热喷涂生物陶瓷涂层的研究进展

采用热喷涂技术在金属(合金)基材表面制备的生物陶瓷涂层, 兼具金属材料较高力学强度和陶瓷材料优良生物学性能, 作为骨植入材料的研究和应用备受关注。本文介绍骨植入涂层材料的研究概况, 重点阐述热喷涂羟基磷灰石(HA)涂层的研究现状, 并概述新型生物活性硅酸钙陶瓷涂层的研究进展。     

Review of the biocompatibility of micro-arc oxidation coated titanium alloys

Titanium and its alloys are expected to be ideal materials for biomedical applications. Various approaches have been used for biological properties improvement. Among various surface modification techniques, micro-arc oxidation (MAO), which can produce porous, adhesive and bioactive coatings for implantation, has aroused considerable attention. This paper gives a brief overview of biological assessment of bioactive coatings. It focuses mainly on the strategies of improving biological properties of MAO coated titanium and its alloys. The influence of the electrolyte, process parameters, pretreatment and post-treatment on the coating characteristics (surface micrograph, adhesion strength and biological compatibility etc.) is detailed in this article. MAO assisted by other methods to achieve superior biocompatibility is also discussed. Finally, the trend of development in the future is forecasted.     

Synthesis of biomaterial thin films by pulsed laser technologies: Electrochemical evaluation of bioactive glass-based nanocomposite coatings for biomedical applications

The surface of biomedical titanium implants has been covered with thin films of bioactive glass and bioactive glass + poly(methyl methacrylate nanocomposite) in order to increase the resistance to corrosion and improve the bioactivity of their area in contact with bone tissue. To this purpose Pulsed Laser Deposition and Matrix Assisted Pulsed Laser Evaporation with an excimer laser source have been applied.The layer assessments under conditions that simulate their biological interaction with the human body fluids and resistance to degradation have been studied by electrochemical polarization and electrochemical impedance spectroscopy. The poly(methyl methacrylate) addition to bioglass has reduced the bone ability to bond but resulted in a significant increase of the shielding efficiency against corrosion of the applied coatings.The obtained results support the application of bioactive glass and composite bioactive glass + poly(methyl methacrylate) coatings for the development of advanced highly stable implants and prostheses that cannot be affected by corrosion.     

Plasma spraying of biologically derived hydroxyapatite on implantable materials

Plasma spraying of hydroxyapatite (HA) coatings on human implants is considered to provide a promising means of enhancing their biocompatibility and improving tissue growth. This paper briefly describes a method of extracting HA powder from a biological source, namely human teeth. The physical and chemical characteristics of the derived powder are studied and the suitability of this powder for plasma spraying applications is ascertained. The deposited coatings are found to retain the chemistry characteristic of the apatite. Typical results of metallographic and scanning electron microscopy (SEM) studies and hardness measurements on the sprayed HA coatings are presented.     

In vivo evaluation of titanium implants coated with bioactive glass by pulsed laser deposition

During the past years, different techniques, like chemical treatment, plasma spraying, sputtering, enamelling or sol–gel; and materials, like metals, hydroxylapatite, calcium phosphates, among others, have been applied in different combinations to improve the performance of prostheses. Among the techniques, Pulsed Laser Deposition (PLD) is very promising to produce coatings of bioactive glass on any metal alloy used as implant. In this work the biocompatibility of PLD coatings deposited on titanium substrates was examined by implantation in vivo. Different coating compositions were checked to find the most bioactive that was then applied on titanium and implanted into paravertebral muscle of rabbit.     

Effects of Feedstock and Laser Post-spray Treatment on Plasma Sprayed Bioceramic Coatings*

Hydroxyapatite (HA) is a bioactive material with Ca to P ratio similar to that of natural bone. This can encourage early bonding between bony tissues and the implant surface. Plasma spraying is efficient in coating HA onto biomedical implants. However, the biocompatibility of hydroxyapatite (HA) changes after plasma spraying. This paper reports the preparation and characterization of HA coatings using different feedstocks; calcined HA (CHA) that has angular geometry, and spray dried HA (SDHA) that is predominantly spherical in shape. The results indicates that the state of the starting powder adversely influences the coating characteristics. Both types of HA, calcined and crushed HA powders and spray dried HA powders, are plasma sprayed on steel substrates to produce HA coatings. The results indicate that particle cohesion, size range and thermal treatment during thermal spray processing alter the phase and structure of the as-sprayed coatings. Post-spray treatment by pulsed lasers is performed on the coatings to modify the surface characteristics and phase composition of the surface layer. This, in addition, may be necessary to produce a dense and well-bonded coating having the desired biocompatible properties. Laser treatments show overall melting of the HAcoating to yield a smooth surface. However, the presence of crack networks is undesirable.     

