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PubMed2003

Expansion and fixation properties of a new braided biodegradable urethral stent: an experimental study in the rabbit.

PURPOSE: Biodegradable spiral urethral stents have been used with favorable results combined with thermal treatments of the prostate and for recurrent urethral strictures but the configuration of the helical spiral is not ideal. We developed a new tubular mesh configuration for the biodegradable urethral stent and evaluated its expansion and locking properties in the rabbit urethra. MATERIALS AND METHODS: The stents were made of self-reinforced polylactic acid polymer (Bionx Implants, Ltd., Tampere, Finland) blended with BaSO (Alfa Chem, New York, New York) to achieve radiopacity. Two braiding patterns, that is 1 over 1 and 2 over 2 + 1, were used to produce a tubular mesh structure. Stainless steel stents (pattern 1 over 1) served as controls. The stents were inserted into the posterior urethra of 27 male rabbits. The animals were sacrificed after 1 week, 1 and 6 months, respectively. X-rays were done immediately after stent insertion and at sacrifice. Longitudinal movement and expansion were assessed on the x-rays.(4) RESULTS: All stents maintained position in the urethra without fixation. Macroscopic disorientation of the structure of the 2 over 2 + 1 braided self-reinforced polylactic acid polymer stents began before 1 month, while 1 over 1 braided stents retained their construction. At 6 months 3 of 6 biodegradable stents were degraded. Average longitudinal movement was 2 mm. (range 1 to 3) in the 1 over 1 self-reinforced polylactic acid polymer group, 2 mm. (range 0 to 7) in the 2 over 2 + 1 polylactic acid group and 3 mm. (range 3 to 3) in controls at 1 month. CONCLUSIONS: Biodegradable polymers are suitable materials for braided urethral stents. The expansion properties of the 2 braiding models tested in this study sufficed to fix the stents in situ in the prostatic urethra. However, the 1 over 1 braiding pattern was superior to the 2 over 2 + 1 pattern, in that it retained its macroscopic construction until the degradation of single self-reinforced polylactic acid polymer fibers.

Absorbable Implants↗

PubMed1979

Effect of concentration of organic chemicals on their biodegradation by natural microbial communities.

The effect of concentration on the biodegradation of synthetic organic chemicals by natural microbial communities was investigated by adding individual C-labeled organic compounds to stream water at various initial concentrations and measuring the formation of CO(2). The rate of degradation of p-chlorobenzoate and chloroacetate at initial concentrations of 47 pg/ml to 47 mug/ml fell markedly with lower initial concentrations, although half or more of the compound was converted to CO(2) in 8 days or less. On the other hand, little mineralization of 2,4-dichlorophenoxyacetate and 1-naphthyl-N-methylcarbamate, or the naphthol formed from the latter, occurred when these compounds were present at initial concentrations of 2 to 3 ng/ml or less, although 60% or more of the chemical initially present at higher concentrations was converted to CO(2) in 6 days. It is concluded that laboratory tests of biodegradation involving chemical concentrations greater than those in nature may not correctly assess the rate of biodegradation in natural ecosystems and that low substrate concentration may be important in limiting biodegradation in natural waters.

Journal Article↗

PubMed1980

Tenax-GC Extraction Technique for Residual Polychlorinated Biphenyl and Polyaromatic Hydrocarbon Analysis in Biodegradation Assays.

A rapid Tenax-GC extraction technique has been evaluated for use in conjunction with aqueous biodegradation assays for polyaromatic hydrocarbons and polychlorinated biphenyls. The method was quantitatively efficient and reproducible for phenanthrene, but variable and not quantitative for Aroclor 1254 (polychlorinated biphenyls). Aqueous sample volumes and varying concentrations of organic matter influenced polychlorinated biphenyl and polyaromatic hydrocarbon extraction efficiency. Phenanthrene recovery was decreased by soil extract but unaffected by spent bacteriological culture medium. Both types of organic matter caused significant reduction of Aroclor 1254 recovery. Polyaromatic hydrocarbon and polychlorinated biphenyl biodegradation assays, performed with reservoir samples, supported the laboratory evaluation. The study demonstrated the utility of the Tenax-GC extraction technique for phenanthrene analysis in biodegradation assessment; however, Tenax-GC extraction was not appropriate for Aroclor 1254 biodegradation studies.

Journal Article↗

PubMed1980

Phenanthrene biodegradation in freshwater environments.

