生物降解聚合物的研究和产业化进展及展望

结合作者等近十年来在生物降解聚合物领域的研究和产业化工作,本文概述了聚乳酸、聚氨基酸、聚对二氧六环酮及其它生物降解聚合物的合成进展,综述了可生物降解温度敏感水凝胶、形状记忆高分子材料的研究概况,阐述了可生物降解聚合物在生物活性大分子控释体系、超细纤维组织工程支架上的应用研究,介绍了可生物降解聚合物在食品包装、纺织和汽车电子等方面的应用,总结了可生物降解聚合物、医疗器械、药物制剂和组织工程等领域产业化近况.最后展望了生物降解聚合物的研究、应用和产业化前景.     

Functionalized Synthetic Biodegradable Polymer Scaffolds for Tissue Engineering

Scaffolds (artificial ECMs) play a pivotal role in the process of regenerating tissues in 3D. Biodegradable synthetic polymers are the most widely used scaffolding materials. However, synthetic polymers usually lack the biological cues found in the natural extracellular matrix. Significant efforts have been made to synthesize biodegradable polymers with functional groups that are used to couple bioactive agents. Presenting bioactive agents on scaffolding surfaces is the most efficient way to elicit desired cell/material interactions. This paper reviews recent advancements in the development of functionalized biodegradable polymer scaffolds for tissue engineering, emphasizing the syntheses of functional biodegradable polymers, and surface modification of polymeric scaffolds.

     

Thermoanalytical studies on specialty polymers in Japan

Thermoanalytical studies on specialty polymers in Japan are reviewed. The basic and applied researches for the developments of new specialty polymers such as high-performance polymers, liquid crystalline polymers, and biodegradable polymers during the 1990's are introduced from the standpoint of thermal analysis. Many studies were performed for the improvements of durability and thermal stability of engineering polymers, biodegradable polymers and so on. A special topic of researches on the thermal behavior of polymers by high-pressure differential thermal analysis is included in this review. This revised version was published online in July 2006 with corrections to the Cover Date.     

Plastics of the Future? The Impact of Biodegradable Polymers on the Environment and on Society

In recent years the littering of plastics and the problems related to their persistence in the environment have become a major focus in both research and the news. Biodegradable polymers like poly(lactic acid) are seen as a suitable alternative to commodity plastics. However, poly(lactic acid) is basically non‐degradable in seawater. Similarly, the degradation rate of other biodegradable polymers also crucially depends on the environments they end up in, such as soil or marine water, or when used in biomedical devices. In this Minireview, we show that biodegradation tests carried out in artificial environments lack transferability to real conditions and, therefore, highlight the necessity of environmentally authentic and relevant field‐testing conditions. In addition, we focus on ecotoxicological implications of biodegradable polymers. We also consider the social aspects and ask how biodegradable polymers influence consumer behavior and municipal waste management. Taken together, this study is intended as a contribution towards evaluating the potential of biodegradable polymers as alternative materials to commodity plastics.     

Biodegradable polymer matrix nanocomposites for tissue engineering: A review

Nanocomposites have emerged in the last two decades as an efficient strategy to upgrade the structural and functional properties of synthetic polymers. Aliphatic polyesters as polylactide (PLA), poly(glycolides) (PGA), poly(?-caprolactone) (PCL) have attracted wide attention for their biodegradability and biocompatibility in the human body. A logic consequence has been the introduction of organic and inorganic nanofillers into biodegradable polymers to produce nanocomposites based on hydroxyapatite, metal nanoparticles or carbon nanotructures, in order to prepare new biomaterials with enhanced properties. Consequently, the improvement of interfacial adhesion between the polymer and the nanostructures has become the key technique in the nanocomposite process. In this review, different results on the fabrication of nanocomposites based on biodegradable polymers for specific field of tissue engineering are presented. The combination of bioresorbable polymers and nanostructures open new perspectives in the self-assembly of nanomaterials for biomedical applications with tuneable mechanical, thermal and electrical properties.     

