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Biodegradable Materials (biodegradable + material)
Selected AbstractsMating disruption of codling moth Cydia pomonella with high densities of Ecodian sex pheromone dispensersJOURNAL OF APPLIED ENTOMOLOGY, Issue 5 2007G. Angeli Abstract: A mating disruption approach using high densities of pheromone dispensers, has recently been proposed for controlling codling moth, Cydia pomonella (L.) (Lep., Tortricidae). Ecodian® CP dispensers, made of low-cost biodegradable material and easy to apply, were formulated with 10 mg of codlemone and placed at a rate of 1400,2000 dispensers/ha. Seasonal dispenser performance was evaluated using different methods. The release rate of new Ecodian dispensers, measured directly by solid-phase micro-extraction (SPME), was significantly higher than that of the standard monitoring lure. The release rate of field-aged dispensers decreased over time; it was comparable with that of the standard monitoring lure after 55,90 days of field exposure and significantly lower beyond. Electroantennographic (EAG) recordings showed that field-aged dispensers strongly stimulated virgin male moths' antennae. Dispensers elicited close-range approaches in wind tunnel irrespective of their age. Traps baited with aged Ecodian CP dispensers captured males throughout the season. Our results demonstrate that Ecodian dispensers achieved a good level of activity and longevity over the season. Field trials carried out from 2002 to 2004 confirmed the efficacy of Ecodian CP dispensers for codling moth control, regardless of the size of the treated area. The potential of this strategy for the control of C. pomonella is discussed. [source] Controlling the biodegradation rate of magnesium using biomimetic apatite coatingJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2009Yajing Zhang Abstract Magnesium is light, biocompatible and has similar mechanical properties to natural bone, so it has the potential to be used as a biodegradable material for orthopedic applications. However, pure magnesium severely corrodes in a physiological environment, which may result in fracture prior to substantial tissue healing. Hydroxyapatite (HA) is the main composition of natural bone. It has excellent bioactivity and osteoconductivity. In this study, HA coating with two different thicknesses was applied onto the surface of pure magnesium substrates using a biomimetic technique. The corrosion rate of the surface-treated substrates was tested. It was found that both types of coatings substantially slowed down the corrosion of the substrate, and the dual coating was more effective than the single coating in hindering the degradation of the substrate. Thus, the corrosion rate of magnesium implants can be closely tailored by adjusting apatite coating thickness and thereby monitoring the release of magnesium ions into the body. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009 [source] In vitro change in mechanical strength of ,-tricalcium phosphate/copolymerized poly- L -lactide composites and their application for guided bone regenerationJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2002Masanori Kikuchi Abstract Novel composites of bioactive ,-tricalcium phosphate [Ca3(PO4)2] and biodegradable copolymerized poly- L -lactide (CPLA) were prepared by a heat-kneading method. The mechanical and chemical changes of the composites were evaluated in vitro by soaking in physiological saline and Dulbecco's phosphate buffered saline. When soaked in physiological saline, the 3-point mechanical strength decreased rapidly from 60 to 30 MPa in the initial 4 weeks and then gradually reached a plateau; the initial decrease in the mechanical strength was ascribed to the dissolution of ,-tricalcium phosphate from the surface. The mechanical properties evident at 8,12 weeks were sufficient for the composites to be used as a biodegradable material for regeneration of bone because the hydrolysis of CPLA was inhibited in both physiological saline and phosphate-buffered saline as a result of a pH-buffering effect. Composite membranes 250-,m thick were used to regenerate large bone defects in beagle dogs: 10 × 10 × 10 mm3 in volume in the mandible and 20 mm in length in the tibia. The afflicted areas covered with the composite membranes were almost perfectly filled with new bone 12 weeks after the operation, whereas those covered with a CPLA membrane or without any membranes were invaded by soft tissue. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 62: 265,272, 2002 [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] Processed porcine collagen tubulization versus conventional suturing in peripheral nerve reconstruction: An experimental study in rabbitsMICROSURGERY, Issue 3 2001Guda C.M. Heijke M.D. In peripheral nerve reconstruction, various procedures are used. One of the procedures that received the most interest in the past decade is the tubulization technique for small nerve gaps. A disadvantage in the use of non-biodegradable tubes is that the material often has to be removed owing to its mechanical properties. Some investigators, in exploring the use of collagen tubes, being a natural biodegradable material, found either allogenicity or xenogenicity and immune responses that may inhibit nerve regeneration. Processed porcine collagen (PPC) is a new inert and biodegradable material that has a favorable effect on wound healing, as demonstrated by experiments on other tissues. The aim of our study was to compare the healing of nerve sutures with PPC tubes with conventional end-to-end sutures. In our experiments, we