Effect of Poly(L-lactic acid) on Hydrolytic Degradation of Poly(glycolic acid)

The in-vitro degradation behavior of poly(glycolic acid) (PGA) rods and the composite rods containing poly(L-lactic acid) (PLLA) were investigated via mass loss, pH value change, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). Since the degradation rate of PLLA is lower than that of PGA, PLLA/PGA composite rods exhibit a slower degradation rate in comparison with PGA. This finding indicated that it was possible to control the degradation rate of the composites by changing their composition. This result indicates that this kind of composite biomaterial may be applicable to devices for the need of prolonged degradation.     

In vitro degradation behavior of electrospun polyglycolide,polylactide, and poly(lactide‐co‐glycolide)

The electrospinning of polyglycolide (PGA), poly(L ‐lactide) (PLA), and poly(lactide‐co‐glycolide) (PLGA; L ‐lactide/glycolide = 50/50) was performed with chloroform or 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFIP) as a spinning solvent to fabricate their nanofiber matrices. The morphology of the electrospun PGA, PLA, and PLGA nanofibers was investigated with scanning electron microscopy (SEM). The PLGA nanofibers, electrospun with a nonpolar chloroform solvent, had a relatively large average diameter (760 nm), and it had a relatively broad distribution in the range of 200–1800 nm. On the other hand, the PGA and PLA fibers, electrospun with a polar HFIP solvent, had a small average diameter (～300 nm) with a narrow distribution. This difference in the fiber diameters may be associated with the polarity of the solvent. Also, the in vitro degradation of PGA, PLA, and PLGA nanofiber matrices was examined in phosphate buffer solutions (pH 7.4) at 37°C. The degradation rates of the nanofiber matrices were fast, in the order of PGA > PLGA ? PLA. Structural and morphological changes during in vitro degradation were investigated with differential scanning calorimetry and wide‐angle X‐ray diffraction. For the PGA matrix, a significant increase in the crystallinity during the early stage was detected, as well as a gradual decrease during the later period, and this indicated that preferential hydrolytic degradation in the amorphous regions occurred with cleavage‐induced crystallization, followed by further degradation in the crystalline region. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 193–200, 2005     

聚乙交酯、聚丙交酯及聚乙交酯丙交酯纤维的研究进展

聚乙交酯（PGA）、聚丙交酯（PLA）和聚乙交酯丙交酯（PGLA）纤维作为生物可降解材料,广泛应用于医疗等领域,其中PLA纤维还作为绿色环保纤维广泛应用于服装、家纺等传统纺织品领域。纤维的制备、降解及应用是这类纤维在近年来研究的重点。介绍了国内外此类纤维在制备、降解以及应用方面的研究进展。     

Effect of pseudomonas lipase enzyme on the degradation of polycaprolactone/polycaprolactone-polyglycolide fiber blended nanocomposites

This study describes the interaction resulting from adding pseudomonas lipase (PS) enzyme to polycaprolactone-based composites designed for orthopedic applications. The biopolymer composite evaluated in this study consists of electrospun polycaprolactone (PCL)/polyglycolide (PGA) blended fibers impregnated with double stranded deoxyribonucleic acid wrapped single-walled carbon nanotubes encapsulated by a PCL matrix. PS enzyme was used to catalyze the degradation of PCL-based biocomposites. PCL present in the biocomposites showed considerable degradation in 4 weeks in the presence of the enzyme, exhibiting a contrast to hydrolytic degradation which lasts several years. PGA-consisting fibers degraded completely within one week of exposure to the enzyme.     

Biodegradable polyurethanes: Comparative study of electrospun scaffolds and films

The development of elastomeric, bioresorbable, and biocompatible segmented polyurethanes (SPUs) for use in tissue‐engineering applications has attracted considerable interest in recent years. In this work, nonporous films and microfiber/nanofiber scaffolds, which were prepared from two different poly(?‐caprolactone)‐based SPUs previously synthesized from 1,6‐hexamethylene diisocyanate and novel chain extenders containing urea groups or an aromatic amino acid derivative, were studied. Their thermal properties were influenced by both the different chemical structures of the hard segments and the processing conditions. The mechanical properties of the scaffolds (the elastic modulus, ultimate strain, and tensile stress) were adequate for engineered soft‐tissue constructs (e.g., myocardial tissue). The film samples displayed a low swelling degree (<2 wt %) in a phosphate‐buffered solution at 37°C. The introduction of the amino acid derivative chain extender with hydrolyzable ester bonds contributed to greater degradation. The fibrous scaffolds exhibited higher hydrolytic stability than the films after short assay times because of their more crystalline structures and higher degrees of association by hydrogen bonding, but they also experienced higher mass losses under accelerated conditions (70°C). This suggested that the degradation rate was not constant but depended on the degradation time and the processing technique. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

