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Biodegradable Poly (biodegradable + poly)
Selected AbstractsFree-Standing Biodegradable Poly(lactic acid) Nanosheet for Sealing Operations in SurgeryADVANCED MATERIALS, Issue 43 2009Yosuke Okamura A free-standing biodegradable nanosheet composed of poly(L -lactic acid) (PLLA) was shown to have excellent sealing efficacy for a gastric incision as a novel wound dressing material that did not require adhesive agents, and the PLLA nanosheet-induced wound repair showed neither scars nor tissue adhesion. This material may, therefore, be an ideal alternative to conventional tissue repairing procedures using suture/ligation in surgery. [source] in vitro Evaluation of Biodegradable Poly(butylene succinate) as a Novel BiomaterialMACROMOLECULAR BIOSCIENCE, Issue 5 2005Haiyan Li Abstract Summary: Poly(butylene succinate) (PBSU) can be easily synthesized by condensation polymerization of the starting materials of succinic acid and butan-1,4-diol. It has good degradability and possesses excellent processability. Due to these advantages, PBSU was first evaluated in the present study for its potential application as a novel biomaterial. The in vitro biocompatibility of the PBSU was evaluated by monitoring proliferation and differentiation of osteoblasts cultured on the PBSU film substrates for different periods. The results showed that the PBSU was biocompatible as the osteoblasts could proliferate and differentiate on the PBSU plates. In addition, the hydrolytic degradation behavior of the PBSU films in the phosphate-buffered saline (PBS) was also investigated and the results suggested that the PBSU degraded in the PBS solution with the same behavior as that of the degradable poly(, -hydroxyesters). In addition to the biocompatibility and hydrolytic degradation, some physical properties, including hydrophilicity, and mechanical and thermal properties of the PBSU substrates, were also determined and the results revealed that the PBSU was hydrophilic and ductile with excellent processability. The biocompatibility of the PBSU, together with the advantages of hydrolytic degradability, hydrophilicity, and excellent processability, indicated that PBSU has the potential to be used as a biomaterial for tissue repair. Alkaline phosphate activity of osteoblasts cultured on PBSU and TCPS substrates for different time periods. [source] Synthesis and Characterization of Biodegradable Poly(, -caprolactone)-Polyglycolide-Poly(ethylene glycol) Monomethyl Ether Random CopolymerMACROMOLECULAR MATERIALS & ENGINEERING, Issue 6 2004Shaobing Zhou Abstract Summary: Poly(, -caprolactone)-polyglycolide-poly(ethylene glycol) monomethyl ether random copolymers were synthesized from , -caprolactone (, -CL), glycolide (GA) and poly(ethylene glycol) monomethyl ether (MPEG) using stannous octoate as catalyst at 160,°C by bulk polymerization. The copolymers with different composition were synthesized by adjusting the weight ration of reaction mixture. The resultant copolymer with a weight ratio (10:15:75) of MPEG2000, GA, and CL was characterized by IR, 1H NMR, GPC and DSC. The new biodegradable copolymer has potential for medical applications since it is combined with properties of PCL, PGA and MPEG. [source] Biodegradable Poly(ester hydrazide)s via Enzymatic PolymerizationMACROMOLECULAR RAPID COMMUNICATIONS, Issue 16 2005Guillaume Métral Abstract Summary: The reaction of hydrazine with ethyl glycolate results in 1,2-bisglycoylhydrazine, a monomer that was used for the lipase-catalyzed synthesis of biodegradable poly(ester hydrazide)s. The polymers derived from the hydrazide-containing monomer and vinyl-activated adipic, suberic, and sebacic acid, respectively, showed low melting temperatures of 136 to 141,°C and are thermally stable up to 300,°C. The aliphatic poly(ester hydrazide)s (PEHs) are highly crystalline, as proven by polarization microscopy and atomic force microscopy. Further, the PEHs represent the first described biodegradable poly(hydrazide)s. They degrade in the presence of lipase at 37,°C within a few weeks. Synthetic route to poly(ester hydrazide)s. [source] Processing of a Strong Biodegradable Poly[(R)-3-hydroxybutyrate] Fiber and a New Fiber Structure Revealed by Micro-Beam X-Ray Diffraction with Synchrotron RadiationMACROMOLECULAR RAPID COMMUNICATIONS, Issue 11 2004Tadahisa Iwata Abstract Summary: Biodegradable poly[(R)-3-hydroxybutyrate] (P(3HB)) fibers with high tensile strength of 1.32 GPa were processed from ultra-high-molecular-weight P(3HB) by a method combining cold-drawing and two-step-drawing procedures at room temperature. The distribution of molecular structures in a mono-filament was analyzed by