Review of crosslinked and non‐crosslinked copolyesters for tissue engineering and drug delivery

Novel degradable biomedical materials are found to have huge potential applications in fields such as drug delivery and release, orthopedic fixation support and tissue engineering. Utilization of polymers as biomaterials has greatly impacted the advancement of modern medicine. In this review, some new degradable biomedical copolyesters reported in recent years are introduced and discussed in combination with some of our research results, including non‐crosslinked copolyesters, crosslinked copolyesters and their corresponding derivatives. The molecular design, chemical structures and related properties of these biodegradable copolyesters are reported. In summarizing the review, the development, potential applications and future directions of degradable biomedical copolyesters are discussed. © 2013 Society of Chemical Industry     

Rubber toughening of poly(lactide) by blending and block copolymerization

Copolymers of L-lactide with 15 or more mole % D-lactide are amorphous, noncrystallizable hydrolytically degradable materials. These glassy materials are brittle in tension and bending. To make these materials suitable for use as load-bearing devices in biomedical applications, toughness has to be enhanced. This is effectively accomplished by introducing a separate degradable rubber phase in the amorphous matrix. Several approaches have been explored: solution blending and coprecipitation of trimethylene carbonate and ?-caprolactone rubbers and poly(lactide), preparation of ABA triblock copolymers and blending of ABA block copolymers with the amorphous poly(lactide) matrix. In all cases very tough materials could be prepared. These materials are easily processable by compression molding at relatively low temperatures.     

Synthesis, preparation, in vitro degradation, and application of novel degradable bioelastomers—A review

Degradable bioelastomers are novel polymer biomaterials mainly applied in soft tissue engineering and drug delivery. Synthetic degradable bioelastomers present four remarkable features: three-dimensional crosslinking network structure similar to that of natural elastins, high flexibility and elasticity capable of providing mechanical stimuli for tissue engineering constructs, matched mechanical properties especially with soft body tissues, and broad biodegradability that can be adjusted directly by crosslink density. In this review, degradable bioelastomers are divided into chemically and physically crosslinked bioelastomers. In view of the influence of crosslinking structures on the properties of bioelastomers, chemically crosslinked bioelastomers are further classified into thermo-cured and photo-cured bioelastomers, and physically crosslinked bioelastomers correspond to thermoplastic bioelastomers. In this contribution, after a discussion on the definition of and design strategies for degradable bioelastomers is delivered, the recent advances in the synthesis, properties (especially the in vitro degradation), and potential biomedical applications of these materials are described. Simultaneously, some insights on degradable bioelastomers have also been illuminated. Degradable bioelastomers are sure to play an increasingly significant role in the future developments of polymer biomaterials.     

Thermal degradation of butadiene–styrene-based rubber

Thermal degradation of some commerically available rubber based on butadiene–styrene copolymers are studies as a function of composition, temperature, and heating periods using photoacoustic spectroscopy (PAS) technique. It was found that random copolymers are more degradable than block copolymers and that the latter is more degradable than alternate copolymers. Mechanistic schemes leading to the thermal degradation of these synthetic rubbers are given together with a qualitative explanation of the relation between their composition and their thermal stabilites.     

Horseradish peroxidase‐mediated in situ forming hydrogels from degradable tyramine‐based poly(amido amine)s

