Bioactive composite gradient coatings of nano-hydroxyapatite/polyamide66 fabricated on polyamide66 substrates

Tightly bonding of bioactive coating is the first crucial need for orthopaedic implants. This study describes a novel and convenient technique to prepare bioactive coating with high adhesion on orthopaedic substitutes made of polymeric matrix. Here, a chemical corrosion method has been adopted to fabricate a coating on the surface of injection-moulded polyamide66 (PA66) substrates by corrosive nano-hydroxyapatite/polyamide66 (n-HA/PA66) composite slurry. Scanning electron microscopy observation shows that a porous chemical corrosion region presents between the coating and dense PA66 substrate. Energy-dispersive X-ray spectroscopy analysis indicates that the chemical corrosion region is mainly composed of PA66 matrix, and the coating layer is an n-HA-rich layer. Both the pore size and n-HA composition increase gradually from the polymeric substrate towards the coating surface. Mechanical testing shows the bonding strength can reach 13.7 ± 0.2 MPa, which is much higher than that fabricated on polymeric matrix by other coating methods. The gradual transition in coating structure and composition benefits for the interface bonding and for the surface bone-bonding bioactivity. Subsequent cell experiments corroborate n-HA-rich coating and a porous structure is benefitting for cell attachment and proliferation. The convenient coating method could be popularized and applied on similar polymer implants to produce a tightly and porous bioactive coating for bone tissue regeneration.     

Preparation and characterization of nano-hydroxyapatite/polyamide 66 composite GBR membrane with asymmetric porous structure

In this study, a nano-hydroxyapatite/polyamide 66 (nHA/PA66) composite with good biocompatibility and high bioactivity is employed to develop novel asymmetric structure porous membranes for guided bone regeneration (GBR). FT-IR and XRD analyses suggest that chemical bonds are formed between nHA and PA66 both in composite powders and membranes. The fabricated membranes show gradient porous structure. SEM analysis reveal that pores less than 10 μm and pores with a size ranging from 30 μm to 200 μm distribute in the micropore layer and the spongy structure layer, respectively. The surface energy determination also reveals that the fabricated membranes have asymmetric surface properties on the two sides of the membrane. The incorporation of nHA in PA66 matrix improves the properties of the membrane. The elongation at break and the tensile strength of nHA/PA66-40 suggest that the composite membrane has good strength and toughness. The rough porous structure surface with high surface energy of nHA/PA66 composite membrane may be beneficial to promote cells immobility and differentiation into a mature phenotype producing mineralized matrix. The biocompatibility, bioactivity, osteoconductivity, asymmetric porous structure, mechanical properties and hydrophilicity of the composite membrane can meet the requirement of GBR technique.     

A new composite made of polyurethane and glass ceramic in a loaded implant model: a biomechanical and histological analysis

The biocompatibility and osseous integration of a new composite material made of polyurethane and a calcium silicophosphate ceramic was investigated in a loaded implant model in sheep and compared to that of commercially pure titanium. Six months after implantation, interfacial shear strength was higher between the titanium and bone than between the composite and bone. After 2 years, however, the shear strength was significantly higher in the composite group. Histologically, both implants were surrounded by bone and fibrous tissue and there were no signs of inflammation. Direct contact of bone on the composite surface increased significantly with time, whereas there was no time-dependent increase of bone contact on titanium. It can be concluded that the biocompatibility and osseous integration of the composite was very good in the loaded implant model used. It is therefore suggested that the new composite is a promising biomaterial for orthopaedic implants.     