micro-beam X-ray diffraction with synchrotron radiation. It was revealed that the P(3HB) fiber has a new core-sheath structure consistent with two types of molecular conformations: a 21 helix conformation in the sheath region and a planar zigzag conformation in the core region. P(3HB) fiber processed by cold-drawing in ice water and two-step drawing at room temperature, and subsequently annealing at 50,°C. [source] Reinforcement of Biodegradable Poly(DL -lactic acid) Material by Equal-Channel Angular ExtrusionMACROMOLECULAR SYMPOSIA, Issue 1 2006Hongxiang Cui Abstract The purpose of this study was to reinforce biodegradable poly(DL -lactic acid) (PDLLA) material using a new method, equal-channel angular extrusion (ECAE). Different processing parameters, including the number of extrusion passes and the process temperature, were investigated to analyze their effect on the PDLLA properties. Experimental results indicate that the mechanical strength of PDLLA increased with the number of extrusion passes. The extrusion temperature also affected the mechanical strength of the PDLLA. After two ECAE passes, the bending strength of PDLLA increased from 83.3 to 178.7 MPa. The bending fracture mode for PDLLA changed from brittle failure for initial specimens to ductile fracture after ECAE processing. SEM micrographs showed that the longitudinal split surfaces of PDLLA are of a fibrillar structure. Taken together, the results suggest that ECAE might represent a useful approach for the preparation of reinforced PDLLA. [source] Poly(,-caprolactone)-Functionalized Carbon Nanotubes and Their Biodegradation Properties,ADVANCED FUNCTIONAL MATERIALS, Issue 6 2006H.-L. Zeng Abstract Biodegradable poly(,-caprolactone) (PCL) has been covalently grafted onto the surfaces of multiwalled carbon nanotubes (MWNTs) by the "grafting from" approach based on in-situ ring-opening polymerization of ,-caprolactone. The grafted PCL content can be controlled easily by adjusting the feed ratio of monomer to MWNT-supported macroinitiators (MWNT-OH). The resulting products have been characterized with Fourier-transform IR (FTIR), NMR, and Raman spectroscopies, transmission electron microscopy (TEM), and scanning electron microscopy (SEM). After PCL was coated onto MWNT surfaces, core/shell structures with nanotubes as the "hard" core and the hairy polymer layer as the "soft" shell are formed, especially for MWNTs coated with a high density of polymer chains. Such a polymer shell promises good solubility/dispersibility of the MWNT,PCL nanohybrids in low-boiling-point organic solvents such as chloroform and tetrahydrofuran. Biodegradation experiments have shown that the PCL grafted onto MWNTs can be completely enzymatically degraded within 4,days in a phosphate buffer solution in the presence of pseudomonas (PS) lipase, and the carbon nanotubes retain their tubelike morphologies, as observed by SEM and TEM. The results present possible applications for these biocompatible PCL-functionalized CNTs in bionanomaterials, biomedicine, and artificial bones. [source] Biodegradable poly(vinyl alcohol)- graft - poly(,-caprolactone) comb-like polyester: Microwave synthesis and its characterizationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007Zhaoju Yu Abstract Poly(vinyl alcohol)-initiated microwave-assisted ring opening polymerization of ,-caprolactone in bulk was investigated, and a series of poly(vinyl alcohol)- graft -poly(,-caprolactone) (PVA- g -PCL) copolymers were prepared, with the degree of polymerization (DP) of PCL side chains and the degree of substitution (DS) of PVA by PCL being in the range of 3,24 and 0.35,0.89, respectively. The resultant comb-like PVA- g -PCL copolymers were confirmed by means of FTIR, 1H NMR, and viscometry measurement. The introduction of hydrophilic backbone resulted in the decrease in both melting point and crystallization property of the PVA- g -PCL copolymers comparing with linear PCL. With higher microwave power, the DP of PCL side chains and DS of PVA backbone were higher, and the polymerization reaction proceeded more rapidly. Both the DP and monomer conversion increased with irradiation time, while the DS increased first and then remained constant. With initiator in low concentration, the DP and DS were higher, while the monomer was converted more slowly. Microwaves dramatically improved the polymerization reaction in comparison of conventional heating method. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104, 3973,3979, 2007 [source] Biodegradable poly(D,L -lactide) coating of implants for continuous release of growth factorsJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 4 2001G. Schmidmaier Abstract Local application of growth factors like insulin like growth factor-I (IGF-I) and transforming growth factor-beta 1 (TGF-,1) from a biodegradable thin layer of poly(D,L -lactide) (PDLLA) coated implants could stimulate fracture healing. A new "cold coating technique" for metallic implants was established to produce a biodegradable coating with a high mechanical stability that provides a continuous release of incorporated growth factors. The properties of this bioactive coating were investigated in vitro and in vivo. Scanning electron microscope analysis revealed a coating thickness of in average 14.8 ,m on titanium and 10.7 ,m on steel wires. Intramedullary implantation and extraction experiments depicted a loss of PDLLA coating from titanium and steel implants of less than 5%. After explantation of the implants, the coating displayed a complete and regular layer without any defects of PDLLA uncovering the metallic surface. Smear tests demonstrate that the coating can be performed under sterile conditions. The PDLLA depicted a reduction of about 8% within 6 weeks in vitro and in vivo. The growth factors were incorporated in a stable form and demonstrated a loss of stability of less than 3% within 42 days and less than 5% within one year. In an elution experiment, 54% IGF-I and 48% TGF-,1 were released within the first 48 h. After 42 days, 76% of IGF-I and 71% of TGF-,1 were detected in the elution fluid by ELISA. Comparable results were obtained in the in vivo experiments after 42 days. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 58: 449,455, 2001 [source] Chemical degradation of peptides and proteins in PLGA: A review of reactions and mechanismsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 7 2008M.L. Houchin Abstract Biodegradable poly(lactide-co-glycolide) (PLGA) polymers have been studied extensively for the controlled release of peptide and protein drugs. In addition to polymer biodegradation, chemical degradation of the incorporated peptide/protein has also been reported in PLGA devices, and the role of the polymer in promoting these reactions has been debated. This review summarizes the peptide/protein chemical degradation reactions that have been reported in PLGA systems and their mechanisms. Reported methods for stabilizing peptides and proteins in PLGA devices are also discussed. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:2395,2404, 2008 [source] Processing of a Strong Biodegradable Poly[(R)-3-hydroxybutyrate] Fiber and a New Fiber Structure Revealed by Micro-Beam X-Ray Diffraction with Synchrotron RadiationMACROMOLECULAR RAPID COMMUNICATIONS, Issue 11 2004Tadahisa Iwata Abstract Summary: Biodegradable poly[(R)-3-hydroxybutyrate] (P(3HB)) fibers with high tensile strength of 1.32 GPa were processed from ultra-high-molecular-weight P(3HB) by a method combining cold-drawing and two-step-drawing procedures at room temperature. The distribution of molecular structures in a mono-filament was analyzed by micro-beam X-ray diffraction with synchrotron radiation. It was revealed that the P(3HB) fiber has a new core-sheath structure consistent with two types of molecular conformations: a 21 helix conformation in the sheath region and a planar zigzag conformation in the core region. P(3HB) fiber processed by cold-drawing in ice water and two-step drawing at room temperature, and subsequently annealing at 50,°C. [source] Biodegradable poly(ester-ether)s: ring-opening polymerization of D,L-3-methyl-1,4-dioxan-2-one using various initiator systemsPOLYMER INTERNATIONAL, Issue 9 2010Yemanlall Lochee Abstract The synthesis and detailed characterization of racemic 3-methyl-1,4-dioxan-2-one (3-MeDX) are reported. The bulk ring-opening polymerization of 3-MeDX, to yield a poly(ester-ether) meant for biomedical applications, in the presence of various initiators such as tin(II) octanoate, tin(II) octanoate/n -butyl alcohol, aluminium tris -isopropoxide and an aluminium Schiff base complex (HAPENAlOiPr) under varying experimental conditions is here detailed for the first time. Polymerization kinetics were investigated and compared with those of 1,4-dioxan-2-one. The studies reveal that the rate of polymerization of 3-MeDX is less than that of 1,4-dioxan-2-one. Experimental conditions to achieve relatively high molar masses have been established. Thermodynamic parameters such as enthalpy and entropy of 3-MeDX polymerization as well as ceiling temperature have been determined. Poly(D,L -3-MeDX) is found to possess a much lower ceiling temperature than poly(1,4-dioxan-2-one). Poly(D,L -3-MeDX) was characterized using NMR spectroscopy, matrix-assisted laser desorption ionization mass spectrometry, size exclusion chromatography and