Horseradish peroxidase (HRP)‐mediated crosslinking of poly(amido amine) (PAA) copolymers was successfully applied in the preparation of in situ forming degradable hydrogels under physiological conditions. PAA copolymers containing different amounts of tyramine residues (termed as pAEEOL/TA) could be synthesized through Michael‐type addition between methylenebisacryamide and amine mixture of 2‐(2‐aminoethoxy) ethanol and tyramine (TA). Depending on the amount of TA residue, the HRP, and H₂O₂ concentration, the gelation times could be varied from about 50 to 350 s. The swelling and degradation experiments indicated under physiological conditions the pAEEOL/TA‐based hydrogels are completely degradable within 6–8 days. Rheological analysis revealed that storage modulus of the hydrogels increased from 2500 to 4100 Pa when increasing HRP concentrations. Importantly, pAEEOL/TA copolymers have low cytotoxicity. Moreover, NIH 3T3 (mouse embryonic fibroblast) cells exposed in the degradation products of pAEEOL/TA‐based hydrogels retained high cell viability, implying that the hydrogels are cyto‐biocompatible. In vitro release of methylene blue and IgG protein from pAEEOL/TA‐based hydrogels could be effectively sustained by encapsulation of the drug in the hydrogels. The results indicate that HRP‐crosslinked, degradable pAEEOL/TA‐based hydrogels are promising for biomedical applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Biodegradable Polyurethane Elastomers for Biomedical Applications – Synthesis Methods and Properties

Biodegradable polyurethane elastomers (BioEPUR) are becoming increasingly important as biomaterials because they have excellent chemical, physico-mechanical and biological properties. This review presents the recent developments on BioEPUR and their potential applications in the biomedical and pharmaceutical fields. The aim of this work is to present an overview of the various methods of synthesis and properties of biomedical BioEPUR. Polyurethanes-based aliphatic or cycloaliphatic diisocyanates and polyesters, poly(ester-carbonate)s or copolymers of heterocyclic monomers were discussed.     

Synthesis of new versatile functionalized polyesters for biomedical applications

A new family of branched polymers was synthesized for different biomedical applications such as the preparation of targeted nanoparticulate drug carriers. They are new copolymers of hydroxy-acids and allyl glycidyl ether. The functional groups (allyl-, hydroxyl- and carboxyl-) to which various groups will be grafted are linked to the polymer backbone. The resulting polymers were characterized by ¹H NMR, ¹³C NMR, size exclusion chromatography (SEC), elemental analysis and differential scanning calorimetry (DSC). In vitro cytotoxicity assays were also conducted to ensure biocompatibility of the polymers. In order to obtain some structural evidences, different molecules have been grafted on the pendant groups. The method allows a rapid and easy synthesis of allyl-, hydroxyl- and carboxyl-branched degradable polymers for grafting various bioactive molecules.     

Designing Molecular Building Blocks for Functional Polymersomes

In recent years various polymeric vesicles have been reported that show promising results for drug delivery applications, nanomotors and/or nanoreactors. These polymeric vesicles can be assembled from many different materials and various coupling reactions have been applied for functionalization of the vesicles. However, the designs reported are still rather simple, as it is challenging to mimic biological complex systems. In this review we focus on the properties of widely used hydrophobic polymers to better understand polymersome properties for various applications. Examples are shown of how researchers have used and modulated block‐copolymers and their properties to their advantage. Furthermore, an overview of possible end group functionalizations of nanoparticles is reported, giving insight in recent developments of smart nanoparticles for biomedical applications.     

Biodegradable and electrically conducting polymers for biomedical applications

Conducting polymers have been widely used in biomedical applications such as biosensors and tissue engineering but their non-degradability still poses a limitation. Therefore, great attention has been directed toward the recently developed degradable and electrically conductive polymers (DECPs). The different strategies for synthesis of degradable and conducting polymers containing conducting oligomers are summarized and discussed here as well as the influence of different macromolecular architectures such as linear, star-shaped, hyperbranched and cross-linked DECPs. Blends and composites of biodegradable and conductive polymers are also discussed. The developing trends and challenges with the design of DECPs are also presented.     

