Graphene-calcium carbonate coating to improve the degradation resistance and mechanical integrity of a biodegradable implant

Biodegradable implants are critical for regenerative orthopaedic procedures,but they may suffer from too fast corrosion in human-body environment.This necessitates the synthesis of a suitable coating that may improve the corrosion resistance of these implants without compromising their mechanical integrity.In this study,an AZ91 magnesium alloy,as a representative for a biodegradable Mg implant material,was modified with a thin reduced graphene oxide(RGO)-calcium carbonate(CaCO_(3))composite coating.Detailed analytical and in-vitro electrochemical characterization reveals that this coating significantly improves the corrosion resistance and mechanical integrity,and thus has the potential to greatly extend the related application field.

Additive manufacturing of porous magnesium alloys for biodegradable orthopedic implants:Process,design,and modification

Biodegradable magnesium(Mg)alloys exhibit excellent biocompatibility,adequate mechanical properties,and osteogenic effect.They can contribute to complete recovery of damaged tissues without concerns about a second surgery and have achieved clinical applications in orthopedic and cardiovascular fields.Porous scaffolds can provide functions such as bone integration and adjustable mechanical properties,thus widely used for bone repair.Additive manufacturing(AM)offers the advantages of design freedom and high precision,enabling the reliable production of porous scaffolds with customized structures.The combination of biodegradable Mg alloys,porous scaffolds,and AM processes has created tremendous opportunities for the precision treatment of bone defects.This article reviews the current development in the additive manufacturing process and design of Mg alloy biodegradable orthopedic implants,fo-cusing on chemical compositions,structural design,surface treatment,and their effects on mechanical properties,degradation behavior,and biocompatibility.Finally,the future perspective of porous Mg alloy biodegradable orthopedic implants is proposed.

Calcium phosphate conversion technique:A versatile route to develop corrosion resistant hydroxyapatite coating over Mg/Mg alloys based implants

Globally,vast research interest is emerging towards the development of biodegradable orthopedic implants as it overcomes the toxicity exerted by non-degradable implants when fixed in the human body for a longer period.In this context,magnesium(Mg)plays a major role in the production of biodegradable implants owing to their characteristic degradation nature under the influence of body fluids.Also,Mg is one of the essential nutrients required to perform various metabolic activities by the human cells,and therefore,the degraded Mg products will be readily absorbed by the nearby tissues.Nevertheless,the higher corrosion rate in the biological environment is the primary downside of using Mg implants that liberate H2gas resulting in the formation of cavities.Further,in certain cases,Mg undergoes complete degradation before the healing of damaged bone tissue and cannot serve the purpose of providing mechanical support.So,many studies have been focused on the development of different strategies to improve the corrosion-resistant behavior of Mg according to the requirement.In this regard,the present review focused on the limitations of using pure Mg and Mg alloys for the fabrication of medical implants and how the calcium phosphate conversion coating alters the corrosive tendency through the formation of hydroxyapatite protective films for enhanced performance in medical implant applications.

Surface Modification on Biodegradable Magnesium Alloys as Orthopedic Implant Materials to Improve the Bio-adaptability:A Review

Magnesium （Mg） and its alloys as a novel kind of biodegradable material have attracted much funda- mental research and valuable exploration to develop its clinical application, Mg alloys degrade too fast at the early stage after implantation, thus commonly leading to some problems such as osteolysis, early fast mechanical loss, hydric bubble aggregation, gap formation between the implants and the tissue. Surface modification is one of the effective methods to control the degradation property of Mg alloys to adapt to the need of organism. Some coatings with bioactive elements have been developed, especially for the micro-arc oxidation coating, which has high adhesion strength and can be added with Ca, P, and Sr elements. Chemical deposition coating including bio-mimetic deposition coating, electro-deposition coating and chemical conversion coating can provide good anticorrosion property as well as better bioactivity with higher Ca and P content in the coating. From the biodegradation study, it can be seen that surface coating protected the Mg alloys at the early stage providing the Mg alloy substrate with lower degra-dation rate. The biocompatibility study showed that the surface modification could provide the cell and tissue stable and weak alkaline surface micro-environment adapting to the cell adhesion and tissue growth. The surface modification also decreased the mechanical loss at the early stage adapting to the load- bearing requirement at this stage. From the interface strength between Mg alloys implants and the surrounding tissue study, it can be seen that the surface modification improved the bio-adhesion of Mg alloys with the surrounding tissue, which is believed to be contributed to the tissue adaptability of the surface modification. Therefore, the surface modification adapts the biodegradable magnesium alloys to the need of hiodegradation, biocompatibility and mechanical loss property. For the different clinical application, different surface modification methods can be provided to adapt to the clinical requirements for the Mg alloy implants.