Phenanthrene, a low-molecular-weight polycyclic aromatic hydrocarbon, was incubated with water samples from various reservoir systems in Tennessee to evaluate the potential for significant polycyclic aromatic hydrocarbon degradation by the indigenous microbial populations. Biodegradation was assessed by comparison of total polycyclic aromatic hydrocarbon substrate recovery in degradation flasks relative to sterile control flasks. During 1977 field studies, the mean phenanthrene biodegradation was approximately 80% after a 4-week incubation. Within a given habitat, 45% of the total variability in phenanthrene biodegradation was attributable to the physical, chemical, and microbiological site characteristics examined. Polycyclic aromatic hydrocarbon degradation was directly related to the historical environmental pollution of the sampling sites examined, the length of biodegradation assessment, temperature, and the molecular size of the polycyclic aromatic hydrocarbon substrate.

Journal Article↗

PubMed1984

Comparison of p-Nitrophenol Biodegradation in Field and Laboratory Test Systems.

Acclimation of microbial communities exposed to p-nitrophenol (PNP) was measured in laboratory test systems and in a freshwater pond. Laboratory tests were conducted in shake flasks with water, shake flasks with water and sediment, eco-cores, and two sizes of microcosm. The sediment and water samples used in the laboratory experiments were obtained from the pond. After a 6-day acclimation period, PNP was biodegraded rapidly in the pond. When the pond was treated with PNP a second time, biodegradation began immediately. The acclimation periods in laboratory test systems that contained sediment were similar to that in the pond. The acclimation period was threefold longer in shake flasks without sediment. PNP was biodegraded more slowly by microbial communities acclimated in the laboratory than it was in the pond, and the rate of biodegradation varied with the type of test. The number of bacteria able to mineralize PNP increased by 3 orders of magnitude in the pond during the acclimation period. Similar increases accompanied acclimation in the laboratory systems.

Journal Article↗

PubMed1988

Trichloroethylene biodegradation by a methane-oxidizing bacterium.

Trichloroethylene (TCE), a common groundwater contaminant, is a suspected carcinogen that is highly resistant to aerobic biodegradation. An aerobic, methane-oxidizing bacterium was isolated that degrades TCE in pure culture at concentrations commonly observed in contaminated groundwater. Strain 46-1, a type I methanotrophic bacterium, degraded TCE if grown on methane or methanol, producing CO(2) and water-soluble products. Gas chromatography and C radiotracer techniques were used to determine the rate, methane dependence, and mechanism of TCE biodegradation. TCE biodegradation by strain 46-1 appears to be a cometabolic process that occurs when the organism is actively metabolizing a suitable growth substrate such as methane or methanol. It is proposed that TCE biodegradation by methanotrophs occurs by formation of TCE epoxide, which breaks down spontaneously in water to form dichloroacetic and glyoxylic acids and one-carbon products.

Journal Article↗

PubMed1989

Effect of emulsan on biodegradation of crude oil by pure and mixed bacterial cultures.

Crude oil was treated with purified emulsan, the heteropolysaccharide bioemulsifier produced by Acinetobacter calcoaceticus RAG-1. A mixed bacterial population as well as nine different pure cultures isolated from various sources was tested for biodegradation of emulsan-treated and untreated crude oil. Biodegradation was measured both quantitatively and qualitatively. Recovery of CO(2) from mineralized C-labeled substrates yielded quantitative data on degradation of specific compounds, and capillary gas chromatography of residual unlabeled oil yielded qualitative data on a broad spectrum of crude oil components. Biodegradation of linear alkanes and other saturated hydrocarbons, both by pure cultures and by the mixed population, was reduced some 50 to 90% after emulsan pretreatment. In addition, degradation of aromatic compounds by the mixed population was reduced some 90% in emulsan-treated oil. In sharp contrast, aromatic biodegradation by pure cultures was either unaffected or slightly stimulated by emulsification of the oil.

Journal Article↗

PubMed1997

Efficiency of indigenous and inoculated cold-adapted soil microorganisms for biodegradation of diesel oil in alpine soils.