生物医用高强度水凝胶的研究进展

水凝胶是一种高含水量的三维网状聚合物,广泛应用于各个领域,但力学性能较差的特点限制了其在生物医用领域的应用。因此,如何提高水凝胶的力学强度成为国内外专家学者研究的重点。本文主要介绍了几种新型高强度水凝胶的合成及研究进展,包括滑动水凝胶、双网络水凝胶、复合水凝胶以及其它水凝胶,详细分析了影响这些水凝胶力学性能的因素。指出研制具有生物相容性、可生物降解、可注射、可负载活性因子并且具备良好的力学性能水凝胶是今后的研究方向。     

Poly(N-vinylcaprolactam), a comprehensive review on a thermoresponsive polymer becoming popular

Poly(N-vinylcaprolactam) (PNVCL) is a temperature-responsive polymer, only second to poly(N-isopropylacrylamide), the most popular temperature-responsive polymer. Its applications include its use in cosmetics, as an anticlogging agent in pipelines and increasingly, in biomedical applications. This review highlights the controlled synthesis of PNVCL in different architectures: random copolymers, block copolymers, graft copolymers, nanogels, and their applications in the biomedical field, e.g., drug delivery, cell detachment, entrapment of enzymes, tissue engineering, among others. Emerging applications in areas that are expected to grow are also presented where PNVCL will play a pivotal roll: nanotechnology and the environment.     

Biodegradable polymers exhibiting temperature-responsive sol–gel transition as injectable biomedical materials

Injectable biodegradable copolymer hydrogels, which exhibit temperature-responsive sol-to-gel transition, have recently drawn much attention as promising biomedical materials such as drug delivery, cell implantation, and tissue engineering. These injectable hydrogels can be implanted in the human body with minimal surgical invasion. Temperature-responsive gelling copolymers usually possess block- and/or branched architectures and amphiphilicity with a delicate hydrophobic/hydrophilic balance. Poly(ethylene glycol) (PEG) has typically been used as hydrophilic segments due to its biocompatibility and temperature-dependent dehydration nature. Aliphatic polyesters such as polylactide, poly(lactide-co-glycolide), poly(ε-caprolactone), and their modified copolymers have been used as hydrophobic segments based on their biodegradability and biocompatibility. Copolymers of PEG with other hydrophobic polymers such as polypeptides, polydepsipeptides have also been recently reported as injectable hydrogels. In this review, brief history and recent advances in injectable biodegradable polymer hydrogels are summarized especially focusing on the relationship between polymer architecture and their gelation properties. Moreover, the applications of these injectable polymer gels for biomedical use such as drug delivery and tissue engineering are also described.     

Carbohydrate-based Biomedical Copolymers for Targeted Delivery of Anticancer Drugs

A variety of strategies and carrier molecules have been used to direct therapeutic agents to tumor sites. The incorporation of a specific targeting moiety to drug carrier may result in active drug uptake by malignant cells. Carbohydrates are important mediators of cell–cell recognition events and have been implicated in related processes such as cell signaling regulation, cellular differentiation, and immune response. The biocompatibility of carbohydrates and their ability to be specifically recognized by cell-surface receptors indicate their potential utility as ligands in targeted drug delivery for therapeutic applications. Yet, carbohydrates are not ideal targeting ligands because they are difficult to synthesize, bind weakly to carbohydrate receptors, and are prone to suffer from enzyme degradation due to labile glycosidic linkages. This review describes the design and development of HPMA-based biomedical copolymers to facilitate the selective delivery of drugs to tumor tissues via carbohydrate–endogenous lectin interactions. Various carbohydrate-decorated HPMA copolymer–drug conjugates are presented and the application of the copolymers for drug delivery is discussed. Current efforts to increase the affinity of carbohydrate ligands for their target receptors through multivalent display are also discussed. These novel HPMA copolymer carbohydrate conjugates hold promise as clinically relevant drug delivery systems for cancer therapy.     

