCs and a novel mechanical reinforced porous hydroxyapatite, can result in more bone tissue formation in vivo. Within 26 weeks postimplantation, we examined in vivo bone formation of the experimental group with 100 mmHg pressure applied to porous HA blocks loaded with MSCs. For in vivo testing, the 2-week subcultured HA/MSC composites were implanted into subcutaneous sites of syngeneic rats. These implants were harvested at 13 and 26 weeks after implantation. SEM showed that the pore surface is covered by osteoblasts as well as collagenous extracellular matrix at 13 weeks. Light microscopy revealed the quantity of bone at 26 weeks was greater than at 13 weeks. These results showed that the novel mechanical reinforced porous HA combined with MSC has more potential for bone formation at 100 mmHg, making this method very efficient for bone reconstruction.     

Poly-epsilon-caprolactone/hydroxyapatite composites for bone regeneration: in vitro characterization and human osteoblast response

Polycaprolactone (PCL), a semicrystalline linear resorbable aliphatic polyester, is a good candidate as a scaffold for bone tissue engineering, due to its biocompatibility and biodegradability. However, the poor mechanical properties of PCL impair its use as scaffold for hard tissue regeneration, unless mechanical reinforcement is provided. To enhance mechanical properties and promote osteoconductivity, hydroxyapatite (HA) particles were added to the PCL matrix: three PCL-based composites with different volume ratio of HA (13%, 20%, and 32%) were studied. Mechanical properties and structure were analysed, along with biocompatibility and osteoconductivity. The addition of HA particles (in particular in the range of 20% and 32%) led to a significant improvement in mechanical performance (e.g., elastic modulus) of scaffold. Saos-2 cells and osteoblasts from human trabecular bone (hOB) retrieved during total hip replacement surgery were seeded onto 3D PCL samples for 1-4 weeks. Following the assessment of cell viability, proliferation, morphology, and ALP release, HA-loaded PCL was found to improve osteoconduction compared to the PCL alone. The results indicated that PCL represents a potential candidate as an efficient substrate for bone substitution through an accurate balance between structural/ mechanical properties of polymer and biological activities.     

Early weight bearing of porous HA/TCP (60/40) ceramics in vivo: a longitudinal study in a segmental bone defect model of rabbit

Porous interconnected hydroxyapatite (HA) and HA/tricalcium phosphate (TCP) (60/40) ceramics are promising materials for hard tissue repair. However, the mechanical properties of these materials have not been accurately determined under weight-bearing conditions. In this study, newly developed HA and HA/TCP (60/40) ceramics were used with intramedullary fixation in segmental bone defects of rabbits. Early radiological, histological, densitometric and biomechanical changes were evaluated. The mean radiological grade of healing and bonding to bone was higher in HA/TCP (60/40) ceramics than that of pure HA ceramics but the difference was not statistically significant. The densities of both implanted ceramics improved with time, supported by the histological evaluation of bone matrix ingrowth into ceramic pores, whereas the densities at the bone–ceramic interface decreased gradually. Flexural resonant frequencies and three-point bending strength increased, revealing an increase in mechanical stability during this early critical time interval where implant and/or bone–implant interface failures occur frequently. It can be concluded that both HA and HA/TCP (60/40) ceramics have a limited application in the treatment of load-bearing segmental bone defects but did not fail at the early stages of implantation.     

Poly-L-lactic acid/hydroxyapatite hybrid membrane for bone tissue regeneration

Poly-L-lactic acid (PLLA)/hydroxyapatite (HA) hybrid membranes were fabricated via electrospinning of the PLLA/HA dispersion for use in bone tissue regeneration. The structural properties and morphologies of PLLA and PLLA/HA hybrid membrane were investigated by measuring the Brunauer-Emmett-Teller specific surface area, observations of SEM, and TEM. The dispersion and integrating of HA nanoparticles in the hybrid membrane were studied by energy dispersion X-ray analysis and FTIR. The mechanical properties of PLLA/HA membrane were also measured by tensile tests. For exploring biological behaviors of the hybrid membrane, in vitro degradation tests were carried out. The osteoblast cell (MG-63) was cultured in PLLA/HA hybrid membrane extract containing medium; the cell adhesion and growth capability were investigated by SEM observation and MTT assay. HA nanoparticles were not only dispersed in the PLLA but also reacted with the functional group of PLLA, resulting in strong surface bonding and high tensile strength of hybrid membrane. The cell adhesion and growth on the PLLA/HA hybrid membrane were far better than those on the pure PLLA membrane, which proves that the PLLA/HA hybrid membrane can be one of the promising biomaterials for bone tissue regeneration.     

