Porous TiNbZr alloy scaffolds for biomedical applications

In the present study, porous Ti–10Nb–10Zr alloy scaffolds with different porosities were successfully fabricated by a “space-holder” sintering method. By the addition of biocompatible alloying elements the porous TiNbZr scaffolds achieved significantly higher strength than unalloyed Ti scaffolds of the same porosity. In particular, the porous TiNbZr alloy with 59% porosity exhibited an elastic modulus and plateau stress of 5.6 GPa and 137 MPa, respectively. The porous alloys exhibited excellent ductility during compression tests and the deformation mechanism is mainly governed by bending and buckling of the struts. Cell cultures revealed that SaOS2 osteoblast-like cells grew on the surface and inside the pores and showed good spreading. Cell viability for the porous scaffold was three times higher than the solid counterpart. The present study has demonstrated that the porous TiNbZr alloy scaffolds are promising scaffold biomaterials for bone tissue engineering by virtue of their appropriate mechanical properties, highly porous structure and excellent biocompatibility.     

Elastic deformation behaviour of Ti-24Nb-4Zr-7.9Sn for biomedical applications

In this paper, the elastic deformation behaviour of a recently developed beta-type titanium alloy Ti-24Nb-4Zr-7.9Sn (wt.%) that consists of non-toxic elements and is intended for biomedical applications is described. Tensile tests show that this alloy in the as hot-rolled state exhibits peculiar non-linear elastic behaviour with maximum recoverable strain up to 3.3% and incipient Young's modulus of 42GPa. Solution treatment at high temperature has trivial effect on super-elasticity but decreases strength and slightly increases the incipient Young's modulus. Ageing treatment in the (alpha+beta) two-phase field increases both strength and Young's modulus and results in a combination of high strength and relatively low elastic modulus. In spite of the formation of the alpha phase, short time ageing has no effect on super-elasticity, whereas the non-linear elastic behaviour transforms gradually to normal linear elasticity with the increase of ageing time. We suggest sluggish, partially reversible processes of stress-induced phase transformation and/or incipient kink bands as the origin of the above peculiar elastic behaviour.     

年龄与位置对牙本质力学性质的影响

目的研究人牙本质弹性模量和硬度随年龄和位置的变化情况。方法采集下颌无龋坏第3磨牙,按照年龄分为青年、中年、老年3组。采用纳米压痕对牙本质切片的多个位置进行力学测试。结果外层和中层牙本质的弹性模量和硬度大于内层牙本质的弹性模量和硬度;随着年龄的增长,各个区域的牙本质弹性模量和硬度都增大。结论牙本质具有梯度力学特性,外层和中层牙本质具有很高的刚度,其抵抗变形的能力要强于内层牙本质。同时,随着年龄增长牙本质弹性模量和硬度增大。     

牙本质微结构性质的重新评价

目的相比以前一些模型,蛋白质-矿物质多孔力学模型被验证可以提供更精确的生物材料性质评价。因此,本文对牙本质微结构相互作用对其材料性质的影响进行了重新评价。方法采用蛋白质-矿物质多孔力学模型,讨论了牙小管、管周基质和管间基质相互作用对牙本质微结构性质的影响。结果通过分析发现,牙本质微结构力学性质依赖于牙小管的方向和牙小管中的压力值;同时,牙本质微结构力学性质会随着年龄以及管周基质与管间基质的蛋白质和矿物质分布而改变。结论文章中的理论分析和讨论说明牙小管、管周基质和管间基质相互作用对牙本质微结构性质有一定的影响,说明蛋白质-矿物质多孔力学模型的有效性,以及不考虑相互作用的微结构力学模型具有一定的局限性。     

Microstructure, mechanical properties and cytocompatibility of stable beta Ti–Mo–Ta sintered alloys

We have synthesized titanium-based alloys containing molybdenum and tantalum elements by powder metallurgy. The microstructure, the residual porosity and the mechanical properties of the sintered Ti–Mo and Ti–Ta–Mo alloys were investigated by using optical and electronic microscopy, X-ray diffraction, microhardness and compression tests. The cytocompatibility of the different alloys was evaluated by the assessment of bone cell density, migration and adhesion after 14 days incubation. All the alloys present a high ductility and an excellent cytocompatibility, which make these materials useful for medical implants.     