PGLA热降解性能的研究

使用热重分析仪（TG）对聚乙丙交酯（PGLA）与聚乙交酯（PGA）的热降解性能进行测试,并通过Kissinger、Flynn-wan-ozawa和Friedman 3种方法计算其降解过程中的活化能Ea。结果表明,PGLA的热稳定性较PGA更好,3种方法均能较好的分析其降解过程,当使用Flynn-wan-ozawa法拟合时,其线性相关性较好。     

Development of a Novel Polygalacturonic Acid-Gelatin Blend Scaffold Fabrication and Biocompatibility Studies for Tissue-Engineering Applications

In this study, we report the enhanced osteoblast differentiation of mouse embryonic stem cell (mESC) on a novel polygalacturonic acid (PGA)/gelatin scaffold. The matrices of various PGA/geletin ratios were fabricated, biophysically characterized, and optimized for cell culture applications. Blended 2% PGA/gelatin scaffolds were highly porous and were robust with enhanced mechanical strength. Swelling studies showed they had high swelling capacity (six-fold higher than only gelatin scaffold) along with complete degradation in the presence of phosphate-buffered saline. Cytocompatibility of the matrices was evaluated using mouse fibroblast 3T3-L1 cell line showing normal spreading and proliferation as assessed by scanning electron microscopy (SEM) and MTT assay. Among different blends of PGA/gelatin, 2% PGA/gelatin (2PG) scaffold showed the optimum physical and biological compatibility for use in cell culture and differentiation of mESC, especially for osteoblast differentiation. The scaffold, as reported in this study, presents a promising tool for tissue engineering applications.     

A chemical means to study the in vitro hydrolytic degradation of poly(glycolic acid)

A chemical means was developed to examine the in vitro hydrolytic degradation of both γ-irradiated and nonirradiated poly(glycolic acid) (PGA)-absorbable polymers for the purpose of obtaining information how irradiation affected PGA degradation and how the results related to the previously observed mechanical and morphological data. The method was based on the chemical reaction between the degradation product of the polymer, glycolic acid, and chromotropic acid, and the subsequent measurement of the absorbance of the reaction products by a UV/visible spectrophotometer. It was found that the unirradiated PGA specimens exhibited a two-stage hydrolytic degradation mechanism. This observation supported the previously hypothesized hydrolytic degradation mechanism on the basis of the level of crystallinity data. As the dosage of irradiation increases, the characteristic two-stage degradation mechanism becomes less profound and eventually disappears at 20 Mrads. A monotonic degradation profile was then observed at this dosage level. As reported in the literature, the widespread use of mechanical properties to evaluate the degradation phenomena of this class of polymer does not, however, provide the details of the degradation mechanism as revealed by the present study. The interrelationship between tensile strength, level of crystallinity, glycolic acid concentration, and pH levels of the medium, and their changes as hydrolytic degradation proceeds, are discussed for the purpose of elucidating the mechanism in more detail.     

Delivering on Cell-Selective Protein Degradation Using Chemically Tailored PROTACs

PROTACs (Proteolysis-Targeting Chimeras) have emerged as a groundbreaking class of chemical tools that facilitate the degradation of target proteins by leveraging the ubiquitin-proteasome system (UPS). However, the effective utilization of PROTACs in chemical biology studies and therapeutics encounters significant challenges when it comes to achieving cell-selective protein degradation and in vivo applications. This review article aims to shed light on recent advancements in the development of Pro-PROTACs, which exhibit controlled protein degradation capabilities in response to external stimuli or disease-related endogenous biochemical signals. The article delves into the specific chemical strategies employed to regulate the interaction between PROTACs and E3 ubiquitin ligases or target proteins. These strategies enable spatial and temporal control over the protein degradation potential of Pro-PROTACs. Furthermore, the review summarizes recent investigations regarding the delivery of PROTACs using biodegradable nanoparticles for in vivo applications and targeted protein degradation. Such delivery systems hold great promise for enabling efficient and selective protein degradation in vivo. Lastly, the article provides a perspective on the future design of multifunctional PROTACs and their intracellular delivery mechanisms, with a particular focus on achieving cell-selective protein degradation.     

