Degradation Rate Assessment of Biodegradable Magnesium Alloys

Biodegradable magnesium alloys have been widely used in medical implants. But safety concerns were put forward for the high degradation rate of biodegradable magnesium alloy. The optimal biodegradable magnesium alloys that give rise to the desired degradation rate hasn’t yet to be defined. Assessing the degradation rate of biodegradable magnesium alloys involves in vitro testing, in vivo testing, numerical modeling, understanding the factors influencing their degradation in physiological environments, biocompatibility testing, and clinical studies. It is important to standardize analytical tools aimed at assessing the degradation rate of biodegradable magnesium alloys. It is advisable to identify the threshold for safe degradation rate of biodegradable magnesium alloys in biomedical applications.

Evaluation of corrosion resistance, mechanical integrity loss and biocompatibility of PCL/HA/TiO_(2) hybrid coated biodegradable ZM21 Mg alloy

A novel PCL/HA/TiO_(2)hybrid coating on ZM21 Mg alloy substrate has been investigated for corrosion resistance, biocompatibility and mechanical integrity loss in terms of bending, compressive and tensile strength in physiological media. The prepared hybrid coating was dip coated over ZM21 from HA/TiO_(2)and PCL solutions followed by creating a microporous PCL layer by utilizing Non-solvent Induced Phase Separation(NIPS) technique. The electrochemical measurement and in-vitro degradation study in SBF after 28 days showed that the PCL/HA/TiO_(2) hybrid coating reduced H2 evolution rate, weight loss, and corrosion rate by 64, 116 and 118 times respectively, as compared to uncoated ZM21 samples. The surface studies carried out using SEM-EDX, FTIR and XRD revealed formation of highly stable 3d flower-like HA crystals with Ca/P ratio of 1.60 in the PCL micropores. This dense apatite growth effectively protected the PCL/HA/TiO_(2)hybrid coated samples to maintain the good mechanical integrity even after 28 days of immersion as compared to HA/TiO_(2)composite coated, As-polished(A/P) and As-machined(A/M) samples. The failure analysis of samples under mechanical loading were performed using SEM-BSE-EBSD.The in-vitro cellular viability of L929 fibroblast cells on PCL/HA/TiO_(2)hybrid coating was found 50.47% higher with respect to control group,whereas bacterial viability was supressed by 57.15 and 62.35% against gram-positive Staphylococcus aureus and gram-negative Escherichia coli bacterial models. The comprehensive assessment indicates PCL/HA/TiO_(2)hybrid coating as a suitable candidate to delay early degradation and mechanical integrity loss of Mg-based alloys for devising biodegradable orthopaedic implant.

In vitro degradation and biocompatibility of Mg-Li-Ca alloys—the influence of Li content

Mg-Li based alloys hold much attention as potential biomedical materials due to their excellent ductility. A reduced mechanical strength and concern for biocompatibility are exhibited for Mg-Li binary alloys due to the presence of Li element. Addition of the Ca element into Mg-Li alloys leads to an improvement in mechanical strength and biocompatibility.In the present work, the microstructure, mechanical property and corrosion behaviors of three kinds（α, α＋β, β） of as-extruded Mg-Li（1, 9 and 15 wt.%）-1 Ca alloys were investigated using optical microscope, X-ray diffraction（XRD）, tensile,immersion and electrochemical polarization measurements.In vitro biocompatibility was evaluated by cytotoxicity assays,hemolysis and four coagluation tests. The results indicated that the Mg-1 Li-1 Ca and Mg-15 Li-1 Ca alloys were characterized by α-Mg and β-Li phases besides Mg2 Ca particles, respectively; while the Mg-9 Li-1 Ca by dual（α-Mg＋β-Li） phase together with Mg2 Ca phase. The Mg-1 Li-1 Ca alloy had the highest ultimate tensile strength（UTS） and yield strength（YS）and the lowest elongation（EL） to failure（10.1±1.24%） as well.The EL for the Mg-9 Li-1 Ca alloy was the highest（52.2±0.01%）.The long-term immersion tests revealed a decrease in corrosion resistance with increasing Li content. The results of cytotoxicity assays clearly showed that the Mg-Li-Ca alloys demonstrated no toxicity to L-929 cells in 10% concentration of extracts. The Mg-1 Li-1 Ca alloy also exhibited an acceptable hemolysis ratio. The results of four coagulation tests designated no sign of thrombogenicity for the Mg-Li-Ca alloys except for the Mg-15 Li-1 Ca alloy.