Engineering the bone-ligament interface using polyethylene glycol diacrylate incorporated with hydroxyapatite

Ligaments and tendons have previously been tissue engineered. However, without the bone attachment, implantation of a tissue-engineered ligament would require it to be sutured to the remnant of the injured native tissue. Due to slow repair and remodeling, this would result in a chronically weak tissue that may never return to preinjury function. In contrast, orthopaedic autograft reconstruction of the ligament often uses a bone-to-bone technique for optimal repair. Since bone-to-bone repairs heal better than other methods, implantation of an artificial ligament should also occur from bone-to-bone. The aim of this study was to investigate the use of a poly(ethylene glycol) diacrylate (PEGDA) hydrogel incorporated with hydroxyapatite (HA) and the cell-adhesion peptide RGD (Arg-Gly-Asp) as a material for creating an in vitro tissue interface to engineer intact ligaments (i.e., bone-ligament-bone). Incorporation of HA into PEG hydrogels reduced the swelling ratio but increased mechanical strength and stiffness of the hydrogels. Further, HA addition increased the capacity for cell growth and interface formation. RGD incorporation increased the swelling ratio but decreased mechanical strength and stiffness of the material. Optimum levels of cell attachment were met using a combination of both HA and RGD, but this material had no better mechanical properties than PEG alone. Although adherence of the hydrogels containing HA was achieved, failure occurs at about 4 days with 5% HA. Increasing the proportion of HA improved interface formation; however, with high levels of HA, the PEG HA composite became brittle. This data suggests that HA, by itself or with other materials, might be well suited for engineering the ligament-bone interface.     

基于丝素/胶原/羟基磷灰石仿生骨材料的多维结构及其性能

目的 体外构建丝素蛋白（silk fibroin,SF）、I型胶原(type I collagen,Col-I)和羟基磷灰石(hydroxyapatite, HA)共混体系制备二维复合膜和三维仿生支架,研究其理化性质和生物相容性,探讨其在组织工程支架材料中应用的可行性。方法 通过在细胞培养小室底部共混SF/Col-I/HA以及低温3D打印结合真空冷冻干燥法制备二维复合膜及三维支架。通过机械性能测试、电子显微镜和Micro-CT检测材料的理化性质,检测细胞的增殖评估其生物相容性。结果 通过共混和低温3D打印获得稳定的二维复合膜及三维多孔结构支架;力学性能具有较好的一致性,孔径、吸水率、孔隙率和弹性模量均符合构建组织工程骨的要求;支架为网格状的白色立方体,内部孔隙连通性较好; HA均匀分布在复合膜中,细胞黏附在复合膜上,呈扁平状;细胞分布在支架孔壁周围,呈梭形状,生长及增殖良好。结论 利用SF/Col-I/HA共混体系成功制备复合膜及三维支架,具有较好的孔连通性与孔结构,有利于细胞和组织的生长以及营养输送,其理化性能以及生物相容性符合骨组织工程生物材料的要求。     

纳米羟基磷灰石/Ⅰ型胶原/壳聚糖复合支架材料的制备与优化

目的制备适合于骨组织工程的高强度纳米羟基磷灰石/Ⅰ型胶原/壳聚糖复合支架材料。方法用原位合成法代替传统的直接分散法,以胶原和壳聚糖为模板原位合成羟基磷灰石,再用冷冻干燥法使材料成型,制成可用于骨组织工程的多孔支架材料。结果制备的材料孔隙率高,孔的连通性好,材料中羟基磷灰石结晶度更小,表面能大,与有机物基底结合紧密,也能为成骨细胞的粘附提供更多的活性位点。结论用紫外辐照对材料进行处理,能使其抗压性能得到提高。制备的支架材料适用于骨组织工程。     