“限塑令”是治理“白色污染”重要举措

使用非降解塑料袋,由于管控不严等,导致成了"白色污染"。国家两次出台"限塑令",尤其是2020年的"限塑令"规定了限用时间节点。本文就国家两次提出"限塑令"与不可降解塑料袋作了介绍,对开发降解塑料和部分已经取得成功降解塑料原理和成果进行了阐述,对未来的降解塑料开发展望。做好降解塑料袋开发,管控好非降解塑料袋使用和处置工作,推动"白色污染"治理,"限塑令"一定会有好的成效。     

可降解塑料的发展现状

介绍了可降解塑料的种类及研究开发现状，对其研究中存在的问题和发展趋势进行了讨论，指出降解塑料的应用重点在不便回收或回收成本较高的制品上，复合型降解塑料将会有较快的发展。     

Biodegradable zinc-based materials with a polymer coating designed for biomedical applications

Over the last decades, biodegradable metals have gained popularity for biomedical applications due to their ability to assist in tissue healing. These materials degrade in vivo, while the corrosion products formed are either absorbed or excreted by the body, and no further surgical intervention is required for removal. Intensive research has been carried out mainly on degradable biomaterials based on Mg and Fe. In recent years, zinc-based degradable biomaterials have been explored by the biomedical community for their intrinsic physiological relevance, desirable biocompatibility, intermediate degradation rate, tuneable mechanical properties and pro-regeneration properties. Since pure Zn does not exhibit sufficient mechanical properties for orthopedic applications, various Zn alloys with better properties are being developed. In this work, the combined effect of minor Fe addition to Zn and a polyethyleneglycol (PEG) coating on the surface morphology, degradation, cytotoxicity and mechanical properties of Zn-based materials was studied. There are several studies regarding the influence of the production of Zn alloys, but the effect of polymer coating on the properties of Zn-based materials has not been reported yet. A positive effect of Fe addition and polymer coating on the degradation rate and mechanical properties was observed. However, a reduction in biocompatibility was also detected.     

Multifaceted polymersome platforms: Spanning from self-assembly to drug delivery and protocells

Biologically inspired self-assembly processes of amphiphilic copolymers have received an increasing attention for creating innovative and highly advanced functional materials for various biomedical applications. Polymersomes are versatile nanosystems with tremendous potential due to their increased colloidal stability, tunable membrane properties, chemical versatility, and the ability to accommodate a broad range of drugs and biomolecules. In this review, we present the principles of copolymers self-assembly and associated parameters that control the resulting self-assembled morphologies, and various methodologies developed for fabrication of polymersomes. We attempt to discuss how polymersome platforms can be applied for versatile biomedical research, from simple passive nanocarriers for drug delivery to functionalized polymersomes for active targeting approaches and advanced nanoreactors, and protocells to mimic structure and functions of biological systems.     

可降解生物弹性体的研究进展

可降解生物弹性体是医用高分子材料的一种,由于具有高的柔韧性和弹性,以及与人体许多软组织相匹配的力学性能,因此在生物医学上展示出巨大的应用潜力。综述了几种目前正在研究的可降解生物弹性体,还特别报道了笔者所在课题组正在开展的关于可降解生物弹性体的研究。     

降解塑料在包装方面的应用

介绍了全降解型塑料和掺混型降解塑料2大品种的基本情况，简要论述了我国生产降解塑料的现状。通过对上海地区降解塑料在包装领域应用情况的分析，指出了当前在降解塑料开发应用中存在的主要问题，并提出了解决问题的建议。     

Long-term stability of PEG-based antifouling surfaces in seawater

Poly(ethylene glycol) (PEG) is a hydrophilic polymer that has been extensively used in the biomedical and marine environment due to its antifouling properties. In the biomedical field, PEG has been successfully used to functionalize surfaces due to its resistance to cell and nonspecific protein adsorption. However, the long-term stability of PEG has limited its use in some areas. In the shipping industry, there is a great need for long-term solutions to keep the hulls of the ships fouling-free. The long-term stability of PEG in polydimethylsiloxane (PDMS) fouling-release coatings is studied here, in both accelerated laboratory tests and real seawater conditions. This article shows how PEG-based copolymers, which have been exposed in fouling-release coatings to real-life seawater conditions, are isolated and compared to those exposed to accelerated laboratory testing with successful results. The influence of the chemistry of the PEG compounds, the chosen laboratory degrading agents, and the possible degradation pathways and products are discussed.