纳米复合支架结构与生物学性能

通过复合成型致孔一体技术制备纳米羟基磷灰石/聚酰胺66 (n-HA/PA66) 硬组织修复支架,采用SEM、XRD、IR和燃烧实验等测试手段对复合支架进行表征。结果表明:n-HA粒子以纳米尺度均匀分布于复合支架材料中;复合材料的两相界面为氢键键合和配位键合;支架的孔隙相互贯通,不仅有平均孔径约450 μ m的大孔,大孔壁上还富含0.5~50 μ m的微孔。动物实验证实,该纳米复合支架具有高的生物活性和好的组织相容性,能与硬组织形成骨性结合,其孔隙范围有利于骨组织、血管、骨细胞的长入,可作为硬组织修复的良好载体。      

n-HA/PA66/HDPE复合生物材料的制备和性能研究

应用纳米羟基磷灰石(n-HA)、聚酰胺66(PA66)和高密度聚乙烯(HDPE)制备了生物医用复合材料。用化学分析法、燃烧实验、热分析、AFM、IR、XRD对复合材料的组成和结构进行了分析,并对复合材料的力学性能进行了研究。结果表明所制备的复合材料组成均一,具有高强柔韧的力学性能,纳米羟基磷灰石、聚酰胺66、高密度聚乙烯三者之间产生了一定的相互作用,形成了稳定的界面结合。因此,该三元复合材料可能成为一种新型的骨修复材料,在生物医学材料的开发和应用研究中具有重要意义。     

骨修复用生物玻璃复合材料研究进展

生物玻璃是一类性能优良的生物材料,具有良好的生物活性和生物相容性,作为骨修复植入体可以在材料界面与人体骨组织之间形成化学键合,诱导骨的修复与再生.将生物玻璃与其它材料进行复合,可以制备出生物活性和机械性能优良的骨修复复合材料.综述了生物玻璃复合材料的研究现状,并探讨了该类材料目前存在的不足,展望了其发展趋势.     

Enhanced osteointegration of orthopaedic implant gradient coating composed of bioactive glass and nanohydroxyapatite

We conducted histologic and histomorphometric studies to evaluate the osteointegration of gradient coatings composed of bioactive glass and nanohydroxyapatite (BG–nHA) on titanium-alloy orthopaedic implants and surrounding bone tissue in vivo. Titanium-alloy implants with a gradient coating (gradient coating group), uncoated implants (uncoated group), and implants with a conventional hydroxyapatite (HA) coating (HA coating group) were randomly implanted in bilateral femoral condyles of 36 male New Zealand rabbits. The bone–implant contact at 12 and 24 weeks and the new bone volume in the notch created for observing bone ingrowth at 4, 12, and 24 weeks were found greater in the gradient coating group than those in both the uncoated group and the HA coating group (p < 0.05). Fluorescence micrographs showed active osteogenesis in the gradient coating group at 4 weeks after implantation. These findings indicated that BG–nHA gradient coatings could enhance the osteointegration of orthopaedic implant.     

两步电沉积法制备HA-Ti/HA复合涂层的研究

为了提高金属基羟基磷灰石（HA）涂层的结合强度,采用复合电沉积一电沉积两步法在含Ti粉的钙磷电解液中制备HA—Ti／HA复合涂层,对涂层的组分结构、表面形貌、热稳定性、结合强度和生物活性进行了研究．实验结果表明：两步法制备的底层为HA—Ti复合涂层,外层为纯HA涂层的HA—Ti／HA复合涂层既提高了涂层的结合强度,又保证了涂层的生物活性．当涂层中Ti粉的质量分数为51．2wt％时,涂层与基体的结合强度达到21．2MPa,约为纯HA涂层的3倍．模拟体液浸泡7天后,涂层表面即被一层球状碳磷灰石覆盖,具有良好的生物活性,与纯HA涂层相比,复合涂层具有更好的耐蚀性能．     

用于软骨和软骨下骨修复的纳米羟基磷灰石/聚乙烯醇/聚酰胺66功能梯度材料的制备和表征

利用反复冷冻-解冻法和相分离法,制备出用于软骨和软骨下骨修复的纳米羟基磷灰石(nHA)/聚乙烯醇(PVA)/聚酰胺(PA66)功能梯度材料。研究表面层PVA的力学性能和摩擦学性能,及软骨下骨nHA/PA66(m(HA)∶m(PA66)=1∶1)支架的力学性能及生物学性能。结果表明PVA拉伸强度为1.938MPa,平均摩擦系数在生理盐水及代血浆润滑条件下分别为0.076和0.085;nHA/PA66复合多孔支架孔隙率为80.93%,孔径为50～500μm,压缩强度和压缩模量分别为0.88和15.21MPa,且具有良好的生物相容性。     