differential scanning calorimetry. This polymer is an amorphous material with a glass transition temperature of about ,20 °C. Copyright © 2010 Society of Chemical Industry [source] Synthesis and Properties of Novel Biodegradable/Biocompatible Poly[propylene- co -(ethylene succinate)] Random CopolyestersMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 17 2009George Z. Papageorgiou Abstract Random biocompatible/biodegradable poly[propylene- co -(ethylene succinate)]s were prepared. Mechanical properties and crystallization rates decreased with propylene succinate content. Glass transition temperatures (Tg) varied between those for the homopolymers. DSC and TMDSC findings showed that multiple melting behaviour of PPESu samples is related to melting,recrystallization,remelting. WAXD observations, eutectic behaviour, and thermodynamic analysis of the equilibrium melting point depression indicated isodimorphic cocrystallization. The copolymers showed enzymatic hydrolysis rates between those of the homopolymers and cytotoxicity/biocompatibility similar to PLA. [source] Antigen co-encapsulated with adjuvants efficiently drive protective T cell immunityEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 8 2007Antje Heit Abstract Compared to "live" vaccines, the immunogenicity of "subunit" vaccines based on recombinant antigen (Ag) is poor, presumably because exogenous Ag fails to effectively access the endosomal Ag-processing pathways of Ag-presenting cells (APC). To overcome this limitation, we exploited biodegradable poly(lactic-co-glycolic) microspheres (MP) co-entrapping Ag and Toll-like receptor (TLR) 9 or 7 ligands as an endosomal delivery device. In vitro, microspheres were rapidly phagocytosed by APC and translocated into phago-endosomal compartments, followed by degradation of the Ag and concurrent activation of endosomal TLR. As a consequence, full maturation of and cytokine secretion by APC as well as Ag-cross-presentation ensued. In vivo, "loaded" microspheres triggered clonal expansion of primary and secondary Ag-specific CD4 and CD8 T cells. The efficacy of CD8 T cell cross-priming was comparable to that of live vectors. The potency of T cell vaccination was demonstrated by protective and therapeutic interventions using infection- and tumor-model systems. These preclinical "subunit" vaccination data thus recommend MP as a generally applicable and powerful endosomal delivery device of exogenous Ag plus TLR-based adjuvants to vaccinate for protective and therapeutic CD4 and CD8 T cell immunity. [source] Polymer Scaffolds for Small-Diameter Vascular Tissue EngineeringADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Haiyun Ma Abstract To better engineer small-diameter blood vessels, a few types of novel scaffolds are fabricated from biodegradable poly(L -lactic acid) (PLLA) by means of thermally induced phase-separation (TIPS) techniques. By utilizing the differences in thermal conductivities of the mold materials and using benzene as the solvent scaffolds with oriented gradient microtubular structures in the axial or radial direction can be created. The porosity, tubular size, and the orientational direction of the microtubules can be controlled by the polymer concentration, the TIPS temperature, and by utilizing materials of different thermal conductivities. These gradient microtubular structures facilitate cell seeding and mass transfer for cell growth and function. Nanofibrous scaffolds with an oriented and interconnected microtubular pore network are also developed by a one-step TIPS method using a benzene/tetrahydrofuran mixture as the solvent without the need for porogen materials. The structural features of such scaffolds can be conveniently adjusted by varying the solvent ratio, phase-separation temperature, and polymer concentration to mimic the nanofibrous features of an extracellular matrix. These scaffolds were fabricated for the tissue engineering of small-diameter blood vessels by utilizing their advantageous structural features to facilitate blood-vessel regeneration. [source] Magnetic-Field-Assisted Electrospinning of Aligned Straight and Wavy Polymeric NanofibersADVANCED MATERIALS, Issue 22 2010Yaqing Liu Aligned straight and wavy fibers of biodegradable poly(D,L-lactic- co -glycolic acid) (PLGA) are fabricated using a magnetic-field-assisted electrospinning method. PLGA fibrous matrices prepared by this method can guide the growth of pluripotent murine mesenchymal stem cells. While the stem cells on the randomly oriented fibers adapt pseudo-sphere-like shape, those on aligned fibers exhibit elongated morphology along the long axes (see figure). [source] Magnetite-Loaded Polymeric Micelles as Ultrasensitive