Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “biodegradation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources
PubMed2006

Biocompatibility properties of a new braided biodegradable urethral stent: a comparison with a biodegradable spiral and a braided metallic stent in the rabbit urethra.

OBJECTIVE: To compare the biocompatibility properties of a new braided biodegradable self-reinforced poly-L-lactic acid (SR-PLLA) urethral stent to the former spiral biodegradable SR-PLLA stent and the stainless steel stent in a rabbit model. MATERIALS AND METHODS: In all, 54 male New Zealand White rabbits were anaesthetized and stents inserted into the prostatic urethra, three of each kind for each sample time. The rabbits were killed after 1, 3, 6, 9, 12 or 15 months and light microscopy and scanning electron microscopy used to analyse the effects. RESULTS: The disintegration of the braided SR-PLLA stent was more closely controlled than that of the spiral SR-PLLA stent. The metallic stent induced epithelial hyperplasia and polyposis earlier than the biodegradable stents, and in these rabbits the polyposis disappeared after the disintegration process. There were no differences in the histological analyses between the biodegradable stents, whereas the metallic stents caused the strongest inflammatory reactions. CONCLUSIONS: The braided SR-PLLA urethral stent functioned well in the rabbit urethra and clinical studies are already planned.

Absorbable Implants↗
PubMed2006

Biodegradability and biodegradation of poly(lactide).

Poly(lactide) (PLA) has been developed and made commercially available in recent years. One of the major tasks to be taken before the widespread application of PLA is the fundamental understanding of its biodegradation mechanisms. This paper provides a short overview on the biodegradability and biodegradation of PLA. Emphasis is focused mainly on microbial and enzymatic degradation. Most of the PLA-degrading microorganisms phylogenetically belong to the family of Pseudonocardiaceae and related genera such as Amycolatopsis, Lentzea, Kibdelosporangium, Streptoalloteichus, and Saccharothrix. Several proteinous materials such as silk fibroin, elastin, gelatin, and some peptides and amino acids were found to stimulate the production of enzymes from PLA-degrading microorganisms. In addition to proteinase K from Tritirachium album, subtilisin, a microbial serine protease and some mammalian serine proteases such as alpha-chymotrypsin, trypsin, and elastase could also degrade PLA.

Bacteria↗
PubMedDate not supplied

Novel biodegradable aliphatic poly(butylene succinate-co-cyclic carbonate)s bearing functionalizable carbonate building blocks: II. Enzymatic biodegradation and in vitro biocompatibility assay.

In a previous study, we have reported chemical synthesis of novel aliphatic poly(butylene succinate-co-cyclic carbonate) P(BS-co-CC)s bearing various functionalizable carbonate building blocks, and this work will continue to present our new studies on their enzymatic degradation and in vitro cell biocompatibility assay. First, enzymatic degradation of the novel P(BS-co-CC) film samples was investigated with two enzymes of lipase B Candida Antartic (Novozyme 435) and lipase Porcine Pancreas PPL, and it was revealed that copolymerizing linear poly(butylene succinate) PBS with a functionalizable carbonate building block could remarkably accelerate the enzymatic degradation of a synthesized product P(BS-co-CC), and its biodegradation behavior was found to strongly depend on the overall impacts of several important factors as the cyclic carbonate (CC) comonomer structure and molar content, molar mass, thermal characteristics, morphology, the enzyme-substrate specificity, and so forth. Further, the biodegraded residual film samples and water-soluble enzymatic degradation products were allowed to be analyzed by means of proton nuclear magnetic resonance (1H NMR), gel permeation chromatograph (GPC), differential scanning calorimeter (DSC), attenuated total reflection FTIR (ATR-FTIR), scanning electron microscope (SEM), and liquid chromatograph-mass spectrometry (LC-MS). On the experimental evidences, an exo-type mechanism of enzymatic chain hydrolysis preferentially occurring in the noncrystalline domains was suggested for the synthesized new P(BS-co-CC) film samples. With regard to their cell biocompatibilities, an assay with NIH 3T3 mouse fibroblast cell was conducted using the novel synthesized P(BS-co-CC) films as substrates with respect to the cell adhesion and proliferation, and these new biodegradable P(BS-co-CC) samples were found to exhibit as low cell toxicity as the PLLA control, particularly the two samples of poly(butylene succinate-co-18.7 mol % dimethyl trimethylene carbonate) P(BS-co-18.7 mol % DMTMC) and poly(butylene succinate-co-21.9 mol % 5-benzyloxy trimethylene carbonate) P(BS-co-21.9 mol % BTMC) were interestingly found to show much better cell biocompatibilities than the PLLA reference.