可注射纳米磷灰石/高分子复合骨修复材料的性能

制备了一种新型可注射纳米磷灰石／聚酰胺66复合材料，研究了其可注射性能、在生理盐水中的凝结时间以及抗压强度．结果表明：纳米磷灰石／聚酰胺66复合材料可用针管注射，能在空气、生理盐水和血液中固化，有合理的凝结时间，高的抗压强度，可用于骨缺损的修复．在固化过程中，材料中的聚酰胺发生了物相变化，聚酰胺从结晶型相转变成无定型相，在水中固化后又转变成结晶型相；金属盐的存在破坏了聚酰胺分子间的氢链，导致了材料在固化过程中聚酰胺结构发生了变化．该材料生物相容性和生物活性好，能促进骨缺损的修复和重建。     

Bone substitute biomedical material of multi-(amino acid) copolymer: in vitro degradation and biocompatibility

Degradable polymers with good mechanical strength as bone repair biomaterials have been paid more attention in biomedical application. In this study, a multi-(amino acid) copolymer consisting of 6-aminocaproic acid and five natural amino acids was prepared by a reaction of acid-catalyzed condensation. The results revealed that the copolymer could be slowly degradable in Tris-HCl solution, and lost its initial weight of 31.9 wt% after immersion for 12 weeks, and the changes of pH value of Tris-HCl solution were in range from 6.9 to 7.4 during soaking. The compressive strength of the copolymer decreased from 107 to 68 MPa after immersion for 12 weeks. The proliferation and differentiation of MG-63 cells on the copolymer significantly increased with time, and the cells with normal phenotype extended and spread well on the copolymer surfaces. When the copolymer was implanted in muscle and bone defects of femoral cortex of dogs for 12 weeks, the histological evaluation confirmed that the copolymer exhibited excellent biocompatibility and more effective osteogenesis in vivo. When implanted into cortical bone defects of dogs, the copolymer could be combined directly with the natural bone without fibrous capsule tissue between implants and host bone. The results indicated that the multi-(amino acid) copolymer with sufficient strength, good biocompatibility and osteoconductivity had clinical potential for load-bearing bone repair or substitution.     

Titanium dental implants coated with Bonelike®: Clinical case report

The aim of the study was to evaluate the direct bone bonding and osteointegration of the commercial pure (cp Ti) implants coated with Bonelike® synthetic bone graft by plasma spraying. The Bonelike® coated implant was placed in the mandible of a 40-year-old patient and it was removed after a healing period of 3 months with a trephine of 6 mm diameter. The structure of the coating and new bone/implant interface of retrieved samples were evaluated using scanning electron microscopy (SEM) and histological analysis using light microscopy. In vivo microstructure observations of Bonelike® coated retrieved implants showed excellent bone remnants on its surface without any tissue and inflammatory signs observed. The reported Bonelike® coated (cp Ti) implants improved primary stability, which may increase the lifetime of the implant. Bonelike® coated dental implants proved to be highly bioactive with extensive new bone formation and strongly bonded to Bonelike® coating.     

Long-term evaluation of titania-based ceramics compared with commercially pure titanium in vivo