可注射、组织黏附性PVA/淀粉水凝胶对力学失稳条件下关节软骨退变抑制作用的研究

目的 制备一种仿生正常关节滑液流变学特征的组织黏附性可注射水凝胶,并研究该水凝胶抑制膝关节创伤后软骨退变的效果及其可能的机制。方法 以聚乙烯醇溶液（PVA）、淀粉和氯化钠为主要原料制备可注射、组织黏附性水凝胶（PWN）。通过流变学测试、注射器推出实验、体外降解实验、CCK-8实验、活/死细胞染色、细菌黏附实验、组织黏附实验分别对其流变学性能、可注射性、降解性能、细胞相容性、抗细菌黏附性能和组织黏附性能进行表征。构建大鼠膝关节力学失稳模型,并分为正常组、PWN组、透明质酸组（HA组）与未治疗组,其中PWN组、HA组术后1周时注射PWN与HA进行治疗。治疗4周后取大鼠膝关节标本进行Micro-CT分析和组织学染色分析,对比评估PWN对关节软骨退变的抑制作用。结果 PWN具有良好的细胞相容性和可注射性。此外,相比于HA,PWN的流变学特征更接近正常关节滑液,并且PWN具有缓慢降解的特性、更高的组织黏附性能和抗细菌黏附的能力。动物实验Micro-CT分析结果显示,PWN组软骨下骨的骨密度和骨体积/组织体积均显著高于未治疗组和HA组（P<0.05）。同时,番红快绿染色结果显示,相比于HA组...     

Biphasic calcium phosphate nanocomposite porous scaffolds for load-bearing bone tissue engineering

A novel biodegradable nanocomposite porous scaffold comprising a beta-tricalcium phosphate (beta-TCP) matrix and hydroxyl apatite (HA) nanofibers was developed and studied for load-bearing bone tissue engineering. HA nanofibers were prepared with a biomimetic precipitation method. The composite scaffolds were fabricated by a method combining the gel casting and polymer sponge techniques. The role of HA nanofibers in enhancing the mechanical properties of the scaffold was investigated. Compression tests were performed to measure the compressive strength, modulus and toughness of the porous scaffolds. The identification and morphology of HA nanofibers were determined by X-ray diffraction and transmission electron microscopy, respectively. Scanning electron microscopy was used to examine the morphology of porous scaffolds and fracture surfaces to reveal the dominant toughening mechanisms. The results showed that the mechanical property of the scaffold was significantly enhanced by the inclusion of HA nanofibers. The porous composite scaffold attained a compressive strength of 9.8 +/- 0.3 MPa, comparable to the high-end value (2-10 MPa) of cancellous bone. The toughness of the scaffold increased from 1.00+/-0.04 to 1.72+/-0.02 kN/m, as the concentration of HA nanofibers increased from 0 to 5 wt %.     

Hydroxyapatite/PMMA composites as bone cements

Currently PMMA is the polymer most commonly used as a bone cement for the fixation of total hip prostheses. Ideally, a bone cement material should be easy to handle, biologically compatible, nonsupporting of oral microbial growth, available in the particulate and molded forms, easy to obtain, nonallergenic, adaptable to a broad range of dental and medical applications, in possession of high compressive strength, and effective in guided tissue regenerative procedures. One of the problems associated with the conventional types of bone cement used is their unsatisfactory mechanical and exothermic reaction properties. The purpose of this in vitro study was to investigate and compare the mechanical properties (three-point bending strength, energy-to-break, and modulus of elasticity) and physical properties (setting time, water sorption, and exothermic heat) of HA/PMMA (HA group) and bovine-bone originated HA/PMMA (BB group) composites. Composites samples were fabricated by admixing method. It was found that the addition of HA and BB particles increased the water sorption. Generally 10 v/o 20 v/o HA and 0 v/o to 10 v/o BB ratio combinations had significant beneficial effects on the mechanical properties. The heat generated during polymerization was influenced by the different admixtures. More than 40 v/o HA and 40 v/o BB should be mixed into PMMA to reduce the peak temperature. Overall evaluation indicated that the BB group had better properties than the HA group.     

