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PubMed1990

[Biodegradable osteosynthesis applied to craniofacial surgery].

Since skin problems as decubitus and infections are well known risks in osteoplastic trepanations in congenital malformations in children, we searched for a reduction in size of the implants and the possibility to use biodegradable materials. After design of special constructions regarding dimension and stability purposes for children below one year, we performed osteoplastic trepanations in 27 minipigs. In 78% the healing was uneventful and the osteoplasty remained in place whereas in 22% (= 6 animals) we observed a local infection which lead to loss of implants as well as cranioplasty in 3 animals. Based on this research, we used our biodegradable implants in osteoplastic trepanations of congenital craniostenosis in children. The postoperative follow-up is now from 3 to 6 months in 4 children and the results are perfect in all. We did not observe any local infection, neither cutaneous problems, even not in bilateral frontal advancement and floating forehead procedures. The implants are presented as well as the results in animal research and the first follow-up in 4 children.

Acrocephalosyndactylia↗

PubMed1990

[Intravitreal drug delivery by microspheres of biodegradable polymers].

We evaluated the efficacy of microspheres of biodegradable polymers as a slow releasing drug delivery system in the vitreous body. Microspheres containing 5-FU were prepared with polymers of poly-(lactic acid) or copolymers of glycolic acid and lactic acid. The release of the drug was studied in vitro. Poly-(lactic acid) microspheres released 5-FU for 7 days. The intravitreal kinetics of the microspheres was studied in rabbits in vivo. The microspheres disappeared from the vitreous cavity of normal eyes by 48 +/- 5 days after injection. Disappearance was accelerated from the vitreous cavity of vitrectomized rabbits (14 +/- 2 days, p less than 10(-6)). No abnormality was found on electroretinographic or histological examinations after microspheres injection. These results suggested that microspheres of biodegradable polymers could be useful as a potential drug delivery system for sustained drug release in the vitreous body.

Animals↗

PubMed1989

Scanning electron microscopic study of cell attachment to biodegradable polymer implants.

The biodegradable polymers--polylactic acid (PLA) and polyglycolic acid (PGA)--are currently being studied as carriers for bioactive bone regeneration compounds. The inclusion of osteo-inductive substances in poly-(DL, lactide-co-glycolide) copolymer alloplastic implants has been shown to enhance the repair of osseous defects. The purpose of this study was to examine, by SEM, the attachment relationship of biodegradable polymer implants to cells and tissue matrix. Three groups of copolymer implants were studied: (1) plain 50:50 PLA-PGA copolymer, (2) PLA-PGA copolymer with hydroxyapatite (HA), and (3) PLA-PGA copolymer with autolyzed, antigen-extracted (AA) bone particles. Polymer discs were surgically implanted into the pectoralis muscles of rats. At seven, 14, and 21 days post-implantation, the baskets were removed and the contents prepared for SEM. Results showed that at one week, implants were coated primarily with red and white blood cells in a fibrinoid clot. Degradation of the polymers was evidenced by irregular enlarging of polymer surface pores. At two and three weeks, polymers became lobular and then fibrinoid as degradation progressed. Inflammatory cell and red blood cell adhesions were increasingly replaced by fibroblasts and collagen matrix deposition. As polymer degradation progressed, AA and HA particles were exposed; however, the lack of cell or tissue adhesion in these areas suggests that degradation may be more influenced by the fluid environment than by direct cell attachment. Furthermore, degradation may inhibit direct cell attachment.

Animals↗

PubMed1989

Anaerobic biodegradation of hydrocarbons.

The anaerobic biodegradation of hydrocarbons has long been a subject of controversy but enough data have now been accumulated to support the view that hydrocarbons can be metabolized in the natural environment in the absence of molecular oxygen. For a limited number of molecules, anaerobic hydrocarbon metabolism has been demonstrated under fermentative or denitrifying conditions with samples collected from several different biotopes. However, the micro-organisms responsible for anaerobic metabolism generally still need to be isolated and identified and the biochemical mechanisms of the strictly anaerobic strains which carry out hydrocarbon metabolism are still unknown. Despite this restricted knowledge, the improvement in sampling techniques and in experimental methods is now sufficient to confirm the existence of anaerobic hydrocarbon biodegradation. The importance of such metabolism should stimulate research in this field.

