下肢动脉粥样硬化闭塞症支架术后再狭窄机制及防治进展

目前,血管腔内治疗技术已广泛应用于血管狭窄和闭塞性疾病的治疗,具有较高的成功率和较好的远期疗效[1],支架在动脉硬化闭塞症(ASO)介入治疗中的应用已成为研究者和使用者的共识[2]。支架成形术避免了血管急性回缩及晚期的收缩,但仍有一定再狭窄率[2],严重影响了治疗效果和患者的预     

在控制药物投递中应用可生物降解微球和超微球的最新进展

在控制药物投递中应用可生物降解微球和超微球的最新进展1引言使用和研究最广泛的可生物降解聚合物是聚酯类，包括多乳酸、多羟基乙酸及它们的异分子聚合物。多羟基乙酸（PGA）于1970年作为可生物降解性缝线首次进入市场。多乳酸（PLA）早在1971年就被当作药物投递物质而...     

可生物降解聚合物作为药物载体的应用进展

目前作为控制释放体系的药物载体材料大多是高分子聚合物材料。生物降解聚合物在一定时间内能被水解或酶解成小分子,可通过生理途径代谢排出体外,不需二次手术取出载体材料,因此比生物惰性材料更安全、更可靠,有更好的生物相容性,成为了药物载体的首选材料。简要综述了主要常用生物降解性聚合物在药物控释体系中的应用进展。     

生物降解性聚合物在外科中的应用

生物降解性合成聚合物人们已经发现许多聚合物在生物体内是可生物降解的。目前外科上采用的最重要的生物降解性聚合物是α—羟基酸衍生物的脂肪族聚酯。表1列出了一些已有或具有潜在外科用途的重要和有意义的生物降解性聚合物。     

纳米纤维素在柔性传感器中的应用EI北大核心CSCD

医疗资源紧缺推进医疗方式变革,智能医疗正在成为解决医疗资源短缺问题的理想方法。随着互联网的发展,人们期待使用柔性医疗保健系统在居家状态下实现实时健康状态监测,这对传感器所需使用的柔性基材提出了新需求。目前所使用的柔性基材一般是传统的石油基聚合物,不可再生。纤维素作为一种天然聚合物,具有来源广泛,加工方便以及可生物降解等优点,是一种可以替代石油基聚合物的理想材料。本文综述纳米纤维素在柔性传感器中的应用进展,首先介绍纤维素及纳米纤维素的结构及改性方法,然后归纳了纳米纤维素柔性传感器在实时医疗监测中的应用,最后讨论了纳米纤维素在柔性传感器领域的优势及面临的挑战。     

聚乳酸在血管支架中的应用及研究进展

聚乳酸及其共聚物是一类可生物降解的高分子聚合材料,不仅具有优良的机械性能和化学稳定性,还具备良好的生物相容性、可吸收性以及可降解性,因此被广泛应用于医学领域.主要介绍聚乳酸在血管支架方面的应用和研究进展.     

生产生物降解的血管移植物的先进的界面技术获奖

生产生物降解的血管移植物的先进的界面技术获奖［英］／Ｂｉｏｍｅｄｉｃａｌ　Ｍａｔｅｒｉｃａｌｓ．－１９９３，９美国ＡＳＴ公司研究生物降解血管移植物表面改善以生产一种生物血管修复的先进技术获奖。此项目的的关健就是探讨与生物相容性聚合物做的血管移植物有关...     

激光技术在医学领域中的新应用及我国的发展概况

1 在医学领域中的新应用 1960年美国科学家制造出世界第一台红宝石激光器,翌年立即用于临床治疗.激光技术在40余年来取得了巨大成就.在医学领域内,激光技术已广泛应用于诊断、治疗及基础理论研究.由于激光器具有切割、凝固、气化、打孔、截骨等功能,目前已广泛应用于眼科、耳鼻喉科、皮肤科、普外科、神经外科和肿瘤科等.医用激光器作为手术治疗的器械,已充分显示了它无与伦比的优越性.近年在医学领域中的应用更是举世瞩目,拓展了临床应用,主要表现在以下一些范围中.     

