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Polylactic Acid (polylactic + acid)
Selected AbstractsEFFECT OF SOLUBLE POLYLACTIC ACID DURING REFRIGERATED STORAGE OF GROUND MEATS INOCULATED WITH ESCHERICHIA COLI O157:H7,JOURNAL OF FOOD SAFETY, Issue 1 2000ANN ALLANSON ABSTRACT Ground beef, ground pork, and commercial breakfast sausage were inoculated (6.5 log10 CFU/mL) with a five strain mixture of Escherichia coli 0157:H7 and treated either with sterile water, or 1% or 2% solutions of soluble polylactic acid (SPLA) in sterile water and stored at 4C for 1, 24, 72 and 168 h. After 168 h, 2% SPLA was significantly (p0.05) more effective than both 1% SPLA and sterile water in reducing E. coli 0157:H7 and resulted in overall reductions of 1.68, 1.70, and 1.32 log10 CFU/mL for beef, pork, and pork sausage, respectively, when compared to control samples. The meat samples treated with 1% and 2% SPLA maintained significantly (p 0.05) lower pH values throughout refrigerated storage of 168 h with the higher concentration sustaining pH values from 3.83 to 3.92. Although the inhibitory effect of this acid increased with storage time, E. coli 0157:H7 survived these acidic conditions, with water activity levels ranging from 0.972 to 0.991. [source] Study on Enzymatic Hydrolysis of Polylactic Acid by Endogenous Depolymerizaion ModelMACROMOLECULAR THEORY AND SIMULATIONS, Issue 6 2007Masaji Watanabe Abstract Enzymatic degradation of polylactic acid is studied experimentally and analytically. Gel permeation chromatography profiles obtained before and after the enzymatic degradation of polylactic acid (PLA) were introduced into the analysis based on a mathematical model. Previously developed techniques were successfully adapted to the analysis of an initial value problem consisting of an endogenous depolymerization model and an initial condition, and an inverse problem to determine the degradation rate for which the solution of the initial value problem also satisfies a final condition. Those problems were solved numerically and numerical results are introduced. Degradabilities of PLA and polyvinyl alcohol are compared. [source] Cosmetic use of polylactic acid: report of 568 patientsJOURNAL OF COSMETIC DERMATOLOGY, Issue 4 2009Alessio Redaelli MD Summary Background, There are few methods for the correction of the reduction of subcutaneous volumes. Polylactic acid is a new material with which we can achieve interesting results. Objective, To review our case histories in the assessment of this material's safety and effectiveness, its best indications, and to outline our technique. Materials and Method, Polylactic acid was prepared and diluted with 5,8 mL depending on injection sites, which included patients' face, neck and hands volume restoration, as well as arm and thigh revitalization. A total of 568 patients were treated from January 1999 to December 2007. Results, The Definitive Graduated Score varied from 6.3 to 8.4 with an average score of 7.8. The principal side effect, collagen late nodules, appeared with a very low frequency (1%) and were the result of incorrect technique. Conclusions, The fibro-connective restoration of face contours and volumes is the winning strategy for a holistic, three-dimensional approach to the aged face, neck, and hands. Since the introduction of certified courses, side effects have become less common than in other methods, and can probably be further reduced to a minimum. [source] Polylactide copolymers: Effect of copolymer ratio and end capping on their propertiesADVANCES IN POLYMER TECHNOLOGY, Issue 2 2005D. M. Bigg Abstract Racemic copolymers of polylactic acid were investigated to determine the effect of copolymer ratio on melting point, degree of crystallinity, mechanical properties, and processing behavior. The copolymer ratio was found to have a strong influence on the crystallization behavior of the polymer. In addition to the ratio of the L -form to a random mixture of the D and L forms of the lactic acid in the copolymer, the effect of the polymer's molecular weight was examined. The copolymers were produced from the lactide form of the monomer to achieve weight average molecular weights above 100,000. The molecular weight had a profound influence on processability and rate of crystallization. Other notable factors influencing the properties and processing of the copolymers were the concentration of residual monomer in the polymer, the processing time-temperature history, and the extent of molecular weight degradation during processing. An important factor in the commercial development of biodegradable polymers is the ability to control the rate of degradation. Ideally, the polymer should not degrade during functional use, but degrade quite rapidly when discarded. This paper discusses various aspects associated with the control of the rate of degradation of polylactide copolymers; both from the perspective of stabilizing the polymer during processing and product use, and subsequently accelerating the rate of degradation after disposal. Of particular interest are the influences of molecular weight, crystallinity, end capping, and plasticization. © 2005 Wiley Periodicals, Inc. Adv Polym Techn 