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Magnesium and its alloys are intriguing as possible biodegradable biomaterials due to their unique combination of biodegradability and high specific mechanical properties. However, uncontrolled biodegradation of magnesium during implantation remains a major challenge in spite of the use of alloying and protective coatings. In this study, a hybrid c...
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... incorporation of PLA into the hybrid structure clearly decreases the mechanical strength of the Mg due to its lower yield strength (e.g. Stress strain curves for the bulk Mg and Mg-PLA composite are shown in Figure 3. It is interesting to note that the stress-strain curve for the Mg-PLA composite is similar to characteristic curves for metal foams [26,27], with an initial elastic region, followed by stress plateauing after the material yields, before a further increase due to the cross-sectional area increasing under compression. ...
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The demand for metallic materials of exceptional tribological performance is rapidly growing due to constant development of automotive, tool or implant industry. As great attention nowadays is being paid to the surfacemodified materials, there is a need of establishing reliable methods for evaluation of coated metallic alloys. In this paper, method...
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... The first work of indirect 3D AM was achieved in pure Mg in 2010 [127] . Since then, very few studies have been conducted to develop this method [125][126][127][128][129] . All researchers to date have focused on the fabrication of Mg scaffolds with structured porosity made of pure Mg and their investigations Fig. 17. ...
Magnesium alloys remain critical in the context of light-weighting and advanced devices. The increased utilisation of magnesium (Mg) each year reveals growing demand for its Mg-based alloys. Additive manufacturing (AM) provides the possibility to directly manufacture components in net-shape, providing new possibilities and applications for the use of Mg-alloys, and new prospects in the utilisation of novel physical structures made possible from ‘3D printing’. The review herein seeks to holistically explore the additive manufacturing of Mg-alloys to date, including a synopsis of processes used and properties measured (with a comparison to conventionally prepared Mg-alloys). The challenges and possibilities of AM Mg-alloys are critically elaborated for the field of mechanical metallurgy.
... Very recently, the composite composed with magnesium alloys and aliphatic polyesters shows greatly potential bioapplications for degradable implant materials. The studies suggest this kind composite would emerge the following advantages [7][8][9][10][11][12][13]: (1) The mechanical properties are tailorable for different bone fixation requirements; (2) pH values of the surrounding environment could be stabilized where the rapid degradation of Mg could be mitigated and the acid degradation products of aliphatic polyester could be neutralized; (3) The presence of Mg could promote the biomineralization and cell adhesion. Under the loading condition, Mg alloy and aliphatic polyester would emerge quite different degradation behaviors from those under the unloading condition. ...
Influence of static compression loading on the degradation behaviors of polylactic acid-based composite reinforced with 20 vol% magnesium alloy wires (MAWs) is investigated. The external stress would enhance the degradation of the composite. As the applied stress is increased from 1 to 3 MPa, the overall degradation rate goes up. After immersion for 30 days, the degradation rate of PLA matrix in the composite at the stress level of 3 MPa is about 1.46 and 2.4 times those at 1 and 0 MPa (unloading condition) while the bending strength retention is 0.73 and 0.63 times those of the latter ones. The relationship between the degradation rate of PLA matrix in the composite and the external compression stress is further elucidated. The external stress deteriorates the strength retention of the composite but a high MAWs content could mitigate the deterioration.
... In the work of Oosterbeek et al [51], a structurally organized composite was formed from biodegradable Mg-based metal and a biopolymer by combining techniques of metallic foam with injection molding. This novel structure would be conducive to drug loading in future applications of BMCs. ...
In recent years, materials science research based on magnesium (Mg) alloys has increased significantly due to their notable advantages over traditional metals. However, magnesium alloys are susceptible to excessive degradation and subsequent disruption of mechanical integrity; this phenomenon limits the utility of these materials. Mg alloys can thus be combined with other materials to form composites for medical applications.
The present article describes key advances in and considerations for the development of biodegradable Mg-based composites (BMCs). The primary characteristics of these materials include their controllable degradation rates, tunable mechanical properties, adjustable structures to promote tissue repair, improved biocompatibility, and added functionality according to the purpose of the applications. Here we provide an overview of the current research on and development status of BMCs for biomedical materials, including the present limitations and challenges of their use. Finally, this paper comprehensively discusses the most promising directions of future development for these materials.
... In comparison with pure PLLA, the PLLA/Mg hybrid composites have higher pH value during immersion in Hank's solution because degradation of Mg neutralizes the acidic environment caused by hydrolytic degradation via bulk erosion and accelerated corrosion of the composites. Changing the content of Mg particles affects the corrosion resistance of the PLLA/Mg hybrids [208]. Moreover, Oosterbeek et al. have designed a Mg-Polylactic acid-(C 3 H 4 O 2 )n (PLA) hybrid composite by injecting PLA into a porous Mg scaffold. ...
... Moreover, Oosterbeek et al. have designed a Mg-Polylactic acid-(C 3 H 4 O 2 )n (PLA) hybrid composite by injecting PLA into a porous Mg scaffold. The Mg/PLA hybrid corrodes rapidly due to the degradation of PLA into lactic acid resulting in reduced pH and accelerated corrosion of Mg [208]. ...