Photocrosslinkable polyesters and poly(ester anhydride)s for biomedical applications

Crosslinking is a feasible way to prepare biodegradable polymers with potential in biomedical applications such as controlled release of active agents and tissue engineering. A synthesis route in which functional telechelic aliphatic polyester oligomers are used as precursors for the preparation of crosslinked polyesters and poly(ester anhydride)s is described. Mechanical properties, degradation characteristics and rate, and bioactivity can be modified widely by controlling the chemical composition and architecture of the crosslinkable oligomers. In tissue engineering, photocrosslinking allows to use crosslinkable oligomers in advanced manufacturing techniques like micromolding in capillaries, stereolithography and two-photon polymerization.     

Effects of an avidin-biotin binding system on chondrocyte adhesion and growth on biodegradable polymers

Cell adhesion to a scaffold is a prerequisite for tissue engineering. Many studies have been focused on enhancing cell adhesion to synthetic materials that are used for scaffold fabrication. In this study, we applied an avidin-biotin binding system to enhance chondrocyte adhesion to biodegradable polymers. Biotin molecules were conjugated to the cell membrane of chondrocytes, and mediated cell adhesion to avidin-coated surfaces. We demonstrated that immobilization of biotin molecules to chondrocyte surfaces enhanced cell adhesion to avidin-coated biodegradable polymers such as poly(L-lactic acid), poly(D,L-lactic acid), and polycaprolactone, compared to the adhesion of normal chondrocytes to the same type of biodegradable polymer. The biotinylated chondrocytes still maintained their proliferation ability. This study showed the promise of applying the avidin-biotin system in cartilage tissue engineering. [diagram in text].     

Polymeric Scaffolds for Cartilage Tissue Engineering

Polymeric scaffolds are three-dimensional, porous structures that may be used as a vehicle to deliver cells or therapeutic factors to repair tissue defects. Both biodegradable and non-biodegradable polymers have been developed for this purpose. In this review, we survey the polymers that have been investigated for cartilage tissue engineering and discuss the critical parameters for successful applications in the future.     

骨组织工程支架材料研究进展*

骨在组织工程中得到了非常广泛、深入的研究.支架材料与许多可降解材料一起也在进行探索性研究.用于骨组织工程的生物材料可以是三维多孔的刚硬材料,也可以是可注射材料.本文从聚合物角度综述了骨组织工程对支架材料的基本要求,用于骨组织工程的可降解生物材料、支架材料的设计和制备技术以及支架材料的表面修饰等方面的研究进展.     

Biodegradation of water-soluble and water-dispersible polymers for agricultural,consumer, and industrial applications—Challenges and opportunities for sustainable materials solutions

The development of more sustainable material solutions is one of the key challenges today. New materials are subject to an overall risk assessment of which their impact on the environment is an important aspect. The biodegradability of a material may support a positive risk assessment. Water-soluble and water-dispersible polymers are widely used in daily life in a very broad range of applications. In anticipation of a further tightening of regulatory requirements and as a consequence of the introduction of sustainability targets in industry, in the next decade or so, industry targets to replace the currently used and predominantly non-biodegradable high value water-soluble and water-dispersible polymers by biodegradable alternatives, wherever sustainably possible. This review provides an overview of the currently used water-soluble and water-dispersible polymers in detergent formulations for home care, in water treatment and in crop protection. These polymers have been engineered to near perfect performance at minimum costs. We address the challenges faced when introducing biodegradable alternatives in existing product value chains, and we highlight opportunities to further improve and fine-tune the biodegradation of these materials. This overview is intended to contribute to the development of novel biodegradable water-soluble and water-dispersible polymers, both at academia and industry.     

