Modification of Iron with Degradable Silver Phases Processed via Laser Beam Melting for Implants with Adapted Degradation Rate

In medical technology, implants are used to improve the quality of patients’ lives. The development of materials with adapted properties can further increase the benefit of implants. If implants are only needed temporarily, biodegradable materials are beneficial. In this context, iron-based materials are promising due to their biocompatibility and mechanical properties, but the degradation rate needs to be accelerated. Apart from alloying, the creation of noble phases to cause anodic dissolution of the iron-based matrix is promising. Due to its high electrochemical potential, immiscibility with iron, biocompatibility, and antibacterial properties, silver is suited for the creation of such phases. A suitable technology for processing immiscible material combinations is powder-bed-based procedure like laser beam melting. This procedure offers short exposure times to high temperatures and therefore a limited time for diffusion of alloying elements. As the silver phases remain after the dissolution of the iron matrix, a modification is needed to ensure their degradability. Following this strategy, pure iron with 5 wt% of a degradable silver–calcium–lanthanum alloy is processed via laser beam melting. Investigation of the microstructure yields achievement of the intended microstructure and long-term degradation tests indicates an impact on the degradation, but no increased degradation rate.     

Anhydride‐Assisted Spontaneous Room Temperature Sintering of Printed Bioresorbable Electronics

Bioresorbable electronic devices are promising replacements for conventional build‐to‐last electronics in implantable biomedical systems and consumer electronics. However, bioresorbable devices are typically achieved by complex complementary metal oxide semiconductor fabrication processes that minimize exposure to humidity. Emerging printable techniques for bioresorbable electronics demand further improvement in electrical conductivity and mechanical robustness. This paper presents a room‐temperature spontaneous sintering method of bioresorbable inks that contain zinc nanoparticles and anhydride. The entire process can be conducted in atmosphere environment under 90% humidity within 300 min. It has minimum requirement for external heating and special ambient conditions, allowing humidity to trigger the surface chemistry of zinc nanoparticles and spontaneous welding between neighboring nanoparticles. The resulting bioresorbable patterns are highly conductive (σ = 72 400 S m^?1) and mechanically robust (>1500 bending cycles) to enable practical applications. A radio circuit achieved through the above method can operate stably over 14 days in air and disappear in water for less than 30 min. The spontaneous room‐temperature sintering represents a rapid and energy‐efficient approach to achieve high‐performance bioresorbable electronics with improved mechanical robustness and electrical performance, leading to broader impacts in the areas of healthcare, information security, and consumer electronics.     

可降解镁锌合金支架材料加工改性方法的研究进展

药物洗脱支架是冠心病支架治疗中的首选材料,但其永久存留在体内易损害内皮细胞,还有可能发生支架内血栓形成、支架内再狭窄等严重问题,而且现在冠心病发展越来越年轻化,导致药物洗脱支架在临床工作中的应用越来越受到限制。近年来,生物可降解材料逐渐被开发和探索,作为心脏支架材料的新生力量,被国内外多个研究机构看好。主要介绍了可降解镁锌合金材料。首先介绍了镁、锌元素的良好的生物相容性,它们是人体内含量丰富的元素,在体内多种生命活动中都发挥重要作用,缺乏镁、锌元素会增加人体患心血管等疾病的风险,镁锌元素组合还有助于改善各自不适宜的性能,使其更接近临床对可降解材料的需求。然而,镁锌合金支架降解产物局部浓度过高、支架的力学性能和降解速率可控机制等仍需要进一步提高。针对这些问题,重点讨论了近些年来常用于改善合金材料性能的加工改性方法,常用于改进镁锌合金材料的技术包括添加元素、表面改性、热处理、塑性加工、快速凝固、多种技术相结合等方法。介绍了这些方法的原理、效果、优点以及作为可降解血管支架改性方法的局限性,最后对生物可降解镁锌合金支架进行了展望。     

用于骨折内固定板的可吸收聚合物及其复合材料

综述了骨折内板材料的最新研究进展,阐述了可吸收聚合物（如聚乳酸,聚乙醇酸等）,自增强可吸收聚合物复合材料及碳纤维增强可吸收聚合物复合材料的机械性能及生物相容性,碳纤维增强可吸收聚合物复合材料是最有前途的内固定板材料。     