Biodegradation of diesel oil (5 g(middot)kg [soil dry weight](sup-1)) was investigated in five alpine subsoils, differing in soil type and bedrock, in laboratory experiments during 20 days at 10(deg)C. The biodegradation activities of the indigenous soil microorganisms and of a psychrotrophic diesel oil-degrading inoculum and the effect of biostimulation by inorganic fertilization (C/N/P ratio = 100:10:2) were determined. Fertilization significantly enhanced diesel oil biodegradation activity of the indigenous soil microorganisms. Biostimulation by fertilization enhanced diesel oil biodegradation to a significantly greater degree than bioaugmentation with the psychrotrophic inoculum. In none of the five soils did fertilization plus inoculation result in a higher decontamination than fertilization alone. A total of 16 to 23% of the added diesel oil contamination was lost by abiotic processes. Total decontamination without and with fertilization was in the range of 16 to 31 and 27 to 53%, respectively.

Journal Article↗

PubMed2001

Comparison of neonicotinoid insecticides for use with biodegradable and wooden spheres for control of key Rhagoletis species (Diptera: Tephritidae).

Field-based studies and laboratory bioassays were conducted with apple maggot, Rhagoletis pomonella (Walsh), and blueberry maggot, Rhgoletis mendax Curran, flies to investigate the performance and duration of activity of insecticide-treated biodegradable and wooden spheres for control of Rhagoletis species. Four neonicotinoid insecticide treatments including imidacloprid, thiamethoxam, and thiocloprid at 2% (AI) were evaluated with biodegradable spheres. In 1999, significantly more apple maggot flies were found killed by imidacloprid-treated spheres compared with thiamethoxam-treated spheres during early and late season. In 2000, spheres treated with either of two formulations of imidacloprid killed significantly more apple maggot flies compared with thiamethoxam, thiocloprid, and untreated spheres. In blueberries, there were no significant differences between the numbers of blueberry maggot flies killed by both imidacloprid-treated or thiamethoxam-treated spheres in 1999. However, during the 2000 blueberry field season, both formulations of imidacloprid were significantly more effective in killing blueberry maggot flies compared with spheres treated with thiamethoxam, thiocloprid and untreated controls. Overall, spheres treated with thiocloprid were ineffective and did not kill significantly more apple maggot or blueberry maggot flies compared with the controls. Laboratory bioassays showed that the effectiveness of field-exposed spheres treated with imidacloprid at 4 and d 8% (AI) and thiamethoxam at 4% (AI) in killing apple maggot flies was not significantly reduced over a 12-wk aging period. Additionally, wooden spheres aged outdoors for 12 wk with and without mold maintained residual activity in laboratory tests, whereas biodegradable spheres of equal aging, with and without mold lost their effectiveness in killing apple maggot flies. In other studies, we confirmed that the addition of an external feeding stimulant (sucrose) significantly increases the effectiveness of both biodegradable and wooden spheres treated with imidacloprid at 2% (AI).

Animals↗

PubMed2003

Biodegradable synthetic polymers for tissue engineering.

This paper reviews biodegradable synthetic polymers focusing on their potential in tissue engineering applications. The major classes of polymers are briefly discussed with regard to synthesis, properties and biodegradability, and known degradation modes and products are indicated based on studies reported in the literature. A vast majority of biodegradable polymers studied belongs to the polyester family, which includes polyglycolides and polylactides. Some disadvantages of these polymers in tissue engineering applications are their poor biocompatibility, release of acidic degradation products, poor processability and loss of mechanical properties very early during degradation. Other degradable polymers such as polyorthoesters, polyanhydrides, polyphosphazenes, and polyurethanes are also discussed and their advantages and disadvantages summarised. With advancements in tissue engineering it has become necessary to develop polymers that meet more demanding requirements. Recent work has focused on developing injectable polymer compositions based on poly (propylene fumarate) and poly (anhydrides) to meet these requirements in orthopaedic tissue engineering. Polyurethanes have received recent attention for development of degradable polymers because of their great potential in tailoring polymer structure to achieve mechanical properties and biodegradability to suit a variety of applications.

Biocompatible Materials↗

PubMed2001

Biodegradable Polymeric Stents.

To overcome several problems of conventional metallic stents, there have been many attempts to manufacture stents made of biodegradable materials. Although some studies have noted various degrees of inflammatory responses after biodegradable stent implantation, stents made of poly-l-lactic acid (PLLA) showed high biocompatibility with minimal inflammatory response and neointimal formation in porcine coronary arteries. Therefore, PLLA materials are more likely to cover the specific need for human coronary arteries in terms of biodegradation period and scaffolding ability over 6 months. A clinical study of PLLA self-expanding stent implantation is underway in Japan. The initial and 6-month results are favorable and suggest the feasibility, safety, and efficacy of the PLLA biodegradable stent in humans. However, long-term follow-up with larger numbers of patients will be required to validate the long-term efficacy of PLLA stents.

