Influence of laser parameters on the microstructures and surface properties in laser surface modification of biomedical magnesium alloys

Biodegradable implants from magnesium(Mg)alloys have emerged in the biomedical field especially in the orthopedic and cardiovascular stent applications owing to their low density,high specific strength,excellent machinability,good biocompatibility,and biodegradability.The primary shortcoming of Mg-based implants is their low corrosion resistance in the physiological environment,which results in premature mechanical integrity loss before adequate healing and the production of excessive hydrogen gas,which is harmful to the body tissues and negatively affects the biocompatibility of the implant.Laser surface modification has recently received attention because it can improve the surface properties such as surface chemistry,roughness,topography,corrosion resistance,wear resistance,hydrophilicity,and thus cell response to the surface of the material.The composition and microstructures including textures and phases of laser-treated surfaces depend largely on the laser processing parameters(input laser power,laser scan velocity,frequency,pulse duration,pressure,gas circulation,working time,spot size,beam focal position,and laser track overlap)and the thermophysical properties of the substrate(solubility,melting point,and boiling point).This review investigates the impacts of various laser surface modification techniques including laser surface melting,laser surface alloying,laser cladding,laser surface texturing,and laser shock peening,and highlights their significance in improving the surface properties of biodegradable Mg alloys for implant applications.Additionally,we explore how different laser process parameters affect its composition,microstructure,and surface properties in each laser surface modification technique.

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.

Development and prospects of degradable magnesium alloys for structural and functional applications in the fields of environment and energy

Magnesium and its alloys have such advantages with lightweight, high specific strength, good damping, high castability and machinability,which make them an attractive choice for applications where weight reduction is important, such as in the aerospace and automotive industries.However, their practical applications are still limited because of their poor corrosion resistance, low high temperature strength and ambient formability. Based on such their property shortcomings, recently degradable magnesium alloys were developed for broadening their potential applications. Considering the degradable Mg alloys for medical applications were well reviewed, the present review put an emphasis on such degradable magnesium alloys for structural and functional applications, especially the applications in the environmental and energy fields. Their applications as fracture ball in fossil energy, sacrificial anode, washing ball, and as battery anodes, transient electronics, were summarized. The roles of alloying elements in magnesium and the design concept of such degradable magnesium alloys were discussed. The existing challenges for extending their future applications are explored.

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,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.

Abnormal Blood Glucose Concentration on Degradation Behavior of AZ31 Magnesium Alloy

In order to evaluate the effect of blood glucose concentration on the reliability of AZ31 magnesium alloy medical implant,the corrosion of AZ31 alloy was studied in a simulated physiological saline solution.It is found that when the glucose concentration is in the normal range of ca.1g/L,the corrosion of AZ31 alloy can be inhibited However,when the glucose concentration becomes higher like that of diabetic patients,the degradation of AZ31 alloy is significantly accelerated.Therefore,for diabetic patients,the change in glucose concentration must be taken into consideration in order to ensure the reliability ofAZ31 medical implants.

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.

Predicting the degradation behavior of magnesium alloys with a diffusion-based theoretical model and in vitro corrosion testing

Magnesium alloys have shown great potential for their use in the medical device field, due to the promising biodegradability. However, it remains a challenge to characterize the degradation behavior of the Mg alloys in a quantitative manner. As such, controlling the degradation rate of the Mg alloys as per our needs is still hard, which greatly limits the practical application of the Mg alloys as a degradable biomaterial.This paper discussed a numerical model developed based on the diffusion theory, which can capture the experimental degradation behavior of the Mg alloys precisely. The numerical model is then implemented into a finite element scheme, where the model is calibrated with the data from our previous studies on the corrosion of the as-cast Mg-1 Ca and the as-rolled Mg-3 Ge binary alloys. The degradation behavior of a pin implant is predicted using the calibrated model to demonstrate the model’s capability. A standard flow is provided in a practical framework for obtaining the degradation behavior of any biomedical Mg alloys. This methodology was further verified via the comparison with enormous available experimental results. Lastly, the material parameters defined in this model were provided as a new kind of material property.

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 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.

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.

医用镁合金元素选择的研究现状

背景:镁合金具有的天然降解性、优秀的生物相容性和良好的力学性能,已成为生物医学领域十分具有研究价值的植入材料,然而镁合金快速的降解速率限制了其进一步的发展和应用。目的:综述镁及其合金处于生理环境下降解的一般基本原理,重点从安全性及对镁及其合金性能的影响两方面介绍镁合金化元素选择的研究现状。方法:利用计算机检索中国知网、PubMed、Web of Science和Elsevier等数据库中的相关文献,以“镁(合金),铋/铝等(金属名称),腐蚀,生物相容性,金属毒性,支架/螺钉”为中文主题检索词,以“magnesium(alloy),metal name(such as:bismuth(Bi),aluminium(Al)),corrosion,biocompatibility,metal toxicity,scaffold(stent)/screw”为英文检索词进行检索,检索时限为2013-2023年,通过阅读文献内容进行筛选,最终纳入70篇文献进行结果分析。结果与结论:镁合金在医学领域的研究已相当广泛,虽然目前有一些产品已应用于临床,但镁合金在人体环境中的高降解速率仍然是临床大规模应用的主要限制,未来发展的焦点是对其腐蚀速率的控制。合金化是一种提升镁合金耐腐蚀性能的方法,并可通过不同合金成分添加来改善镁合金的各种性能,但单纯的合金化已不能满足对镁合金多元化性能的追求。为开发优异性能的多功能镁合金产品,未来需要将合金化、表面改性等多种优化方式结合来弥补各自方法的不足,同时结合合金结构更新以及制备工艺改良,共同提升镁合金的性能。

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。

生物可降解镁合金的发展现状与展望

镁合金作为新型可降解医用金属材料,近年来成为生物材料领域的研究热点,并越来越受到生物、材料和医学界的关注和重视。从工程用镁合金、新型医用镁合金、表面改性镁合金和新颖结构镁合金4个方面综述了国际和国内生物可降解镁合金方面的研究现状,系统地介绍和总结了目前生物可降解镁合金材料的合金设计、力学性能、体液腐蚀特性、细胞毒性和动物体内植入实验的相关结果,展望了未来生物可降解镁合金亟待解决的科学问题和应用前景。

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。

医用镁金属材料的研究进展

镁及其合金具有优良的综合力学性能、与人体良好的生物相容性能以及生物可降解吸收等特点,有望成为一类新型医用植入材料。综述了镁金属作为医用植入材料的研究发展现状,分析了其应用上的优势与不足,对医用镁金属的表面改性技术进行了简单的论述,并对其作为医用植入材料的发展前景进行了展望。

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。

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。