Biodegradable polymers for use in surgery — poly(glycolic)/poly(Iactic acid) homo and copolymers: 2. In vitro degradation

The degradation mechanism of a series of polyglycolic/polylactic acid, (PGA/PLA), homo and copolymers synthesized as in Part 1¹, has been studied _vitro. An in vitro test model similar to that described in a previous study⁹, was used. The effects of time, temperature and pH on the rate and mechanism of degradation were elucidated. The degree of degradation was monitored molecularly by gel permeation chromatography (g.p.c.), tensile strength determination and mass loss measurements. The mechanism of degradation is shown to be by hydrolysis. The copolymers of PGA and PLA are shown to have a wide range of degradation rates governed by the hydrophilic/hydrophobic balance and crystallinity of the respective copolymer. The effect of the glass transition temperature (T_g) of PGA on its sensitivity to degradation is also demonstrated.     

微生物降解木质素的研究进展

木质纤维是地球上最丰富的可再生生物质资源,其三大成分之一的纤维素是生产生物基材料、生物燃料及生物基化学品的重要原料,但是木质素复杂的化学结构阻碍了木质纤维的应用.常规木质素的物理、化学及物理-化学等降解方法常需要高温、高压条件,并且易产生抑制物、造成高能耗和环境污染等问题.微生物介导的生物催化过程通常在温和条件下进行,...     

微生物降解有机磷农药残留的研究进展

从微生物降解有机磷农药的种类、降解机理、降解基因等方面综述了微生物降解有机磷农药近年来的研究进展,探讨了微生物降解有机磷农药研究领域的发展趋势及进一步的研究方向,并提出建议。     

Vibrational dynamics and heat capacity of poly(glycolic acid)

Polyglycolic acid (PGA) (-CH₂-COO-)_n is the first bioresorbable synthetic polymer which is used to make biomedical and pharmaceutical devices. It has a planar zigzag conformation. A comprehensive study of the normal modes and their dispersion in PGA using Urey Bradley force field is being reported. Characteristic features of the dispersion curves have been reported. The heat capacity derived from the dispersion curves via the density-of-states, is in good agreement with the experimental data of Lebedev and Yevstropov.     

Hydrolytic degradation of polyglycolic acid: Tensile strength and crystallinity study

The hydrolytic degradation of polyglycolic acid (PGA) was studied by examining the changes of tensile strength and the level of crystallinity of the suture material. It was found that the breaking stress decreased from 6.369 × 10^?1 at 0 day to 3.97 × 10^?3 Newton/Tex at 49 days. The sigmodial shape of the stress–strain curves gradually disappeared with increase in the duration of in vitra degradation. The endpoint titration method used to assess the degree of degradation beyond the period of measurable tensile strength showed that the percent of PGA degraded were 42, 56, and 70% at 49, 60, and 90 days, respectively. The level of crystallinity of PGA at various durations of degradation exhibited an initial increase in the degree of crystallinity from 40% at 0 day to an upper limit of 52% at 21 days, then gradual decrease to 23% at 90 days. This observation is essentially parallel to hydrolysis of cellulose and polyethylene terephthalate. The concept of microfibrillar structure of fibers provides the basis for the proposed degradation mechanism of PGA in vitro. It is believed that degradation proceeds through two main stages which are different in rate of degradation.     

