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PubMed1986

A comparative study of different beta-whitlockite ceramics in rabbit cortical bone with regard to their biodegradation behaviour.

Different beta-whitlockite ceramic cylinders of standard size were implanted in the tibiae of rabbits to study the influence of micropores and chemistry on the biodegradation rate. The materials were evaluated by radiography and light microscopy. Surface chemistry was varied by the addition of impurities, while different applied pressures before sintering and different sintering temperatures gave rise to different micropores. Both factors influenced the biodegradation rate.

Animals↗

PubMed1986

Polymer-hydroxyapatite composites for biodegradable bone fillers.

A number of composites made from biodegradable polymers and hydroxyapatite were studied in vivo and in vitro in an attempt to develop biodegradable artificial bone fillers. Histological observation in rats revealed that polylactic acid, of low molecular weight (PLAoligomer), was rapidly resorbed and replaced by newly formed bone tissue when incorporated with hydroxyapatite and this suggested that the incorporated hydroxyapatite seemed to play an active role in the new bone formation. In vitro testing revealed that the solubility of hydroxyapatite was markedly enhanced when mixed with PLAoligomer.

Animals↗

PubMed1987

Synthesis and biodegradation of polymers derived from aspartic acid.

The synthesis of copolymers derived from aspartic acid hydrochloride, their characterization and their hydrolytic degradation and biodegradation by Aspergillus niger and E. coli have been described. The alpha-amino dicarboxylic acid has been copolymerized with 1,2-ethane diol, 1,3-butane diol, 1,4-butane diol, 1,6-hexane diol and glycerol to get copolyesters I, II, III, IV and V respectively. The polymer samples have been characterized by their number average molecular weight (Mn), elemental analysis and their i.r. spectra. The copolyester V is crosslinked. All of the copolyesters I-V undergo slow hydrolytic degradation in aqueous solution at ambient temperatures as studied by the measurement of the decrease in reduced viscosity and increase in specific conductance of their aqueous solutions. They are also degraded in aqueous suspension by the fungus Aspergillus niger and by the bacterium E. coli. Degradation by Aspergillus niger mainly depends on the polarity of the polymers, the more polar polymers being less degradable. On the other hand, degradation by E. coli is primarily dependent upon the alpha-NH2 group contents of the polymers, the alpha-NH2 group rich polymers being more degradable. The possible use of these polymers as biodegradable drug carriers has been suggested.

Aspartic Acid↗

PubMed1988

Biodegradable hollow fibres for the controlled release of drugs.

Biodegradable hollow fibres of poly-L-lactic acid (PLLA) filled with a suspension of the contraceptive hormone levonorgestrel in castor oil were implanted subcutaneously in rats to study the rate of drug release, rate of biodegradation and tissue reaction caused by the implant. The in vivo drug release was compared with the release in vitro using different release media. Fibres, disinfected with alcohol showed a zero-order release, both in vitro and in vivo, for over 6 months. Fibres, either gamma-sterilized or disinfected with alcohol were harvested at time intervals ranging from 1 d to 6 months after implantation. Molecular weights of PLLA, tensile strengths, and remaining amounts of drug were determined as a function of time. The tissue reaction can be described as a very moderate foreign body reaction with the initial presence of macrophages, which are gradually replaced by fibroblasts which form a collagen capsule. Molecular weight determinations of PLLA showed a decrease from an initial Mw of 1.59 X 10(5) to 5.5 X 10(4) in 4 months (after alcohol sterilization). A gradual decrease in fibre strength with time was observed which did not significantly impair the release rate of levonorgestrel.

Animals↗

PubMed1989

Macroporous calcium phosphate bioceramics in dog femora: a histological study of interface and biodegradation.

This study examines the biodegradation behaviour of calcium phosphate macroporous bioceramics consisting of hydroxylapatite or beta-whitlockite implants. The implantations were performed in hard tissue of femora and muscular tissue of dogs for periods of 6 and 12 month. With microradiography and light microscopy, respectively, of ground and thin sections it was shown that hydroxylapatite remained unchanged and beta-whitlockite degraded within 6 month in bone tissue. In the muscular tissue, the biodegradation of beta-whitlockite was slower. In addition, beta-whitlockite gave rise to a cellular response of lymphocytes and plasma cells rather than hydroxylapatite in the soft tissue region. For tissue response hydroxylapatite is more suitable as an implant material than beta-whitlockite.