组织工程中生物可降解高分子的功能化及生物学修饰

可生物降解高分子在组织工程中有十分重要的作用。本文从组织工程对支架材料的生物学要求出发,对可生物吸收高分子的本体改性引入功能基团,进而通过化学键合促进细胞特异性黏附的短肽序列(ROD)、含功能性基团的水凝胶通过化学键合或物理包覆固定RGD以及聚合物表面修饰固定RGD三个方面进行了综述。     

聚乙醇酸类生物降解高分子

聚乙醇酸类生物降解高分子具有良好的生物相容性,在药物缓释材料、组织工程材料、手术缝合线等医用领域有广泛的应用。文章按聚乙醇酸类生物降解高分子的种类不同,介绍了它们的合成、性能与应用,尤其是乙醇酸-乳酸共聚物的研究进展。展望聚乙醇酸类生物降解高分子的未来,降低合成成本是广泛应用的关键,因此简单易行的、以乙醇酸等单体为原料的直接缩聚法合成值得关注。     

Molecular Design of Synthetic Biodegradable Polymers as Cell Scaffold Materials

Poly(lactic acid) and its copolymers are regarded as the most useful biomaterials. The good biocompatibility, biodegradability and mechanical properties of them make the synthetic biodegradable polymers have primary application to tissue engineering. The advantages and disadvantages of the synthetic biodegradable polymers as cell scaffold materials are evaluated, This article reviews the modification of polylactide-family aliphatic polymers to improve the cell affinity when the polymers are used as cell scaffolds. We have developed four main approaches: to modify polyester cell scaffolds in combination of plasma treating and collagencoating; to introduce hydrophilic segments into aliphatic polyester backbones; to introduce pendant functional groups into polyester chains ; to modify polyester with dextran. The results of the cell cultures prove that the approaches mentioned above have improved the cell affinity of the polyesters and have modulated cell function such as adhesion, proliferation and migration.     

Polymer Networks: From Plastics and Gels to Porous Frameworks

Polymer networks, which are materials composed of many smaller components—referred to as “junctions” and “strands”—connected together via covalent or non‐covalent/supramolecular interactions, are arguably the most versatile, widely studied, broadly used, and important materials known. From the first commercial polymers through the plastics revolution of the 20^th century to today, there are almost no aspects of modern life that are not impacted by polymer networks. Nevertheless, there are still many challenges that must be addressed to enable a complete understanding of these materials and facilitate their development for emerging applications ranging from sustainability and energy harvesting/storage to tissue engineering and additive manufacturing. Here, we provide a unifying overview of the fundamentals of polymer network synthesis, structure, and properties, tying together recent trends in the field that are not always associated with classical polymer networks, such as the advent of crystalline “framework” materials. We also highlight recent advances in using molecular design and control of topology to showcase how a deep understanding of structure–property relationships can lead to advanced networks with exceptional properties.     

Gelatin/PLLA sponge-like scaffolds allow proliferation and osteogenic differentiation of human mesenchymal stromal cells

Tissue engineering has the potential to supply constructs capable of restoring the normal function of native tissue following injury. Poly(L-lactic acid) (PLLA) scaffolds are amongst the most commonly used biodegradable polymers in tissue engineering and previous studies performed on ovine fibroblasts have showed that addition of gelatin creates a favorable hydrophilic microenvironment for the growth of these cells. The attractiveness of using mesenchymal stromal cells (MSCs) in tissue regeneration is that they are able to differentiate into several lines including osteoblasts. In this study, we investigated the ability of gelatin/PLLA sponges to support the adhesion, proliferation, and osteogenic differentiation of human MSCs isolated from the bone marrow of four donors. [Figure: see text].     