Bacteria, Anaerobic↗

PubMed1989

Biodegradation of crude oils.

Petroleum from well sites in the Gifhorn Trough (Lower Saxony, NW-Germany) and the Maracaibo Basin (Venezuela) contained various types of microorganisms capable of degrading crude oils. Genetically related oils were inoculated with the isolated microorganisms and the degradation of the oils was followed by chromatographic techniques. Parameters important for the reactions (pH, supply of oxygen, nitrogen and phosphorus, reaction medium) were monitored and optimized. The degradation of n-alkanes was followed closely. Microorganisms active in degradation (yeast, bacteria) easily survived a period of inactivity due to missing nutrients and were reactivated within hours to degrade newly added crude oil. Under substrate-limiting conditions selectivity of degradation was found, destroying medium-chain n-alkanes (C20, C21) at a faster rate than long-chain n-alkanes (C30, C31). During degradation the physical parameters of the crude oils (e.g. density, viscosity, average molecular weight) were altered and shifted into the direction of heavy oil. In vitro degraded oil is very similar to oil degraded in nature. Aromatic hydrocarbons and biomarker molecules (steranes and triterpanes) were not degraded under the conditions used. Pyrolysis-GC analysis of asphaltenes revealed no significant changes in the composition of pyrolyzates during biodegradation. There is sufficient evidence that heavy oils - besides some other effects - are generated by the in situ-biodegradation of conventional oils.

Alkanes↗

PubMed1979

Biodegradation of nylon loops of intraocular implants in children.

In none of the 418 first-stage intraocular implant insertions with intracapsular cataract extractions I have carried out in adults is there any clinical evidence of nylon loop degradation. Although there are no previous reports of clinically observable implant loop degradation, clinically detectable biodegradation was found in eleven eyes of seven children and four adults among the 34 second-stage iris-clip or iridocapsular implants I inserted after aspiration of cataract in children and young adults. The degradation has not produced any uveitis, keratopathy, or instability of the implants in any of these patients. Two children had unilateral glaucoma in the eye containing an iris-clip implant. One of them had dense amblyopia in that eye and the iris-clip implant was removed at the time of trabeculectomy. Scanning electron microscopy of this implant is reported. Active search for nylon particles in the trabeculectomy specimen of the second child has shown the presence of strongly birefringent particles in the trabecular tissue. The possible mechanism of biodegradation of the nylon loops is discussed.

Adult↗

PubMed1988

[Biodegradation of pollutants in the aerial discharges from antibiotic biosynthesis].

Possible biodegradation of air pollution from antibiotic biosynthesis in the form of water condensates was studied in a 1000 ml laboratory bioreactor with using active sludge. The biodegradation of such a pollution was shown possible. The process kinetics was described by the Michaelis-Menten equation. The values of the equation constants were calculated.

Air Pollutants↗

PubMed1971

Biodegradable analogues of DDT.

Despite the immense utility of DDT for vector control its usefulness is prejudiced by its stability in the environment and by the low rate at which it can be degraded biologically. Metabolic studies in insects, in mice, and in a model ecosystem with several food chains have shown that DDT analogues with substituent groups readily attacked by multifunction oxidases undergo a substantial degree of biological degradation and do not appear to be stored readily in animal tissues or concentrated in food chains. Detailed metabolic pathways have been worked out and it is clear that comparative biochemistry can be used to develop DDT analogues that are adequately persistent yet biodegradable. A number of new DDT analogues have been evaluated for insecticidal activity against flies and mosquitos and for their potential usefulness as safe, persistent, and biodegradable insecticides.

Animals↗

PubMedDate not supplied

[Thermosensitivity of naphthalene biodegradation plasmids].

