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PubMed2000

Biodegradable pH-sensitive surfactants (BPS) in liposome-mediated nucleic acid cellular uptake and distribution.

The impact of biodegradable pH-sensitive surfactant (BPS)-liposomes on nucleic acid, i.e., oligonucleotide and plasmid DNA, cellular delivery was examined. Fluorescein-labeled nucleic acids complexed with 1,2-dioleoyl-3-trimethylammonium propane cationic liposomes and BPS at a charge ratio (+/-) of 10 were incubated in CV-1 cells and analyzed by flow cytometry. The fluorescence intensity of oligonucleotides but not plasmid DNA complexed with BPS-liposomes was higher than those complexed with BPS-free liposomes at early time points. However, when cells were fixed to equalize the intracellular pH since fluorescein, a pH-sensitive fluorophore, has higher fluorescence intensity in alkaline pH than acidic, no difference in intensity was observed. This indicated the incorporation of BPS in liposomes did not increase oligonucleotide cellular uptake over control liposomes, but redistributed oligonucleotides into a more basic environment, e.g., cytoplasm. An explanation consistent with the presented data is the formation of small transient membrane defects within the endosomal membrane as presented previously [Liang, E., Hughes, J.A., 1998a. Membrane fusion and rupture in liposomes: effect of biodegradable pH-sensitive surfactants. J. Membr. Biol. 166, 37-49.]. The above findings suggested that BPS may be effective agents of disrupting one of the major barriers, endosomal membrane, to enhance nucleic acid cellular transport.

Animals↗

PubMed1999

In vitro biodegradation study of acetyl and methyl inulins by Bifidobacteria and inulinase.

The purpose of this study was to investigate if acetylated and methylated inulins can be degraded by inulinase from Aspergillus niger and by Bifidobacteria, in order to determine their potential in colonic drug delivery. Methyl and acetyl inulins were synthesized by the reaction of inulin (Raftiline HP) with methyl sulfate and acetic anhydride, respectively. The degree of substitution (DS) and the structure of the reaction products were confirmed by 13C-NMR. Degradation by inulinase was investigated in a citrate buffer (0.05 M, pH 4) or with a mixture of citrate buffer and DMSO at 37 degrees C. Biodegradation by Bifidobacteria was investigated under anaerobic conditions using an in-house prepared broth at 37 degrees C for 2 days. The resulting products were analyzed chromatographically; the formation of short chain fatty acids was followed by measuring the pH of the incubation media. The results obtained suggest that acetylated and methylated inulins are not biodegradable, since no degradation product could be detected after incubation; a decrease in pH was clearly observed in control samples (pure fructose and inulin), but not in the derivatized inulin samples. The results can probably be explained by a change in conformation of inulin due to derivatization.

Acetylation↗

PubMed2003

Assessment of the environmental impact of management measures for the biodegradable fraction of municipal solid waste in São Paulo City.

There is increasing concern about landfilling of biodegradable wastes. Therefore, biological treatment processes such as composting and biogasification have been considered as alternative strategies for managing those wastes. In this work, life cycle assessment was employed to compare the environmental impacts of landfilling, composting, and biological treatment of municipal solid waste in São Paulo City, Brazil. Energy consumption, recovered resources, and emissions to air and water were quantified and analyzed in terms of their potential contribution to global warming, acidification, and nutrient enrichment impact. The results demonstrated that processes that require high levels of energy consumption, such as wastewater treatment, play an important role in the outcome of environmental impact potentials. It was found that the landfilling of all waste is generally the worst strategy from an environmental point of view. However, significant reductions in the resulting impacts can be accomplished through biogasification and composting of the biodegradable fraction. Regarding composting, the application of a biofilter for gas treatment reduced significantly the gaseous emissions.

Biodegradation, Environmental↗

PubMed2001

Biodegradation of plastics.

Widespread studies on the biodegradation of plastics have been carried out in order to overcome the environmental problems associated with synthetic plastic waste. Recent work has included studies of the distribution of synthetic polymer-degrading microorganisms in the environment, the isolation of new microorganisms for biodegradation, the discovery of new degradation enzymes, and the cloning of genes for synthetic polymer-degrading enzymes.