Journal Article↗

PubMed2002

Biodegradable microspheres of curcumin for treatment of inflammation.

Curcumin, a natural constituent of Curcuma longa (turmeric, CAS 458-37-7) was formulated as prolonged release biodegradable microspheres for treatment of inflammation. Natural biodegradable polymers, namely, bovine serum albumin and chitosan were used to encapsulate curcumin to form a depot forming drug delivery system. Microspheres were prepared by emulsion-solvent evaporation method coupled with chemical cross-linking of the natural polymers. Curcumin could be encapsulated into the biodegradable carriers upto an extent of 79.49 and 39.66% respectively with albumin and chitosan. Different drug:polymer ratios did not affect the mean particle size or particle size distribution significantly. However, the concentration of the crosslinking agent had remarkable influence on the drug release. In-vitro release studies indicated a biphasic drug release pattern, characterized by a typical burst-effect followed by a slow release which continued for several days. Evaluation of antinflammatory activity using Freund's adjuvant induced arthritic model in Wistar rats revealed significant difference between both the formulations, albumin microspheres and chitosan micropheres as well as against control. It was evident from the present study that the curcumin biodegradable microspheres could be successfully employed as prolonged release drug delivery system for better therapeutic management of inflammation as compared to oral or subcutaneous route.

Absorbable Implants↗

PubMed1989

Fixation of cancellous bone and physeal fractures in dogs and cats. A comparison of the use of self-reinforced biodegradable devices to the use of metallic devices and external fixations.

The use of self-reinforced biodegradable devices made of polyglycolide in the cancellous bone and physeal fractures of dogs and cats was compared to the use of metallic devices and external fixations on similar fractures. The series consisted of 64 dogs and 22 cats divided into 6 comparable groups. The patients in the 2 groups fixed with biodegradable devices started to use their operated limbs earlier than in the other groups. The same 2 groups also healed clinically (showed no lameness) earlier than the other groups. Radiographically there was no statistical difference between the 6 groups. On the basis of this study it may be concluded that the fixation with self-reinforced biodegradable devices is as suitable for the fixation of cancellous bone and physeal fractures of dogs and cats as the fixation with metallic devices or external fixation. This biodegradable technique has additional benefits allowing the patients to feel less pain in their operated limbs and making secondary operations to remove the devices unnecessary.

Animals↗

PubMed1994

Fixation with biodegradable devices of acetabular components in a canine model.

Cementless total hip arthroplasty was performed in 13 dogs. The acetabular component was anchored with two biodegradable devices (polylactic acid) in seven dogs and with two titanium screws in six dogs. At 14 weeks, histomorphometric determinations of bony ingrowth into the porous coating of the acetabular weight bearing dome was 54.4% when fixed with the biodegradable devices and 58.9% when fixed with the titanium screws (no statistically significant difference; p = 0.556). At the sites of fixation, less bony ingrowth occurred with the biodegradable devices. The use of biodegradable devices in total hip arthroplasty should overcome the potential metal corrosion of titanium screws that can lead to polyethylene wear.

Animals↗

PubMed1998

Influence of hydrodynamic conditions on naphthalene dissolution and subsequent biodegradation.

The influence of hydrodynamic conditions on the dissolution rate of crystalline naphthalene as a model polycyclic aromatic hydrocarbon (PAH) was studied in stirred batch reactors with varying impeller speeds. Mass transfer from naphthalene melts of different surface areas to the aqueous phase was measured and results were modeled according to the film theory. Results were generalized using dimensionless numbers (Reynolds, Schmidt, and Sherwood). In combined mass transfer and biodegradation experiments, the effect of hydrodynamic conditions on the degradation rate of naphthalene by Pseudomonas 8909N was studied. Experimental results were mathematically described using mass-transfer and microbiological models. The experiments allowed determination of mass-transfer and microbiological parameters separately in a single run. The biomass formation rate under mass transfer limited conditions, which is related to the naphthalene biodegradation rate, was correlated to the dimensionless Reynolds number, indicating increased bioavailability at increased mixing in the reactor liquid. The methodology presented in which mass transfer processes are quantified under sterile conditions followed by a biodegradation experiment can also be adapted to more complex and realistic systems, such as particulate, suspended PAH solids or soils with intrapartically sorbed contaminants when the appropriate mass-transfer equations are incorporated.