In vitro degradation and biocompatibility of Mg-Nd-Zn-Zr alloy

In this study,in vitro degradation and biocompatibility of Mg-Nd-Zn-Zr(NZK) alloy were investigated to determine its suitability as a degradable medical biomaterial.Its corrosion properties were evaluated by static immersion test,electrochemical corrosion test,scanning electron microscopy(SEM),and energy dispersive spectroscopic(EDS) analysis,and in vitro biocompatibilities were assessed by hemolysis and cytotoxicity tests.Pure magnesium was used as control.The results of static immersion test and electrochemical corrosion test in simulated body fluid(SBF) demonstrated that the addition of alloying elements could improve the corrosion resistance.The hemolysis test found that the hemolysis rate of calcium phosphate coated NZK alloy was 4.8%,which was lower than the safe value of 5%.The cytotoxicity test indicated that NZK alloy extracts did not significantly reduce MC3T3-E1 cell viability.Hemolysis test and cytotoxicity test display excellent hemocompatibility and cytocompatibility of NZK alloy in vitro.Our data indicate that NZK alloy has excellent biocompatibility and thus can be considered as a potential degradable medical biomaterial for orthopedic applications.

In vitro and in vivo studies on pure Mg, Mg-1Ca and Mg-2Sr alloys processed by equal channel angular pressing

In the present work,the biomedical as-cast pure Mg,Mg–1 Ca and Mg–2 Sr alloys were processed with equal channel angular pressing(ECAP)technique to develop ultrafine microstructure within the materials,and their microstructures,mechanical properties,degradation behavior,cytocompatibility in vitro and biocompatibility in vivo were studied comprehensively.Finer-gained microstructures and improved mechanical properties of these three materials after ECAP were confirmed compared to their as-cast counterparts.Moreover,after ECAP the degradation rate of pure Mg was increased while that of Mg–1 Ca or Mg–2 Sr alloys decreased compared to the ascast counterparts.Additionally,good in vitro cytocompatibility and in vivo biocompatibility of these three materials were revealed by cell cultural tests using osteoblastic MC3 T3-E1 and human mesenchymal stem cells(h MSC)and in vivo animal tests at the lateral epicondyle of SD-rats’femur.This study offers an alternative powerful avenue to achieve good comprehensive properties of magnesium-based biodegradable metals.It might also help to extend the applied range of magnesium-based biodegradable metals in orthopedic field.

新型可降解生物医用镁合金JDBM的研究进展

镁合金因具有与人体骨头接近的密度和弹性模量、高比强度和比刚度、生物可降解性以及生物相容性等优点,近10年来国内外研究人员对其应用于骨内植物、骨组织工程支架和心血管支架等领域进行了广泛的研究。然而,目前大多数研究均以现有商用镁合金为对象,如含Al元素的AZ31、AZ91以及含重稀土元素的WE43等,并未考虑到作为生物材料的安全性等问题。本文作者阐述镁合金作为生物医用材料的优势、面临的挑战以及应对策略;重点介绍上海交通大学轻合金精密成型国家工程研究中心近年来围绕自行研发的新型生物医用镁合金JDBM开展的研究工作;最后展望可降解生物医用镁合金的应用前景和发展方向。

生物可降解镁合金临床应用研究进展

近年来作为生物医学材料领域的研究热点,镁合金因其优良的力学性能,与人体良好的生物相容性以及可降解吸收等特点越来越受到医学界的关注和重视,但总体说来,在医学领域的研究还处于探索阶段。综述了镁合金在临床应用方面的研究,分析了其在体内的降解机理及近年来提高其耐腐蚀性能的改进方法,指出镁合金作为医用植入材料的优势与不足,并展望了其作为一类新型医用材料的前景。