The object of the work was to study the functional expression of naphthalene and salicylic acid catabolism systems and the stability of naphthalene biodegradation plasmids NAH, pBS2, pBS3 and NPL-41 in Pseudomonas aeruginosa PAO. The catabolic systems of the plasmids were shown to be thermosensitive, with a slight variation between one another. The plasmids became unstable at a high temperature; the temperature of effective elimination was 41 degrees C for plasmids NPL-41 and pBS3, and 42 degrees C for plasmids NAH and pBS2. NAH and pBS2 produced a weak inhibiting effect while NPL-41 and pBS3 caused a strong inhibition of the PAO strain growth at 42 degrees C. As a result, many anomalous filamentous cells (partly in the state of lysis) appeared in the cultural broth. Only PAO cells that had lost their plasmid were capable of normal growth in a medium with MPA at an elevated temperature; this creates a convenient system for selection of clones that have lost the plasmids of naphthalene biodegradation. Some of these plasmids can inhibit growth of Pseudomonas strains at an elevated temperature; this fact should be taken into account when the capability of Pseudomonas to grow at a high temperature is used as a taxonomic feature.

Adaptation, Physiological↗

PubMed1981

Use of synthetic polypeptides in the preparation of biodegradable delivery systems for narcotic antagonists.

The goal of this program was the development of biocompatible sustained-release systems that would release naltrexone at a rate of 20 to 25 microgram/hr for 30 days, and that would biodegrade within 90 days. The focus was on the use of macrocapsules prepared from synthetic polypeptides, specifically copolymers of glutamic acid and ethyl glutamate (i.e., Glu/EGlu copolymers). Tubular capsules prepared from 18/82 Glu/EGlu were the most promising systems developed. Capsules 1 cm in length, 0.19 cm in outside diameter, and 0.005 cm in wall thickness released naltrexone in mice at rates in the range of 20 to 40 microgram/hr for 18 days. The rates then decreased during the next 12 days as the capsules became exhausted of drug. These capsules were biocompatible and they appeared to biodegrade within 90 days. In general, the Glu/EGlu copolymers exhibit permeation and degradation rates that increase as the glutamic acid content is increased. Radiotracing studies revealed that the ultimate degradation product was carbon dioxide, which appeared in the expired air. This result is consistent with a polypeptide degradation process that involves hydrolysis of the ethyl esters followed by hydrolysis of the peptide bonds to produce glutamic acid, which enters the metabolic pool.

Animals↗

PubMed1981

Biodegradable drug delivery systems based on aliphatic polyesters: application to contraceptives and narcotic antagonists.

The classes of polymer which form the basis of different types of drug delivery systems are discussed, and the relationships between the chemical structure of the polymer and its permeability, morphology, biodegradability, and mechanical properties are considered, using polyesters as specific examples. Studies of the permeability and biodegradability of poly epsilon-caprolactone), poly(DL-lactic acid), and various copolymers are described and used to illustrate how these properties may be varied by the choice of polymer structure. An induction period prior to bioerosion of these polymers, coupled with high permeability, permits their use as reservoir devices (capsules) which exhibit constant, diffusion-controlled drug release rates and which erode after the drug is exhausted. The applications of this approach to the long term delivery (1 year) of levonorgestrel, a contraceptive agent, and the short term delivery (1-2 months) of naltrexone, a narcotic antagonist, are described.

Animals↗

PubMed1995

Biodegradable self-reinforced polyglycolic acid spiral stent in prevention of postoperative urinary retention after visual laser ablation of the prostate-laser prostatectomy.

PURPOSE: The efficacy and safety of a new biodegradable (self-reinforced polyglycolic acid) spiral stent in securing free voiding despite edema after visual laser ablation of the prostate were studied. MATERIALS AND METHODS: A biodegradable spiral stent was inserted into the prostatic urethra in 22 patients immediately after visual laser ablation of the prostate. Uroflowmetry, measurement of residual urine volume, urine culture, cystoscopy and assessment of symptomatic improvement were done before, and 1, 3 and 6 months after visual laser ablation of the prostate. RESULTS: All 22 patients voided freely on day 1 or 2 after visual laser ablation of the prostate. However, 4 patients later had urinary retention due to a short spiral or too rapid spiral degradation. Half of the patients experienced a transient decrease in flow with some obstructive symptoms at 3 weeks that lasted 1 to 2 weeks. At 4 weeks all spirals were degraded and 3 patients had a positive urine culture. The maximum flow rate increased and the residual urine volume decreased significantly concomitantly with significant symptomatic improvement. CONCLUSIONS: The self-reinforced polyglycolic acid spiral stent can effectively and safely prevent postoperative urinary retention after visual laser ablation of the prostate.