Advances in Polymeric Systems for Tissue Engineering and Biomedical Applications

The characteristics of tissue engineered scaffolds are major concerns in the quest to fabricate ideal scaffolds for tissue engineering applications. The polymer scaffolds employed for tissue engineering applications should possess multifunctional properties such as biocompatibility, biodegradability and favorable mechanical properties as it comes in direct contact with the body fluids in vivo. Additionally, the polymer system should also possess biomimetic architecture and should support stem cell adhesion, proliferation and differentiation. As the progress in polymer technology continues, polymeric biomaterials have taken characteristics more closely related to that desired for tissue engineering and clinical needs. Stimuli responsive polymers also termed as smart biomaterials respond to stimuli such as pH, temperature, enzyme, antigen, glucose and electrical stimuli that are inherently present in living systems. This review highlights the exciting advancements in these polymeric systems that relate to biological and tissue engineering applications. Additionally, several aspects of technology namely scaffold fabrication methods and surface modifications to confer biological functionality to the polymers have also been discussed. The ultimate objective is to emphasize on these underutilized adaptive behaviors of the polymers so that novel applications and new generations of smart polymeric materials can be realized for biomedical and tissue engineering applications.

     

可注射温敏性聚合物的研究进展

可注射温敏性聚合物广泛用于药物释放载体及组织工程支架,本文综述了一些可溶胶一凝胶转变的温敏性聚合物的最新研究进展,包括天然及改性的天然高分子、异丙基丙烯酰胺共聚物和聚乙二醇,聚(D,L乳酸-co-乙醇酸)共聚物等体系,并简要介绍了它们在医学领域的应用。     

Biodegradable polymer blends and composites: An overview

Biodegradable polymers belong to a family of polymer materials that found applications ranged from medical applications including tissue engineering, wound management, drugs delivery, and orthopedic devices, to packaging and films applications. For broadening their potential applications, biodegradable polymers are modified utilizing several methods such as blending and composites forming, which lead to new materials with unique properties including high performance, low cost, and good processability. This paper reviews the recent information about the morphology of blends consisting of both biodegradable and non-biodegradable polymers and associated mechanical, rheological, and thermal properties of these systems as well as their degradation behavior. In addition, the mechanical performance of composites based on biodegradable polymers is described.     

Photo-crosslinking copolymers based polyanhydride and 1G polyamidoamine-methacrylamide as bone tissue engineering: Synthesis, characterization, and in vitro degradation

In the past decade, Biodegradable materials that are capable of in situ formation have attracted increased attention for use in restorative orthopedic devices. In this communication, the surface erosion biodegradable polymers derived from 1.0G-polyamidoamine-double bond (PAMAM-DB) and methacrylated sebacic anhydrides (MSA) were evaluated over 2 months period under physiological conditions. Rectangular shaped samples were prepared by crosslinking the components using both chemical and photo initiators and exposure to UV light. The effects of PAMAM-DB: MSA ratio on local pH, water uptake, mass loss, and mechanical properties were explored. Polymers were characterized by ¹H NMR, ¹³C NMR, FT-IR, compressive strength testing and SEM. It is found that copolymer with 50-60% PAMAM-DB (mass fraction) show more excellent mechanical properties compared with other formulations. Copolymers degraded mainly by surface erosion but the bulk erosion pattern also appeared at the initial time of degradation for formulation 30% and 40%. The material was expected to be useful for drug controlled delivery, tissue engineering scaffold and other biomedical applications.     

Injectable and biodegradable hydrogels: gelation, biodegradation and biomedical applications

Injectable hydrogels with biodegradability have in situ formability which in vitro/in vivo allows an effective and homogeneous encapsulation of drugs/cells, and convenient in vivo surgical operation in a minimally invasive way, causing smaller scar size and less pain for patients. Therefore, they have found a variety of biomedical applications, such as drug delivery, cell encapsulation, and tissue engineering. This critical review systematically summarizes the recent progresses on biodegradable and injectable hydrogels fabricated from natural polymers (chitosan, hyaluronic acid, alginates, gelatin, heparin, chondroitin sulfate, etc.) and biodegradable synthetic polymers (polypeptides, polyesters, polyphosphazenes, etc.). The review includes the novel naturally based hydrogels with high potential for biomedical applications developed in the past five years which integrate the excellent biocompatibility of natural polymers/synthetic polypeptides with structural controllability via chemical modification. The gelation and biodegradation which are two key factors to affect the cell fate or drug delivery are highlighted. A brief outlook on the future of injectable and biodegradable hydrogels is also presented (326 references).