Statement of significance:
Owing to their unique mechanical properties, biodegradability, biocompatibility, Mg based biomaterials are becoming the most promising substitutes for tissue regeneration for impaired bone, vascular and other tissues because these scaffolds can provide not only ideal space for the growth and differentiation of seeded cells but also enough strength before the formation of normal tissues. The most important is that these scaffolds can be fully degraded after tissue regeneration, which can satisfy the increasing demand for better biomedical devices and functional tissue engineering biomaterials in the world. However, the rapid degradation rate of these scaffolds restricts the wide application in clinic. This paper reviews recent progress on how to control the degrdation rate based on the relevant corrosion mechanisms through the design of porous structure, phase structure, grains, and amorphous structure as well as surface modification, which will be beneficial to the better understanding and functional design of Mg-based scaffolds for wide clinical applications in tissue reconstruction in near futures.
Surface modification for improving corrosion resistance of Mg alloys is highly demanded for degradable orthopedic and cardiovascular devices. The research reports the design and development of TiO2–HA composite and novel TiO2–HA–PCL hybrid coating belonging to the unique class of inorganic organic hybrid with striking features that are explored for the first time in the corrosion resistance of Mg alloys. Sol–gel dip coating combined with non-solvent induced phase separation is used to create the hybrid coating. TiO2–HA–PCL hybrid coating introduces strong hydrogen bonding between TiO2–HA inorganic matrix and PCL organic layer in addition to the Vander wall electrostatic interaction of the later with the Mg substrate which in turn enhance adhesion strength to about 1.5 times of TiO2–HA coating. The corrosion potentials for TiO2–HA–PCL and TiO2–HA were found to be −0.407V and −1.017V (vs Ag/AgCl), respectively. The current densities of TiO2 –HA–PCL and TiO2 –HA were found to be 7.31 × 10−8 A/cm2 and 4.03 × 10−4 A/cm2 respectively. The corrosion resistance of coatings was confirmed by immersion testing by weight loss, pH changes and H2 evolution measurements at interval of 7 days till 28 days. The present TiO2–HA–PCL coating in comparison to TiO2–HA coating demonstrate nearly 6% less weight loss. The outcome of the present work was compared with the similar coatings in recent past. The work done ingresses enhancing the corrosion resistance of Mg alloys, which fulfill the dreams of future degradable orthopedic and cardiovascular devices.
Magnesium (Mg) alloys have great potential as materials for biodegradable implants and devices because of their excellent mechanical and biological properties; such as the similarity of their mechanical properties to cortical bone and their osteoconductivity. However, Mg alloys degrade rapidly in vivo, which reduces the local pH and can harm cells. Coatings and surface treatments can control the degradation rate of Mg alloys by limiting the diffusion of water and ions to the Mg surface. Coatings can also increase the osteoconductivity of the surface of Mg implants. Polymers and ceramics are frequently used as coating materials, and the processes of their deposition can further tailor the properties of coatings for their intended roles. The controlled degradation and osteoconductivity of Mg implants using coatings will lead to their replacement with natural tissue after they have fulfilled their function; which will avoid foreign body complications and prevent the need for implant removal surgeries.
Current metallic implants still face intrinsic problems such as metallic ion release and insufficient bioactivity during long-term performance. Therefore, the design of revolutionizing metallic biomaterials or modifications of revolutionizing metallic biomaterials are indispensable in order to meet the demand of long-lasting and excellent biofunctional devices. In this chapter, we propose the future development directions of revolutionizing metallic biomaterials.
Statement of significance:
We systematically evaluate the effects of compression stress and temperature on the degradation properties of two materials: (pure-PLA) and MAO-MAWs/PLA (or Mg/PLA). The initial in vitro degradation kinetics of the unstressed or stressed pure-PLA and MAO-MAWs/PLA composite is confirmed to be Arrhenius-like. MAO-MAWs and external compression stress would influence the degradation activation energy (Ea) and pre-exponential factor (k0) of PLA, and we noticed there is a linear relationship between Ea and ln k0. Thereafter, we noticed that Mg(2+), not H(+), plays a significant role on the mitigation of the PLA degradation and external compression stress brings the molecular structure change of PLA. Finally, we proposed a model to predict the bending strength of the specimens versus immersion time at different immersion temperatures. This fundamental study could provide some scientific basis in our understanding for the evaluations and biomedical applications of these biodegradable materials.
A novel biodegradable and conductive composite consisting of magnesium (Mg), polypyrrole-block-ploycaprolactone (PPy-PCL), and poly (lactic-co-glycolic acid) (PLGA) is synthesized in a core-shell-skeleton manner for tissue engineering applications. Mg particles in the composite are first coated with a conductive nanostructured PPy-PCL layer for corrosion resistance via the UV-induced photopolymerization method. PLGA matrix is then added to tailor the biodegradability of the resultant composite. Composites with different composition ratios are examined through experiments, and their material properties are characterized. The in vitro experiments on culture of 293FT-GFP cells show that the composites are suitable for cell growth and culture. Biodegradability of the composite is also evaluated. By adding PLGA matrix to the composite, the degrading time of the composite can last for more than eight weeks, hence providing a longer period for tissue formation as compared to Mg composites or alloys. The findings of this research will offer a new opportunity to utilize a conductive, nanostructured-coated Mg/PLGA composite as the scaffold material for implants and tissue regeneration. This article is protected by copyright. All rights reserved.
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