Influence of microstructure and chemical composition of sputter deposited TiO<Subscript>2</Subscript> thin films on in vitro bioactivity

Functionalisation of biomedical implants via surface modifications for tailored tissue response is a growing field of research. Crystalline TiO₂ has been proven to be a bone bioactive, non-resorbable material. In contact with body fluids a hydroxyapaptite (HA) layer forms on its surface facilitating the bone contact. Thus, the path of improving biomedical implants via deposition of crystalline TiO₂ on the surface is interesting to follow. In this study we have evaluated the influence of microstructure and chemical composition of sputter deposited titanium oxide thin films on the in vitro bioactivity. We find that both substrate bias, topography and the flow ratio of the gases used during sputtering affect the HA layer formed on the films after immersion in simulated body fluid at 37°C. A random distribution of anatase and rutile crystals, formed at negative substrate bias and low Ar to O₂ gas flow ratios, are shown to favor the growth of flat HA crystal structures whereas higher flow ratios and positive substrate bias induced growth of more spherical HA structures. These findings should provide valuable information when optimizing the bioactivity of titanium oxide coatings as well as for tailoring process parameters for sputtered-based production of bioactive titanium oxide implant surfaces.     

Formation and bioactivity of porous and nanostructured TiO2/beta-TCP coating on titanium

Titanium and its alloys have been widely used as hard tissue implants due to their excellent mechanical properties and biocompatibility. However, their near bio-inertness and metallic ion release are still the problems with clinical uses. In this paper, porous and nanostructured TiO2/beta-tricalcium phosphate (beta-TCP) composite coatings were prepared on titanium substrates by plasma electrolytic oxidation (PEO) in a Ca and P-containing electrolyte. The influence of PEO electric current density on phase composition and bioactivity of the coatings were studied. X-ray diffraction, scanning electron microscopy and Fourier transfer infrared spectroscopy were utilized to characterize the phase composition and microstructure of the coatings. Simulated body fluid immersion tests were employed on the coatings to evaluate their bioactivity. The results reveal that TiO2/beta-TCP composite coating with pores size less than 10 microm and grains of 50-100 nm in size was prepared. The electric current density of PEO is an important factor in the formation of the composite coating. The TiO2/beta-TCP composite coating shows good bioactivity, which are attributed to the incorporation of beta-TCP.     

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 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.     

Nano-structured titanium coating for improving biological performance

Nano-structured titanium coating was obtained by alkali treating the vacuum plasma sprayed samples following hot water immersing for 24 h. The influences of the surface microstructure on the biological performance were studied. A canine model was applied for in vivo evaluation of the bone bonding ability of the coatings. The histological examination results demonstrate that new bone was formed more rapidly on the nano-structured coating implants and grew into the porosity than the as-sprayed one. After 4 weeks implantation, the nano-structured implants were found to appose directly to the surrounding bone while large lacunae could still be observed at the interface between the as-sprayed samples and bone. All these results indicate that a nano-structured surface on the porous titanium coating is favorable for bone bonding.     

Effects of ions dissolved from bioactive glass-ceramic on surface apatite formation

Non-bioactive glass-ceramic A-W(Al) containing apatite and wollastonite in a MgO–CaO–SiO₂–Al₂O₃ glassy matrix did not form an apatite layer on its surface in a simulated body fluid with ion concentrations nearly equal to those of human blood plasma and also in the fluids with small amounts of the calcium and silicate ions added individually, but formed the apatite layer in the fluid with the calcium and silicate ions added simultaneously. This indicates that the calcium and silicate ions dissolved from bioactive glass-ceramic A-W containing the apatite and wollastonite in a MgO–CaO–SiO₂ glassy matrix play a cooperative and important role in forming an apatite layer on its surface in the body, to give the glass-ceramic bioactivity. The calcium ion might increase the degree of the supersaturation of the surrounding body fluid, and the silicate ion might provide favourable sites for nucleation of the apatite on the surfaces of glass-ceramic.     

Electrospray deposition of nanohydroxyapatite coatings: A strategy to mimic bone apatite mineral

The biological performance of orthopaedic and oral metallic implants can be enhanced significantly by the application of bioactive coatings. In this work, a cost-efficient alternative to the traditional technique to produce a hydroxyapatite (HA) coating with a nanostructured feature onto a metallic implant surface at room temperature via electrospray deposition, is presented. To evaluate the bioactive capacity of these nanoHA (nHA) coatings in vitro, an acellular simulated body fluid soaking experiment and a human osteoblast (HOB) cell culture work were conducted. Under these physiological conditions, the accelerated apatite precipitation process occurred on the nHA-coated titanium surfaces as compared to the uncoated titanium surfaces. HOB cells developed mature cytoskeletons with distinct evidence of actin stress fibres and vinculin adhesion plaques, on these nHA coatings. Hence, this deposition technique holds great potential in producing high quality nHA coatings for biomedical applications.     

Stress Corrosion Crack Growth Behavior of Titanium Alloy／Bioactive Glasses Sandwiches in Simulated Human Physiological Environment

Based on a series of newly developed bioactive glasses having suitable thermo-mechanical properties to allow application as fixation agents between bone and titanium alloy biomedical implants,the stress corrosion crack growth (SCCG) behavior of their interfaces with Ti6Al4V was investigated in simulated body fluid (SBF) with the objective of discerning the salient mechanisms of crack advance and to assess the reliability of the bonds.Results indicated that crack growth rates in Ti6Al4V/glass/Ti6Al4V sandwich specimens were nearly the same as or slightly lower than those in the bulk glasses at comparable stress intensities;indeed,cracks would prefer to propagate off the interface,suggesting that the Ti6Al4V/glass interface has relatively good crack-growth resistance.Mechanistically, interfacial crack growth appears to be controlled by the classic stress corrosion mechanisms for silicate glasses,with no discernible effect of bioactivity on the SCCG behavior being observed.     