reconstructed the saphenous nerves of 27 rabbits. In series 1 (n = 12) and 2 (n = 12), PPC tubes were slid over an end-to-end nerve suture without or with a 10-mm nerve gap, respectively. In series 3 (n = 12), conventional suturing was performed in the collateral saphenous nerves of the animals of series 1. Epineurial suturing was performed. Three other non-operated saphenous nerves served as controls. The healing was studied after 3, 6, and 12 months in sections stained by monoclonal antibodies and by conventional histologic staining. Morphometric analysis of the regenerating axons was done by using confocal scanning laser microscopy (CLSM). Data analysis was carried out using a software program especially developed for this purpose. All results were evaluated statistically. Our results showed that during the healing period in the distal nerve stump, the number of axons of the PPC procedure with a 10-mm gap was significantly higher than that in the procedure without a gap. At 12 months, the mean number of axons of all procedures was significantly lower than in the non-operated nerve, and the mean axon diameter in all distal stumps did not differ significantly from that of the non-operated nerve. In the distal nerve stump, the ratio of total axon area to total fascicle area in the PPC procedure with a gap was significantly higher than that in the conventional suturing procedure. After 12 months, there was no significant difference between the percentages of axon outgrowth of the PPC procedure without a gap, the conventional suturing procedure, and the non-operated nerve (100%). The percentage of axon outgrowth in PPC with a gap was significantly higher than in the other procedures. © 2001 Wiley-Liss, Inc. Microsurgery 21:84,95 2001 [source] Synthesis, characterization and application of poly[(1-vinyl-2-pyrrolidone)- co -(2-hydroxyethyl methacrylate)] as controlled-release polymeric system for 2,4-dichlorophenoxyacetic chloride using an ultrafiltration techniquePOLYMER INTERNATIONAL, Issue 7 2008Guadalupe del C Pizarro Abstract BACKGROUND: Polymers supporting chemicals used in agriculture have recently been developed to overcome the serious environmental problems of conventional agrochemicals. The success of these formulations is based on a suitable choice of polymer support. Degradable polymeric hydrogels are of particular interest. The gradual release of the bioactive agent can be achieved by hydrolytic or enzymatic cleavage of the linking bond. RESULTS: In this context, poly[(1-vinyl-2-pyrrolidone)- co -(2-hydroxyethyl methacrylate)] [poly(NVP- co -HEMA)] has been used as a bioactive carrier reagent. Herein, we report a controlled-release system with the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) using an ultrafiltration system. Hydrolysis was studied by testing the release at various pH values. A high release with poly(NVP- co -HEMA),2,4-D was observed at pH = 7 and 10 after two days (Z = 2). The release percentage of copolymer,herbicide increased at pH = 10. It showed release values between 79.0 and 94.5%. Poly(NVP- co -HEMA),herbicide can release a bioactive compound in aqueous solution at pH = 3, 7 and 10. CONCLUSION: Based on the results of homogeneous hydrolysis, it is argued that the herbicide release rate depends on the pH of the reaction environment. This functional polymer could be employed as a biodegradable material for applications in agrichemical release. Copyright © 2008 Society of Chemical Industry [source] Organic Thin-Film Transistors Fabricated on Resorbable Biomaterial SubstratesADVANCED MATERIALS, Issue 5 2010Christopher J. Bettinger Organic electronics and biodegradable materials have the potential to be integrated to create a new class of electronic devices for the use in biomedical and environmental applications. Organic thin-film field-effect transistors fabricated using a biodegradable material platform exhibit water stable performance and degrade in vitro. [source] Synthesis and characterization of novel biodegradable aliphatic poly(ester amide)s containing cyclohexane unitsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2006Hélène A. Lecomte Abstract Polyesters provide a good basis to work on for designing novel biodegradable materials that are also mechanically and thermally resistant. In this study, a series of aliphatic poly(ester amide)s (PEA) based on cyclohexane units was synthesized. Block-copolymers of cyclohexyl sebacate and cyclohexyl sebacamide were produced by controlling the length of the ester block and the amount of amide during a two-step melt/interfacial polycondensation reaction. Films produced from these materials could retain their shape above 373 K due to the physical network of amide hydrogen-bonding. Thermal properties were also evaluated, with various melting and softening points obtained depending on the PEA composition. The determining factor for mechanical properties was the amount of amide introduced, with films containing up to 10 mol % amide showing the best handleability and flexibility. Tensile properties typical of an amorphous viscoelastic material were observed, but with much superior elongation to break achievable (,1700%). These materials were also shown to be hydrolyzable, noncytotoxic, and favorable for cell attachment: they may therefore have a promising future in the area of medical devices or packaging, especially as their properties can be tuned by changing their composition. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1785,1795, 2006 [source] Nerve conduits and growth factor delivery in peripheral nerve repairJOURNAL OF THE PERIPHERAL NERVOUS SYSTEM, Issue 2 2007Lukas A. Pfister Abstract Peripheral nerves possess the capacity of self-regeneration after traumatic injury. Transected peripheral nerves can be bridged by direct surgical coaptation of the two nerve stumps or by interposing autografts or biological (veins) or synthetic nerve conduits (NC). NC are tubular structures that guide the regenerating axons to the distal nerve stump. Early synthetic NC have primarily been made of silicone because of the relative flexibility and biocompatibility of this material and because medical-grade silicone tubes were readily available in various dimensions. Nowadays, NC are preferably made of biodegradable materials such as collagen, aliphatic polyesters, or polyurethanes. Although NC assist in guiding regenerating nerves, satisfactory functional restoration of severed nerves may further require exogenous growth factors. Therefore, authors have proposed NC with integrated delivery systems for growth factors or growth factor,producing cells. This article reviews the most important designs of NC with integrated delivery systems for localized release of growth factors. The various systems discussed comprise NC with growth factors being released from various types of matrices, from transplanted cells (Schwann cells or mesenchymal stem cells), or through genetic modification of cells naturally present at the site of injured tissue. Acellular delivery systems for growth factors include the NC wall itself, biodegradable microspheres seeded onto the internal surface of the NC wall, or matrices that are filled into the lumen of the NC and immobilize the growth factors through physical-chemical interactions or specific ligand-receptor interactions. A very promising and elegant system appears to be longitudinally aligned fibers inserted in the lumen of a NC that deliver the growth factors and provide additional guidance for Schwann cells and axons. This review also attempts to appreciate the most promising approaches and emphasize the importance of growth factor delivery kinetics. [source] An In Vivo Study of the Host Response to Starch-Based Polymers and Composites Subcutaneously Implanted in RatsMACROMOLECULAR BIOSCIENCE, Issue 8 2005Alexandra P. Marques Abstract Summary: Implant failure is one of the major concerns in the biomaterials field. Several factors have been related to the fail but in general these biomaterials do not exhibit comparable physical, chemical or biological properties to natural tissues and ultimately, these devices can lead to chronic inflammation and foreign-body reactions. Starch-based biodegradable materials and composites have shown promising properties for a wide range of biomedical applications as well as a reduced capacity to elicit a strong reaction from immune system cells in vitro. In this work, blends of corn starch with ethylene vinyl alcohol (SEVA-C), cellulose acetate (SCA) and polycaprolactone (SPCL), as well as hydroxyapatite (HA) reinforced starch-based composites, were investigated in vivo. The aim of the work was to assess the host response evoked for starch-based biomaterials, identifying the presence of key cell types. The tissues surrounding the implant were harvested together with the material and processed histologically for evaluation using immunohistochemistry. At implant retrieval there was no cellular exudate around the implants and no macroscopic signs of an inflammatory reaction in any of the animals. The histological analysis of the sectioned interface tissue after immunohistochemical staining using ED1, ED2, CD54, MHC class II and ,/, antibodies showed positively stained cells for all antibodies, except for ,/, for all the implantation periods, where it was different for the various polymers and for the period of implantation. SPCL and SCA composites were the materials that stimulated the greatest cellular tissue responses, but generally biodegradable starch-based materials did not induce a severe reaction for the studied implantation times, which contrasts with other types of degradable polymeric biomaterials. [source] Effects of Crosslinking Methods on Structure and Properties of Cellulose/PVA HydrogelsMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 12 2008Chunyu Chang Abstract A series of hydrogels were prepared from cellulose and PVA in NaOH/urea aqueous solution using both physical and chemical crosslinking methods. The hydrogels were secure and biodegradable materials. Their structure and properties were characterized by FTIR spectroscopy, DSC, XRD and SEM. The results indicated that all of the cellulose/PVA hydrogels exhibited homogeneous porous structures and a certain miscibility. The swelling degree and water uptake of the chemical hydrogels were markedly higher than those of the physical hydrogel. This work demonstrates two novel methods to prepare cellulose/PVA hydrogels with different functional properties via a green process. [source] Electrospun Hybrid Soy Protein/PVA FibersMACROMOLECULAR MATERIALS & ENGINEERING, Issue 8 2010Daehwan Cho Abstract Rheological behavior and spinnability of biodegradable materials based on SPI and PVA were studied for the production of electrospun fibers. pH level, processing temperature, and heating time were adjusted to investigate the effects of denaturing of soy protein on the rheology of SPI/PVA solutions. The results show that zero shear viscosity and degree of shear thinning of the SPI solution can be controlled by adjusting pH level and thermal treatment. The continuous production of uniform SPI/PVA fibers was achieved by electrospinning. The presence and amount of soy protein in the electrospun fibers was determined by