Magnetic-Resonance Probes,ADVANCED MATERIALS, Issue 16 2005H. Ai Increased contrast in magnetic resonance imaging (MRI) is accomplished using polymeric micelles loaded with superparamagnetic iron oxide (SPIO) nanoparticles encapsulated in biocompatible, biodegradable poly(,-caprolactone)- b -poly(ethylene glycol) (PCL- b -PEG) copolymers (see Figure). The loaded micelles show significantly improved T2 relaxivities and remarkable MRI detection sensitivity. [source] Synthesis and characterization of amphiphilic biodegradable poly(glutamic acid- co -lactic acid- co -glycolic acid) by direct polycondensationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Dedai Lu Abstract Poly(glutamic acid- co -lactic acid- co -glycolic acid) (PGLG), an amphiphilic biodegradable copolymer, was synthesized by simply heating a mixture of L -glutamic acid (Glu), DL -lactic acid, and glycolic acid with the present of stannous chloride. The unique branched architecture comprising of glutarimide unit, polyester unit, and polyamide unit was confirmed by NMR spectrum. The PGLG was soluble in many organic solvents and aqueous solution of sodium hydroxide (pH , 9.0). The thermal properties were evaluated using thermogravimetric analysis and differential scanning calorimetry. Molecular weights were determined by 1H NMR end-group analysis and GPC, respectively, and the results indicated that the higher Glu content resulted in a decrease of the molecular weight. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Poly(,-glutamic acid) nanoparticles as an efficient antigen delivery and adjuvant system: Potential for an AIDS vaccineJOURNAL OF MEDICAL VIROLOGY, Issue 1 2008Xin Wang Abstract Antigen delivery systems using polymeric nanoparticles are of special interest as stable protein-based antigen carriers. In the present study, novel biodegradable poly(,-glutamic acid) (,-PGA) nanoparticles were examined for their antigen delivery and immunostimulatory activities in vitro and in vivo. The uptake of ovalbumin by dendritic cells was markedly enhanced by ,-PGA nanoparticles, and the ovalbumin was gradually released from ,-PGA nanoparticles into the cells. In addition, ,-PGA nanoparticles appeared to have great potential as an adjuvant, because they could induce the maturation of dendritic cells. Although not only ovalbumin-encapsulating nanoparticles (OVA-NPs) but also a simple mixture of ovalbumin and nanoparticles induced dendritic cell maturation, the only dendritic cells exposed to OVA-NPs could strongly activate antigen-specific interferon (IFN)-,-producing T cells. Subcutaneous immunization of mice with human immunodeficiency virus type 1 (HIV-1) p24-encapsulating nanoparticles activated antigen-specific IFN-,-producing T cells in spleen cells and induced p24-specific serum antibodies, as compared to immunization with p24 alone. Like ovalbumin, a mixture of p24 and nanoparticles also induced antigen-specific serum antibodies but did not activate IFN-,-producing T cells in spleen cells, suggesting that nanoparticles play a critical role in inducing cellular immune responses. Furthermore, ,-PGA nanoparticles had a capacity comparable to that of the complete Freund's adjuvant (CFA) in inducing p24-specific serum antibody. However, unlike CFA, they predominantly activated p24-specific IFN-,-producing T cells. Thus, ,-PGA nanoparticles encapsulating various antigens may have great potential as novel and efficient protein-based vaccines against infectious diseases, including HIV-1 infection. J. Med. Virol. 80:11,19, 2008. © 2007 Wiley-Liss, Inc. [source] Synthesis and rheology of biodegradable poly(glycolic acid) prepared by melt ring-opening polymerization of glycolideJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2009Estelle Gautier Abstract Ring-opening polymerization (ROP) of glycolide was studied in melt conditions and in the presence of two different initiators: 1-dodecanol and 1,4-butanediol and tin(II) 2-ethylhexanoate as catalyst. Its subsequent polymerization provided poly(glycolic acid) with controlled molar masses ranging from 2000 to 42,000 g/mol with well-defined structures characterized by NMR. Their thermal properties were evaluated by DSC analysis, and a glass transition temperature at infinite molar mass (Tg,) of 44.8 °C was thus calculated. From rheological data, the critical molar mass for entanglement, Mc, was estimated to be near 11,000 g/mol. Furthermore, in situ polymerizations were also performed between the plates of the rheometer within a same temperature range from 210 to 235 °C. The variation of the storage and loss moduli during the polymerization step have been monitored by time sweep oscillatory experiments under an angular frequency , = 10 rad/s. Finally, the development of an inverse rheological method allowed to calculate the bulk polymerization kinetics in the temperature range 200,230 °C. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1440,1449, 2009 [source] Sugars-grafted aliphatic biodegradable poly(L -lactide- co -carbonate)s by click reaction and their specific interaction with lectin moleculesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2007Changhai Lu Abstract A novel biodegradable aliphatic poly(L -lactide- co -carbonate) bearing pendant acetylene groups was successfully prepared by ring-opening copolymerization of L -lactide (LA) with 5-methyl-5-propargyloxycarbonyl-1,3-dioxan-2-one (PC) in the presence of benzyl alcohol as initiator with ZnEt2 as catalyst in bulk at 100 °C and subsequently used for grafting 2-azidoethyl ,- D -glucopyranoside and 2-azidoethyl ,-lactoside by the typical "click reaction," that is Cu(I)-catalyzed cycloaddition of azide and alkyne. The density of acetylene groups in the copolymer can be tailored by the molar ratio of PC to LA during the copolymerization. The aliphatic copolymers grafted with sugars showed low cytotoxicity to L929 cells, improved hydrophilic properties and specific recognition and binding ability with lectins, that is Concanavalin A (Con A) and Ricinus communis agglutinin (RCA). Therefore, this kind of sugar-grafted copolymer could be a good candidate in variety of biomedical applications. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3204 ,3217, 2007 [source] Poly(,-caprolactone)- b -poly(ethylene glycol)- b -poly(,-caprolactone) triblock copolymers: Synthesis and self-assembly in aqueous solutionsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2007Yaqiong Zhang Abstract Nontoxic and biodegradable poly(,-caprolactone)- b -poly(ethylene glycol)- b -poly(,-caprolactone) triblock copolymers were synthesized by the solution polymerization of ,-caprolactone in the presence of poly(ethylene glycol). The chemical structure of the resulting triblock copolymer was characterized with 1H NMR and gel permeation chromatography. In aqueous solutions of the triblock copolymers, the micellization and sol,gel-transition behaviors were investigated. The experimental results showed that the unimer-to-micelle transition did occur. In a sol,gel-transition phase diagram obtained by the vial-tilting method, the boundary curve shifted to the left, and the gel regions expanded with the increasing molecular weight of the poly(,-caprolactone) block. In addition, the hydrodynamic diameters of the micelles were almost independent of the investigated temperature (25,55 °C). The atomic force microscopy results showed that spherical micelles formed at the copolymer concentration of 2.5 × 10,4 g/mL, whereas necklace-like and worm-like shapes were adopted when the concentration was 0.25 g/mL, which was high enough to form a gel. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 605,613, 2007 [source] Preparation and characterization of biodegradable poly(trimethylenecarbonate-,-caprolactone)-block-poly(p -dioxanone) copolymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2005J.-T. Hong Abstract A series of poly(trimethylenecarbonate-,-caprolactone)-block-poly(p- dioxanone) copolymers were prepared with varying feed rations by using two step polymerization reactions. Poly(trimethylenecarbonate)(,-caprolactone) random copolymer was synthesized with stannous-2-ethylhexanoate and followed by adding p- dioxanone monomer as the other block. The ring opening polymerization was carried out at high temperature and long reaction time to get high molecular weight polymers. The monofilament fibers were obtained using conventional melting spun methods. The copolymers were identified by 1H and 13C NMR spectroscopy and gel permeation chromatography (GPC). The physicochemical properties, such as viscosity, molecular weight, melting point, glass transition temperature, and crystallinity, were studied. The hydrolytic degradation of copolymers was studied in a phosphate buffer solution, pH = 7.2, 37 °C, and a biological absorbable test was performed in rats. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2790,2799, 2005 [source] Evaluation of articular cartilage repair using biodegradable nanofibrous scaffolds in a swine model: a pilot studyJOURNAL OF TISSUE ENGINEERING AND REGENERATIVE MEDICINE, Issue 1 2009Wan-Ju Li Abstract The aim of this study was to evaluate a cell-seeded nanofibrous scaffold for cartilage repair in vivo. We used a biodegradable poly(,-caprolactone) (PCL) nanofibrous scaffold seeded with allogeneic chondrocytes or xenogeneic human mesenchymal stem cells (MSCs), or acellular PCL scaffolds, with no implant as a control to repair iatrogenic, 7 mm full-thickness cartilage defects in a swine model. Six months after implantation, MSC-seeded constructs showed the most complete repair in the defects compared to other groups. Macroscopically, the MSC-seeded constructs regenerated hyaline cartilage-like tissue and restored a smooth cartilage surface, while the chondrocyte-seeded constructs produced mostly fibrocartilage-like tissue with a discontinuous superficial cartilage contour. Incomplete repair containing fibrocartilage or fibrous tissue was found in the acellular constructs and the no-implant control group. Quantitative histological evaluation showed overall higher scores for the chondrocyte- and MSC-seeded constructs than the acellular construct and the no-implant groups. Mechanical testing showed the highest equilibrium compressive stress of 1.5 MPa in the regenerated cartilage produced by the MSC-seeded constructs, compared to 1.2 MPa in the chondrocyte-seeded constructs, 1.0 MPa in the acellular constructs and 0.2 MPa in the no-implant group. No evidence of immune reaction to the allogeneically- and xenogeneically-derived regenerated cartilage was observed, possibly related to the immunosuppressive activities of MSCs, suggesting the feasibility of allogeneic or xenogeneic transplantation of MSCs for cell-based therapy. Taken together, our results showed that biodegradable nanofibrous scaffolds seeded with MSCs effectively repair cartilage defects in vivo, and that the current approach is promising for cartilage repair. Copyright © 2008 John Wiley & Sons, Ltd. [source] Biodegradable Polymeric Microcarriers with Controllable Porous Structure for Tissue EngineeringMACROMOLECULAR BIOSCIENCE, Issue 12 2009Xudong Shi Abstract Porous microspheres fabricated by biodegradable polymers show great potential as microcarriers for cell cultivation in tissue engineering. Herein biodegradable poly(DL -lactide) (PLA) was used to fabricate porous microspheres through a modified double emulsion solvent evaporation method. The influence of fabrication parameters, such as the stirring speed of the primary and secondary emulsion, the polymer concentration of the oil phase, and solvent type, as well as the post-hydrolysis treatment of the porous structure of the PLA microspheres are discussed. Good attachment and an active spread of MG-63 cells on the microspheres is observed, which indicates that the PLA microspheres with controllable porous structure are of great potential as cell delivery carriers for tissue engineering. [source] Construction of Polycation-Based Non-Viral DNA Nanoparticles and Polyanion Multilayers via Layer-by-Layer Self-Assembly,MACROMOLECULAR RAPID COMMUNICATIONS, Issue 20 2005Kefeng Ren Abstract Summary: The multilayers of polycation-based non-viral DNA nanoparticles and biodegradable poly(L -glutamic acid) (PGA) were constructed by a layer-by-layer (LbL) technique. Poly(ethyleneimine) (PEI) was used to condense DNA to develop non-viral DNA nanoparticles. AFM, UV-visible spectrometry, and TEM measurements revealed that the PEI-DNA nanoparticles were successfully incorporated into the multilayers. The well-structured, easily processed multilayers with the non-viral DNA nanoparticles may provide a novel approach to precisely control the delivery of DNA, which may have great potential for gene therapy applications in tissue engineering, medical implants, etc. A TEM image of the cross section of a (PGA/PEI-DNA nanoparticle)20 multilayer. [source] Biodegradable Poly(ester hydrazide)s via Enzymatic PolymerizationMACROMOLECULAR RAPID COMMUNICATIONS, Issue 16 2005Guillaume Métral Abstract Summary: The reaction of hydrazine with ethyl glycolate results in 1,2-bisglycoylhydrazine, a monomer that was used for the lipase-catalyzed synthesis of biodegradable poly(ester hydrazide)s. The polymers derived from the hydrazide-containing monomer and vinyl-activated adipic, suberic, and sebacic acid, respectively, showed low melting temperatures of 136 to 141,°C and are thermally stable up to 300,°C. The aliphatic poly(ester hydrazide)s (PEHs) are highly crystalline, as proven by polarization microscopy and atomic force microscopy. Further, the PEHs represent the first described biodegradable poly(hydrazide)s. They degrade in the presence of lipase at 37,°C within a few weeks. Synthetic route to poly(ester hydrazide)s. [source] Reinforcement of Biodegradable Poly(DL -lactic acid) Material by Equal-Channel Angular ExtrusionMACROMOLECULAR SYMPOSIA, Issue 1 2006Hongxiang Cui Abstract The purpose of this study was to reinforce biodegradable poly(DL -lactic acid) (PDLLA) material using a new method, equal-channel angular extrusion (ECAE). Different processing parameters, including the number of extrusion passes and the process temperature, were investigated to analyze their effect on the PDLLA properties. Experimental results indicate that the mechanical strength of PDLLA increased with the number of extrusion passes. The extrusion temperature also affected the mechanical strength of the PDLLA. After two ECAE passes, the bending strength of PDLLA increased from 83.3 to 178.7 MPa. The bending fracture mode for PDLLA changed from brittle failure for initial specimens to ductile fracture after ECAE processing. SEM micrographs showed that the longitudinal split surfaces of PDLLA are of a fibrillar structure. Taken together, the results suggest that ECAE might represent a useful approach for the preparation of reinforced PDLLA. [source] Reactive compatibilization of biodegradable poly(lactic acid)/poly(,-caprolactone) blends with reactive processing agentsPOLYMER ENGINEERING & SCIENCE, Issue 7 2008Masaki Harada Poly(lactic acid) (PLA) blended with poly(,-caprolactone) (PCL) was prepared with various reactive processing agents. Four isocyanates-lysine triisocyanate (LTI); lysine diisocyanate (LDI); 1,3,5-tris(6-isocyanatohexyl)-1,3,5-triazinane-2,4,6-trione (Duranate TPA-100); 1,3,5-tris(6-isocyanatohexyl)biuret (Duranate 24A-100)-and an industrial epoxide-trimethylolpropane triglycidyl ether (Epiclon 725)-were used as reactive processing agents. PLA/PCL blended in the presence of LTI had the highest torque in a mixer test. The test specimens were prepared by injection molding. The mechanical properties, thermal properties, molecular weight, melt viscosity, phase behavior, and morphology were investigated using tensile strength, impact strength, differential scanning calorimetry, melt mass-flow rate measurements, capillary rheometery, gel permeation chromatography, laser scanning confocal microscopy (LSCM), and visco-elasticity atomic force microscopy (VE-AFM). The impact strength increased considerably at 20 wt% PCL. The nominal tensile strain of PLA/PCL blended with LTI increased by 270%. The MFR values of PLA/PCL blends decreased with increasing LTI. Similar results were observed for shear viscosity. LSCM measurements showed that the diameters of PCL were dispersed about 0.4 ,m in the presence of LTI. VE-AFM showed that spherical particles with diameters of 50 nm were PCL-rich domain. These results indicate that isocyanate groups of LTI react with both terminal hydroxyl or carboxyl groups of polymers, and the compatibility of PLA/PCL blends improves with LTI by reactive processing. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers [source] Viscoelastic properties of extrusion cast sheets of natural and synthetic aliphatic polyestersPOLYMER ENGINEERING & SCIENCE, Issue 10 2005Mrinal Bhattacharya The objective of this study was to determine the viscoelastic properties of natural (starch and protein) blends and synthetic biodegradable aliphatic copolyester blends. Blends of natural and synthetic biodegradable poly(butylene succinate) were cast into sheets using a coathanger die and then subjected to stress relaxation and creep tests at various temperatures. The natural content was varied at 10%, 30%, and 50% by weight. In some formulations a small (5% by weight) amount of compatibilizer was added. The materials were blended using a twin screw-extruder, pelletized, and sheeted using a coathanger die. The decay of stress upon the imposition of constant strain showed two regions, an exponential and power law; the stresses relaxed sharply at the initial stage and then decayed at a reduced rate for the duration of the experiment. The addition of compatibilizers increased the time required for the stress to relax compared to uncompatibilized blends of the same composition. Similarly, as the natural content increased the time taken to relax to a specified stress level decreased. Increased temperature enhanced the relaxation process. The initial strain of the creep curves was affected by the natural content; the higher the natural content, the lower the initial strain for the samples upon imposition of a constant stress. Similarly, the presence of compatibilizer in the blend reduced the initial strain for samples containing the same natural content. As the natural content of the blend decreases, the time required to attain the plateau compliance is reduced. The equilibrium compliance increased with temperature. These behaviors are described in terms of blend morphology. The empirical Struik and power law models can be used to fit the compliance data well. POLYM. ENG. SCI., 45:1452,1460, 2005. © 2005 Society of Plastics Engineers [source] | ||||||||||||||||||||||||||||||||||