检索结果-内蒙古大学图书馆

Synthesis and characterization of biodegradable poly(L-aspartic acid-co-PEG)

Journal of polymer science 2000年第16期36卷

作者： Chee-Youb Won Chih-Chang Chu Jong Doo Lee Fiber and Polymer Science Program and Biomedical Engineering Program Cornell University Ithaca New York 14853 Department of Materials Science and Engineering Cornell University Ithaca New York 14853

The melt polycondensation reaction of the prepolymer prepared from N -(benzyloxycarbonyl)- L -aspartic acid anhydride ( N -CBz- L -aspartic acid anhydride) and low molecular weight poly(ethylene glycol) (PEG) using titanium isopropoxide (TIP) as a catalyst produced the new biodegradable poly( L -aspartic acid- co -PEG). This new copolymer had pendant amine functional groups along the polymer backbone chain. The optimal reaction conditions for the preparation of the prepolymer were obtained by using a 0.12 mol % of p -toluenesulfonic acid with PEG 200 for 48 h. The weight-average molecular weight of the prepolymer increased from 1,290 to 31,700 upon melt polycondensation for 6 h at 130°C under vacuum using 0.5 wt % TIP as a catalyst. The synthesized monomer, prepolymer, and copolymer were characterized by FTIR, 1 H- and 13 C-NMR, and UV spectrophotometers. Thermal properties of the prepolymer and the protected copolymer were measured by DSC. The glass transition temperature ( T g ) of the prepolymer shifted to a significantly higher temperature with increasing molecular weight via melt polycondensation reaction, and no melting temperature was observed. The in vitro hydrolytic degradation of these poly( L -aspartic acid- co -PEG) was measured in terms of molecular weight loss at different times and pHs at 37°C. This pH-dependent molecular weight loss was due to a simple hydrolysis of the backbone ester linkages and was characterized by more rapid rates of hydrolysis at an alkaline pH. These new biodegradable poly( L -aspartic acid- co -PEG)s may have potential applications in the biomedical field. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2949–2959, 1998

关键词： aspartic acid anhydride poly(ethylene glycol) poly(L-aspartic acid-co-PEG) biodegradable polymers

来源：评论

学校读者我要写书评

暂无评论

Amino acid-based bioanalogous polymers. Synthesis, and study of regular poly(ester amide)s based on bis(α-amino acid) α,ω-alkylene diesters, and aliphatic dicarboxylic acids

引用

Journal of polymer science 2000年第4期37卷

作者： R. Katsarava V. Beridze N. Arabuli D. Kharadze C. C. Chu C. Y. Won Centre for Medical Polymers and Biomaterials of Ministry of Health and Institute of Molecular Biology & Biophysics of Georgian Academy of Sciences P.O. Box 24 380079 Tbilisi-79 Georgia Fiber and Polymer Science Program Department of Textiles & Apparel & Biomedical Engineering Program Cornell University Ithaca New York 14853-4401

The purpose of this research was to synthesize new regular poly(ester amide)s (PEAs) consisting of nontoxic building blocks like hydrophobic α-amino acids, α,ω-diols, and aliphatic dicarboxylic acids, and to examine the effects of the structure of these building block components on some physico-chemical and biochemical properties of the polymers. PEAs were prepared by solution polycondensation of di- p -toluenesulfonic acid salts of bis-(α-amino acid) α,ω-alkylene diesters and di- p -nitrophenyl esters of diacids. Optimal conditions of this reaction have been studied. High molecular weight PEAs ( M w = 24,000–167,000) with narrow polydispersity ( M w / M n = 1.20–1.81) were prepared under the optimal reaction conditions and exhibited excellent film-forming properties. PEAs obtained are mostly amorphous materials with T g from 11 to 59°C. α-Chymotrypsin catalyzed in vitro hydrolysis of these new PEA substrates was studied to assess the effect of the building blocks of these new polymers on their biodegradation properties. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 391–407, 1999

关键词： α-amino acids biodegradable polymers regular poly(ester amide)s α-chymotrypsinolysis

来源：评论

学校读者我要写书评

暂无评论

Structure development and physical properties achieved in the drawing and/or annealing of PEN fibers

引用

Journal of polymer science 2000年第11期38卷

作者： Gang Wu Ming Liu Xiaoning Li John A. Cuculo College of Material Science and Engineering Beijing University of Chemical Technology Beijing 100029 China Department of Fibrous Material Engineering Beijing Institute of Clothing Technology Beijing 100029 China Fiber & Polymer Science Program College of Textiles North Carolina State University Raleigh North Carolina 27695