Animals↗
PubMed2006

Evaluation of isotopic enrichment factors for the biodegradation of chlorinated ethenes using a parameter estimation model: toward an improved quantification of biodegradation.

A model was developed to predict the concentrations of chlorinated ethenes and ethene during sequential reductive dechlorination of tetrachloroethene (PCE) from stable carbon isotope values using Rayleigh model principles and specified isotopic enrichment factors for each step of dechlorination. The model was tested using three separate datasets of concentration and isotope values measured during three experiments involving the degradation of PCE to vinyl chloride (VC), trichloroethene (TCE) to ethene, and cis-1,2-dichloroethene (cDCE) to ethene. The model was then coupled to a parameter estimation method to estimate values for the isotopic enrichment factors of TCE, cDCE, and VC when they are intermediates in the dechlorination to ethene. The enrichment factors estimated for TCE and cDCE when they were intermediates in biodegradation experiments were close to or within the published range of enrichment factors determined from experiments where TCE or cDCE were the initial substrates. In contrast, the enrichment factors determined by parameter estimation for experiments in which VC was an intermediate in biodegradation experiments were consistently more negative (by approximately 10 per thousandth) than the most negative published enrichment factor determined from experiments where VC was the initial substrate. This finding suggests that the range of enrichment factors for VC dechlorination may not be as narrow as previously suggested (-21.5 per thousandth to -26.6 per thousandth) and that fractionation during VC dechlorination when VC is an intermediate compound may be significantly larger than when VC is the initial substrate. These findings have important implications both for the current practice of extrapolating laboratory-derived isotopic enrichment factors to quantify biodegradation of chlorinated ethenes in the field and for understanding the details of enzymatic reductive dechlorination.

Biodegradation, Environmental↗
PubMed1995

Healing of mandibular defects with different biodegradable and non-biodegradable membranes: an experimental study in rats.

Membranes, clinically used to improve bone regeneration according to the osteopromotion principle, have primarily been made of expanded polytetrafluoroethylene (Gore-Tex Membrane). Recently, different types of biodegradable membranes have become available. This investigation explored the osteopromotive potential of 10 different biodegradable and non-biodegradable membrane materials. Scanning electron microscopy revealed quite different surface configurations of these membranes, even though some of them were chemically closely related. Standardized, transosseous, critical size mandibular defects were made bilaterally in adult rats and were randomly covered with the different types of membrane. After 6 wk of healing, evaluation was performed by light microscopy according to a histological scoring system. Varying degrees of bone healing were seen beneath the different membranes. Some of the membranes (such as Gore-Tex Augmentation Material, Millipore and Resolut 'long term') revealed a good osteopromotive effect, whereas others had little or no beneficial effects on bone healing. Certain membrane materials caused a pronounced inflammatory response in the surrounding soft tissue, while others displayed a low inflammatory reaction. The study shows that different membranes differ strongly in osteopromotive efficacy, even if seemingly chemically closely related. Furthermore, the study demonstrates that membranes developed primarily for periodontal regeneration purposes may not be adequate to promote bone healing.

Animals↗
PubMed2000

Histological evaluation of different biodegradable and non-biodegradable membranes implanted subcutaneously in rats.