焦化废水中的杂环化合物及多环芳烃降解的研究进展

综述了近年来焦化废水中的杂环化合物和多环芳烃降解的研究进展,总结了物理法的降解研究,归纳了生物法的降解机理,概括了化学法的研究进展,最后指出了焦化废水降解的研究方向。     

聚碳酸酯老化行为研究进展

双酚A型聚碳酸酯性能优异,应用广泛。但在户外使用时,由于光、一氧和湿度等环境因素的作用,导致聚碳酸酯力学强度和外观发生变化。为提高PC的抗老化性能,必须通过研究。充分认识聚碳酸酯的老化反应和老化进程。综述了近年来聚碳酸酯老化行为的研究,并提出存在的问题和今后研究的方向。     

聚乙醇酸材料的加工改性及其水下降解特性的研究进展

从具有广阔应用前景的聚乙醇酸（PGA）材料的物性、加工改性及应用等方面概括了PGA的基本改性原理、改性方法以及加工过程中需要注意的问题；从增韧、增强、增塑、增容等角度，阐述了不同助剂，如增容剂、扩链剂及增塑剂等对PGA材料的改性机理，比较了不同增韧材料与PGA材料相容性及界面互溶增强技术；最终总结了PGA加工性能及使用性能的调控规律。     

Influence of polycaprolactone/polyglycolide blended electrospun fibers on the morphology and mechanical properties of polycaprolactone

Polycaprolactone (PCL) and polyglycolide (PGA) are two biopolymers that have been used as in situ biomedical devices for various applications. The obstacle of creating a composite that captures the benefit of PCL's long degradation time, while acquiring the strength from PGA is overcoming the lack of surface adhesion between the two biopolymers for stress transfer to occur. This study investigates the use of miscible PCL‐PGA blended fibers, created by electrospinning, to increase the interfacial bonding of fibers to the PCL matrix of the polymer–polymer composite. The use of the blended fibers will thereby create the ability of load transfer from the long‐term PCL matrix to the stronger PCL‐PGA fiber reinforcement. The incorporation of the PCL‐PGA fibers was able to increase the tensile yield strength and Young's modulus over that of the bulk PCL, while decreasing the percent elongation at break. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40224.     

Aerobic and Anaerobic Bacterial and Fungal Degradation of Pyrene: Mechanism Pathway Including Biochemical Reaction and Catabolic Genes

Microbial biodegradation is one of the acceptable technologies to remediate and control the pollution by polycyclic aromatic hydrocarbon (PAH). Several bacteria, fungi, and cyanobacteria strains have been isolated and used for bioremediation purpose. This review paper is intended to provide key information on the various steps and actors involved in the bacterial and fungal aerobic and anaerobic degradation of pyrene, a high molecular weight PAH, including catabolic genes and enzymes, in order to expand our understanding on pyrene degradation. The aerobic degradation pathway by Mycobacterium vanbaalenii PRY-1 and Mycobactetrium sp. KMS and the anaerobic one, by the facultative bacteria anaerobe Pseudomonas sp. JP1 and Klebsiella sp. LZ6 are reviewed and presented, to describe the complete and integrated degradation mechanism pathway of pyrene. The different microbial strains with the ability to degrade pyrene are listed, and the degradation of pyrene by consortium is also discussed. The future studies on the anaerobic degradation of pyrene would be a great initiative to understand and address the degradation mechanism pathway, since, although some strains are identified to degrade pyrene in reduced or total absence of oxygen, the degradation pathway of more than 90% remains unclear and incomplete. Additionally, the present review recommends the use of the combination of various strains of anaerobic fungi and a fungi consortium and anaerobic bacteria to achieve maximum efficiency of the pyrene biodegradation mechanism.     

生物电化学技术降解疏水性新兴污染物的研究进展

疏水性新兴污染物（hydrophobic emerging contaminants,HECs）具有环境危害大、分布范围广和处理难度高等特点,利用生物电化学系统（bioelectrochemical system,BES）实现HECs的降解和脱毒是当前研究热点。本文综述了BES降解转化HECs的研究现状,分析了影响BES去除HECs效果的关键因素,着重介绍了BES降解转化不同类型HECs（包括药物类、个人护理品类、卤代烃类和抗生素及抗性基因类）的效能,然后回顾了BES与其他技术（传统厌氧工艺、芬顿、复合湿地及光催化等）结合协同降解HECs的最新进展,最后在功能电极材料设计研发、HECs降解去除与安全转化的理论研究及工程化应用等方面进行了总结和展望,以期对该领域的研究人员提供一定的理论参考和技术支持,从而推进生物电化学技术在疏水性新兴污染物降解领域的应用和发展。