Recent biomedical advances with polyampholyte polymers

Polyampholyte polymer systems are composed of varying mixtures of charged monomer subunits. These polymeric systems have gained increasing attention because it is possible to design the final material properties through careful selection of the charged monomer subunits and controlling the polymer architecture. Characteristics that have been manipulated include the hydration, mechanical properties, pH responsive swelling, temperature responsive swelling, resistance to nonspecific protein adsorption, and protein conjugation capability. This had led researchers to propose the use of polyampholyte polymers as biosensor platforms, fouling release membranes, drug delivery vehicles, and tissue engineering scaffolds. This review is focused on advances that have been made over the last 5 years to develop polyampholyte polymers for these biomedical applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 40069.     

Functional biomedical polymers for corneal regenerative medicine

Recent progress in biomedical polymer science has greatly contributed to rapid development of corneal regenerative medicine. In the past decades, scientists have achieved several major breakthroughs in corneal tissue reconstruction. Studies regarding the findings of core-and-skirt keratoprostheses for visual rehabilitation, biosynthetic tissue replacements for corneal transplantation, and thermo-responsive cell-detachable substrates for corneal cell sheet engineering have been reported by several groups of investigators. This brief overview focuses on the contributions of functional polymers in the applications of corneal regenerative medicine. The keratoprosthetic devices developed by our group using heterobifunctional silicone rubber membranes grafted with different bioactive functional groups showed promising results in animal studies. In addition, the fabrication and transplantation of bioengineered human corneal endothelial cell sheets by utilizing the functional biomedical polymers such as poly(N-isopropylacrylamide) and gelatin are discussed, especially for the significance of gelatin in the development of a potential intraocular delivery system for cell sheet grafts.     

Variability of water uptake studies of biomedical polymers

Water uptake influences many properties of polymers and has been widely studied. In the context of polymeric biomaterials, several publications reported an unusual high variability of analytical results, without further investigating the cause for this phenomenon. Using selected polymers from the library of L ‐tyrosine‐derived polyarylates and poly(D ,L lactic acid), we showed that nonaged and nonannealed compression molded film samples exhibit the typical large variation in water uptake observed in previous reports. The introduction of an annealing step allows accurate and reproducible water uptake measurements for these polymers. We evaluated the use of ³H‐radiolabeled water for the determination of water uptake, finding that the use of radiolabeled water yields statistically indistinguishable measurements, compared to gravimetric methods, while providing significant advantages in throughput and sensitivity. Using the recommended methods of annealing and ³H‐radiolabled water, the water uptake profiles of 24 polymers of the library of L ‐tyrosine‐derived polyarylates are reported. This article addresses experimental concerns related to water uptake studies and may assist other researchers in improving the accuracy of their water uptake results. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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.     

Structural considerations and new polymers for biomedical applications

Polymers intended for surgical implantation must satisfy the double requirement of adequate long-term mechanical properties and surface compatibility. Earlier concepts of intertness are being modified to ascribe a more interactive role to polymers mainly resulting from studies on blood compatibility and controlled drug release. The interfacial reactions implied by interactive behaviour determine immediate compatibility whereas longer-term functional acceptance is more related to bulk properties. The relationship between these two requirements in terms of polymer structure is discussed with reference to new polymers in use, studies of polymer orientation and uses of polymer composites containing carbon fibre. Structural order is an important consideration for biomedical applications and when this is achieved in conjunction with composites, interesting developments are possible.     

Surface tailoring of biomedical polymers: An FTIR study

A multistep, surface-tailoring process of polymeric materials was developed with two consecutive plasma treatments and followed by derivatization reactions. In the first step, tetrafluoroethylene was plasma-polymerized, generating a highly crosslinked perfluoric surface layer. The next step introduced amine groups into the plasma polymer through exposure of the surface to plasma of ammonia. The reactive amine moieties were then used as anchoring sites for further derivatization. Finally, poly(ethylene glycol) chains were grafted onto the surface via a hexamethylene diisocyanate spacer. This method, aimed at the chemical modification of polymers for biomedical applications, was first demonstrated with poly(ethylene terephthalate) (PET) as a substrate in a previously published study (Cohn, D.; Stern, T. Macromolecules 2000, 33, 137). The aim of this study was to demonstrate the applicability of the method described previously to different polymers: poly(lactic acid), poly(ethylene) (PE), polystyrene (PST), poly(methyl methacrylate), a polybutadiene-based polyurethane (PEUOXAB-20), and Lycra. Fourier transform infrared (FTIR) spectroscopy was used to characterize the surface-modified substrates and the various control treatments. The results obtained were consistent with the derivatization scheme and in full agreement with the FTIR and ESCA results previously obtained for PET. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2203–2209, 2001     

Evaluation of water uptake and mechanical properties of biomedical polymers

Poly(vinyl alcohol) grafted with poly(d,l ‐lactide) or poly(d,l ‐lactide‐co‐glycolide) oligomers, were synthesized in our laboratory and investigated with respect to their potential for tissue engineering applications. In order to understand their structure–properties relationships the effect of length and composition as well as number of polyester grafts on PVA backbone chain on water uptake capability and hydrophilicity/hydrophobicity balance and on mechanical properties of hydrogels was evaluated. The E moduli of hydrogels display values between 0.01 and 100 MPa. The results indicate the route for the development of polymers with a very broad range of properties similar to those of natural cartilage tissue. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3682–3688, 2013     