As-spun poly(ethylene-2,6-naphthalate) (PEN) fibers (i.e., precursors) prepared from high molecular weight polymer were drawn and/or annealed under various conditions. Structure and property variations taking place during the treatment process were followed via wide-angle X-ray scattering (WAXS), small-angle X-ray scattering, differential scanning calorimetry (DSC), and mechanical testing. Both the WAXS and DSC measurements of the cold-drawn samples stretched from a low-speed-spun amorphous fiber indicate that strain-induced crystallization can occur at a temperature below the glass-transition temperature and that the resultant crystal is in the α-form modification. In contrast, when the same precursor was subjected to constrained annealing, its amorphous characteristics remained unchanged even though the annealing was performed at 200 °C. These results may imply that the application of stretching stress is more important than elevated temperatures in producing α-form crystallization. The crystalline structure of the hot-drawn samples depends significantly on the morphology of the precursor fibers. When the precursor was wound at a very low speed and in a predominantly amorphous state, hot drawing induced the formation of crystals that were apparently pure α-form modification. For the β-form crystallized precursors wound at higher speeds, a partial crystalline transition from the β form to the α form was observed during the hot drawing. In contrast with the mechanical properties of the as-spun fibers, those of the hot-drawn products are not improved remarkably because the draw ratio is extremely limited for most as-spun fibers in which an oriented crystalline structure has already formed. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1424–1435, 2000

关键词： poly(ethylene-2,6-naphthalate) fiber drawing annealing structural change crystalline transition

来源：评论

学校读者我要写书评

暂无评论

Hydrolysis of biodegradable polymers by superoxide ions

引用

Journal of polymer science 2000年第18期37卷

作者： K. H. Lee C. Y. Won C. C. Chu Ivan Gitsov Fiber Science Program Department of Textile and Apparel and Biomedical Engineering Program Cornell University Ithaca NY 14853-4401 Department of Chemistry State University of New York College of Environmental Science and Forestry Syracuse NY 13210 Cornell Center for Materials Research and Department of Chemistry and Chemical Biology Cornell University Ithaca NY 14853-1301

The objective of this study was to examine the reactivity of superoxide ion as an oxygen nucleophile towards biodegradable biomaterials having an aliphatic polyester structure, such as poly( D , L -Lactide) (PDLLA). The changes in molecular weights and thermal properties of PDLLA were studied as a function of the superoxide ion concentration, hydrolysis time, and hydrolysis temperature. The superoxide ion induced fragmentation of PDLLA yielded a mixture of various species with different chain length. A combined size exclusion chromatography (SEC) method with a chemical tagging by phenyl isocyanate revealed that the structure of the oligomer species with the lowest molecular weight formed in the superoxide ion induced degradation mixture was linear. The significant reduction in T g was consistent with the significant reduction in the molecular weight of PDLLA. The linear low molecular fragments (dimers and trimers) in the reaction mixture could act as an internal plasticizers to enhance the T g reduction by increasing the free volume of chain ends. The relationship of T g with molecular weight of PDLLA followed the general theory of Fox–Flory. The mechanism of simple hydrolysis of ester by superoxide ion proposed by Forrester et al. was modified to interpret the data obtained from the synthetic biodegradable polymers. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3558–3567, 1999

关键词： superoxide ion biodegradable polymers hydrolysis polylactide degradation

来源：评论

学校读者我要写书评

暂无评论

Synthesis and characterization of dextran-maleic acid based hydrogel

引用

Journal of biomedical Materials Research Part B: Applied Biomaterials 1999年第2期46卷

作者： Sin-Hee Kim Chee-Youb Won Chih-Chang Chu Fiber and Polymer Science Program Department of Textiles & Apparel and Biomedical Engineering Program Cornell University Ithaca New York 14853-4401

A new class of hydrogel precursor, dextran-maleic acid (Dex-MA), was synthesized by the reaction of dextran with maleic anhydride in the presence of the catalyst triethylamine. The effects of temperature, time, catalyst amount, and reactant concentration on the degree of substitution (DS) by MA was studied to establish an optimum reaction condition. The new hydrogel precursor had excellent solubility in various common organic solvents. The hydrogels based on Dex-MA precursor were made by the irradiation of Dex-MA with a long wave UV lamp. The Dex-MA hydrogels showed a very high swelling ratio in water, and the magnitude of swelling depended on the pH of the medium and the DS by MA. The Dex-MA hydrogels exhibited the highest swelling ratio in neutral pH, followed by acidic (pH 3) and alkaline pH (10). The most distinctive characteristic of Dex-MA hydrogels was that a carboxylic acid group was generated by the reaction of dextran with maleic anhydride. As a result, the swelling ratio increased with an increase of the DS of the MA segment (ionizable moiety that affects swelling ratio) in the Dex-MA hydrogel. © 1999 John Wiley & Sons, Inc. J Biomed Mater Res, 46, 160–170, 1999.