镁基可降解硬组织生物材料的研究进展

介绍了镁与人体健康的关系及镁基生物材料的优势。简要介绍了镁基硬组织生物材料的发展及其最新研究进展,包括镁基硬组织生物材料生理环境下的腐蚀降解、表面改性、生物相容性和多孔镁骨植入材料、镁添加剂生物材料、镁基复合材料等。还讨论了镁基生物材料存在的问题。

镁基合金应用于生物医用材料的研究进展

镁基合金具有较高的强韧性和加工性能以及较好的生物相容性,可应用于骨组织工程、整形外科以及血管支架中。而镁基合金在人体体液环境下的腐蚀性又反过来影响其使用寿命。采用适宜的改性方法不仅可以提高镁基合金的耐腐蚀性能,降低其生物降解速率,而且可以进一步提高其力学性能和表面生物活性。综述了镁基合金的力学相容性、生物相容性、可降解性以及针对以上性能的各种改性方法,并评述了国内外对镁基合金医用生物材料的应用研究概况。

医用材料Mg-Y-Nd-Zr合金的组织及力学性能

采用电阻炉和316L不锈钢坩埚，在RJ-2覆盖剂的保护下制备4种不同质量分数钕（Nd）的Mg-Y-Nd-Zr合金．采用电子探针、X射线衍射分析、拉伸测试、扫描电镜等方法研究4种合金的组织及力学性能．结果表明．Mg—Y—Zr合金主要由α-Mg和Mg24Y5相组成，加入Nd后，形成了新相Mg12Nd；Mg-Y-Nd-Zr合金断口具有准解理和韧性断裂的混合特征，其力学性能因Nd的质量分数不同而变化，弹性模量为25．8～35．8GPa，接近人体骨的模量，可满足医疗器械及用于心脏介入治疗生物可降解材料力学相客性要求．

FHA/Mg-Zn合金体内降解及生物相容性的评价

目的观察氟磷灰石﹙FHA﹚涂层镁锌合金在动物体内降解和生物相容性。方法取8只新西兰健康成年大白兔,随机分为2组:氟磷灰石﹙FHA﹚涂层镁锌合金和无涂层镁锌合金。在动物一侧股骨髁使用克氏针钻洞﹙4.5mm×10mm﹚,将FHA/Mg-Zn合金的棒状物﹙4.5mm×10mm﹚植入,同样办法在另一只兔子股骨髁植入大小一样的Mg-Zn合金的棒状物,术后4周取动物心、肝、肾及关节囊,HE染色后观察组织病理学改变,取股骨髁组织切片品红苦味酸染色,观察植入物的降解及新骨的形成。股骨髁行Micro-CT分析。结果 2组材料对动物心、肝、肾及关节囊的组织病理结果均正常。FHA/Mg-Zn合金与周围骨组织紧密接触,周围有大量新骨形成,未见明显降解。Mg-Zn合金明显降解,与周围骨组织形成缝隙,新骨形成较少。结论 FHA/Mg-Zn合金有效控制降解,具有良好生物相容性。

Mg-Y基生物材料研究进展

近年来,镁合金作为一种新型可降解金属生物材料,受到越来越多研究者的关注。Mg-Y基生物材料具有生物相容性好、力学性能优以及可降解吸收等优点,逐渐成为材料和医学领域的研究重点。本文主要阐述了国内外Mg-Y基生物材料的制备工艺、性能及其应用。同时,指出了Mg-Y基生物材料目前需要解决的问题和未来的研究方向,并展望了未来Mg-Y基生物材料的应用前景。

生物医用镁合金腐蚀的研究现状

介绍了镁合金的分类,生物相容性和作为生物医用材料的优势,论述了镁及其合金的腐蚀机理,综述了纯净化处理、合金化、形变处理,热处理和表面处理等方法提高镁合金耐体液腐蚀的机理和研究现状,并阐述了各种方法的优势,提出综合利用各种方法的思路。