Construction of tantalum/poly(ether imide)coatings on magnesium implants with both corrosion protection and osseointegration properties

Poly(ether imide)(PEI)has shown satisfactory corrosion protection capability with good adhesion strength as a coating for magnesium(Mg),a potential candidate of biodegradable orthopedic implant material.However,its innate hydrophobic property causes insufficient osteoblast affinity and a lack of osseointegration.Herein,we modify the physical and chemical properties of a PEI-coated Mg implant.A plasma immersion ion implantation technique is combined with direct current(DC)magnetron sputtering to introduce biologically compatible tantalum(Ta)onto the surface of the PEI coating.The PEI-coating layer is not damaged during this process owing to the extremely short processing time(30 s),retaining its high corrosion protection property and adhesion stability.The Ta-implanted layer(roughly 10-nm-thick)on the topmost PEI surface generates long-term surface hydrophilicity and favorable surface conditions for pre-osteoblasts to adhere,proliferate,and differentiate.Furthermore,in a rabbit femur study,the Ta/PEI-coated Mg implant demonstrates significantly enhanced bone tissue affinity and osseointegration capability.These results indicate that Ta/PEI-coated Mg is promising for achieving early mechanical fixation and long-term success in biodegradable orthopedic implant applications.

Microstructure, mechanical and bio-corrosion properties of as-extruded Mg-Sn-Ca alloys

The as-extruded Mg？Sn？Ca alloys were prepared and investigated for orthopedic applications via using optical microscopy, scanning electron microscopy, X-ray diffraction, as well as tensile, immersion and electrochemical tests. The results showed that, with the addition of 1% Sn and the Ca content of 0.2%？0.5%, the microstructure of the as-extruded Mg？Sn？Ca alloys became homogenous, which led to increased mechanical properties and improved corrosion resistance. Further increase of Ca content up to 1.5% improved the strength, but deteriorated the ductility and corrosion resistance. For the alloy containing 0.5% Ca, when the Sn content increased from 1% to 3%, the ultimate tensile strength increased with a decreased corrosion resistance, and the lowest yield strength and ductility appeared with the Sn content of 2%. These behaviors were determined by Sn/Ca mass ratio. The analyses showed that as-extruded Mg？1Sn？0.5Ca alloy was promising as a biodegradable orthopedic implant.

Surface modification of biodegradable magnesium and its alloys for biomedical applications

Magnesium and its alloys are being paid much attention recently as temporary implants,such as orthopedic implants and cardiovascular stents.However,the rapid degradation of them in physiological environment is a major obstacle preventing their wide applications to date,which will result in rapid mechanical integrity loss or even collapse of magnesium-based implants before injured tissues heal.Moreover,rapid degradation of the magnesium-based implants will also cause some adverse effects to their surrounding environment,such as local gas cavity around the implant,local alkalization and magnesium ion enrichment,which will reduce the integration between implant and tissue.So,in order to obtain better performance of magnesium-based implants in clinical trials,special alloy designs and surface modifications are prerequisite.Actually,when a magnesium-based implant is inserted in vivo,corrosion firstly happens at the implant-tissue interface and the biological response to implant is also determined by the interaction at this interface.So the surface properties,such as corrosion resistance,hemocompatibility and cytocompatibility of the implant,are critical for their in vivo performance.Compared with alloy designs,surface modification is less costly,flexible to construct multi-functional surface and can prevent addition of toxic alloying elements.In this review,we would like to summarize the current investigations of surface modifications of magnesium and its alloys for biomedical application.The advantages/disadvantages of different surface modification methods are also discussed as a suggestion for their utilization.