Fifty-four cylinders (2.8 mm in diameter) machined from hot isostatically pressed titania (TI) and titania-hydroxyapatite (TI/HA-15 vol%) sintered at 925°C, as well as commercially pure titanium (c.p. Ti), were implanted in the fermoral cortical bone of New Zealand white rabbits for 1, 3 and 12 months. The shear strength between bone and implant was measured by a push-out test. The TI/HA composite showed a significantly higher bonding strength to bone compared to c.p. Ti at all times, while no differences were observed between TI and c. p. Ti at 1 and 3 months after implantation. Titania-based materials had a significantly higher bonding strength than that of c.p. Ti one year after implantation. The results indicate that bioactivity of HA in TI/HA composite contributes to the early bone apposition reflected by high bonding strength, while the stability of the oxide, determines the development of long-term bonding strength. Both effects may be explained by the level and type of ions released from the ceramic implant. HA has a positive conduction to bone ingrowth while TI has a limited interaction to the bone apposition due to the extraordinary low ion release in vivo. Under light microscopy, similar patterns of bone-implant interfaces were seen from titania-based materials and c.p. Ti in 3-month samples, indicating high biocompatibility of these materials. However, histological evaluation by light microscope cannot identify the differences between physical contact and chemical bonding of implant-bone interface, and thus does not give information on bonding mechanism and the level of shear stresses developed.     

口腔义齿固位用软磁种植体表面生物活性涂层的研究

采用两次涂烧法，先后在软磁体上涂烧中间层和多孔生物活性陶瓷，制备出了能防止体液渗透，具有生物活性的多孔陶瓷涂层。分析了影响基体与涂层结构强度的因素及涂层界面的结构。动物体内埋植实验表明其生物学性能良好。     

Electrophoretic deposition of nanobiocomposites for orthopedic applications: influence of current density and coating duration

Frequently metal implants undergo detachment from the host tissue due to inadequate biocompatibility and poor osteointegration. In view of this, bioactive porous apatite-wollastonite/chitosan nanocomposite coating was prepared using electrophoretic deposition (EPD) technique in the present work. The effect of coating duration and current density on surface characteristics of the nanocomposite coating was assessed using optical microscope and scanning electron microscope. EPD led to the formation of thick and homogeneous coating. Adhesion of the composite coating on titanium substrate was evaluated using tape test and bioactivity of the coatings was studied by immersing in simulated body fluid (SBF). The coating with higher current density and longer coating duration was found to be suitable with improved adhesion and bioactivity for intended metal implants.     

Electrophoretic deposition of bioglass reinforced zirconia for biomedical application

Ti-6Al-4V alloy is a bioinert material with low bioactive properties, which may hamper its bonding ability with body tissues that can be overcome by coating the metal with a bioactive glass layer, 45S5 reinforced zirconia. This coating can be deposited using an electrophoretic deposition process. In this study, a comparison is made between three types of coatings which are bioglass, pure zirconia and bioglass reinforced zirconia before and after heat treated. Mechanical evaluations using scratch tests and micro-hardness tests are conducted to evaluate the adhesion strengths and hardness properties of the coatings. The results show the presence of oxygen, and variations in the amounts of bioglass and zirconia, due to the activity of crystallization. X-ray diffraction confirms presence of all precursor elements in the coatings. The highest hardness value of 414 HV 2.942 is obtained for the sintered bioglass-zirconia composite coating, as compared to the hardness of bare titanium alloy of 266 HV 2.942. The highest adhesion strength of 1929 mN is also obtained for the bioglass-zirconia composite coating. These results show excellent performance for sintered bioglass-zirconia composite coating, making it a potential coating material for biomedical implants.     

Electrophoretic deposition of nanobiocomposites for orthopedic applications: influence of current density and coating duration

Frequently metal implants undergo detachment from the host tissue due to inadequate biocompatibility and poor osteointegration. In view of this, bioactive porous apatite-wollastonite/chitosan nanocomposite coating was prepared using electrophoretic deposition (EPD) technique in the present work. The effect of coating duration and current density on surface characteristics of the nanocomposite coating was assessed using optical microscope and scanning electron microscope. EPD led to the formation of thick and homogeneous coating. Adhesion of the composite coating on titanium substrate was evaluated using tape test and bioactivity of the coatings was studied by immersing in simulated body fluid (SBF). The coating with higher current density and longer coating duration was found to be suitable with improved adhesion and bioactivity for intended metal implants.     