EMPA and elemental analysis, confirming that the SPI was well incorporated into the PVA and remained in the electrospun fibers. [source] Dissolution and Enzymatic Degradation Studies Before and After Artificial Ageing of Silk- or Linen-Reinforced Gelatin Laminates, 1MACROMOLECULAR MATERIALS & ENGINEERING, Issue 5 2003M. Boyanova Abstract In an attempt to overcome the poor mechanical properties of native, i.e., untreated gelatin, laminates based on gelatin and gelatin/starch blend reinforced with fabrics (linen or silk) were prepared by melt pressing. The mechanical properties of fresh and artificially aged samples were reported previously. In the present series of two consecutive papers we present data concerning the dissolution and biodegradation of these laminates. A two-step procedure for treatment of the laminates was used. The first step is treatment with an aqueous buffer solution, the second with a buffered solution of the enzyme subtilisin. The time-course of the absorbance at 280 nm of the "washing" solutions was followed. A number of kinetic characteristics was determined and discussed with respect to laminate composition and their treatments. In the present Part 1 about the environmental behavior of these new biodegradable materials, the non-enzymatic solubilization in water and buffer solution (i.e., simple dissolution) of fresh and artificially aged samples is described. The dissolution process was followed spectrophotometrically as well as by the weight losses. It was found that gelatin-based silk- or linen-reinforced laminates were subject to dissolution, similarly to the gelatin and gelatin-based materials studied in previous works. In addition, it was established that the thermal treatment of the laminates during their melt pressing leads to postcondensation reactions and crosslinking of the gelatin macromolecules. Similar reactions occur between the matrix and the reinforcing element silk, thus improving their mutual adhesion. Decreased gelatin dissolution ability was observed after the thermal treatment, in the presence of reinforced fabrics and upon "additional" crosslinking with methylenedi(p -phenyl) diisocyanate. The untreated gelatin is the only one that dissolves completely in water. The artificially aged samples tend to dissolve better than the respective fresh samples due to degradation processes during aging. [source] Study of pseudo-multilayer structures based on starch-polycaprolactone extruded blendsPOLYMER ENGINEERING & SCIENCE, Issue 6 2009Laurent Bélard This article is focused on the analysis of the structure-process relationships of biodegradable materials. It is mainly focused on the analysis of phase separation phenomenon occurring during the extrusion of plasticized starch/polycaprolactone blends, in a slit die. Rheological characterizations are carried out, in-line in an instrumented slit die at the exit of the extruder and, out-line with different rheometers. In certain conditions, a pseudo-multilayer structure can be generated with a polyester rich skin. Then, Electron Spectroscopy for Chemical Analysis (ESCA) and Fourier Transformed Infrared Attenuated Total Reflectance (FTIR-ATR) analyses are conducted to evaluate semi-quantitatively the polyester surface enrichment. In the range of available shear rates, the phase separation is mainly driven by the molecular weight of polycaprolactone, linked to its molten state viscosity. Three zones of surface enrichment, dependent on the molecular weights, are identified. Above 60,000 g·mol,1, no surface enrichment could be detected; below 37,000 g·mol,1, the phase separation occurs with no dependence on the processing conditions; between these two limits, the phase separation depends on both, the formulation and the processing conditions. A correlation between the rheological measurements and the phase separation is given. A predictive criterion based on the viscous behavior of the blend is established. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source] Synthesis and characterization of hydrogels containing biodegradable polymersPOLYMER INTERNATIONAL, Issue 7 2008Adina Cretu Abstract BACKGROUND: Amphiphilic block and graft copolymers constitute a very interesting class of polymers with potential for biomedical applications, due to their special characteristics, which derive from the combination of properties of hydrophilic and hydrophobic moieties. In this work, the synthesis and biodegradation of poly(2-hydroxyethyl methacrylate)- graft -poly(L -lactide) are studied. RESULTS: The graft copolymers were synthesized using the macromonomer technique. In a first step, methacryloyl-terminated poly(L -lactide) macromonomers were synthesized in a wide molecular weight range using different catalysts. Subsequently, these macromonomers were copolymerized with 2-hydroxyethyl methacrylate in order to obtain a graft copolymer. These new materials resemble hydrogel scaffolds with a biodegradable component. The biodegradation was studied in hydrolytic and enzymatic environments. The influence of different parameters (molecular weight, crystallinity, ratio between hydrophilic and hydrophobic components) on the degradation rate was investigated. CONCLUSION: Based on this study it will be possible to tailor the release properties of biodegradable materials. In addition, the materials will show good biocompatibility due to the hydrophilic poly(2-hydroxyethyl methacrylate) hydrogel scaffold. This kind of material has potential for many applications, like controlled drug-delivery systems or biodegradable implants. Copyright © 2008 Society of Chemical Industry [source] | |||||||||||||