可降解医用镁基生物材料的研究进展

生物体内可降解吸收材料是生物材料发展的重要方向,由于金属材料具有较好的强度和塑韧性,因此金属基可降解吸收材料具有重要的临床应用价值。镁是所有金属材料中生物力学性能与人体骨最接近的金属材料,具有理想的生物力学相容性,因此,镁合金作为可降解生物材料具有巨大的应用潜力。首先介绍了镁基材料作为生物体内可降解植入材料的优点,然后简要回顾了镁基可降解生物材料的早期研究情况,同时系统地介绍和总结了目前的研究进展和遇到的挑战,最后展望了镁合金医用材料的应用前景和发展方向。

可降解镁及镁合金作为骨植入材料的研究进展

镁及镁合金具有良好的力学相容性、可降解性、生物安全性,并且其资源丰富,在骨科领域有巨大的应用前景。然而,镁及其合金在骨科临床应用中也存在降解过快,长时间力学性能完整性不够的问题。文章全面综述了可降解镁及镁合金作为骨植入材料的研究进展。

生物可降解镁合金骨科植入材料的临床应用及其有限元分析

在骨-器械界面建立和维持成熟骨是骨科植入材料长期成功的关键.镁合金由于其生物可降解性、天然骨组织的力学相似性以及成骨潜力,并且在体内不抑制间充质干细胞(hBMSCs)的成骨特性,成为有前途的承重骨科植入物的候选材料.但其高降解率和植入物相关感染的风险以及不佳的力学性能,对其临床应用提出了巨大的挑战.有限元分析方法能对复杂结构、形态、载荷和材料力学性能进行应力分析,可有效地帮助临床医生了解镁合金植入器械的应力及生物力学性能.

骨植入镁合金表面缓蚀剂覆载的微弧氧化/PLGA 复合涂层的制备与表征

目的在可降解镁合金表面制备缓蚀剂覆载的微弧氧化/聚乳酸-羟基乙酸(PLGA)复合涂层,提高其耐蚀性。方法首先利用微弧氧化技术在镁合金表面制备出适合复合缓蚀剂涂层的微弧氧化(Micro-Arc Oxidation,MAO)涂层,之后在微弧氧化多孔涂层上浸涂PLGA-缓蚀剂涂层,得到复合涂层,缓蚀剂选择天然植物提取物姜黄素(Curcumin,Cur)。利用SEM&EDS、FTIR和AFM等实验对涂层形貌、成分及结构进行分析,通过电化学测试、体外浸泡实验评价涂层的耐蚀性能。结果FTIR结果表明Cur可成功覆载在涂层中,且不与PLGA发生反应。电化学测试和体外浸泡实验表明MAO/PLGA-Cur涂层能有效提高镁合金的耐蚀性。动电位极化曲线显示MAO/PLGA-Cur涂覆样品的腐蚀电流密度比基体下降了3个数量级,浸泡14 d的质量损失比基体下降62.04%,比未覆载的样品减少26.63%。结论MAO时间为10 min为最合适复合缓蚀剂涂层的参数。Cur作为缓蚀剂的最佳添加量为0.12%,PLGA的最佳添加量为12%,最佳浸涂角度为0°。

镁合金骨植入材料表面改性的研究进展

镁合金材料作为可生物降解植入材料因其可在体内逐渐降解、吸收、消耗和排泄,手术区域愈合后无需二次手术取出。该材料有良好的生物降解性和生物相容性,有与骨骼相似的机械性能,使其在临床上被广泛研究。然而,镁合金在生物体内易腐蚀,限制了其作为骨植入材料的应用。本文从镁合金的腐蚀机理出发,对近年来通过镁合金骨植入材料表面改性从而控制材料的降解速率和改善生物相容性的研究作一综述。

新型镁合金生物材料的体内外相容性研究

近年来,镁合金材料由于其生物可降解、且机械性能与皮质骨相似而备受关注。探讨了含不同质量分数镓和锶元素的镁合金材料在体内外的相容性及是否具有促进骨愈合的能力。将各组材料在杜氏改良Eagle培养基(DMEM)中与人骨髓间充质干细胞(hBMSCs)共同培养,然后通过荧光染色判断材料在体外的细胞毒性;将材料植入大鼠股骨内并通过X射线透视、Micro-CT评价植入材料在体内的相容性以及作用,通过扫描电镜观察植入材料表面形貌的改变。研究结果表明,相较于纯钛,镁合金材料会对细胞增殖产生一定的抑制作用;含锶的镁合金材料具有更好的促成骨能力,镁合金材料的降解速率小于纯镁。