生物降解聚合物-聚乳酸泡沫材料(D.L-PLA)的研制及物理机械性能检测

本研究以生物降解聚合物-聚乳酸（D.L-PLA ）为原料,在测定材料分子量、筛选颗粒型氯化钠及轮廓制图的基础上,应用溶煤投放、颗粒沥滤技术制备了单片方形或圆形的D.L-PLA 多孔生物降解膜,并采用层压技术,将2～3层D.L-PLA 多乳性膜状物加工成三维立体聚合物泡沫材料。随后,对加工的泡沫材料物理、机械性能进行了检测,通过对检测结果的分析表明：采用层压技术可以研制、加工出均匀多孔、可用于细胞移植的支架材料。     

荧光共振能量转移聚合物胶束及其作为药物载体的研究进展EI北大核心CSCD

双亲性聚合物自组装形成的胶束团聚体,因具有特殊的内核疏水、外壳亲水的核/壳结构及纳米尺寸,在药物传递、基因传递和生物传感器等领域具有广泛应用。然而,聚合物胶束的结构稳定性容易受到环境因素影响,如温度、pH、血液中存在的剪切力以及胶束表面修饰的基团与靶外细胞的相互作用等,作为药物载体材料应用时易发生药物泄露等问题。因此,胶束载体的结构完整性及体内分布行为研究对评价其治疗效果及临床应用可行性至关重要。目前,荧光共振能量转移(FRET)技术被广泛用于聚合物胶束的体内/外团聚、解离及分布情况的实时监测。本文对聚合物胶束、FRET技术的特点、FRET-聚合物胶束的结构及性质进行了简要介绍,着重综述了几类常用荧光探针对与聚合物胶束复合的机制,以及FRET-聚合物胶束作为药物载体的稳定性和体内/外分布行为研究进展,并对当前该技术面临的一些问题及可能的发展方向进行了概述。     

Materials and surface modification for tissue engineered vascular scaffolds

Although vascular implantation has been used as an effective treatment for cardiovascular disease for many years, off-the-shelf and regenerable vascular scaffolds are still not available. Tissue engineers have tested various materials and methods of surface modification in the attempt to develop a scaffold that is more suitable for implantation. Extracellular matrix-based natural materials and biodegradable polymers, which are the focus of this review, are considered to be suitable materials for production of tissue-engineered vascular grafts. Various methods of surface modification that have been developed will also be introduced, their impacts will be summarized and assessed, and challenges for further research will briefly be discussed.     

生物可降解性消化道支架的应用及其生物相容性

背景：生物可降解支架可在消化道管腔内短期成形,具有良好的生物相容性,随后完全降解,并可以根据临床需要调节支架降解时间,避免了永久性支架的并发症。 目的：评价不同材料制成的生物可降解性消化道支架的应用、相容性评价以及研究进展。 方法：以 “生物可降解,消化道,支架,相容性” 为关键词,采用电子检索方式在万方数据库中检索1999-01/2009-12有关生物可降解性消化道支架的研究。排除重复研究、普通综述或Meta分析类文章,筛选纳入22篇文献进行评价。 结果与结论：可降解支架在消化道疾病中的应用已经显示其有效的扩张性及临床安全性等。可降解材料大多是高分子材料,包括天然可降解高分子、微生物合成高分子材料和合成可降解高分子3类。天然可降解高分子大多是多糖类。天然可降解高分子一般生物相容性良好,但是力学性能较差。微生物合成高分子材料目前研究及应用尚较少。合成高分子种类比较多,常见的有聚丙交酯、聚己内酯、聚乙二醇等。合成高分子优点在于可以比较灵活的设计分子结构,通过发展共聚物、共混物来得到不同性质的材料。可降解支架可以解决良恶性狭窄的再通及瘘口的封堵等,但可降解支架在消化道系统中应用的效力还需要未来进行大量的研究工作来评估。     

Biodegradable Polymers: Present Opportunities and Challenges in Providing a Microplastic‐Free Environment

The stability of polymers against environmental factors, chemicals, microorganisms, and hydrolysis has challenged society with the accumulation of plastic waste and its management worldwide. Large amounts of plastic litter accumulate in the environment and disintegrate into microplastics (small pieces less than 5 mm in size), a topic of real concern especially for products and applications where the plastics are used for a short time before becoming waste, and where they are difficult to recover after use and remain in the environment. Whether biodegradable polymers can be one of the solutions to the problem of plastic waste is a question very often raised in this context. Although the use of biodegradable polymers appears to be highly promising based on recent and past studies, several aspects need to be considered further regarding environmental sustainability, acceptability, and degradability in the complex natural environment. Intensive efforts need to be invested in developing new environmentally biodegradable polymers and smart mechanisms of degradation after use in the environment. The present viewpoint article discusses the present scenario of the environmental acceptability of biodegradable polymers and the opportunities and challenges they offer regarding solving the problem of microplastics and their impact on the environment.     