经碱处理的等离子喷涂钛涂层的成骨性能研究

用碱处理方法对等离子喷涂的钛涂层进行了表面改性.涂层的骨结合能力通过植入到狗股骨中进行探查.涂层与骨组织之间的结合强度用推出实验进行测量.获得的结果表明改性的涂层不但能直接与骨组织结合,还促进了骨组织的长入.植入一个月后,改性的涂层展示了较好的成骨性能,取得了较高的结合强度.对碱处理改善钛涂层成骨性能的机理作了进一步的分析.这主要是由于碱处理后涂层表面的微观结构以及化学组成的改变所引起的.     

等离子喷涂HA／Ti复合涂层研究

对等离子喷涂HA／Ti复合涂层进行模拟体液和体外细胞试验,以考察涂层的生物学性能．结果指出,涂层经模拟体液浸泡后,表面覆盖一层碳酸磷灰石(carbonate-apatite),这表明涂层具有良好的生物活性．粗糙的涂层表面易于形成碳酸磷灰石．模拟体液的浓度太小或pH值太大,均会导致碳酸磷灰石层不能在涂层表面形成．体外细胞试验显示,成骨细胞能在涂层表面紧密贴壁并正常生长,显示涂层具有优良的生物相容性．     

等离子喷涂HA/Ti复合涂层研究 Ⅱ.生物学性能

对等离子喷涂ＨＡ／Ｔｉ复合涂层进行模拟体液和体外细胞试验,以考察涂层的生物学性能。结果指出,涂层经模拟体液浸泡后,表面覆盖一层碳酸磷灰石（ｃａｒｂｏｎａｔｅ－ａｐａｔｉｔｅ）,这表明涂层具有良好的生物活性,粗糙的涂层表面易于形成碳酸磷灰石,,模拟体液的浓度太小或ｐＨ值太大,均会导致碳酸磷灰石层不能在涂层表面形成,体外细胞试验显示,成骨细胞能在涂层表面紧密贴壁并正常生长,显示涂层具有优良的生物相容性     

In vivo evaluation of modified titanium implant surfaces produced using a hybrid plasma spraying processing

In this study, the biological responses to surface-modified titanium (Ti) was investigated using a dog model. Titanium plasma spraying and ion implantation of amino (NH₂⁺) groups were used as means of modifying Ti surfaces. Characterization of the modified Ti surfaces was performed using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning Auger electron spectroscopy. In vivo evaluations were performed using fluorescence microscope, scanning electron microscope and energy disperse spectroscopy. It was observed in this study that ion-implanted porous-graded titanium coatings had a thick surface oxide layer, containing a small amount of nitride. In vivo study indicates direct bone contact between surface-modified Ti implants and osseous tissues. In addition, osseous tissues were observed to grow into the pores inside the coatings, thereby allowing the formation of a gradual calcium phosphate interface layer. It was concluded from this study that ion implantation of Ti surfaces with amino groups, induced higher concentration of calcium and phosphorus precipitation and more mineralization as compared to non-ion-implanted Ti surfaces.     

碳/碳复合材料表面改性及其生物响应特性

碳/碳复合材料继承了碳材料固有的生物相容性,它具有优异的力学性能,特别是它的弹性模量与人骨相当,是一种具有潜力的骨修复和替代生物材料.但是由于碳/碳复合材料为生物惰性材料,其与骨组织表面仅仅是机械结合,通过表面改性,可在其表面构筑生物活性涂层以提高其生物活性和减少碳颗粒的释放.本文在综述了碳/碳复合材料表面生物活性涂层制备方法及其生物学响应特性的基础上,分析了目前研究中存在的问题,提出一些解决的办法,并展望了其发展前景.     

Improved stability of plasma-sprayed dicalcium silicate/zirconia composite coating

Dicalcium silicate/zirconia composite coatings were produced on Ti-6Al-4V substrates using atmospheric plasma spraying. Different weight ratios of zirconia (50 wt.%, 70 wt.%, 90 wt.%) were mechanically blended with dicalcium silicate (C₂S) powders as feedstocks. The composite coatings were immersed in a simulated body fluid (SBF) and a Tris-HCl solution for the in vitro appraisement of stability and long-term performance in a biological environment. The ion concentration changes of Ca, Si, and P in SBF and Tris-HCl solution were monitored using inductively-coupled plasma atomic emission spectroscopy (ICP-AES). Compared to the pure C₂S coating, our results show that the dissolution rate of the composite coatings is effectively reduced and the stability is improved by the addition of zirconia. The high content of zirconia in the coatings ensures the long-term performance in biological environment, while dissolution of C₂S in the coatings results in a higher Ca ion concentration in SBF and rapid precipitation of bone-like apatite on the composite coating surfaces indicating good bioconductivity of the coatings.