热处理对WE43合金组织及力学性能的影响

本文采用覆盖剂法制备了WE43稀土镁合金,并对其进行了热处理。采用SEM、EPMA和XRD研究铸态、T4和T6态显微组织演变和力学性能变化。结果表明,铸态合金主要由Mg24Y5,Mg12Nd,Mg17La2,Mg17Ce2相组成,经T6热处理后,合金的第二相均匀弥散分布,组织明显得到改善,合金的力学性能得到提高,断口具有准解理和韧性断裂混合特征,其中延伸率室温达到5.57%,在250℃下,可达到13.5%,塑性成形能力好,易于支架材料的生产加工,而且弹性模量约42.6 GPa,接近人体骨的模量,满足支架材料的生物力学相容性。因此WE43合金的T6态可成为生物可降解支架基体材料。

Mg-Zn-Y-Nd合金胆囊夹在兔体内的降解行为及生物相容性

目的探讨Mg-Zn-Y-Nd合金胆囊夹在兔体内的降解行为及生物相容性。方法将36只兔随机分为裸合金夹组(A组)、植酸涂层合金夹组(B组)、MAO/植酸涂层合金夹组(C组)和空白对照组(D组),每组9只。D组兔不进行手术;其余各组兔行开腹手术,取灭菌处理后的不同涂层Mg-Zn-Y-Nd合金夹夹闭选取的胆囊壁组织。观察各组兔术后一般情况;检测各组兔手术前后血清镁离子、钙离子浓度及肝肾功能;术后7、14、21 d,采用X射线衍射观察各手术组兔合金夹降解情况;术后7、14、21 d分批处死各手术组兔并取出合金夹,通过扫描电镜观察合金夹降解情况。结果术后各组兔生命体征平稳,未出现并发症。X射线衍射和扫描电镜结果显示,随着术后时间的延长,A组兔合金夹表面结构缺损最为明显;B组兔合金夹表面裂纹加深;C组兔合金夹表面仅可见轻微裂纹,结构完整。手术前后各时间点4组兔血清镁离子、钙离子浓度及肝、肾功能指标比较差异均无统计学意义(P>0.05)。结论Mg-Zn-Y-Nd合金夹在兔体内生物相容性良好,且生物学毒性小,安全性高。MAO/植酸涂层合金夹在兔体内降解速率明显低于裸合金夹,且其生物相容性更好。

生物医用镁合金表面改性涂层研究进展

镁合金凭借其优异的生物安全性、良好的载荷传递性及独特的降解性,在医用植入领域表现出巨大的应用潜力和发展前景。然而镁合金在生理环境下的腐蚀溶解速率过快,导致材料力学性能衰减加速进而过早失效。表面改性作为镁合金耐蚀性能提升的重要途径,不仅能通过表层物理屏障的形成来减缓金属材料的溶解速率,还能抑制合金内部腐蚀电偶反应的强烈程度及调控其生物相容性。概述了典型表面改性工艺的技术优势,包括涂层在合金表面的多覆盖度、高膜层厚度、强附着力以及良好生物相容性等。同时归纳了几种表面改性工艺所存在的问题,包括较差的长期耐蚀性、低应力承受能力以及技术安全性等。在此基础上,重点综述了近年来镁合金表面改性涂层的最新研究动态,其中简要介绍了化学转化、微弧氧化、等离子喷涂等几种常见的表面改性涂层形成机制。系统阐述了涂层对镁合金降解过程和生物相容性的影响规律,以及部分元素或粒子对涂层微观结构以及生物性能的作用机理。最后展望了医用镁合金表面改性涂层的发展方向。

医用镁合金材料研究进展

由于具有可降解性、良好的生物相容性和力学性能等优点,镁及其合金近年来成了生物医用材料领域的研究热点。目前,已经开发的医用镁合金体系包括Mg-Ca、Mg-Zn、Mg-Si和Mg-RE(稀土)等多种合金体系。分析了镁合金材料作为可降解生物医用材料的优势和不足,对已经开发的部分医用镁合金体系作了详细的介绍。