24:69,82, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20032 [source] Cosmetic use of polylactic acid: report of 568 patientsJOURNAL OF COSMETIC DERMATOLOGY, Issue 4 2009Alessio Redaelli MD Summary Background, There are few methods for the correction of the reduction of subcutaneous volumes. Polylactic acid is a new material with which we can achieve interesting results. Objective, To review our case histories in the assessment of this material's safety and effectiveness, its best indications, and to outline our technique. Materials and Method, Polylactic acid was prepared and diluted with 5,8 mL depending on injection sites, which included patients' face, neck and hands volume restoration, as well as arm and thigh revitalization. A total of 568 patients were treated from January 1999 to December 2007. Results, The Definitive Graduated Score varied from 6.3 to 8.4 with an average score of 7.8. The principal side effect, collagen late nodules, appeared with a very low frequency (1%) and were the result of incorrect technique. Conclusions, The fibro-connective restoration of face contours and volumes is the winning strategy for a holistic, three-dimensional approach to the aged face, neck, and hands. Since the introduction of certified courses, side effects have become less common than in other methods, and can probably be further reduced to a minimum. [source] EFFECT OF SOLUBLE POLYLACTIC ACID DURING REFRIGERATED STORAGE OF GROUND MEATS INOCULATED WITH ESCHERICHIA COLI O157:H7,JOURNAL OF FOOD SAFETY, Issue 1 2000ANN ALLANSON ABSTRACT Ground beef, ground pork, and commercial breakfast sausage were inoculated (6.5 log10 CFU/mL) with a five strain mixture of Escherichia coli 0157:H7 and treated either with sterile water, or 1% or 2% solutions of soluble polylactic acid (SPLA) in sterile water and stored at 4C for 1, 24, 72 and 168 h. After 168 h, 2% SPLA was significantly (p0.05) more effective than both 1% SPLA and sterile water in reducing E. coli 0157:H7 and resulted in overall reductions of 1.68, 1.70, and 1.32 log10 CFU/mL for beef, pork, and pork sausage, respectively, when compared to control samples. The meat samples treated with 1% and 2% SPLA maintained significantly (p 0.05) lower pH values throughout refrigerated storage of 168 h with the higher concentration sustaining pH values from 3.83 to 3.92. Although the inhibitory effect of this acid increased with storage time, E. coli 0157:H7 survived these acidic conditions, with water activity levels ranging from 0.972 to 0.991. [source] Adhesion of perichondrial cells to a polylactic acid scaffoldJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 4 2003Alexander Giurea Abstract The number of chondrogenic cells available locally is an important factor in the repair process for cartilage defects. Previous studies demonstrated that the number of transplanted rabbit perichondrial cells (PC) remaining in a cartilage defect in vivo, after being carried into the site in a polylactic acid (PLA) scaffold, declined markedly within two days. This study examined the ability of in vitro culture of PC/PLA constructs to enhance subsequent biomechanical stability of the cells and the matrix content in an in vitro screening assay. PC/PLA constructs were analyzed after 1 h, 1 and 2 weeks of culture. The biomechanical adherence of PC to the PLA scaffold was tested by subjecting the PC/PLA constructs to a range of flow velocities (0.25,25 mm/s), spanning the range estimated to occur under conditions of construct insertion in vivo. The adhesion of PC to the PLA carrier was increased significantly by 1 and 2 weeks of incubation, with 25 mm/s flow causing a 57% detachment of cells after 1 h of seeding, but only 7% and 16% after 1 and 2 weeks of culture, respectively (p > 0.001). This adherence was associated with marked deposition of glycosaminoglycan and collagen. These findings suggest that pre-incubation of PC-laden PLA scaffolds markedly enhances the stability of the indwelling cells. © 2003 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved. [source] Formation and resolution of ankylosis under application of recombinant human bone morphogenetic protein-2 (rhBMP-2) to class III furcation defects in catsJOURNAL OF PERIODONTAL RESEARCH, Issue 4 2005D. Takahashi Objectives:, Periodontal regeneration under application of bone morphogenetic protein (BMP) is compromised by ankylosis. Ankylosis disappearance following application of BMP has been observed in the case of a small defect, which might be beneficial change for periodontal regeneration. However, the histological observation of ankylosis disappearance has not been demonstrated in a large defect. The purpose of this present study was to confirm resolution of ankylosis during periodontal regeneration by recombinant human BMP-2 (rhBMP-2) applied to class III furcation defects. Material and methods:, Class III furcation defects were created in the premolars of six adult cats. The rhBMP-2 material, prepared by applying rhBMP-2 to a combination of polylactic acid,polygricolic copolymer and gelatin sponge (PGS; 0.33 µg rhBMP-2/mm3 PGS) or control material containing only PGS, was implanted into each defect. The cats were