孔隙率对多孔镍钛合金力学性能及离子析出量的影响

目的筛选生物力学相容性优良的颌骨内植入用多孔镍钛合金,比较二氧化钛(TiO2)与羟基磷灰石(HA)涂层后的镍离子析出量。方法采用粉末冶金法制备多孔镍钛合金,用金相显微镜观察孔隙形貌,进行压缩与抗折破坏实验,记录其弹性模量与断裂强度值;采用溶胶-凝胶法分别涂覆TiO2与HA涂层,测定1、3、7、15 d镍离子析出量。结果孔隙由相互连通的50～200μm大孔和～50μm微孔组成,孔隙率为(23.5±5.24)%～(38.8±1.82)%;弹性模量为(9.55±0.19)～(4.28±0.32)GPa,断裂强度值为(133±6.75)～(80.5±5.58)MPa。表面涂层组与未涂层组比较,离子析出量显著降低;氧化钛与羟基磷灰石涂层组间差异无统计学意义。结论随造孔剂增加,孔隙率增大,多孔镍钛合金的力学性能呈下降趋势;涂层能有效抑制多孔镍钛材料中镍离子析出。     

Mechanical properties and bioactive surface modification via alkali-heat treatment of a porous Ti-18Nb-4Sn alloy for biomedical applications

A porous Ti-18 at.%Nb-4 at.%Sn (hereafter, Ti-18Nb-4Sn) alloy was prepared by powder metallurgy. The porous structures were examined by scanning electron microscopy and the phase constituents were analysed by X-ray diffraction. Mechanical properties of the porous alloy were investigated using a compressive test. To enhance the bioactivity of the alloy surface, alkali-heat treatment was used to modify the surface. The bioactivity of the pre-treated alloy sample was investigated using a biomimetic process by soaking the sample into simulated body fluid (SBF). Results indicate that the elastic modulus and plateau stress of the porous Ti-18Nb-4Sn alloy decrease with decreasing relative density. The mechanical properties of the porous alloy can be tailored to match those of human bone. After soaking in SBF for 7 days, a hydroxyapatite layer formed on the surface of the pre-treated porous Ti-18Nb-4Sn alloy. The pre-treated porous Ti-18Nb-4Sn alloy therefore has the potential to be a bioactive implant material.     

Effect of nickel addition on microstructure and properties of Ti-Co-Ni alloys

The focus of this study was placed on the effect of nickel addition (5 wt%) on the microstructure, castability, biocorrosion resistance and some other properties of a series of cast high-cobalt (up to 25 wt%) Ti-Co-Ni alloys. Results indicated that melting temperatures of the present alloys were much lower than the melting temperature of pure titanium. Addition of 5 wt% Ni to replace an equivalent amount of Co slightly lowered the eutectoid and melting temperatures. Castability of the alloys was enhanced by the high alloy content and higher mould temperature. Substitution of 5 wt% Ni for Co increased the castability values. The phase transformation of β-Ti to -Ti was enhanced by nickel addition and higher mould temperature. Microhardness of the alloys increased with cobalt content and decreased with mould temperature. The addition of nickel lowered the hardness of the alloys. Breakdown potentials of the alloys were all higher than 900 mV and the critical anodic current densities were all lower than 8 μA cm⁻².     

Microstructures and mechanical properties of metastable Ti-30Zr-(Cr, Mo) alloys with changeable Young's modulus for spinal fixation applications

In order to develop a novel alloy with a changeable Young's modulus for spinal fixation applications, we investigated the microstructures, Young's moduli, and tensile properties of metastable Ti-30Zr-(Cr, Mo) alloys subjected to solution treatment (ST) and cold rolling (CR). All the alloys comprise a β phase and small athermal ω phase, and they exhibit low Young's moduli after ST. During CR, deformation-induced phase transformation occurs in all the alloys. The change in Young's modulus after CR is highly dependent on the type of deformation-induced phase. The increase in Young's modulus after CR is attributed to the deformation-induced ω phase on {3 3 2} mechanical twinning. Ti-30Zr-3Cr-3Mo (3Cr3Mo), which exhibits excellent tensile properties and a changeable Young's modulus, shows a smaller springback than Ti-29Nb-13Ta-4.6Zr, a β-type titanium alloy expected to be useful in spinal fixation applications. Thus, 3Cr3Mo is a potential candidate for spinal fixation applications.     