Modification of polysiloxane polymers for biomedical applications: a review

This paper reviews methods of modifying polydimethylsiloxane (PDMS) polymers to improve their properties for biomedical applications. The modification methods are discussed under three different categories: bulk, surface and other modification techniques. Surface modification techniques include physical and chemical techniques to modify polymer surfaces. Bulk modification techniques include blending, copolymerization, interpenetrating polymer networks (IPNs) and functionalization. The third category includes less common modification techniques. © 2001 Society of Chemical Industry     

The mechanisms of oxidative degradation of biomedical polymers by free radicals

Degradation is an essential factor in polymer biocompatibility. The physiological environment of the human body can be aggressive to polymers. Most implanted polymers suffer degradation and the kinetics and mechanisms of the processes can be significantly affected by various biologically active species, especially enzymes, lipids, peroxides, free radicals, and phagocytic cells. Iron enhances the toxicity of oxygen free radicals. Superoxide and hydrogen peroxide can interact to form the very toxic hydroxyl radical in the presence of iron. The data have shown that the hydroxyl radical is likely to be one of the main causes of polymer degradation in implantable devices. © 1994 John Wiley & Sons, Inc.     

Biodegradable synthetic polymers: Preparation, functionalization and biomedical application

Biodegradable polymers have been widely used and have greatly promoted the development of biomedical fields because of their biocompatibility and biodegradability. The development of biotechnology and medical technology has set higher requirements for biomedical materials. Novel biodegradable polymers with specific properties are in great demand. Biodegradable polymers can be classified as natural or synthetic polymers according to the source. Synthetic biodegradable polymers have found more versatile and diverse biomedical applications owing to their tailorable designs or modifications. This review presents a comprehensive introduction to various types of synthetic biodegradable polymers with reactive groups and bioactive groups, and further describes their structure, preparation procedures and properties. The focus is on advances in the past decade in functionalization and responsive strategies of biodegradable polymers and their biomedical applications. The possible future developments of the materials are also discussed.     

Role of polymers in the design of 3D carbon nanotube-based scaffolds for biomedical applications

Since pioneer works by Iijima in 1991, carbon nanotubes (CNTs) have received a great deal of attention as confirmed by the increasing number of papers in the topic. Their unique and attractive properties have made them extensively demanded materials for a wide variety of technological applications, including their promising use as scaffolds in tissue engineering. In this review, we focus on the role that polymers (both natural and synthetic) play on the fabrication of three-dimensional (3D) CNT-based scaffolds for biomedical applications, with emphasis on biocompatible fabrication strategies such as freeze-casting, electrospinning and gel formation. These 3D matrices may be an interesting and alternative platform to circumvent structural limitations and toxicity problems of bare CNTs by the use of biocompatible dispersant polymers that allow the preparation of substrates better resembling native extracellular matrices. In any case, due to the relevance of CNT toxicity in this context, we also discuss significant works concerning cell and tissue responses to CNTs in dispersion, highlighting: (1) the asbestos-like behavior of CNTs, (2) surface functionalization as a tool to reduce CNT toxicity and (3) CNT biodistribution from the blood stream and posterior excretion. In this sense, literature revision has evidenced major toxicity issues related to: (a) the inherent insolubility and tendency to aggregate of pristine CNTs, (b) the rigidity of their structures that makes them resemble asbestos, (c) the presence of residual metal impurities or amorphous carbon from their synthesis, and (d) the depletion of culture media components due to the adsorptive properties of CNTs. Nevertheless, as expected for almost any material, we also illustrate how dose plays a key role in the biological responses induced. Overall, this critic review is expected to help research community working on polymers and CNTs, as well as other carbon nanomaterials such as graphene, to identify useful guidelines that help advancing the use of 3D CNT-based scaffolds in biomedical applications.     

Biodegradation of coals

Selected strains of bacteria [from the Brookhaven National Laboratory (BNL) collection], capable of degrading heavy crude oils, were used to treat bituminous and lignite coals. Products resulting from biochemical reactions among several microorganisms and different coals were examined by pyrolysis gas chromatography-mass spectrometry (Py. g.c.-m.s.), and X-ray absorption near edge structure (XANES) spectroscopy. The results indicated considerable variations in the organic sulfur as well as modifications in coal structure. Furthermore, biochemical reactions involved in the microbial interactions with coals appeared to be microbial species dependent.     