Bacteria↗

PubMed1996

Anaerobic biodegradation of hydrocarbons.

Anaerobic biodegradation of aliphatic and aromatic hydrocarbons is a promising alternative to aerobic biodegradation treatments in bioremediation processes. It is now proven that, besides toluene, benzene and ethylbenzene can be oxidized under anaerobic redox conditions. Anaerobic bacteria have also been shown capable of utilizing substrates not only in the pure form, but also in complex hydrocarbon mixtures, such as crude oil. In addition, crucial steps in anaerobic treatment processes have been studied in vitro to better understand the enzymes involved in monoaromatic hydrocarbon degradation. Knowledge remains incomplete, however, about the anaerobic degradation of aliphatic and polycyclic aromatic hydrocarbons.

Anaerobiosis↗

PubMed2002

Anaerobic biodegradation of spent sulphite liquor in a UASB reactor.

Anaerobic biodegradation of fermented spent sulphite liquor, SSL, which is produced during the manufacture of sulphite pulp, was investigated. SSL contains a high concentration of lignin products in addition to hemicellulose and has a very high COD load (173 g COD l(-1)). Batch experiments with diluted SSL and pretreated SSL indicated a potential of 12-22 l methane per litre SSL, which corresponds to 0.13-0.22 l methane (g VS)(-1) and COD removal of up to 37%. COD removal in a mesophilic upflow anaerobic sludge blanket, UASB. reactor ranged from 10% to 31% at an organic loading rate, OLR, of 10-51 g (1 d)(-1) and hydraulic retention time from 3.7 to 1.5 days. The biogas productivity was 3 1 (l(reactor d)(-1), with a yield of 0.05 l gas (g VS)(-1). These results suggest that anaerobic digestion in UASB reactors may provide a new alternative for the treatment of SSL to other treatment strategies such as incineration. Although the total COD reduction achieved is limited, bioenergy is produced and readily biodegradable matter is removed causing less load on post-treatment installations.

Anaerobiosis↗

PubMed2003

Preparation and characterization of biodegradable poly-3-hydroxybutyrate-starch blend films.

Bacterial polyesters have attracted much attention as biodegradable biocompatible polymers. Poly-3-hydroxybutyrate, a microbially produced thermoplastic, has similar material properties to polypropylene. Its potential application as biodegradable and biocompatible plastics is well documented. However, due to high cost it is used mainly in biomaterials for medical applications. Materials with useful properties may result from blending bacterial polyhydroxybutyrate (PHB) with other polymers. In this paper, the compatibility of PHB with starch for improved properties and cost reduction is discussed. The thermal and mechanical properties of the blended films were studied by means of thermogravimetry, differential scanning calorimetry and an automated material testing system. The results revealed that blend films had a single glass transition temperature for all the proportions of PHB:starch tested. The nature of all combinations was found to be crystalline. The tensile strength was optimum for the PHB:starch ratio of 0.7:0.3 (wt/wt). The variation in tensile strength, Young's modulus, extension needed to break, thermal stability, glass transition temperature, melting temperature, for the different proportions of PHB:starch are discussed.

Bacteria↗

PubMed2003

Biodegradation of hexadecane in liquid and solid-state fermentations by Aspergillus niger.

The biodegradation and mineralisation of hexadecane (HXD) by Aspergillus niger were studied in SmF and Solid-state fermentation (SSF). HXD concentrations ranging from 45 to 180 g/l (SSF) and from 20 to 80 g/l (SmF) were tested. HXD consumption was three times higher and fungal growth was up to 30 times faster in SSF than in SmF. The maximum HXD consumption in SmF was 62% (18% mineralised) and in SSF 100% (52% mineralised) for initial HXD concentrations of 20 and 45 g/l, respectively. The respiratory quotient in SmF increased (from 0.85 to 1.08) with increase in HXD concentration, while it was independent (approximately 0.68) of the initial HXD concentration in SSF. These results showed that the consumption rate and biodegradation efficiency for HXD were higher in SSF than in SmF.

Alkanes↗

PubMedDate not supplied

Guided bone regeneration of cranial defects, using biodegradable barriers: an experimental pilot study in the rabbit.