Different types of biodegradable membranes have become available for guided tissue regeneration. The purpose of this study was to evaluate histologically three different biodegradable membranes (Bio-Gide, Resolut and Vicryl) and one non-biodegradable membrane (expanded polytetrafluoroethylene/e-PTFE) implanted subcutaneously in rats. Five subcutaneous pouches were created in each of 24 rats. One of the four test membranes was randomly placed in each of the four pouches and one pouch was left empty to serve as a control. Histological evaluation was performed after 4, 10 and 21 days which demonstrated that e-PTFE was well tolerated and encapsulated by a fibrous connective tissue capsule. There was capsule formation around Resolut and Vicryl and around Bio-Gide in the early phase there was a wide inflammatory zone already. e-PTFE and Vicryl were stable materials while Resolut and Bio-Gide fragmented in the early phase. In the late phase Vicryl was surrounded by an increasing amount of multinucleated macrophages and a thin capsule, whilst around Resolut and Bio-Gide a strong foreign body reaction was observed. Also granuloma formation was noted around the fragmented Resolut material in its capsule and a mild inflammatory reaction surrounding Bio-Gide within its thin capsule.

Absorbable Implants↗
PubMed1999

An 'inherent' biodegradability test for oil products: description and results of an international ring test. CONCAWE Biodegradation Task Force.

Current test guidelines for assessing 'inherent' (potential) biodegradability were designed for water-soluble, organic compounds of low volatility and are unsuitable for most oil products. It was against this background, that CONCAWE (the oil companies' European organisation for environment, health and safety) formed a task force to develop a standard test protocol for assessing the 'inherent' biodegradability of oil products.

Biodegradation, Environmental↗
PubMed1994

Degradation kinetics of biodegradable DL-polylactic acid biodegradable implants depending on the site of implantation.

A recently developed biodegradable system made of DL-polylactic acid (DL-PLA) for internal fixation of non-weight-bearing bones of the craniofacial skeleton was investigated. The plates were used for rigid fixation of experimental nasal bone fractures in 20 New Zealand white rabbits. In addition, prebent plates were placed in subcutaneous pockets in the backs of the animals. The material was removed after 7, 14, 28, and 42 days, and bending angles, plate stability, molecular weights (MW), and histologic analyses were studied. A significant decrease of MW over time and a difference in MW loss, showing a faster degradation subcutaneously, were observed. Plate stability did not decrease during the interval of 6 weeks, but a loss of bending angle was found in all prebent implants. This effect was caused by memory of DL-PLA. The results suggest that memory of biodegradable materials should be investigated before clinical application and that degradation rates differ according to the site of implantation.

Animals↗
PubMed2002

Towards biodegradable polyolefins: strategy of anchoring minute quantities of monosaccharides and disaccharides onto functionalized polystyrene, and their effect on facilitating polymer biodegradation.

A hypothesis was developed, and successfully tested, to greatly increase the rates of biodegradation of polyolefins, by anchoring minute quantities of glucose, sucrose or lactose, onto functionalized polystyrene (polystyrene-co-maleic anhydride copolymer) and measuring their rates of biodegradation, which were found to be significantly improved.

Bacillus↗
PubMed1996

Biodegradable polyurethanes: biodegradable low adherence films for the prevention of adhesions after surgery.

Adhesions commonly occur after internal disease or surgery. The natural healing response leads to the formation of vascular and avascular adhesions after inflammatory diseases and surgical interventions. A barrier film could be incorporated during surgery between layers of tissues that must not adhere to one another. The film would be biodegradable so that it disappears over a period of time, and would ideally be two sided, allowing relative movement at that interface, while being firmly anchored on the opposite side to prevent displacement. Polyesterurethane-polydimethylsiloxane graft polymers are synthesised. Chemical characterisation of the polymer is performed by using Fourier transform infrared spectroscopy and gel permeation chromatography. In vitro hydrolytic degradation is carried out in which films are immersed at 37 degrees C in alkaline solution. Degradation is assessed by tensile testing as a function of time to determine the degradation of mechanical strength, infrared spectroscopy, and mass loss. A titration method is also used to determine quantitatively the hydrolytic degradation. In order to study the adhesions of films, an in-vitro model based on a gelatine test, which is simple and rapid, is described. Suitable candidate films investigated from the in-vitro work are subjected to in vivo tests for both biodegradation and their ability to prevent adhesion.