可生物降解塑料

<正>可降解塑料是指一类其制品的各项性能可满足使用要求,在使用和保存期内性能不变,而使用后在自然环境条件下能降解成对环境无害物质的塑料。从20世纪80年代中期,国内开始研发可降     

Molecularly imprinted polymers by phase inversion technique for the selective recognition of saccharides of biomedical interest in aqueous solutions

The purpose of this work was the preparation and characterization of polymeric membranes for the selective recognition of saccharides using molecular imprinting technology associated with phase inversion. A system able to bind saccharides with high selectivity is particularly important in the pharmaceutical sector, since some of these compounds are constituents of molecules which can exert serious toxic effects even at very low concentrations. Two polymeric matrices were prepared using poly(ethylene‐co‐vinyl alcohol) copolymers, with an ethylene molar content of 32% and 44%, and were imprinted with two different saccharide molecules: maltose and 2‐keto‐3‐deoxy‐d ‐manno‐octulosonate (KDO). Matrices imprinted against maltose and KDO showed an easy template extraction, high binding capability and satisfactory selectivity, particularly for the matrix with an ethylene molar content of 44%. © 2017 Society of Chemical Industry     

大力开发生物降解聚合物

根据国外近几年文献汇总,论述生物降解聚合物在日常生活以及医学、光电材料、精细化工等高新技术领域的广泛应用;国外大力开发的各种类型降解聚合物：单一型生物降解聚合物、复合型生物降解聚合物和可生物降解水溶性聚合物。     

Biodegradation of Silk Biomaterials

Silk fibroin from the silkworm, Bombyx mori, has excellent properties such as biocompatibility, biodegradation, non-toxicity, adsorption properties, etc. As a kind of ideal biomaterial, silk fibroin has been widely used since it was first utilized for sutures a long time ago. The degradation behavior of silk biomaterials is obviously important for medical applications. This article will focus on silk-based biomaterials and review the degradation behaviors of silk materials.     

Biodegradation of nonionic surfactants

This paper discusses the biodegradability of alcohol-based nonionics measured by the recommended legislative test procedures and how the results obtained are affected by the chemical structure of the surfactant, and thus provides guidance on the selection of materials. More detailed studies on the biodegradation of alcohol ethoxylates during the activated sludge sewage treatment process are also reported. Examination of a wide range of alcohol ethoxylates in the legislative tests shows that the majority of those nonionics of practical importance will be extensively biodegraded. Although the mathematical model used to design the treatability test is very simple and has frequently come under criticism, the predictions seem to be upheld and the results obtained appear to provide a reliable guide to what is likely to happen in practice. The sludge residence time, which has long been regarded as of particular importance by those involved in the field of sewage treatment, is clearly demonstrated to be a highly significant factor whose influence should be taken into account in any detailed laboratory study of treatability. The study of alcohol ethoxylates indicates that extensive primary biodegradation will occur even in overloaded treatment plants where sludge retention times (SRT) are likely to be short. The effect of temperature on the biodegradation is small and suggests that effective treatment will be achieved in such plants even at the lower temperatures experienced during winter. Ultimate biodegradation of alcohol ethoxylates was shown to be extensive under practical conditions and levels of “polyethylene glycol” intermediates discharged to surface waters will be low. Although alcohol ethoxylates are rapidly and extensively absorbed on activated sludge, this does not play a significant role in the removal process which is essentially one of biodegradation.     

Biodegradation of nonionic ethoxylates

The biodegradation of alcohol ethoxylates (AE) and alkylphenol ethoxylates (APE) is reviewed. Biodegradation test methods, ranging from laboratory tests to full-scale waste treatment plant studies are described for these surfactants. A comparison is made between primary and ultimate biodegradability criteria and the limitations of the various analytical methods used in these determinations are discussed. The most recently published data suggest sewage bacteria degrade AE by a mechanism which is different from that by which APE degrades. The use of radiolabeled surfactants to elicit more detailed information about the biodegradation mechanisms of AE is described. The role of biodegradation on the impact of surfactants released to the environment is assessed, and future environmental concerns for nonionics are considered.     

生物降解乙二胺四乙酸(EDTA)研究进展

乙二胺四乙酸(EDTA)能形成高度稳定的水溶性金属离子-EDTA络合物,被广泛应用于各种工业和家用领域。由于它很难被常规水和废水处理工艺所去除,EDTA在许多地表水和地下水中成为浓度最高的人工合成有机物。论文简要总结了EDTA的用途、主要环境风险、微生物降解途径、金属离子对EDTA生物降解的影响和生物处理工艺去除EDTA的最新研究进展。     

Biodegradation of Nonylphenol Monopropoxyethoxylates

Aerobic biodegradation behavior of nonylphenol monopropoxyethoxylates was investigated in two tests with different inocula‐sewage sludge and river water. Both primary biodegradation and formation of different biodegradation intermediates were studied. Primary biodegradation of nonylphenol monopropoxyethoxylates was relatively fast and complete with the sewage sludge as the inoculum. On the other hand, biodegradation with river water as the inoculum was slower and primary biodegradation in this test reached only about 60 % during almost 50 days. The biodegradation intermediates from both oxidative and non‐oxidative pathways were found. In the non‐oxidative route monopropoxy poly(ethylene glycol)s were observed which indicate existence of the central fission biodegradation pathway. In the oxidative pathway carboxylic acids were identified. The biodegradation intermediates identified with the use of high performance liquid chromatography with mass spectrometric detection persisted for many days in both tests.