Development of the novel ferrous-based stainless steel for biomedical applications, part I: high-temperature microstructure, mechanical properties and damping behavior

This research investigated the high-temperature microstructure, mechanical properties, and damping behavior of Fe–9Al–30Mn–1C–5Co (wt.%) alloy by means of electron microscopy, experimental model analysis, and hardness and tensile testing. Subsequent microstructural transformation occurred when the alloy under consideration was subjected to heat treatment in the temperature range of 1000–1150 °C: γ→(γ+κ). The κ-phase carbides had an ordered L′1₂-type structure with lattice parameter . The maximum yield strength (σ_y), hardness, elongation, and damping coefficient of this alloy are 645 MPa, Hv 292, ∼54%, and 178.5×10⁻⁴, respectively. These features could be useful in further understanding the relationship between the biocompatibility and the wear and corrosion resistance of the alloy, so as to allow the development of a promising biomedical material.     

The role of oxidative stress in pro-inflammatory activation of human endothelial cells on Ti6Al4V alloy

Inflammation is an important step in the early phase of tissue regeneration around an implanted metallic orthopaedic device. However, prolonged inflammation, which can be induced by metallic corrosion products, can lead to aseptic loosening and implant failure. Cells in peri-implant tissue as well as metal corrosion can induce reactive oxygen species (ROS) formation, thus contributing to an oxidative microenvironment around an implant. Understanding cellular reactions to implant-induced oxidative stress and inflammatory activation is important to help prevent an adverse response to metallic materials. In an earlier study we have shown that endothelial cells grown on Ti6Al4V alloy are subjected to oxidative stress. Since endothelial cells play a critical role in inflammation, in this study we examined the role of oxidative stress in their response to pro-inflammatory activation. Therefore, we stimulated endothelial cells in contact with Ti6Al4V with tumour necrosis factor-α (TNF-α) and monitored the expression of inflammation-associated molecules, such as E-selectin, intercellular adhesion molecule-1 (ICAM-1) and interleukin-8 (IL-8). The induction of these proteins was lower in endothelial cells on Ti6Al4V compared to control tissue culture conditions. There was, however, a discrepancy in pro-inflammatory activation at protein compared to mRNA level in the cells on Ti6Al4V. To examine the role of oxidative stress in this response we utilized different ROS scavengers and showed that ROS depletion improved cellular response to TNF-α on Ti6Al4V. These results could contribute to developing strategies to improve tissue response to metal implants.     

利用后巩膜加固术治疗家兔近视眼后 成纤维细胞生物力学性能变化

目的 研究后巩膜加固术后家兔眼球不同时期成纤维细胞力学特性的变化,从生物力学的角度探讨后巩膜加固术的作用机制。 方法 3周龄新西兰家兔45只随机选取一侧眼球用眼睑缝合方法制备近视动物模型,建模60天后,眼球随机分为两组,A组行后巩膜加固术（PSR）,B组行相似手术（不放置加固条带）。分别于术后3个月和6个月取材培养培养巩膜加固区及过渡组织的成纤维细胞。用免疫细胞化学法对培养的细胞进行鉴定。利用微管吸吮方法结合半无限体细胞力学模型测定各组成纤维细胞的力学特性（包括成纤维细胞的平衡弹性模量E∞和表观黏性μ）。 结果经统计学分析,两组巩膜成纤维细胞的平衡弹性模量及表观黏性均无统计学意义（P>0.05）。后巩膜加固术6个月,经统计学分析,两组巩膜成纤维细胞的平衡弹性模量及表观黏性均无统计学意义（P>0.05）。后巩膜加固术后3月组与6月组的巩膜成纤维细胞比较,E∞和μ的差异均无统计学意义（P>0.05）。后巩膜加固术后3个月与6个月组的过渡区成纤维细胞的力学特性,E∞分别为（289.2±84.3）,（276.9±113.9）Pa;μ分别为（1 575.2±459）Pa·s,（1 492.2±562.6）Pa·s,其差异均无统计学意义（P>0.05）。结论后巩膜加固术的增强作用并不是原位巩膜成纤维细胞本身生物力学的加强,而是由于加固条带及引起过渡区的存在。     