Adhesiveness↗
PubMed2002

Effect of dispersing oil phase on the biodegradability of a solid alkane dissolved in non-biodegradable oil.

Acinetobacter sp. CR was grown on a model oil, which consisted of an inert oil matrix of pristane with n-heneicosane dissolved in it as the sole carbon source, in a stirred-tank bioreactor. This bacterium takes up substrates from the oil phase by direct contact with the oil phase. A previously established mathematical model was applied to reveal the effect of agitation conditions on the growth and n-alkane degradation kinetics of the bacterium. Higher impeller speed resulted in both lower microbial growth and lower n-alkane degradation rate of the bacterium, although it increased the specific surface area of the oil, which was measured by a previously developed device. This result was due to the decreased number of cells adhering to the oil surface, i.e., intense agitation inhibited the adhesion of cells to the oil surface. The addition of a surfactant below a critical micelle concentration (CMC) inhibited the degradation of n-heneicosane dissolved in pristane, although the biodegradability of the substrate recovered gradually with the increase in the dose of surfactant over CMC. The results suggest that efforts to increase the specific surface area of the oil phase have the undesirable result of inhibiting oil degradation when the dominant microbial degraders take up substrates in oil by direct contact with the oil.

Acinetobacter↗
PubMed2002

In vitro release behavior of insulin from biodegradable hybrid hydrogel networks of polysaccharide and synthetic biodegradable polyester.

The controlled release of insulin from a series of biodegradable hybrid hydrogel network containing dextran derivative of allyl isocyanate (dex-AI) and poly (D,L) lactide diacrylate macromer (PDLLAM) over a wide range of composition ratio was investigated. Laser confocal scanning microscope was used to understand the insulin dispersion and release mechanism in the hydrogels. We found that the dispersion of insulin in the hydrogel network appeared to become less homogeneous as the PDLLAM composition in the hydrogel increased. The increase in hydrogel degradability imparted by PDLLAM incorporation shifted the hydrogel to a more open structure at a later release time, which facilitated the release rate and extent of insulin. From the result of release kinetics study (i.e., diffusion coefficient), insulin release occurred through diffusion and degradation controlled mechanisms. In addition, a comparison of the release characteristics of indomethacin, insulin and bovine serum albumin from the hydrogel network showed that the following parameters determined the release kinetics: drug molecular weight and size, hydrogel swellability and degradability, drug solubility in water and the hydrophobic interaction between drugs and the hydrogel network.

Biocompatible Materials↗
PubMed1987

Biodegradation of trichloroethylene and involvement of an aromatic biodegradative pathway.

Biodegradation of trichloroethylene (TCE) by bacterial strain G4 resulted in complete dechlorination of the compound, as indicated by the production of inorganic chloride. A component of the water from which strain G4 was isolated that was required for TCE degradation was identified as phenol. Strain G4 degraded TCE in the presence of chloramphenicol only when preinduced with phenol. Toluene, o-cresol. and m-cresol could replace the phenol requirement. Two of the inducers of TCE metabolism, phenol and toluene, apparently induced the same aromatic degradative pathway that cleaved the aromatic ring by meta fission. Cells induced with either phenol or toluene had similar oxidation rates for several aromatic compounds and had similar levels of catechol-2,3-dioxygenase. The results indicate that one or more enzymes of an inducible pathway for aromatic degradation in strain G4 are responsible for the degradation of TCE.

Bacteria, Aerobic↗
PubMed1995

Biodegradation and tissue reaction to intravitreous biodegradable poly(D,L-lactic-co-glycolic)acid microspheres.