Aged↗

PubMed1994

Biodegradation of magnetite dextran nanoparticles in the rat. A histologic and biophysical study.

BACKGROUND: Superparamagnetic iron oxide particles represent a new class of contrast agents that increase the detectability of hepatic and splenic tumors by magnetic resonance imaging (MRI). Magnetite dextran nanoparticles, a preparation with a small mean particle diameter in solution and null zêta potential present high safety margin and efficacy. The purpose of this investigation was to define the main steps of the metabolism of the iron oxide crystals. EXPERIMENTAL DESIGN: Rats were intravenously administered a single small dose of 59Fe-labeled MD3 (3 mg Fe/kg), and the biodistribution of 59Fe was investigated in the different organs from 2 hours to 25 days postinjection. Magnetic susceptibility studies were conducted in parallel to light microscopy and immunohistochemistry from day 1 to day 14 after administration. RESULTS: Most of the dose accumulated in the carcass (45%), liver (7%), and spleen (7%) in the first 2 hours. In the spleen, a continuously iron uptake was observed up to 48 hours (44%), then decreased to 25 days (22%). The splenic magnetic susceptibility dropped sharply during the first days and then more slightly until day 14. In the liver and blood, the 59Fe-level decreased at 24 hours and then increased until day 25 (11% and 27%, respectively). Histochemistry features essentially confirmed the radiotracer data and showed that iron oxide cores were accumulated into the Kupffer cells and the macrophages of the splenic marginal zone. With time, the number of the granules was decreased whereas the fine iron granules appeared in the cytoplasm. Immunopositive staining for ferritin was markedly increased in the liver hepatocytes to 3 days after injection, and in the splenic marginal zone macrophages to 14 days after injection. CONCLUSIONS: The data point to the early biodegradation of the iron oxide crystals. MD3 thus appear as an interesting biodegradable new contrast agent first devoted to magnetic resonance imaging of liver and spleen diseases that could be further extended to heart, kidneys, and other organs.

Animals↗

PubMed1993

[Studies on in vivo biocompatibility and biodegradation of absorbable material of polylactic acid].

The biocompatibility and biodegradation of polylactic acid (PLA) made in China were investigated in vivo. A total of 20 implants of PLA in 5 rabbits were studied 2 to 16 months after operation to observe the surrounding tissue reaction, degradation and absorption of PLA. The present results demonstrated that the tissue reaction was mild, and there was a capsule around the implant. It was showed there was a degradation of large molecule of PLA firstly, followed by absorption of PLA. The average degradation rate of PLA molecule was 57.02 per cent and the average weight loss of PLA was 8.15 per cent at the end of eight weeks, but no gross change of contour occurred. The biodegradation was gradual and did not cause an accumulation of lactic acid in the body. The present results demonstrate PLA is a promising implant material in surgery.

Absorption↗

PubMed1994

Cartilage engineered in predetermined shapes employing cell transplantation on synthetic biodegradable polymers.

Cartilage is often used as structural support tissue for cosmetic repair in plastic and reconstructive surgery. We describe the efficacy of a new approach for the generation of cartilage in predetermined shapes using specially configured biodegradable synthetic polymer devices as delivery vehicles for transplanted cells. Synthetic biodegradable polymer scaffolds were configured in one of four specific shapes, i.e., a triangle, a rectangle, a cross, and a cylinder. The polymer matrices were seeded with freshly isolated bovine articular chondrocytes and then implanted subcutaneously into nude mice. Gross examination of excised specimens 12 weeks after implantation revealed the presence of new hyaline cartilage of approximately the same dimensions as the original construct. This cartilage showed no signs of resorption or overgrowth over the 12-week time course of the experiment. Histologic evaluation using hematoxylin and eosin stains confirmed the presence of normal mature hyaline cartilage in 46 of 48 specimens. These results suggest that cartilage can be created in predetermined shapes and dimensions using cell transplantation on appropriate polymer templates. This technology would be useful in cosmetic and reconstructive surgery.