Animals↗

PubMed1990

Oxidized cellulose mesh. I. Biodegradable membrane in periodontal surgery.

Regeneration of tissues after surgery has been demonstrated using a variety of membranes placed after surgical exposure of periodontal defects. In this study, biodegradable oxidized cellulose mesh was used in human subjects to improve post-operative healing. Healing was good, with all pockets less than 3 mm post-operatively. Less recession occurred in some of the sites which received the mesh, but this was not significantly different from the sites which did not receive the mesh. A varied healing response was noted in different sites and in different individuals. A number of factors may determine the nature and extent of the healing response, but these are ill defined. Histological investigation of the healing response of the tissues was not possible in this clinical study. The study has shown that oxidized cellulose mesh has the potential to enhance healing after surgery, and it may be useful as an alternative biodegradable material for use in the technique of guided tissue regeneration.

Aged↗

PubMed1991

Partially biodegradable polyacrylic-polyester composites for internal bone fracture fixation.

New partially resorbable composite formulations based on components used in surgery were synthesized in rod form (length 15-20 mm, diameter 4 mm). The biostable components were poly(methyl methacrylate) in hydrophobic implants and poly(2-hydroxy ethyl methacrylate) in hydrophilic ones. The biodegradable components were commercially available suture yarn made from poly (alpha-hydroxy esters): polyglycolide, a polyester derived from glycolic acid; and a copolyester of glycolic and lactic acids, polyglactin 910. Biodegradation in phosphate-buffered solution at pH 7.0 and 37 +/- 0.5 degrees C was analysed gravimetrically. There was no measurable loss of mass after treatment for 20-25 d. Composite microstructure was examined by phase-contrast, cross-polarized light microscopy.

Biocompatible Materials↗

PubMed1992

Biodegradable polymers. I. Synthesis of hydrolysis-sensitive poly[(organo)phosphazenes].

Polyphosphazenes with hydrolytic labile substituents have potential as biodegradable materials. By proper choice of the substituents, polymers can be prepared which degrade in vivo to form harmless products. The rate of biodegradation and the nature of the degradation products can be varied by changing the chemical composition of the polymers. A series of new degradable polyphosphazene derivatives are described. The synthesis of phosphazene polymers with various amounts of ethyl 2-(O-glycyl)lactate or ethyl 2-(O-alanyl)lactate as cosubstituents is described. These polymers are prepared by reaction of poly[(dichloro)phosphazene) with the corresponding amine compound. Total halogen replacement was achieved by subsequent introduction of glycine ethyl ester cosubstituents. Introduction of these hydrolysis-sensitive side-groups along the polymer chain increases the degradability of poly[(amino acid ester]phosphazenes).

Biocompatible Materials↗

PubMed1993

Laminated three-dimensional biodegradable foams for use in tissue engineering.

A novel processing technique is reported to construct three-dimensional biodegradable polymer foams with precise anatomical shapes. The technique involved the lamination of highly-porous membranes of porosities up to 90%. Implants with specific shapes were prepared made of poly(L-lactic acid) and copolymers of poly(DL-lactic-co-glycolic acid) to evaluate feasibility. The biomaterials produced have pore morphologies similar to those of the constituent membranes. The pores of adjacent layers of laminated devices are interconnected, resulting in continuous pore structures. The compressive creep behaviour of multilayered devices is also similar to that of the individual layers. Recent discoveries from our group and others that organs and tissues can be regenerated and reconstructed, using cells cultured on synthetic biodegradable polymers, renders this method useful in creating polymer-cell graft for use in cell transplantation.

Biocompatible Materials↗

PubMed1995

Histological evaluation of a biodegradable Polyactive/hydroxyapatite membrane.

Guided tissue regeneration (GTR) is a technique which is used for the treatment of bone defects associated with periodontal disease or enossal dental implants. In most experimental studies on GTR, non-degradable membranes are used. A drawback inherent to such devices is that at the end or in the course of the wound healing they have to be removed. Therefore, the aim of the present study was to investigate a new biodegradable membrane material for use in GTR, which also has excellent mechanical properties and is biocompatible. The material is a composite consisting of poly(ethyleneglycol terephthalate) and poly(butylene terephthalate) segmented copolymer (PEG/PBT), which for the experiments was used in pure form and also mixed with hydroxyapatite (HA) grains. Subcutaneous and subgingival implantation studies in goats were performed to determine the biocompatibility and biodegradability characteristics of several of these materials. Differences between materials were introduced in the production process, PEG/PBT ratio, material thickness and presence of HA. Implantation periods were 3, 6 and 12 wk. The histological results indicated that all investigated materials were biocompatible with the surrounding tissue. Degradation of the membranes was attended by a mild cellular reaction. The degradation process was mainly influenced by the PEG/PBT ratio. A higher PBT content resulted in a decreased degradation.