The effect of microstructure on fatigue performance of Ti-6Al-4V alloy after EDM surface treatment for application in orthopaedics

Three different microstructures--equiaxed, bi-modal and coarse lamellar--are prepared from Ti-6Al-4V alloy. Electric discharge machining (EDM) with a high peak current (29 A) is performed in order to impose surface roughness and modify the chemical composition of the surface. Detailed scanning electron microscopy (SEM) investigation revealed a martensitic surface layer and subsurface heat affected zone (HAZ). EDX measurements showed carbon enriched remnants of the EDM process on the material surface. Rotating bending fatigue tests are undertaken for EDM processed samples for all three microstructures and also for electropolished-benchmark-samples. The fatigue performance is found to be rather poor and not particularly dependent on microstructure. The bi-modal microstructure shows a slightly superior high cycle fatigue performance. This performance can be further improved by a suitable heat treatment to an endurance limit of 200 MPa.     

The molecular mechanism for effects of TiN coating on NiTi alloy on endothelial cell function

The aim of this study is to systematically investigate the molecular mechanism of different effects of nickel titanium (NiTi) alloy surface and titanium nitride (TiN) coating on endothelial cell function. Release of nickel (Ni) ion from bare and TiN-coated NiTi alloys and proliferation of endothelial cells on the two materials were evaluated, and then influence of the two materials on cellular protein expression profiles was investigated by proteomic technology. Subsequently, proteomic data were analyzed with bioinformatics analyses and further validated using a series of biological experiments. Results showed that although the two materials did not affect cell proliferation, the Ni ions released from bare NiTi alloy generated inhibition on pathways associated with actin cytoskeleton, focal adhesion, energy metabolism, inflammation, and amino acid metabolism. In comparison, TiN coating not only effectively prevented release of Ni ions from NiTi alloy, but also promoted actin cytoskeleton and focal adhesion formation, increased energy metabolism, enhanced regulation of inflammation, and promoted amino acid metabolism. Furthermore, the two processes, “the initial mediation of adsorbed serum protein layer to endothelial cell adhesion and growth on the two materials” from our previous study, and “the following action of the two materials on cellular protein expression profile”, were linked up and comprehensively analyzed. It was found that in stage of cell adhesion (within 4 h), release of Ni ions from bare NiTi alloy was very low, and the activation of adsorbed proteins to cell adhesion and growth related biological pathways (such as regulation of actin cytoskeleton, and focal adhesion pathways) was almost as same as TiN-coated NiTi alloy. This indicated that the released Ni ions did not affect the mediation of adsorbed proteins to endothelial cell adhesion. However, in stage of cell growth and proliferation, the release of Ni ions from bare NiTi alloy increased with time and reached a higher level, which inhibited endothelial cell function at molecular level, whereas TiN coating improved endothelial cell function.     

镁合金AZ31B材料表性与成骨细胞的黏附

背景：镁合金对成骨细胞的生物学行为及早期黏附是否有影响尚不明确。 目的：分析镁合金AZ31B的表性,并评价其对成骨细胞黏附的影响。 方法：采用扫描电镜及能谱分析明确镁合金AZ31B的表面形态及元素组成。以蛋白吸附实验检测镁合金AZ31B与钛合金对蛋白的吸附能力。将镁合金AZ31B与钛合金分别与小鼠前成骨细胞MC3T3-El共培养于24孔板内,观察培养2,6,24 h的细胞黏附情况。 结果与结论：扫描电镜可见镁合金AZ31B表面较为粗糙,有利于细胞在其表面的黏附.能谱分析结果表明镁合金AZ31B的主要元素有镁、铝、锌,其中镁约占96%,铝约占3%,锌约占1%,另有一些其他元素,含量较少。镁合金AZ31B与钛合金的蛋白吸附率差异无显著性意义。培养2 h时,镁合金AZ31B与钛合金上的细胞黏附率差异无显著性意义;培养6,24 h,镁合金AZ31B上的细胞黏附率显著低于钛合金上的细胞黏附率(P < 0.01)。培养于镁合金表面的成骨细胞贴壁展开,形态不规则,大多呈梭形,有较多突起,部分细胞间突起相互连接。表明镁合金AZ31B具有良好的细胞黏附性,适合于成骨细胞的早期黏附。     