Animals↗

PubMed1993

Biodegradation of the polyurethane foam covering of breast implants.

Although it is generally accepted that polyurethane-covered breast implants have decreased the incidence of clinical capsular contracture, there remain many unanswered questions regarding the physical and chemical degradation of the polyurethane foam covering itself. We have systematically studied the fibrous capsule and polyurethane foam recovered from human breast "explants" in an effort to characterize more precisely the biodegradation of polyurethane foam in the human body. Seventy-five freshly retrieved polyurethane-covered implants and surrounding capsule from 47 patients have been analyzed. Capsular tissue from several sampling sites around the surface of the implants was digested in a collagenase solution until foam was recovered or all tissue was digested. Additional samples were fixed in 10% formalin. Scanning electron microscopy was used to look for structural changes in the recovered intact foam and to determine the foam strut widths. Fourier transform IR spectroscopy and x-ray photoelectron spectroscopy were used to analyze the chemical composition of the polyurethane. The formalin-preserved capsule samples were examined histologically for further evidence of foam degradation. Of the 75 prostheses analyzed, 36 (48 percent) were removed because of capsular contracture and 10 (13 percent) because of infection or exposure of the prosthesis. The remaining 29 (39 percent) implants were removed for various other reasons. Visibly intact foam was recovered from 36 (48 percent) prostheses after enzymatic digestion of capsule tissue. There was a progressive decline in the ability to recover intact foam as the total implantation time increased. Scanning electron microscopy revealed fractures and fissures in the foam structure and thinning of the polyurethane struts. The mean strut width of control, unimplanted foam was 49 +/- 1.5 microns (+/- SEM). Retrieved foam from implants which developed capsular contracture and the infected implants had strut widths of 30 +/- 3.1 and 32 +/- 3.1 microns, respectively. In implants removed for other reasons, the polyurethane foam strut width was 41.2 +/- 2.3 microns. Despite an inability to recover visibly intact foam from 39 specimens, standard light microscopy of 37 of these same specimens showed residual polyurethane still present in the capsule. Various degrees of scalloping and fracturing of the foam were seen in the histologic sections. There is convincing evidence by scanning electron microscopy and histology that polyurethane is degrading. It was not possible to quantitate accurately the rate of degradation, but factors such as capsular contracture, infection, and time appear to have a role in the biodegradation of polyurethane in the human body. These relationships require further study.

Biodegradation, Environmental↗

PubMed1993

Effectiveness of phenol biodegradation as a function of the physicochemical parameters of the medium (II).

The effectiveness of phenol biodegradation as a function of the physicochemical parameters of the medium: temperature, pH, aeration, form of the inorganic source of nitrogen, presence of trivial substrates in the medium was studied. Using a two-factor dispersion analysis, the degree of influence of the various physicochemical parameters with regard to specificity of the biological factor was determined. Evaluation was made of the possibility to control the biodegrading process by means of physicochemical parameters of the medium.

Aerobiosis↗

PubMedDate not supplied

[Biodegradation of polycyclic aromatic hydrocarbons and its application to the bioremediation of contaminated soils and sludges].

Polycyclic aromatic hydrocarbons (PAHs) are a group of priority pollutants due to their toxic, mutagenic, and carcinogenic properties. They are found in high concentration in many soils and sludges, mainly those associated with petroleum, gas-production and wood-preservation industries. Application of microorganisms for the remediation of contaminated soils and sludges has gained interest as a promising technique in comparison to the conventional practices of landfilling, incineration or solvent extraction. This paper reviews the controlling variables of the biodegradation of PAHs as well as the use of solid-phase and slurry-phase bioremediation techniques. The acceptance of bioremediation technology requires the demonstration of its efficacy, reliability, predictability of the field performance from lab-scale treatability studies, and economical advantage. Some limitations in the biodegradation of high-molecular-weight PAHs and failures in the control of scale-depending factors (mass transport, spatial heterogeneities, abiotic losses) can reduce its effectiveness. Methodology used for the systematic evaluation of bioremediation is also reviewed.

Biodegradation, Environmental↗