The aim of this study was to test if a biodegradable barrier could be used to achieve proper bone healing of full-thickness trephine skull defects, applying the biological principle of guided tissue regeneration (GTR). Two New Zealand white rabbits were used. In each animal, 2 circular through-and-through bone defects with a diameter of 8 mm were created in the midline of the frontal and parietal bones of the calvarium. One defect was covered with the mucoperiosteal flaps without placement of an intervening membrane barrier (control). One test defect (test 1) was covered by a biodegradable, non-porous polylactic acid membrane on the outer (supra-calvarial) side of the defect, and 2 test defects (tests 2 and 3) were covered by similar membranes on both the outer and the inner aspects of the defects, prior to flap closure. 6 weeks postsurgically, the animals were sacrificed and the defect areas including surrounding tissues were harvested for histological preparation. The control defect was essentially occupied by supra-calvarial soft tissue, located in direct contact with the dural tissue. In the test cavities, there was a continuous bridge of regenerated bone extending from one edge of the defect to the other, although in test 1 not attaining the same thickness as the bone bordering the defect. In the 2 other test defects, the regenerated bone had reached a thickness almost corresponding to that of the surrounding bone. The bone regeneration was achieved without recourse to adjunctive bone graft materials.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1999

Biodegradable osteosynthesis material for stabilization of midface fractures: experimental investigation in sheep.

The most frequently tested biodegradable osteosynthesis materials have up to now largely consisted of poly-L-lactide (PLLA). The PLLA polymers appear to have sufficient mechanical strength for fracture treatment in the midface, but their degradation does not seem to be uniform enough to allow their clinical use. During the degradation process the disintegration products elicit a foreign body reaction due to non-uniform degradation rates. The foreign body reaction is sometimes combined with a fluctuant swelling at the implantation site. Implants injection-moulded from 90:10 PLLA/PGA (polyglycolic acid) have a more uniform degradation rate and seem to lead to a milder foreign body reaction. We bridged Le Fort I osteotomies in sheep using a system of injection-moulded PLLA/PGA 90:10 plates and screws and compared it with 2 mm AO miniplates and mini-screws made from titanium. Light microscopy evaluation showed that the PLLA/PGA copolymer system experienced its highest mechanical stress at the transition from screw head to screw shaft. Nevertheless, the fragments fixed with the copolymers were on the whole only slightly less stable than those fixed with the titanium system. The foreign body reaction solely due to co-polymer degradation was not severe, considering the fibrous tissue response that was found associated with the titanium components. The study does show that the copolymer investigated is adequate for clinical use as a biodegradable osteosynthesis material, at least in low stress bearing areas.

Absorbable Implants↗

PubMed2002

Changes in mutagenicity of herbicide chlornitrofen during biodegradation.

We used the Ames assay to investigate changes in the mutagenicity of chlornitrofen during its aerobic biodegradation. Although a mixed culture of bacteria obtained from river water degraded chlornitrofen and reduced its concentration from 39 to 6 microg/l in 21 days, the indirect mutagenicity of the solution to Salmonella strains TA98, YG1021, and YG1026 increased gradually. This finding suggests that mutagenic metabolites were produced during the aerobic biodegradation. The increase in the mutagenicity was, however, much smaller under aerobic than under anaerobic conditions. The differing sensitivities of our test strains to the functional groups on the mutagens showed that the mutagenic metabolites were indirect frameshift-type mutagens that might have neither nitro nor amino groups.

Aerobiosis↗

PubMed1992

Integrated approach to surfactant environmental safety assessment: fast atom bombardment mass spectrometry and liquid scintillation counting to determine the mechanism and kinetics of surfactant biodegradation.

Fast atom bombardment mass spectrometry and liquid scintillation counting have been used to study the biodegradation of a novel cationic surfactant in live sludge. The rates of primary biodegradation and the extent of complete mineralization were determined. Furthermore, an intermediate degradation product was identified and its rates of formation and subsequent removal have been established. These data find utility in assessing the environmental safety of the surfactant and the accuracy of various environmental fate models.