ASSESSING THE POSSIBILITY OF MACHINING OF THE SELF-REINFORCED BIORESORBABLE POLYMER P(L/DL)LA 70:30

This new study has sought to assess the machining possibility of the self-reinforced bioresorbable polymer P(L/DL)LA 70:30, used in healthcare. To verify the viability of machining of the components and, consequently, the influence of the cutting parameters on the surface quality of the machined samples, experiments were performed with different values for speed, feed, applications of cutting fluid, material and tool geometry. After machining, the roughness was measured and the generated surfaces were analyzed qualitatively. The interaction of the machining parameters and the surface quality were particularly analyzed on the search for surfaces with the characteristics used in the area of implants that interact with bone tissue, to decide on the viability of machining. With these results, it was determined that the material properties have played a decisive role in the resoluteness of the surface quality of the machined samples. To achieve the necessary characteristics for an implant, the machining parameters should be selected based on the material properties, such as glass transition temperature, molecular mobility and mechanical strength. This work has shown that it is possible to establish parameters for an appropriate machining of the material.     

Biodegradable Polyanhydrides as Encapsulation Layers for Transient Electronics

Bioresorbable electronic systems represent an emerging class of technology of interest due to their ability to dissolve, chemically degrade, disintegrate, and/or otherwise physically disappear harmlessly in biological environments, as the basis for temporary implants that avoid the need for secondary surgical extraction procedures. Polyanhydride‐based polymers can serve as hydrophobic encapsulation layers for such systems, as a subset of the broader field of transient electronics, where biodegradation eventually occurs by chain scission. Systematic experimental studies that involve immersion in phosphate‐buffered saline solution at various pH values and/or temperatures demonstrate that dissolution occurs through a surface erosion mechanism, with little swelling. The mechanical properties of this polymer are well suited for use in soft, flexible devices, where integration can occur through a mold‐based photopolymerization technique. Studies of the dependence of the polymer properties on monomer compositions and the rates of permeation on coating thicknesses reveal some of the underlying effects. Simple demonstrations illustrate the ability to sustain operation of underlying biodegradable electronic systems for durations between a few hours to a week during complete immersion in aqueous solutions that approximate physiological conditions. Systematic chemical, physical, and in vivo biological studies in animal models reveal no signs of toxicity or other adverse biological responses.     

Bioresorbable and degradable behaviors of PGA: Current state and future prospects

Polyglycolic acid (PGA) is a class of semicrystalline, bioresorbable polymers that have been widely used in a number of applications. No other bioresorbable materials can fully replace PGA in tissue engineering. Understanding degradation mechanisms in PGA is important for improving the efficiency and effectiveness in various fields including implantation. This review begins with a discussion on terminology of polymer degradation and hydrolytic degradation mechanism with a delineative model. This review also focus on previous degradation studies taking advantage of its fast-degrading behavior and the mechanism behind hexafluoroisopropanol (HFIP) being the sole solvent for PGA. Finally, the merits of PGA are discussed with many potential future applications along with their associated challenges.     

Short poly(ethylene glycol) block initiation of poly(l‐lactide) di‐block copolymers: a strategy for tuning the degradation of resorbable devices

The current range of medical applications of resorbable polyesters could be hugely expanded if more effective strategies for tailoring degradation rate were available. Block copolymerisation with poly(ethylene glycol) (PEG) has been shown to reduce degradation times; however, to date, this has relied on the addition of PEG to short lengths of polyester. This results in copolymers with high fractions of PEG and low molecular weights, reducing the potential range of applications. Furthermore, there has been no systematic study of the relative lengths of the blocks. In this work, we employed short hydroxyl‐functionalised methoxy‐terminated mPEG to initiate the synthesis of poly(l ‐lactide) (PLLA), resulting in controlled di‐block copolymers with short mPEG blocks and long PLLA blocks. A controlled series of polymers was made with PLLA lengths (60 < M_n (kg mol^?1) < 200) and mPEG lengths (550 < M_n (g mol^?1) < 5000) giving very low mPEG content (0.1–1.5 wt%). We found that, despite the low fraction of mPEG, water uptake and the rate of hydrolytic degradation, k, increased. Significantly, k for the polymers was dependent only on the presence of mPEG, and was little affected by mPEG length or PLLA length in the ranges studied. Moreover, mass loss began in all polymers when M_n of the polymer fell below a threshold of about 20 kg mol^?1 and depended on both the initial molecular weight of PLLA and the presence (but not the length) of mPEG. Short‐chain mPEG therefore provides a new route for targeted, temporal control of resorbable polyesters for biomedical devices. © 2018 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.