killed at 3, 6 or 12 weeks after surgery and serial sections were prepared for histological and histometrical observation. Results:, Ankylosis was observed in some of the rhBMP-2/PGS group at 3 and 6 weeks, but not at 12 weeks. At 6 weeks, osteoclast-like cells were visible in the rhBMP-2/PGS group with ankylosis. Residual PGS was evident between the bone and root surface in the rhBMP-2/PGS group without ankylosis at 3 weeks. Conclusions:, Resolution of ankylosis by osteoclast-like cells possibly occurred under application of rhBMP-2. Residual PGS might play an important role in preventing ankylosis formation. [source] Study on Enzymatic Hydrolysis of Polylactic Acid by Endogenous Depolymerizaion ModelMACROMOLECULAR THEORY AND SIMULATIONS, Issue 6 2007Masaji Watanabe Abstract Enzymatic degradation of polylactic acid is studied experimentally and analytically. Gel permeation chromatography profiles obtained before and after the enzymatic degradation of polylactic acid (PLA) were introduced into the analysis based on a mathematical model. Previously developed techniques were successfully adapted to the analysis of an initial value problem consisting of an endogenous depolymerization model and an initial condition, and an inverse problem to determine the degradation rate for which the solution of the initial value problem also satisfies a final condition. Those problems were solved numerically and numerical results are introduced. Degradabilities of PLA and polyvinyl alcohol are compared. [source] In vitro and in vivo evaluation of a biodegradable chitosan,PLA composite peripheral nerve guide conduit materialMICROSURGERY, Issue 6 2008Feng Xie M.D., Ph.D. Chitosan, a nature biodegradable material, has good biocompatibility but poor physical properties to serve as a nerve conduit. In this study, polylactic acid (PLA) was added to chitosan to form a composite material with improved intensity and elasticity, to be used as nerve conduits. The chitosan,PLA nerve conduits were fabricated with a mold casting/infrared dehydration technique. The constituent ratio of PLA and chitosan of 1:5 (v:v) was chosen to give the composite material both good mechanical properties and good biocompatibility. An in vitro cytotoxicity test showed that the chitosan,PLA material was not cytotoxic. The conduits were proved biodegradable and had many micropores to allow permeability. We evaluated chitosan,PLA nerve conduits as a guidance channel to repair 10 mm gaps in rat sciatic nerves. Nerve autograft and silicon conduits were used as the control. After 12 weeks, the regenerating nerves in three groups succeeded in passing through the nerve gap and reinnervating the muscle. Assessments, including ECG, histomorphometric evaluation, and weighing of triceps calf muscle, showed that the functional recovery of sciatic nerve was better in chitosan,PLA conduit group than in the silicon conduit group (P < 0.05), but the differences between the chitosan,PLA conduit group and the nerve autograft group were not significant (P > 0.05). Therefore, the chitosan,PLA guide proved to be a promising nerve conduit. © 2008 Wiley-Liss, Inc. Microsurgery, 2008. [source] Effect of electron beam treatments on degradation kinetics of polylactic acid (PLA) plastic waste under backyard composting conditionsPACKAGING TECHNOLOGY AND SCIENCE, Issue 2 2009L. Fernando Vargas Abstract The effects of electron beam irradiation on backyard composting behaviour of polylactic acid (PLA) polymer were evaluated. Samples (10,mm2 × 0.75,mm) from thermoformed PLA drinking cups were exposed to 10,MeV electron beam irradiation at doses of 0, 72, 144 and 216,kGy. Irradiated PLA samples were placed in heat-sealed, plastic screen and added to organic feedstock in a rotating composter within a computer-controlled environmental chamber for 10 weeks at 35°C. Changes in weight, structural integrity and molecular weight were assessed over time. Results show that irradiation enhanced PLA breakdown. PLA weight decreased by increasing amounts as irradiation dose increased. Sample brittleness increased with irradiation dose and composting time. Finally, PLA molecular weight decreased as irradiation dose and compost time increased. Molecular weight D values for irradiated PLA were found to be about 430,kGy. After 1 week in a typical backyard composter, molecular weight D values increased to about 560,kGy and then fell to about 380,kGy after 2 weeks of composting. Samples irradiated at 216,kGy showed a reduction in weight of 9.4% after 10 weeks of composting, and a reduction of weight-average molecular weight of 93.7% after 6 weeks. Copyright © 2008 John Wiley & Sons, Ltd. [source] Effect of annealing and orientation on microstructures and mechanical properties of polylactic acidPOLYMER ENGINEERING & SCIENCE, Issue 4 2008Long Yu Two types of polylactic acid (PLA) films (one amorphous and one semi-crystalline) were produced by sheet extrusion. Talc was used as a nucleation agent for the semi-crystalline PLA. The films were annealed above their Tg or were uniaxially orientated in two ways: (1) via a drawing system in front of the extruder and die or (2) via a three-roller stretching system. The slower crystallization rate and lower melting stress of the PLA resulted in amorphous film using the drawing system. Annealing above Tg increased crystallinity and polymer chain relaxation, which resulted in increases in both strength and toughness. Stretching above Tg also produced simultaneous crystallization and chain relaxation, which resulted in increases in both modulus and toughness. Both modulus and tensile strength in the stretching direction were higher than in the crosswise direction. Talc acted not only as a rigid filler to reinforce the PLA, but also as a nucleation agent for the PLA, especially during annealing. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers [source] Novel Strategy to Engineer Trachea Cartilage Graft With Marrow Mesenchymal Stem Cell Macroaggregate and Hydrolyzable ScaffoldARTIFICIAL ORGANS, Issue 5 2010Liangqi Liu Abstract Limited donor sites of cartilage and dedifferentiation of chondrocytes during expansion, low tissue reconstruction efficiency, and uncontrollable immune reactions to foreign materials are the main obstacles to overcome before cartilage tissue engineering can be widely used in the clinic. In the current study, we developed a novel strategy to fabricate tissue-engineered trachea cartilage grafts using marrow mesenchymal stem cell (MSC) macroaggregates and hydrolyzable scaffold of polylactic acid,polyglycolic acid copolymer (PLGA). Rabbit MSCs were continuously cultured to prepare macroaggregates in sheet form. The macroaggregates were studied for their potential for chondrogenesis. The macroaggregates were wrapped against the PLGA scaffold to make a tubular composite. The composites were incubated in spinner flasks for 4 weeks to fabricate trachea cartilage grafts. Histological observation and polymerase chain reaction array showed that MSC macroaggregates could obtain the optimal chondrogenic capacity under the induction of transforming growth factor-,. Engineered trachea cartilage consisted of evenly spaced lacunae embedded in a matrix rich in proteoglycans. PLGA scaffold degraded totally during in vitro incubation and the engineered cartilage graft was composed of autologous tissue. Based on this novel, MSC macroaggregate and hydrolyzable scaffold composite strategy, ready-to-implant autologous trachea cartilage grafts could be successfully fabricated. The strategy also had the advantages of high efficiency in cell seeding and tissue regeneration, and could possibly be used in future in vivo experiments. [source] Biopolymere in textilen Anwendungen.CHEMIE IN UNSERER ZEIT (CHIUZ), Issue 3 2009Polyhydroxyalkanoate, Polylactid Abstract Biopolymere stellen eine interessante Polymerklasse dar, deren Potential bisher noch nicht endgültig erfasst ist. Sie gewinnen jedoch zunehmend an Marktwert. Vor allem Polylactid (PLA) hat sich bereits durchsetzen können, da es nicht nur aus nachwachsenden Rohstoffen hergestellt werden kann und abbaubar ist, sondern darüber hinaus ein Eigenschaftsprofil aufweist, das mit herkömmlichen thermoplastischen Kunststoffen vergleichbar ist und sich auch ähnlich gut verarbeiten lässt. Das Anwendungsfeld der Biopolymere reicht von Folien, Obst- und Gemüseschalen bis hin zu Hygiene- und Medizinartikeln und ist daher sehr vielfältig. Diese Vielfältigkeit wird sicherlich in der Zukunft weiter zunehmen. Biopolymers represent an interesting class of polymers whose potential is not yet been fully realised. However, more recently, biopolymers are gaining impetus in the market. Among the biopolymers, polylactic acid (PLA) is being used successfully and is widely accepted because it is produced from natural raw material and is degradable. Furthermore, it has comparable properties to standard thermoplastic polymers and can also be processed using similar process channels as conventional thermoplastic synthetic materials. Biopolymer applications are manifold and range from foils, fruit and vegetable packaging to hygiene and medical products. It can be expected that in future the application spectrum of biopolymers will increase even further. [source] Antimicrobial activity of nisin incorporated in pectin and polylactic acid composite films against Listeria monocytogenesINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 2 2009Tony Jin Summary An extruded composite food packaging film containing pectin, polylactic acids (PLAs) and nisin was developed to inhibit Listeria monocytogenes. The mechanical properties and surface structure of the film were also examined. Cells of L. monocytogenes were reduced by 2.1, 4.5 and 3.7 log units mL,1 by the pectin plus PLA (pectin/PLA) film containing nisin (1000 IU mL,1 of tested liquid) in Brain Heart Infusion (BHI) broth, liquid egg white and orange juice, respectively, after 48 h at 24 °C. Pectin played an important roll in embedding nisin into the film. The pectin/PLA film had a similar stiffness but lower tensile strength, elongation and fracture energy than the pure PLA film. These data suggested that nisin incorporated into the pectin/PLA film was an effective approach to reducing L. monocytogenes in a typical growth medium (e.g. BHI broth) as well as in foods (e.g. orange juice and liquid egg). [source] | ||||||||||||||||