In vitro and in vivo degradation behavior of Mg-2Sr-Ca and Mg-2Sr-Zn alloys

Magnesium alloys with integration of degradability and good mechanical performance are desired for orthopedic implants.In this paper,Mg-2Sr-Ca and Mg-2Sr-Zn alloys were prepared and the degradation as well as the bone response were investigated.Compared with the binary Mg-2Sr alloys,the addition of Ca and Zn improved the in vitro and in vivo corrosion resistance.Mg-2Sr-Ca and Mg-2Sr-Zn alloys exhibited more uniform corrosion and maintained the configuration of the implants 4 weeks post-implantation.The in vivo corrosion rates were 0.85 mm/yr for Mg-2Sr-Zn and 1.10 mm/yr for Mg-2Sr-Ca in comparison with 1.37 mm/yr for Mg-2Sr.The in vitro cell tests indicated that Mg-2Sr-Ca and Mg-2Sr-Zn alloys exhibited higher MG63 cell viability than Mg-2Sr alloy.Furthermore,these two alloys can promote the mineralization and new bone formation without inducing any significant adverse effects and this sound osteogenic properties suggest its attractive clinical potential.

Biodegradation behavior of micro-arc oxidation coating on magnesium alloy-from a protein perspective

Protein exerts a critical influence on the degradation behavior of absorbable magnesium(Mg)-based implants.However,the interaction mechanism between protein and a micro-arc oxidation(MAO)coating on Mg alloys remains unclear.Hereby,a MAO coating was fabricated on AZ31 Mg alloy.And its degradation behavior in phosphate buffer saline(PBS)containing bovine serum albumin(BSA)was investigated and compared with that of the uncoated alloy.Surface morphologies and chemical compositions were studied using Field-emission scanning electron microscope(FE-SEM),Fourier transform infrared spectrophotometer(FT-IR)and X-ray diffraction(XRD).The degradation behavior of the bare Mg alloy and its MAO coating was studied through electrochemical and hydrogen evolution tests.Cytotoxicity assay was applied to evaluate the biocompatibility of Mg alloy substrate and MAO coating.Results indicated that the presence of BSA decreased the degradation rate of Mg alloy substrate because BSA(RCH(NH2)COO‾)molecules combined with Mg2+ions to form(RCH(NH2)COO)2Mg and thus inhibited the dissolution of Mg(OH)2 by impeding the attack of Cl‾ions.In the case of MAO coated Mg alloy,the adsorption of BSA on MAO coating and the formation of(RCH(NH2)COO)2Mg exhibited a synergistic effect and enhanced the corrosion resistance of the coated alloy significantly.Furthermore,cell bioactive assay suggested that the MAO coating had good viability for MG63 cells due to its high surface area.

In vitro degradation,photo-dynamic and thermal antibacterial activities of Cu-bearing chlorophyllin-induced Ca-P coating on magnesium alloy AZ31

Surgical failures,caused by postoperative infections of bone implants,are commonly met,which cannot be treated precisely with intravenous antibiotics.Photothermal therapy(PTT)and photodynamic therapy(PDT)have attracted widespread attention due to their non-invasive antibacterial effects on tissues and no bacterial resistance,which may be an excellent approach to solve infections related to bone implants for biodegradable magnesium alloys.Herein,a sodium copper chlorophyllin(SCC)with a porphyrin ring induced Ca-P coating was prepared on AZ31 magnesium alloy via layer-by-layer(LbL)assembly.The morphology and composition of the samples were characterized through field emission scanning electron microscope(FE-SEM)with affiliated energy dispersive spectrometer(EDS),X-ray diffractometer(XRD),and Fourier infrared spectrometer(FTIR)and X-ray photoelectron spectrometer(XPS)as well.Potentiodynamic polarization,electrochemical impedance spectroscopy(EIS)and hydrogen evolution experiments were employed to evaluate the corrosion behavior of the samples.Atomic absorption spectrophotometer was used to measure Cu elemental content of different immersion periods.Cytocompatibility and antibacterial performance of the coatings were probed using in vitro cytotoxicity tests(MTT assay),live/dead cell staining and plate counting method.The results showed that the obtained(Ca-P/SCC)10 coating exhibited good corrosion resistance,antimicrobial activity(especially under 808 nm irradiation)and biocompatibility.The antibacterial rates for E.coli and S.aureus were 99.9%and 99.8%,respectively;and the photothermal conversion efficiency was as high as 42.1%.Triple antibacterial mechanisms including photodynamic,photothermal reactions and copper-ions release were proposed.This coating exhibited a promising application for biodegradable magnesium alloys.