Mechanical properties of calcium phosphate scaffolds fabricated by robocasting

The mechanical behavior under compressive stresses of beta-tricalcium phosphate (beta-TCP) and hydroxyapatite (HA) scaffolds fabricated by direct-write assembly (robocasting) technique is analyzed. Concentrated colloidal inks prepared from beta-TCP and HA commercial powders were used to fabricate porous structures consisting of a 3-D tetragonal mesh of interpenetrating ceramic rods. The compressive strength and elastic modulus of these model scaffolds were determined by uniaxial testing to compare the relative performance of the selected materials. The effect of a 3-week immersion in simulated body fluid (SBF) on the strength of the scaffolds was also analyzed. The results are compared with those reported in the literature for calcium phosphate scaffolds and human bone. The robocast calcium phosphate scaffolds were found to exhibit excellent mechanical performances in terms of strength, especially the HA structures after SBF immersion, indicating a great potential of this type of scaffolds for use in load-bearing bone tissue engineering applications.     

Glass reinforced hydroxyapatite for hard tissue surgery--part II: in vitro evaluation of bone cell growth and function.

Hydroxyapatite (HA)-based materials are considered to be potentially useful as bone implant materials, particularly those reinforced with glass to improve mechanical strength. However, the precise effects of glass-reinforced HA on the growth and functions of bone cells are still unclear. The present study has therefore examined the response of human osteoblast-like cells to HA and HA reinforced with two different proportions of glass, namely 2.5% and 5%. All materials enabled the cells to attach and proliferate during 7 days in culture and, although the growth was less than on control plastic surfaces, there was no deleterious effect of the 5% glass composite compared with HA alone. Flow cytometry analysis showed that there was no effect on cell size and granularity, but there were marked and highly selective changes in the expression of certain connective tissue proteins. Thus, while bone sialoprotein and osteonectin were down-regulated on HA alone, the expression of these antigens was relatively enhanced on the composite materials, and collagen type I was also up-regulated on the glass-reinforced HA. Thus, modulation of the glass composition of HA materials could be used to produce not only improved mechanical strength, but also enhanced biocompatibility.     

Comparison of plasma-sprayed hydroxyapatite coatings and zirconia-reinforced hydroxyapatite composite coatings: in vivo study

The clinical use of plasma-sprayed hydroxyapatite (HA) coatings on metal implants has been widely adopted because the HA coating can achieve the firmly and directly biological fixation with the surrounding bone tissue. However, the long-term mechanical properties of HA coatings has been concern for the long-term clinical application. Previous research showed that the concept of adding ZrO2 as second phase to HA significantly increased the bonding strength of plasma-sprayed composite material. The present work aimed to explore the biological properties, including the histological responses and shear strength, between the plasma-sprayed HA and HA/ZrO2 coating, using the transcortical implant model in the femora of canines. After 6 and 12 weeks of implantation, the HA coating revealed the direct bone-to-coating contact by the backscattered electron images (BEIs) of scanning electron microscope (SEM), but the osseointegration was not observed at the surface of HA/ZrO2 coating. For new bone healing index (NBHI) and apposition index (AI), the values for HA implants were significantly higher than that for HA/ZrO2 coatings throughout all implant periods. After push-out test, the shear strength of HA-coated implants were statistically higher than HA/ZrO2 coated implants at 6- and 12-week implantation, and the failure mode of HA/ZrO2 coating was observed at the coating-bone interface by SEM. The results indicate that the firm fixation between bone and HA/ZrO2 has not been achieved even after 12-week implantation. Consequently, the addition of ZrO2 could improve the mechanical properties of coatings, while the biocompatibility was influenced by the different material characteristics of HA/ZrO2 coating compared to HA coatings.