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Degradation Properties (degradation + property)
Selected AbstractsCross-Linking and Degradation Properties of Plasma Enhanced Chemical Vapor Deposited Poly(2-hydroxyethyl methacrylate)MACROMOLECULAR RAPID COMMUNICATIONS, Issue 2 2009Courtney A. Pfluger Abstract Plasma Enhanced Chemical Vapor Deposition (PECVD) of poly-2-hydroxyethyl methacrylate (pHEMA) biocompatible, biodegradable polymer films were produced alone and cross-linked with ethylene glycol diacrylate (EGDA). Degree of cross-linking was controlled via manipulation of the EGDA flow rate, which influenced the amount of swelling and the extent of degradation of the films in an aqueous solution over time. Noncross-linked pHEMA films swelled 10% more than cross-linked films after 24 h of incubation in an aqueous environment. Increasing degree of film cross-linking decreased degradation over time. Thus, PECVD pHEMA films with variable cross-linking properties enable tuning of gel formation and degradation properties, making these films useful in a variety of biologically significant applications. [source] Optimizing preparation of NaCS,chitosan complex to form a potential material for the colon-specific drug delivery systemJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010Ming-Jun Wang Abstract A novel polyelectrolyte complex (PEC) formed by sodium cellulose sulfate (NaCS) and chitosan was prepared as a candidate material for colon-specific drug delivery system. It was found in experiments that the properties of two raw materials and the process parameters, such as the degree of substitution (DS) and concentration of NaCS, the viscosity and concentration of chitosan, were very important factors on the properties of the final product,NaCS,chitosan-PEC. The preparation of NaCS,chitosan complex was optimized by using response surface methodology to evaluate the effects of these parameters on the degradation properties of NaCS,chitosan in the simulated colonic fluid (SCF). The DS of NaCS was in the range from 0.2 to 0.6, the concentration of NaCS from 2 to 4% (w/v), the viscosity of chitosan from 50 to 550 mPa s, and the concentration of chitosan from 0.5 to 1.5% (w/v). A mathematical model was developed to describe the effect of these parameters and their interactions on the degradation of NaCS,chitosan complex. The optimum operation conditions for preparing NaCS,chitosan complex were determined to DS of NaCS of 0.2, the concentration of NaCS of 4.0% (w/v), chitosan viscosity of 327 mPa s, and the concentration of chitosan 0.5% (w/v), respectively. Validation of experiments with 5 confirmatory runs indicated the high degree of prognostic ability of response surface methodology. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Synthesis and characterization of poly(butylene terephthalate)/mica nanocomposite fibers via in situ interlayer polymerizationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2007Jin-Hae Chang Abstract Intercalated nanocomposites consisting of poly(butylene terephthalate) (PBT) incorporated between mica layers were synthesized from dimethyl terephthalate (DMT) and 1,4-butanediol (BD) by in situ interlayer polymerization. PBT nanocomposites of varying organoclay content were melt-spun to produce monofilaments. The samples were characterized using wide angle X-ray diffraction, electron microscopy, thermal analysis, and tensile testing. Some of the clay particles were found to be well dispersed in the PBT matrix, but other clay particles were agglomerated at a size level greater than approximately 20 nm. The glass transition temperatures (Tg) and the thermal degradation properties (TDi) of undrawn PBT hybrid fibers were found to improve with increases in the clay content. At draw ratio (DR) = 1, the ultimate tensile strengths of the hybrid fibers increased with the addition of clay up to a critical content and then decreased. However, the initial moduli monotonically increased with increases in the amount of organoclay in the PBT matrix. The ultimate strengths were found to decrease linearly with increases in DR from 1 to 18. In contrast to the trend for the tensile strengths, the initial moduli of the hybrid fibers increased only slightly with increases in DR up to 18. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Elution kinetics, antimicrobial efficacy, and degradation and microvasculature of a new gentamicin-loaded collagen fleeceJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2009Olaf Kilian Abstract Management of bone and soft tissue infections generally includes surgical procedures as well as attendant treatment and prevention with gentamicin-loaded fleeces. Conventional gentamicin-containing collagen fleeces currently in use are strongly acidic and exhibit limited biocompatibility thereby adversely affecting wound healing. To improve the antibiotic delivery system, a new phosphate-buffered, gentamicin-loaded fleece with pH,neutral properties has been developed (Jason G®). This study aimed at comparing the elution kinetics of gentamicin release and the antimicrobial efficacy of conventional fleeces with the newly developed fleece in vitro. In addition, degradation and microvasculature of implanted fleeces were examined in a rat model and assessed using histology, as well as detection of ED-1 and PECAM-expression using immunohistochemistry. We show that the phosphate-buffered fleeces have reduced release (p < 0.05) of the integrated gentamicin. However, all of the fleeces tested had a significant antimicrobial effect on the growth of Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa strains (p < 0.01). Among the fleeces tested, the new Jason G® fleece had the weakest but nevertheless sufficient antimicrobial effectiveness. Evaluation of the antibiotic effect in the prevention of an infection showed no differences between the applied fleeces. Following surgical implantation of fleece in the backs of Wistar rats we observed, on day 5 after implantation, an increase in cell infiltration and microvascularization with the phosphate-buffered fleece as compared with conventional fleeces, which show necrotic cells on their surface. Unlike the acidic fleeces, on day 15 after implantation the pH,neutral fleece was resorbed widely. Here, we show that the new, pH,neutral, gentamicin-containing fleece Jason G® exhibits good overall antimicrobial effectiveness against both gram-positive and gram-negative bacteria in vitro with improved degradation properties and microvasculature formation in vivo. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009 [source] Water Absorption and Degradation Characteristics of Chitosan-Based Polyesters and Hydroxyapatite CompositesMACROMOLECULAR BIOSCIENCE, Issue 3 2007Vitor M. Correlo Abstract Blends of chitosan and biodegradable synthetic aliphatic polyesters (polycaprolactone, poly(butylene succinate), poly[(butylene succinate)- co -adipate], poly[(butylene terephthalate)- co -adipate], and poly(lactic acid)) were injection-molded. These samples were immersed in isotonic solution at 37,°C for a period of 60 d. The water uptake and the degradation properties, as measured by the loss in tensile strength, were evaluated as a function of time. In this study, the rate and the equilibrium water uptake were proportional to the amount of chitosan in the blend. The addition of HA to chitosan and polyester significantly reduced the equilibrium water uptake. The water uptake did not follow the classical Fickian phenomena and could be expressed by a two-stage sorption non-Fickian diffusion model. Contact angle measurement was used to quantify the changes in surface hydrophilicity as a function of chitosan and polyester composition. The glycerol contact angle decreased with increasing synthetic components in the blend. The blends and composites also showed increased degradation, as quantified by a loss in their mechanical properties, with increase in natural content. The degradation of properties was directly related to the water uptake of the blends; the higher the water uptake, the higher the degradation. Pure polyesters, while having low water uptake, nevertheless showed significant degradation by a precipitous drop in the strain at break. Among the polyesters, poly(lactic acid) displayed maximum degradation, while polycaprolactone displayed the least. [source] Cross-Linking and Degradation Properties of Plasma Enhanced Chemical Vapor Deposited Poly(2-hydroxyethyl methacrylate)MACROMOLECULAR RAPID COMMUNICATIONS, Issue 2 2009Courtney A. Pfluger Abstract Plasma Enhanced Chemical Vapor Deposition (PECVD) of poly-2-hydroxyethyl methacrylate (pHEMA) biocompatible, biodegradable polymer films were produced alone and cross-linked with ethylene glycol diacrylate (EGDA). Degree of cross-linking was controlled via manipulation of the EGDA flow rate, which influenced the amount of swelling and the extent of degradation of the films in an aqueous solution over time. Noncross-linked pHEMA films swelled 10% more than cross-linked films after 24 h of incubation in an aqueous environment. Increasing degree of film cross-linking decreased degradation over time. Thus, PECVD pHEMA films with variable cross-linking properties enable tuning of gel formation and degradation properties, making these films useful in a variety of biologically significant applications. [source] Bioactive polyurethanes in clinical applications,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 9-10 2006G. Ciardelli Abstract Biomaterials play an important role in most tissue engineering strategies. They can serve as substrates on which cell populations can attach and migrate, can be used as cell delivery vehicles and as bioactive factor carriers to activate specific cellular functions. A series of biodegradable polyurethanes (PUs) with tunable chemical, physical and degradation properties, showing an adequate response to in vitro tests was proposed for applications in soft tissue engineering. Three-dimensional scaffolds of superimposed square meshed grids were prepared by using a rapid prototyping technique (pressure activated microsyringe, PAM) and tested in vivo. Functionalization of PU systems was performed in order to control the chemistry of the materials for the promotion of highly specific binding interactions between materials and biological environments. Two different approaches were used for the coupling of bioactive molecules such as gelatin. The first involved the modification of the polymer chain through a novel monomer and the second one consisted in a surface modification by plasma-induced graft copolymerization of acrylic acid. Copyright © 2006 John Wiley & Sons, Ltd. [source] Synthesis, UV photo-polymerization and degradation study of PEG containing polyester polyol acrylatesPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 3 2004Venkata M. Nivasu Abstract Succinic acid-co-polyethylene glycol polyester polyol acrylates, capable of in situ polymerization with UV radiation, were synthesized and characterized. Effect of structural changes such as internal branching, external crosslinking on their polymerization and degradation properties were investigated. Use of external crosslinkers reduced the polymerizability of the polymer. Lipases of different origins expedited the degradation to different extents and lipase isolated from porcine pancreas appeared to be more efficient than lipases from other sources. Copyright © 2004 John Wiley & Sons, Ltd. [source] The potential for soluble and transport loss of particulate aquaculture wastesAQUACULTURE RESEARCH, Issue 10 2000M F Tlusty The relative potential for soluble and transport losses of aquaculture waste was examined. The waste was collected at four junctures between introduction to the environment and the culmination of settlement, including samples of feed, faeces, particulate matter in the water column obtained from sediment traps, and the benthos. Organic matter was used as a model system to investigate the fate of these components because it was simple to analyse and previous research has found it to be correlated to carbon and nutrient levels in the samples. A narrow definition of each loss was considered. Soluble losses were examined by measuring change in organic matter content while the samples were in a stationary water field. The potential for transport losses was examined by determining if light and heavy fractions of a sample differed in their amount of organic matter. Faecal matter had a very high solubility potential, and lost approximately 50% of its organic matter in 12 days. No other sample had losses >,10%. The benthic samples gained organic matter while sitting in the stationary water field. There was no discernible trend to the samples' potential for transport losses. However, for all replicates combined, the smaller the proportion of the lighter fraction, the greater the difference (+) in the organic matter content between the light and heavy fractions. Thus, lighter material is the last to settle and thus more prone to be transported further afield. The implications of this study include the need for model studies to examine different types of loss and also elucidation of divergent degradation properties of each component. This study also points to a functional mechanism behind greater environmental impacts associated with poorly managed farms. [source] | ||||||||||