We studied the biodegradation of and the tissue reaction to microspheres of 50:50 poly(D,L-lactic-co-glycolic)acid (PLGA) (viscosity-average MW: 3000 d), injected intravitreous in rabbits. These microspheres are under investigation as injectable devices for intravitreous sustained drug delivery. The rate of intravitreous degradation of PLGA microspheres has not been well documented in the literature. Twenty two pigmented rabbits underwent gas vitrectomy in one eye: 19 eyes received 2.5 mg of PLGA microspheres in 1 ml of balanced salt solution (BSS) and 3 control eyes received 1 ml of BSS only. Slit lamp exam and indirect ophthalmoscopy were performed periodically from day 1 to 6 months after surgery. The eyes were enucleated and studied by light microscopy and immunohistochemistry at various time points. The electroretinogram (ERG) was recorded in a subgroup of rabbits before injection and after 1 and 6 months. The amount of microspheres in the vitreous cavity progressively decreased. At 6 months microspheres were found in 1/4 rabbits at indirect ophthalmoscopy and in 4/4 rabbits histopathologically. A mild localized, non progressive foreign body reaction was observed. The cell reaction was composed mostly of vimentin and glial fibrillary acidic protein positive cells which probably represent glial cells and fibroblasts. The choroid and retina were normal. The ERG showed no abnormalities. No clinical inflammatory signs were observed 4 days postoperatively and thereafter.

Animals↗
PubMed1992

[Relationships between manufacturing parameters and pharmaceutical-technological requirements of biodegradable microparticles. 2. Preparation of injectable microparticles in biodegradable polyester].

Local anesthetics containing biodegradable polyester microparticles are prepared using a modified solvent-evaporation process and a spray drying technique. The preparation methods are compared critically. The modified solvent-evaporation process is preferred for the preparation of microparticles. Yields of 90% and microparticle size distributions can be influenced in a reproducible manner. Using the spray drying technique yields are only 60%. The product is characterized by a high portion of microparticles under 10 microns, which are responsible for the rapid release of cinchocain in 168 h as well.

Anesthetics, Local↗
PubMed1997

Biodegradation of a poly(ester)urea-urethane by cholesterol esterase: isolation and identification of principal biodegradation products.

Synthesized poly(ester)urea-urethanes with 14C-labeled toluene diisocyanate or 14C-labeled chain extender ethylene diamine were incubated with cholesterol esterase in a phosphate buffer solution at 37 degrees C. A number of biodegradation products, generated at the level of 2.8 micrograms/cm2 of polymer surface area, were isolated from this simulated physiologic system. Individual products were obtained by separation with reversed-phase high-performance liquid chromatography. The two different radiolabels were used to assist in the identification of degradation products from hard- and soft-segment domains. Approximately 20 degradation products were isolated; however, toluene diamine (TDA) was not detected from the chromatographic separation. Two principal products were identified by tandem mass spectrometry. Both products are TDA derivatives (secondary aromatic diamine) substituted with end units of the polyester segment at N and N' positions of TDA. The absence of free TDA suggests that there could be a stabilization of urethane and urea linkages within the toluene diisocyanate (TDI) segments of the polyurethanes. For TDI-synthesized polymers, this finding raises awareness to the potential biological importance of degradation products other than TDA, particularly to their interaction with surrounding cells.

Biocompatible Materials↗
PubMed1991

[Biodegradable gentamicin-depot implants made of beta-tricalcium phosphate ceramics. 3. In vivo studies on drug release, tissue tolerance, and biodegradation].

In vivo drug release properties and biocompatibility of gentamicin-loaded controlled release implants made of beta-tricalcium phosphate ceramics designed for the local antibiotic treatment of bone infections were investigated. Controlled release pellets containing 0.4 and 0.8 mg of gentamicin were implanted into the femoral bone of rats. Drug release was measured from renal excretion over a time period of 3 weeks. The excretion pattern can be described by an initial phase of increased drug release was faster at higher drug loading. Drug release from glyceride-containing controlled release pellets occurs at a significantly slower rate than from drug-loaded pellets without glycerides. Histological studies after implantation of the pure ceramic pellets and the controlled release pellets into the bone tissue of rats and rabbits are showing a high tissue tolerance and the biodegradability of the implants. However, the glyceride-containing pellets are degraded at a slower rate than the pure ceramic pellets.

Animals↗