Animals↗

PubMed1995

In situ assessment of cell viability within biodegradable polylactic acid polymer matrices.

Efforts to expand treatment options for articular cartilage repair have increasingly focussed on the implantation of cell polymer constructs. Primary cells cultured from perichondrium, a chondrogenic tissue, were found to survive in vitro within a biodegradable porous polylactic acid matrix. The novel application of an in situ fluorescent double-stain protocol to cell polymer constructs was supported by increased 3H-thymidine uptake and the ability of cell seeded polylactic acid to form first passage explant cultures. This in situ viability staining technique allowed for rapid determination of cell viability and, in conjunction with confocal microscopy, assessment of cellular distribution within a biodegradable scaffold. Advantages of using this method over histological and electron microscopic analysis include in situ observation, absence of distortion in scaffold architecture due to polymer dissolution and disruption during processing, and obtaining a viability assessment within 30 min. Potential applications of this protocol as a screening tool for laboratory engineered tissues and in the evaluation of cellular injury in natural tissues are discussed.

Animals↗

PubMed1995

Glutaraldehyde cross-linked chitosan microspheres as a long acting biodegradable drug delivery vehicle: studies on the in vitro release of mitoxantrone and in vivo degradation of microspheres in rat muscle.

Chitosan microspheres were prepared from 74% deacetylated chitin by the glutaraldehyde cross-linking of an aqueous acetic acid dispersion of chitosan in a mixture of liquid paraffin and petroleum ether stabilized using sorbitan sesquioleate as the surfactant. Cross-linking and hardening of the spherical particles were achieved by the addition of glutaraldehyde-saturated toluene through the organic phase. A relatively novel antineoplastic agent, mitoxantrone, was incorporated into the microspheres and the drug release was studied in vitro into phosphate buffer for over 4 weeks at 27 degrees C. Drug release was found to be effectively controlled by the extent of cross-linking. Only about 25% of the incorporated drug was released over 36 days from microspheres of high cross-linking density. Implantation of placebo chitosan microspheres in the skeletal muscle of rats was carried out in order to assess the biocompatibility and biodegradability of the microspheres. Histological analysis showed that the microspheres were well tolerated by the living tissue. However, no significant biodegradation of the material was noticed over a period of 3 months in the skeletal muscle of rats. Data obtained indicate the possibility of using cross-linked chitosan microspheres as a drug carrier for sustained drug release for very long periods.

Animals↗

PubMed1996

Unacceptable biodegradation of polyethylene in vivo.

The chemical characterization of 19 retrieved ultra-high-molecular-weight polyethylene tibial plateaux, six new ones and one raw bar was performed by means of infrared spectroscopy. The surface and bulk oxidation and biodegradation indexes were calculated. The raw bar has a measurable oxidation, which increases on the bulk and on the surfaces of the new plateaux. In the retrieved plateaux, the average oxidation index increases further both on the bulk and on the surfaces; the worse values were present on the worn area. Similar results were found for the biodegradation index. The data show that the biotic in vivo degradation is promoted by the oxidation present on the new plateaux and that it occurs through a different mechanism, abiotic thermal-, photo-, gamma-radiation oxidation, evaluated by the oxidation index.

Aged↗

PubMed1984

Biodegradability test results related to quality and quantity of the inoculum.

For a series of different biodegradation test methods the biodegradation curves are simulated by computer. Simulations are performed on the basis of Monod growth kinetics corrected for cell decay. The possibility of discriminating between growth rates is related to variability of the inoculum quality and quantity. It is concluded that the variability of the inoculum masks all other information. The Repetitive Die Away test, however, offers a good opportunity to obtain information on growth rates that is highly relevant to environmental assessment. The conclusions derived from the computer-simulated curves are confirmed by experimental data.

Bacteriological Techniques↗

PubMed1985

A respirometric method for the assessment of ready biodegradability: results of a ring test.