体力载荷对废用性兔胫骨超微结构和力量性能的影响

成年健康家兔26只,雌雄各半,单侧后肢用石膏管型固定六周.去固定后分四组.废用组兔胫骨皮质出现骨质疏松,骨胶原受累,暴露了骨单位的轮廓.去固定后四周,骨皮质代谢活跃,积极重建;在此基础上兔接受低强慢跑八周,骨髓腔壁有一厚层纤维骨板及类骨质,骨小梁数量少,线应变值未恢复.成年兔胫骨在体力活动影响下,以骨内膜成骨为主要方式.     

Evidence for apoptosis,MMP-1, MMP-3 and TIMP-2 expression and their effect on the mechanical and biochemical properties of fresh viable knee medial meniscal allografts and autografts in the rabbit

Introduction

The study sought evidence for apoptosis, the expression of MMP-1, MMP-3 and TIMP-2 and their effect on the mechanical and biochemical properties of rabbit fresh knee medial meniscal grafts in a 6-month follow-up.

Material and methods

Forty white male New Zealand rabbits were chosen for the study. The medial meniscus was excised from 28 animals and stored under tissue culture conditions for 2 weeks, following which 14 of them were implanted as autografts and 14 as allografts. When the animals were euthanized, 20 menisci were used for immunohistochemical examinations. Apoptosis (TUNEL method) and MMP-1, MMP-3 and TIMP-2 immunoexpression were estimated semiquantitatively. The other 20 menisci were subjected to biochemical analysis and their degree of elasticity was evaluated.

Results

An increased level of apoptosis (p <0.05) was observed both in allografts (1.57 ±0.98) and autografts (0.86 ±0.69); no statistical differences existed between them. An increased level of metalloproteinases and TIMP-2 expression was observed only in the allografts (p < 0.05). The highest decrease of degree of elasticity and the most significant changes in biochemical composition were observed in allografts (p < 0.05).

Conclusions

The studies confirmed the existence of excessive apoptosis in both kinds of fresh viable medial meniscal implants: auto- and allografts. Our results suggest that apoptosis and increased MMP-1 and MMP-3 expression have an adverse effect on the biological properties of implants. The results of experimental studies on humans indicate the need to devise a method of apoptosis inhibition in transplanted menisci to improve long-term results.     

The effect of processing variables on morphological and mechanical properties of supercritical CO2 foamed scaffolds for tissue engineering

The porous structure of a scaffold determines the ability of bone to regenerate within this environment. In situations where the scaffold is required to provide mechanical function, balance must be achieved between optimizing porosity and maximizing mechanical strength. Supercritical CO₂ foaming can produce open-cell, interconnected structures in a low-temperature, solvent-free process. In this work, we report on foams of varying structural and mechanical properties fabricated from different molecular weights of poly(dl-lactic acid) P_dlLA (57, 25 and 15 kDa) and by varying the depressurization rate. Rapid depressurization rates produced scaffolds with homogeneous pore distributions and some closed pores. Decreasing the depressurization rate produced scaffolds with wider pore size distributions and larger, more interconnected pores. In compressive testing, scaffolds produced from 57 kDa P_dlLA exhibited typical stress-strain curves for elastomeric open-cell foams whereas scaffolds fabricated from 25 and 15 kDa P_dlLA behaved as brittle foams. The structural and mechanical properties of scaffolds produced from 57 kDa P_dlLA by scCO₂ ensure that these scaffolds are suitable for potential applications in bone tissue engineering.