Promotion of osteogenic differentiation of stem cells and increase of bone-bonding ability in vivo using urease-treated titanium coated with calcium phosphate and gelatin

Abstract

Because of its excellent biocompatibility and low allergenicity, titanium has been widely used for bone replacement and tissue engineering. To produce a desirable composite with enhanced bone response and mechanical strength, in this study bioactive calcium phosphate (CaP) and gelatin composites were coated onto titanium (Ti) via a novel urease technique. The cellular responses to the CaP/gelatin/Ti (CaP/gel/Ti) and bone bonding ability were evaluated with proliferation and osteogenic differentiation of mesenchymal stem cells (MSCs) on CaP/gel/Ti and CaP/Ti in vitro. The results showed that the optical density values, alkaline phosphatase expression and genes expression of MSCs on CaP/gel/Ti were similar to those on CaP/Ti, yet significantly higher than those on pure Ti (p < 0.05). CaP/gel/Ti and CaP/Ti rods (2 mm in diameter, 10 mm in length) were also implanted into femoral shaft of rabbits and pure Ti rods served as control (n = 10). Histological examination, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) measurements were performed at 4 and 8 weeks after the operation. The histological and SEM observations demonstrated clearly that more new bone formed on the surface of CaP/gel/Ti than in the other two groups at each time point. The CaP/gel/Ti bonded to the surrounding bone directly with no intervening soft tissue layer. An interfacial layer, containing Ti, Ca and P, was found to form at the interface between bone and the implant on all three groups by EDS analysis. However, the content of Ca, P in the surface of CaP/gel/Ti implants was more than in the other two groups at each time point. The CaP/gel/Ti modified by the urease method was not only beneficial for MSCs proliferation and osteogenic differentiation, but also favorable for bone bonding ability on Ti implants in vivo, suggesting that Ti functionalized with CaP and gelatin might have a great potential in clinical joint replacement or dental implants.     

Assessment of the degradation rates and effectiveness of different coated Mg-Zn-Ca alloy scaffolds for in vivo repair of critical-size bone defects

Surgical repair of bone defects remains challenging, and the search for alternative procedures is ongoing. Devices made of Mg for bone repair have received much attention owing to their good biocompatibility and mechanical properties. We developed a new type of scaffold made of a Mg-Zn-Ca alloy with a shape that mimics cortical bone and can be filled with morselized bone. We evaluated its durability and efficacy in a rabbit ulna-defect model. Three types of scaffold-surface coating were evaluated: group A, no coating; group B, a 10-μm microarc oxidation coating; group C, a hydrothermal duplex composite coating; and group D, an empty-defect control. X-ray and micro-computed tomography(micro-CT) images were acquired over 12 weeks to assess ulnar repair. A mechanical stress test indicated that bone repair within each group improved significantly over time (P?<?0.01). The degradation behavior of the different scaffolds was assessed by micro-CT and quantified according to the amount of hydrogen gas generated; these measurements indicated that the group C scaffold better resisted corrosion than did the other scaffold types (P?<?0.05). Calcein fluorescence and histology revealed that greater mineral densities and better bone responses were achieved for groups B and C than for group A, with group C providing the best response. In conclusion, our Mg-Zn-Ca-alloy scaffold effectively aided bone repair. The group C scaffold exhibited the best corrosion resistance and osteogenesis properties, making it a candidate scaffold for repair of bone defects.     

Fixation of carbon fibre-reinforced carbon composite implanted into bone

The push-out test of three types of biomaterials: carbon fibre-reinforced carbon (CFRC), hydroxyapatite (HA), and surgical steel (SS) implanted into rabbits femurs was carried out. Hydroxyapatite was used as a positive control (good fixation expected in bone) and surgical steel was a negative one (potentially no fixation in bone). Regeneration of bone in contact with all implants was found three months after implantation. The shear strength between CFRC implants and bone was lower than with the HA implants and higher than the shear strength between the surgical steel and bone. Compressive strength of CFRC implants removed after the observation period was significantly lower than the compressive strength of non-implanted samples. It is concluded that the mechanical bonding between the CFRC implants and host tissues exists 3 months after intrabone implantation and is accompanied by a decrease of the strength of implants.