A collaborative exercise involving twelve laboratories was organized for the European Economic Community to check the validity of an enclosed respirometric method for assessing the ready biodegradability of test chemicals, including insoluble substances. The method, based partly on the OECD-Japanese Ministry of International Trade and Industry (MITI) I method (301C) and partly on the U.K. method, allowed the use of a less restrictive, natural inoculum and a wider variety of respirometers than the original MITI I method. Eight compounds of a wide range of degradative behavior were tested over an incubation period of 28 days. The agreement between participating laboratories in the lag period before biodegradation started and in the proportions of theoretical oxygen uptake achieved was at least as good as in other ring tests; it is proposed that the method be accepted. Differences in behavior of pentaerythritol reported here and in the literature are examined and suggestions for future study are discussed.

Aniline Compounds↗

PubMed1988

Anaerobic biodegradation of polychlorinated biphenyls by bacteria from Hudson River sediments.

Anaerobic biodegradation of monochlorobiphenyls; a tetrachlorobiphenyl; Aroclor 1221, a polychlorinated biphenyl (PCB) mixture; and sediment PCBs was investigated by using mixed bacterial populations from Hudson River sediments obtained by PCB enrichment. When the bacteria were incubated with Aroclor 1221, the disappearance of congeners was in general inversely related to GC retention time and thus indirectly to the octanol/water partition coefficient. When incubated with 14C-labeled monochlorobiphenyls, 14CO2 was detected, but methane was not. Radioactivity was also found in the cell material and the aqueous fraction. 2,4,2',4'-Tetrachlorobiphenyl produced little evidence of biodegradation or reductive dechlorination. Inoculation of anaerobic sediments from the Hudson River with the mixed population produced a marked decrease in sediment PCBs, whereas uninoculated sediments were observed to have little change. This decrease was also related to the partition coefficient.

Anaerobiosis↗

PubMed1990

Headspace determination of evolved carbon dioxide in a biodegradability screening test.

A headspace method to measure the carbon dioxide evolved in a screening biodegradability test is described. Use was made of conventional serum bottles, sealed with butyl rubber septa, through which headspace samples were taken after acidification and equilibration of the test solution. For each determination a serum bottle was sacrificed. The gas samples were injected directly into the reaction chamber of a carbon analyzer. Eighteen chemicals varying in solubility and biological properties were submitted to the test. Where possible, mineralization of test compounds was monitored through dissolved organic carbon analysis in addition to CO2 analyses. The reliability of the method was verified by comparing the measured concentration of dissolved inorganic carbon of a standard sodium carbonate solution with values calculated from measured concentrations of carbon dioxide in the headspace after acidification. Results of biodegradability testing are discussed in view of the suitability of the method to poorly soluble compounds.

Biodegradation, Environmental↗

PubMed1992

A comparative study of test methods for assessment of the biodegradability of chemicals in seawater--screening tests and simulation tests.

A comparative study has been performed on test methods for assessing the biodegradability of chemicals in seawater environments. A simple shake flask die-away test with natural seawater and 14C-labeled chemicals added in microgram/liter concentrations is proposed as a "simulation" test. The analytical parameter used in this test is residual dissolved 14C activity. The performance of the simulation test has been compared with the performance of similar screening tests with dissolved organic carbon analysis and test compounds added in mg/liter concentrations to nutrient-enriched seawater. All chemicals investigated that passed the screening tests were also degradable in the simulation test and some results with simulation tests were positive; even screening tests were negative, while some compounds, including maleinhydrazide, known to be degradable in soil, remained undegraded in either type of test. Disappearance times after the ended lag time were smaller in screening tests than in simulation tests, but the rates of biodegradation cannot be meaningfully compared, as zero-order kinetics in combination with an exponentially growing population of degraders prevail in screening tests, while first-order kinetics and frequently a constant activity of degraders (cooxidation) prevail in simulation tests where the test material is a secondary substrate only. In screening tests, lag times are sometimes excessively long and highly variable. Whether the lag times could be decreased and their variability narrowed by supplementation with a cosubstrate (yeast extract) or by inoculation with seawater that had been preadapted to the test material was investigated. In most experiments such test modifications had no significant effect but in one experiment with 4-nitrophenol, inoculation with 1% preadapted seawater decreased the lag phase from greater than 35 to 9 days.

Aniline Compounds↗