关键词： dextran maleic anhydride photocrosslinked hydrogel swelling hydrolytic degradation

来源：评论

学校读者我要写书评

暂无评论

The role of superoxide ions in the degradation of synthetic absorbable sutures

引用

Journal of biomedical Materials Research Part B: Applied Biomaterials 1999年第1期49卷

作者： Keun-Ho Lee C. C. Chu Fiber Science Program Department of Textiles and Apparel and Biomedical Engineering Program Cornell University Ithaca New York 14853-4401

The objective of this study was to examine the effect of superoxide ion-induced degradation on synthetic absorbable biomaterials. Synthetic absorbable sutures were used as the model compounds. Inflammatory cells, particularly leukocytes and macrophages, are able to produce highly reactive oxygen species, such as superoxide (·O 2 − ), during inflammatory reactions to foreign materials. Superoxide ions may act as oxygen nucleophile agents to attack biomaterials. In this study, the changes in tensile breaking force, thermal properties, and the surface morphology of five commercial (2/0 in size) synthetic absorbable sutures (Dexon®, Vicryl®, PDS II®, Maxon®, and Monocryl®) as a function of superoxide ion concentration at 25°C for 24 h were studied. Among the five absorbable sutures and over the concentration range of this study, the monofilament Monocryl® suture was the most sensitive toward superoxide ion-induced degradation, followed by Maxon®, Vicryl®, Dexon®, and PDS II® sutures. The amount of tensile breaking force loss over a 24 h period ranged from as low as 3% to as high as 80%, depending on the type of absorbable sutures, the reaction time, and the superoxide ion concentration. All five absorbable sutures showed significant reductions in both the T m and T g . Unlike the surface morphological changes of absorbable sutures in conventional buffer solutions, the effect of superoxide ion-induced degradation on the surface morphologies of these five absorbable sutures was unique, particularly the moon-crater-shaped impressions of various sizes and depths found in Monocryl® and Maxon® sutures, which defied the anisotropic characteristics of fibers. © 2000 John Wiley & Sons, Inc. J Biomed Mater Res, 49, 25–35, 2000.

关键词： absorbable sutures superoxide hydrolytic degradation free radicals thermal properties surface morphology

来源：评论

学校读者我要写书评

暂无评论

Crosslinking of chitosan fibers with dialdehydes: Proposal of a new reaction mechanism

引用

Journal of polymer science 1999年第11期37卷

作者： Jonathan Z. Knaul Samuel M. Hudson Katherine A. M. Creber Department of Chemistry and Chemical Engineering Royal Military College PO Box 17000 Station Forces Kingston Ontario K7K 7B4 Canada Fiber and Polymer Science Program Box 8301 Centennial Campus North Carolina State University Raleigh North Carolina 27695-8301

A highly deacetylated chitosan from shrimp with a degree of deacetylation of 95.28 ± 3.03% was prepared and spun into a monofilament fiber using a solution of 4% (w/v) chitosan in 4% (v/v) aqueous acetic acid. Samples of the spun fibers were immersed in aqueous solutions containing glutaraldehyde and glyoxal, and subsequently washed and dried. When the concentration of crosslinking agent was varied at room temperature over a constant time of 1 h, dry mechanical properties improved up to a point after which increasing concentrations resulted in degradation. Immersion time was also varied between 1 and 60 min at 25.8°C, and temperature was varied between 25.8 and 70.0°C, at fixed concentrations of both glyoxal and glutaraldehyde. It was demonstrated that mechanical improvements might be rendered at higher temperatures over lesser times. However, it was also shown that at higher temperatures, fiber mechanical properties would begin to diminish. Chitosan films were subjected to similar treatments in aqueous crosslinking solutions. Fourier transform infrared data (FTIR) on the films suggest that some interaction is occurring between the glutaraldehyde or glyoxal and the amine group on the chitosan backbone. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1079–1094, 1999