Biodegradation, Environmental↗

PubMedDate not supplied

Poly(ethylenimine-co-L-lactamide-co-succinamide): a biodegradable polyethylenimine derivative with an advantageous pH-dependent hydrolytic degradation for gene delivery.

A biodegradable gene transfer vector has been synthesized by linking several low molecular weight (MW) polyethylenimine (PEI, 1200 Da) blocks using an oligo(L-lactic acid-co-succinic acid) (OLSA, 1000 Da). The resulting copolymer P(EI-co-LSA) (8 kDa) is soluble in water and degrades via base-catalyzed hydrolytic cleavage of amide bonds. With regard to its application as a gene transfer agent, the polymer showed an interesting pH dependency of degradation. At pH 5, when DNases are highly active, the degradation proceeds at a slower rate than at a physiological pH of 7.4. PEI and P(EI-co-LSA) spontaneously formed complexes with plasmid DNA. Whereas the complexes formed with PEI were not stable and aggregated, forming particles of up to 1 microm hydrodynamic diameter, P(EI-co-LSA) formed complexes, which were about 150 nm in size and of narrow size distribution. The latter complexes were stable, due to their high surface charge (zeta-potential + 18 mV). Similar to low MW PEI, the copolymer exhibited a low toxicity profile. At the same time, the copolymer showed a significant enhancement of transfection activity in comparison to the low MW PEI. This makes P(EI-co-LSA) a promising candidate for long-term gene therapy where biocompatibility and biodegradability become increasingly important.

Animals↗

PubMedDate not supplied

A novel family of L-amino acid-based biodegradable polymer-lipid conjugates for the development of long-circulating liposomes with effective drug-targeting capacity.

The objective of this study was to develop biodegradable polypeptide-lipid conjugates for the design of polymer-coated long-circulating liposomes (LCL). Lipid conjugates of poly(hydroxyalkyl L-asparagine/L-glutamine) were synthesized and incorporated into 0.15 microm dipalmitoyl phosphatidylcholine (DPPC)-cholesterol liposomes. Circulation times and biodistribution were assessed in rats using a radioactive lipid marker. Evaluation of the therapeutic activity of prednisolone phosphate loaded in 0.1 microm PHEA-DPPC-cholesterol liposomes in a rat experimental arthritis model was performed to demonstrate the drug-targeting potential of the polymer-coated liposomes. Coating of liposomes with poly(hydroxyethyl L-asparagine) (PHEA) and poly(hydroxyethyl L-glutamine) (PHEG) extended the circulation half-life to a similar extent as poly(ethylene glycol) (PEG), which is normally used for the preparation of LCL. Glutamine polymers with a hydroxypropyl or a hydroxybutyl group instead of hydroxyethyl group also yield prolonged circulation, however, not to the same extent as PHEA/G. The pharmacokinetic properties of PHEA-liposomes were independent of the lipid dose even at very low lipid doses of around 50 nmol per rat. PLP was successfully entrapped in PHEA-liposomes. These liposomes were shown to be stable in the circulation and equally effective in rat experimental arthritis as PLP encapsulated in PEG-liposomes. PHEA and PHEG are attractive alternative polymers for the design of LCL: their performance is similar to that of PEG-liposomes but they have the advantage of being biodegradable.

1,2-Dipalmitoylphosphatidylcholine↗

PubMedDate not supplied

Synthesis of biodegradable cross-linked poly(beta-amino ester) for gene delivery and its modification, inducing enhanced transfection efficiency and stepwise degradation.

Biodegradable cross-linked poly(beta-amino ester) (CLPAE) was synthesized by Michael addition of pentaerythritol triacrylate and N,N-dimethylethylenediamine and modified with aminohexanoic acid and lysine to CLPAE-Ahx and CLPAE-Lys, respectively, for a gene delivery system. They could self-assemble with plasmid DNA, forming nanosized polyplexes, and CLPAE-Ahx polyplex released plasmid DNA slowly during a week through stepwise degradation. The polymers showed minimal cytotoxicity on 293 cells due to their biodegradability and biocompatibility. Transfection efficiencies of CLPAE-Ahx and CLPAE-Lys were comparable to that of PEI in 293 cells and C2C12 cells. Additionally, high transfection of CLPAE-Ahx on primary rat aorta vascular smooth muscle cells (SMC) and primary mouse embryonic fibroblast cells (MEF) shows a potential for a gene delivery system on primary cells, restenosis treatment of human SMC, and MEF cell function research. In conclusion, CLPAE-Ahx could be used as a nontoxic and highly efficient gene delivery system.