A model for simultaneous crystallisation and biodegradation of biodegradable polymers

This paper completes the model of biodegradation for biodegradable polymers that was previously developed by Wang et al. (Wang Y, Pan J, Han X, Sinka, Ding L. A phenomenological model for the degradation of biodegradable polymers. Biomaterials 2008;29:3393-401). Crystallisation during biodegradation was not considered in the previous work which is the topic of the current paper. For many commonly used biodegradable polymers, there is a strong interplay between crystallisation and hydrolysis reaction during biodegradation - the chain cleavage caused by the hydrolysis reaction provides an extra mobility for the polymer chains to crystallise and the resulting crystalline phase becomes more resistant to further hydrolysis reaction. This paper presents a complete theory to describe this interplay. The fundamental equations in the Avrami's theory for crystallisation are modified and coupled to the diffusion-reaction equations that were developed in our previous work. The mathematical equations are then applied to three biodegradable polymers for which long term degradation data are available in the literature. It is shown that the model can capture the behavior of the major biodegradable polymers very well.     

New stent surface materials: The impact of polymer-dependent interactions of human endothelial cells,smooth muscle cells,and platelets

Despite the development of new coronary stent technologies, in-stent restenosis and stent thrombosis are still clinically relevant. Interactions of blood and tissue cells with the implanted material may represent an important cause of these side effects. We hypothesize material-dependent interaction of blood and tissue cells. The aim of this study is accordingly to investigate the impact of vascular endothelial cells, smooth muscle cells and platelets with various biodegradable polymers to identify a stent coating or platform material that demonstrates excellent endothelial-cell-supportive and non-thrombogenic properties. Human umbilical venous endothelial cells, human coronary arterial endothelial cells and human coronary arterial smooth muscle cells were cultivated on the surfaces of two established biostable polymers used for drug-eluting stents, namely poly(ethylene-co-vinylacetate) (PEVA) and poly(butyl methacrylate) (PBMA). We compared these polymers to new biodegradable polyesters poly(l-lactide) (PLLA), poly(3-hydroxybutyrate) (P(3HB)), poly(4-hydroxybutyrate) (P(4HB)) and a polymeric blend of PLLA/P(4HB) in a ratio of 78/22% (w/w). Biocompatibility tests were performed under static and dynamic conditions. Measurement of cell proliferation, viability, glycocalix width, eNOS and PECAM-1 mRNA expression revealed strong material dependency among the six polymer samples investigated. Only the polymeric blend of PLLA/P(4HB) achieved excellent endothelial markers of biocompatibility. Data show that PLLA and P(4HB) tend to a more thrombotic response, whereas the polymer blend is characterized by a lower thrombotic potential. These data demonstrate material-dependent endothelialization, smooth muscle cell growth and thrombogenicity. Although polymers such as PEVA and PBMA are already commonly used for vascular implants, they did not sufficiently meet the criteria for biocompatibility. The investigated biodegradable polymeric blend PLLA/P(4HB) evidently represents a promising material for vascular stents and stent coatings.     

Conductive polymers: Towards a smart biomaterial for tissue engineering

Developing stimulus-responsive biomaterials with easy-to-tailor properties is a highly desired goal of the tissue engineering community. A novel type of electroactive biomaterial, the conductive polymer, promises to become one such material. Conductive polymers are already used in fuel cells, computer displays and microsurgical tools, and are now finding applications in the field of biomaterials. These versatile polymers can be synthesised alone, as hydrogels, combined into composites or electrospun into microfibres. They can be created to be biocompatible and biodegradable. Their physical properties can easily be optimized for a specific application through binding biologically important molecules into the polymer using one of the many available methods for their functionalization. Their conductive nature allows cells or tissue cultured upon them to be stimulated, the polymers’ own physical properties to be influenced post-synthesis and the drugs bound in them released, through the application of an electrical signal. It is thus little wonder that these polymers are becoming very important materials for biosensors, neural implants, drug delivery devices and tissue engineering scaffolds. Focusing mainly on polypyrrole, polyaniline and poly(3,4-ethylenedioxythiophene), we review conductive polymers from the perspective of tissue engineering. The basic properties of conductive polymers, their chemical and electrochemical synthesis, the phenomena underlying their conductivity and the ways to tailor their properties (functionalization, composites, etc.) are discussed.     