Biodegradation, Environmental↗

PubMed1999

Independent prediction of naphthalene transport and biodegradation in soil with a mathematical model.

Experiments were performed to test the ability of a mathematical model to predict naphthalene transport and biodegradation. Pseudomonas putida G7, a model bacterial strain capable of degrading naphthalene, was added to a column packed with the soil that had been pre-equilibrated with naphthalene. Model prediction for transport and degradation were based on predetermined parameters that described naphthalene desorption kinetics and the utilization of naphthalene by the test bacterium. However, initial prediction for naphthalene biodegradation was high, and the formation of cell aggregates is advanced as a plausible explanation. Access of substrate to cells in the interior of an aggregate would be restricted. When the numerical simulation was conducted with a factor to account for cell aggregation, it successfully described the experimental data. Thus, with a single adjustable parameter (an average effectiveness factor), the model predicted macroscopic responses of naphthalene in soil-columns where naphthalene was subject to transport and biodegradation.

Adsorption↗

PubMed1997

Retinal pigment epithelium cells cultured on synthetic biodegradable polymers.

Alterations in the normal structure or functions of retinal pigment epithelium (RPE) can result in a number of ocular diseases. Implantation of RPE cells cultured on thin, biodegradable polymer films may provide a means of transplanting an organized sheet of RPE cells with distinct apical/basal characteristics for the restoration of normal RPE function. We have investigated the interactions of human RPE cells with different biodegradable polymer films to assess their suitability as substrates for RPE culture. Four biodegradable polymers were used: low molecular weight (MW) 50:50 poly(DL-lactic-co-glycolic acid) (PLGA); high MW 50:50 PLGA; 75:25 PLGA; and poly(L-lactic acid) (PLLA). Polymer film substrates were manufactured using a solvent casting technique. Human fetal RPE cells (10-16 weeks gestational) were plated on the polymer substrates and the cultures assessed with respect to cell attachment and proliferation. Histological and immunohistochemical studies were performed on the cells after 8 days in culture. RPE cells attached to all the polymers studied after 8 h in culture. After 8 h, 80.2 +/- 9.5% and 82.3 +/- 7.9% of the plated cells were attached to substrates of high MW 50:50 PLGA and 75:25 PLGA, respectively. The cells proliferated on all substrates, and there was about a threefold increase in cell number over the 8-day culture period on all the polymers studied. Immunohistochemistry after 8 days in culture demonstrated RPE cells labeled with a distinct reaction product for cytokeratin in the cell cytoplasm. All the polymers studied were suitable for RPE culture; however, high MW 50:50 PLGA and 75:25 PLGA proved to be the best in terms of manufacturing properties, cell attachment, and proliferation. These polymers can provide a suitable substrate for RPE cell culture and hold promise for the subretinal implantation of organized sheets of RPE cells.

Biodegradation, Environmental↗

PubMed2006

Release of bovine serum albumin from a hydrogel-cored biodegradable polymer fiber.

We have developed a novel biodegradable, polymeric fiber construct that is coextruded using a wet-spinning process into a core-sheath format with a polysaccharide pre-hydrogel solution as the core fluid and poly(L-lactic acid) (PLLA) as the sheath. The biodegradable, biocompatible fibers were extruded from polymeric emulsions comprised of solutions of various molecular weights of PLLA dissolved in chloroform and containing dispersed, protein-free aqueous phases comprising up to 10% of the emulsion volume. Biologically sensitive agents can be loaded via a dispersed aqueous phase in the polymer, and/or directly into the polysaccharide. We show that this core-sheath fiber format will load a model protein that can be delivered for extended periods in vitro. Bovine serum albumin (BSA) was loaded into the fiber core as a model protein. We have shown that the greater the volume of the protein-free aqueous phase dispersed into the polymeric continuous-phase emulsion, the greater the total release of BSA encapsulated by a core gel comprised of 1% sodium alginate solution. We conclude this fiber format provides a promising vehicle for in vivo delivery of biological molecules. Its biocompatibility and biodegradability also allow for its use as a possible substrate for tissue engineering applications.

Alginates↗