关键词： chitosan fiber crosslinking mechanical films FTIR wet spinning

来源：评论

学校读者我要写书评

暂无评论

Contributory presentations/posters

引用

Journal of Biosciences 1999年第1期24卷 33-198页

作者： N. Manoj V. R. Srinivas A. Surolia M. Vijayan K. Suguna R. Ravishankar R. Schwarzenbacher K. Zeth Diederichs G. M. Kostner A. Gries P. Laggner R. Prassl Madhusudan Pearl Akamine Nguyen-huu Xuong Susan S. Taylor M. Bidva Sagar K. Saikrishnan S. Roy K. Purnapatre P. Handa U. Varshney B. K. Biswal N. Sukumar J. K. Mohana Rao A. Johnson Vasantha Pattabhi S. Sri Krishna Mira Sastri H. S. Savithri M. R. N. Murthy Bindu Pillai Kannan M. V. Hosur Mukesh Kumar Swati Patwardhan K. K. Kannan B. Padmanabhaa S. Sasaki-Sugio M. Nukaga T. Matsuzaki S. Karthikevan S. Sharma A. K. Sharma M. Paramasivam P. Kumar J. A. Khan S. Yadav A. Srinivasan T. P. Singh S. Gourinath Neelima Alam A. Srintvasan Vikas Chandra Punit Kaur Ch. Betzel S. Ghosh A. K. Bera S. Bhattacharya S. Chakraborty A. K. Pal B. P. Mukhopadhyay I. Dey U. Haldar Asok Baneriee Jozef Sevcik Adriana Solovicova K. Sekar M. Sundaralingam N. Genov Dong-cai Liang Tao Jiang Ji-ping Zhang Wen-rui Chang Wolfgang Jahnke Marcel Blommers S. C. Panchal R. V. Hosur Bindu Pillay Puniti Mathur S. Srivatsun Ratan Mani Joshi N. R. Jaganathan V. S. Chauhan H. S. Atreya S. C. Sahu K. V. R. Chary Girjesh Govil Elisabeth Adjadj Éric Quinjou Nadia Izadi-Pruneyre Yves Blouquit Joël Mispelter Bernadette Heyd Guilhem Lerat Philippe Milnard Michel Desmadreil Y. Lin B. D. Nageswara Rao Vidva Raghunathan Mei H. Chau Prashant Pesais Sudha Srivastava Evans Coutinho Anil Saran Leizl F. Sapico Jayson Gesme Herbert Lijima Raymond Paxton Thamarapu Srikrishnan C. R. Grace G. Nagenagowda A. M. Lynn Sudha M. Cowsik Sarata C. Sahu S. Chauhan A. Bhattacharya G. Govil Anil Kumar Maurizio Pellecchia Erik R. P. Zuiderweg Keiichi Kawano Tomoyasu Aizawa Naoki Fujitani Yoichi Hayakawa Atsushi Ohnishi Tadayasu Ohkubo Yasuhiro Kumaki Kunio Hikichi Katsutoshi Nitta V. Rani Parvathy R. M. Kini Takumi Koshiba Yoshihiro Kobashigawa Min Yao Makoto Demura Astushi Nakagawa Isao Tanaka Kunihiro Kuwajima Jens Linge Seán O. Donoghue Michael Nilges G. Chakshusmathi Girish S. Ratnaparkhi P. K. Madhu R. Varadarajan C. Tetreau Molecular Biophysics Unit Indian Institute of Science Bangalore India Austrian Academy of Sciences Institute of Biophysics and X-ray Structure Research Graz Austria Faculty of Biology University of Konstanz Germany Institute of Medical Biochemistry University of Graz Austria Howard Huges Medical Institute Department of Chemistry & Biochemistry University of California La Jolla USA Department of Chemistry & Biochemistry University of California San Diego La Jolla USA Molecular Biophysics Unit India Department of Microbiology &Cell Biology Indian Institute of Science Bangalore India Macromolecular Structure Laboratory NCI - Frederick Cancer Research and Development Center ABL - Basic Research Program Frederick USA Department of Crystallography and Biophysics University of Madras Chennai Biochemistry Department Indian Institute of Science Bangalore India Condensed Matter Physics Division B.A.R.C. Trombay Mumbai Condensed Matter Physics Division Bhabha Atomic Research Centre Trombay Mumbai IMCB The University of Tokyo Tokyo Japan Mitsubishi Chemical Corporation Yokohama Research Center Yokohama Japan Faculty of Pharmaceutical Sciences Chiba University Chiba Japan Department of Biophysics All India Institute of Medical Sciences New Delhi India Department of Biophysics All India Institute of Medical sciences New Delhi India Institüt Physiologische Chemie Hamburg Germany Biophysics Department Bose Institute Calcutta India Slovak Academy of Sciences Institute of Molecular Biology Bratislava Slovakia Indian Institute of Science Bioinformatics Centre Bangalore Departments of Chemistry and Biochemistry Biological Macromolecular Structure Center USA Bulgarian Academy of Sciences Institute of Organic Chemistry Sofia Bulgaria Chinese Academy of Sciences Institute of Biophysics Beijing China Novartis Pharma AG Preclinical Research Basel Switzerland Department of Chemical Sciences Tata Institute of Fundamental Research Mumbai India Solid State Physics Div