In vitro evaluation of electrospun nanofiber scaffolds for vascular graft application

Blood vessels are diverse in size, mechanical and biochemical properties, cellular content, and ultrastructural organization depending on their location and specific function. Therefore, it is required to control the fabrication of vascular grafts for obtaining desirable characteristics of blood vessel substitutes. In this study we have fabricated various scaffolds using the electrospinning technique with blends of collagen, elastin, and several biodegradable polymers. Biocompatibility, dimensional stability in vitro and mechanical properties were evaluated. Materials were blended at a relative concentration by weight of 45% collagen, 15% elastin, and 40% synthetic polymer to mimic the ratio of collagen and elastin in native blood vessels. The fabricated scaffolds are composed of randomly oriented fibers with diameters ranging from 477 to 765 nm. The electrospun scaffolds are nontoxic, dimensionally stable in an in vitro culture environment, easily fabricated, and possess controlled mechanical properties that simulate the ultrastructure of native blood vessels. The present study suggests that the introduction of synthetic biodegradable polymers enabled tailoring of mechanical properties of vascular substitutes and improving compliance matching for vascular tissue engineering.     

Acceleration of Biodegradation Using Polymer Blends and Composites

Biobased and biodegradable polymers are used in bioplastics as blends or composites of various materials to tune their physical properties but also influence their stability with respect to biodegradation. Biodegradable polymers are often not as biodegradable as they are claimed to be, especially due to different degradation conditions in soil, water, compost, or in vivo. Mixing such polymers with faster degrading polymers (blends) or fillers (composites) is a powerful strategy to adjust degradation rates. This review selects representative examples of bioplastic blends and composites in applications, such as tissue engineering, agriculture, or packaging, with a focus on controlling/accelerating the biodegradation rates. It also focuses on strategies such as hydrolysis enhancement, attraction of microbes for microbial degradation, pore forming fillers, or increase of phase separation in polymer mixtures. A basis for the prevention of microplastic formation or unwanted side effects with too slow degradation rates of biodegradable polymers is set.     

可完全生物降解材料聚乳酸-聚羟基乙酸复合壳聚糖在人工心血管支架制备中的应用

裸金属支架（bare metal stents,BMS）和涂层支架（drug eluting stents,DES）介入治疗冠心病已在临床广泛应用,但由于金属支架的异物刺激或携带药物的干扰容易引起支架内再狭窄和血管栓塞,由聚酯、聚碳酸酐及聚磷酸酯等高分子材料制备的完全可生物降解吸收支架及药物洗脱支架应运而生。目前由共聚物材料制备的人工心血管植入支架的安全性、组织及血液相容性已得到证实,然而这些支架具有各自的问题,如降解的速度、材料的柔韧度、硬度以及支撑力不均一等,尚不能满足实际应用的要求。本文就聚乳酸（polylactic acid,PLA）、聚羟基乙酸（polyglycolic acid,PGA）和壳聚糖在人工冠脉血管支架制备中的应用现状及研发方向予以综述。     

Pasty injectable biodegradable polymers derived from natural acids

Pasty biodegradable polymers that can be mixed with drugs at room temperature and injected to tissue as neat composition are advantageous as they allow simple preparation and delivery of drugs, particularly for heat sensitive drugs. A series of biodegradable pasty poly (ester-anhydride)s were prepared from alkanedicarboxylic acids and ricinoleic acid and its oligomers by transesterification-repolymerization method. The polymers were characterized by common spectroscopic, chromatography, and thermal methods. Polymers containing 70% ricinoleic acid and 30% linear dicarboxylic acids with 4-10 methylene groups were synthesized. The melting point of these poly (ester-anhydride)s increased as the number of methylenes in the alkanedicarboxylic acid increased. Use of short oligomers of ricinoleic acid instead of ricinoleic acid itself increased the melting point and decreased the softness of the resulting polymers. The polymers released model drugs for a few weeks while being degraded to their fatty acid counterparts. Copolymerization of alkanedicarboxylic acids with ricinoleic acid resulted in pasty biodegradable polymers useful as injectable carriers for drugs.