Amination↗

PubMed2001

UV-irradiated biodegradability of ethylene--propylene copolymers, LDPE, and I-PP in composting and culture environments.

The biodegradability of UV-irradiated films of ethylene--propylene copolymers (E--P copolymer), isotactic polypropylene (i-PP), and low-density polyethylene (LDPE), was measured in composting and culture environments by monitoring the variations in intrinsic viscosity [eta], weight loss per surface area, surface changes by SEM, colonization of fungus, chain scission, and evolution of hydroxyl and carbonyl groups by FT-IR spectroscopy. Photooxidation was used as a pretreatment for biodegradation of polymers. A systematic decrease in intrinsic viscosity [eta] and increase in carbonyl/hydroxyl regions in FT-IR spectra was found from 0 to 100-h irradiated samples. The degradation rate was strongly dependent on the composition of copolymers and markedly increased with decrease in ethylene content. Important surface erosion was detected after composting by SEM for longer UV-irradiated samples. It was estimated that chain-scission was directly related to photoirradiation.

Biocompatible Materials↗

PubMedDate not supplied

Biodegradation of lactic acid based polymers under controlled composting conditions and evaluation of the ecotoxicological impact.

The biodegradability of lactic acid based polymers was studied under controlled composting conditions (CEN prEN 14046), and the quality of the compost was evaluated. Poly(lactic acids), poly(ester-urethanes), and poly(ester-amide) were synthesized and the effects of different structure units were investigated. The ecotoxicological impact of compost samples was evaluated by biotests, i.e., by the Flash test, measuring the inhibition of light production of Vibrio fischeri, and by plant growth tests with cress, radish, and barley. All the polymers biodegraded to over 90% of the positive control in 6 months, which is the limit set by the CEN standard. Toxicity was detected in poly(ester-urethane) samples where chain linking of lactic acid oligomers had been carried out with 1,6-hexamethylene diisocyanate (HMDI). Both the Flash test and the plant growth tests indicated equal response to initial HMDI concentration in the polymer. All other polymers, including poly(ester-urethane) chain linked with 1,4-butane diisocyanate, showed no toxicological effect.

Biodegradation, Environmental↗

PubMedDate not supplied

Synthesis of in situ cross-linkable macroporous biodegradable poly(propylene fumarate-co-ethylene glycol) hydrogels.

This study describes a synthesis method of biodegradable macroporous hydrogels suitable as in situ cross-linkable biomaterials. Macroporous hydrogels were based on poly(propylene fumarate-co-ethylene glycol) and prepared via coupled free radical and pore formation reactions. Cross-linking was initiated by a pair of redox initiators, ammonium persulfate and L-ascorbic acid. Pores were formed by the reaction between L-ascorbic acid and sodium bicarbonate, a basic component, which evolved carbon dioxide. Sol fraction of the hydrogels was varied from 0.06 +/- 0.01 to 0.64 +/- 0.01. A stereological approach was used to analyze the morphological properties of the macroporous hydrogels by relating the morphological properties of thin sections to the original three-dimensional macroporous hydrogel. Prepared macroporous hydrogels had porosities between 0.43 +/- 0.08 and 0.84 +/- 0.02 and surface area densities between 55 +/- 3 and 108 +/- 7 cm(-1). Sodium bicarbonate concentration had the greatest effect on both the porosity and surface area density. The effect of copolymer formulation on the porosity and surface area density was insignificant. From thin sections of the macroporous hydrogels, the profile size distributions were determined as an estimate of the pore size distribution. Two formulations synthesized with varying L-ascorbic acid concentration of 0.05 and 0.1 M had median profile sizes of 50-100 and 150-200 microm, respectively. This novel synthesis method allows for the in situ cross-linking of biodegradable macroporous hydrogels with morpholological properties suitable for consideration as an injectable tissue engineering scaffold.

Biodegradation, Environmental↗