来源：评论

学校读者我要写书评

暂无评论

Oriented noncrystalline structure in PET fibers prepared with threadline modification process

引用

Journal of polymer science 1996年第12期34卷

作者： Gang Wu Jiao-Dong Jiang Paul A. Tucker John A. Cuculo Department of Polymer Science Beijing University of Chemical Technology Beijing 100029 China Department of Fibrous Material Engineering Beijing Institute of Clothing Technology Beijing 100029 China Fiber & Polymer Science Program College of Textiles North Carolina State University Raleigh North Carolina 27695

The development of an oriented noncrystalline phase in a semicrystalline polymer filament has been studied via X-ray scattering. These unique PET fibers contain a relatively high noncrystalline content and also have high tenacity, high modulus, and low breaking elongation. fiber properties were found to be very responsive to the oriented amorphous phase content. This phase was utilized for interpreting noncrystalline orientation in PET fibers produced by a new extrusion technique. Here, the oriented noncrystalline regions in a series of PET fibers varies from 6% to 63%, depending strongly on the production conditions. In particular, samples produced with a newly developed threadline modification process possess a high content of oriented noncrystalline polymer. Measurements such as dynamic and static mechanical properties have been performed on various samples, and these properties are related to the oriented noncrystalline phase. The results provide direct evidence for the existence of highly oriented noncrystalline material in these unique PET fibers spun with a threadline modification process. © 1996 John Wiley & Sons, Inc.

关键词： poly(ethylene terephthalate) controlled threadline dynamics orientation oriented noncrystalline phase fiber properties crystallinity

来源：评论

学校读者我要写书评

暂无评论

Bicomponent vascular grafts consisting of synthetic absorbable fibers: Part II: In vivo healing response

引用

Journal of Investigative Surgery 1994年第3期7卷 195-211页

作者： Yu, Tarng-Jenn Ho, Donald M. Chu, C.C. Section of Cardiovascular Surgery Department of Surgery Veterans General Hospitals-Taipei Institute of Biomedical Engineering Yang-Ming Medical College Shih-Pai Taipei Taiwan Department of Pathology Veterans General Hospitals-Taipei Shih-Pai Taipei Taiwan Department of Textiles and Apparel Cornell University Ithaca NY United States Fiber and Polymer Science Program Department of Textiles and Apparel Cornell University Ithaca NY 14853-4401 United States

The objectives of this research were (I) to determine whether the use of partially absorbable vascular grafts would improve their nonthrombogenic performance and whether they are more prone to aneurysmal dilation and subsequent failure in vivo. and (2) to find out the relationships, if any. between these in vivo and the previously reported in vitro data with an emphasis on how the in vitro changes in fabric structure and properties related to these in vivo data. Bicomponent vascular fabrics were made from Dacron and polyglycolic acid (PGA) yarns with a range of composition ratios of the PGA to Dacron. Both woven and single Jersey knit fabrics were made, and implanted in dogs for 4 months. The following findings and relationships were obtained. (1) The bicomponent vascular fabrics resulted in a full-wall healing in the thoracic aorta of dogs. All bicomponent vascular grafts in survived dogs exhibited 100% patency, no thrombus or aneurysmal formation, no hematoma or seroma around the grafts, and no fibrin coagula in the inner capsules. The gross morphology of the regenerated tissues was very similar visually to the adjacent original arterial tissue. Histologically, the luminal surface was lined with a layer of endothelial cells with myofibroblasts, fibroblasts. and collagens underneath. (2) The extent of the full-wall healing depended on the type of fabric structure. the concentration of absorbable yarns, the location of absorbable yarns (for the woven group only), and initial water permeability. It is believed that the concentration effect was related to the level of macrophage activation from the degradation products of the absorbable yarns, while the location effect was attributed to the various types of fabric structure change on the degradation of the absorbable yarns. (3) In general, the knitted group (K), was better than the woven group (W). K3 showed the best in vivo performance in the knitted group. (4) In the woven group, W3 was the best. The incorporation o

关键词： Absorbable fibers Animal implantation Biodegradation Endothelial cell lining Synthetic vascular grafts Tissue ingrowth

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：