Showing papers on "Glutaraldehyde published in 1996"

Comparative sporicidal effects of liquid chemical agents

Abstract: We compared the effectiveness of glutaraldehyde, formaldehyde, hydrogen peroxide, peracetic acid, cupric ascorbate (plus a sublethal amount of hydrogen peroxide), sodium hypochlorite, and phenol to inactivate Bacillus subtilis spores under various conditions. Each chemical agent was distinctly affected by pH, storage time after activation, dilution, and temperature. Only three of the preparations (hypochlorite, peracetic acid, and cupric ascorbate) studied here inactivated more than 99.9% of the spore load after a 30-min incubation at 20 degrees C at concentrations generally used to decontaminate medical devices. Under similar conditions, glutaraldehyde inactivated approximately 90%, and hydrogen peroxide, formaldehyde, and phenol produced little killing of spores in suspension. By kinetic analysis at different temperatures, we calculated the rate of spore inactivation (k) and the activation energy of spore killing (delta E) for each chemical agent. Rates of spore inactivation had a similar delta E value of approximately 20 kcal/mol (ca.83.68 kJ/mol) for every substance tested. The variation among k values allowed a quantitative comparison of liquid germicidal agents.

Crosslinking of tissue-derived biomaterials in 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC)

Abstract: In contrast to bifunctional reagents such as glutaraldehyde or polyfunctional reagents such as polyepoxides, carbodiimides belong to the class of zero-length crosslinkers which modify amino acid side-groups to permit crosslink formation, but do not remain as part of that linkage. The authors have compared the effects of 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) and glutaraldehyde (the de facto industrial standard crosslinker) on the hydrothermal, biochemical, and uniaxial mechanical properties of bovine pericardium. EDC crosslinking was optimized for maximum increase in collagen denaturation temperature using variables of pH, concentration, and ratio of EDC to N-hydroxysuccinimide (NHS): a reagent for formation of activated esters. EDC and glutaraldehyde crosslinked materials were subjected to hydrothermal denaturation tests, biochemical degradation by enzymes (collagenase, trypsin) and CNBr, amino acid analysis for unreacted lysine, and to high strain rate mechanical tests including: large deformation stress-strain studies (0.1 to 10 Hz), stress relaxation experiments (loading time 0.1 s) and small deformation forced vibration (1 and 10 Hz). A protocol for EDC crosslinking was developed which used 1.15% EDC (2:1 EDC:NHS) at pH 5.5 for 24 h. The increase in denaturation temperature for EDC (from 69.7±1.2°C to 86.0±0.3°C) was equivalent to that produced by glutaraldehyde (85.3±0.4°C). Both treatments equivalently increased resistance to collagenase and CNBr degradation; however, after denaturation, the EDC-treated tissue was slightly more resistant to collagenase, and markedly more resistant to trypsin. EDC-treated materials were more extensible and more elastic than glutaraldehyde-treated materials. Despite the differences in crosslinking mechanism, EDC and glutaraldehyde-treated materials are very similar. Subtle but intriguing differences in biochemical structure remain to be investigated.

Regioselective immobilization of short oligonucleotides to acrylic copolymer gels.

Abstract: Four types of polyacrylamide or polydimethyl-acrylamide gels for regioselective (by immobilization at the 3' end) of short oligonucleotides have been designed for use in manufacturing oligonucleotide microchips. Two of these supports contain amino or aldehyde groups in the gel, allowing coupling with oligonucleotides bearing aldehyde or amino groups, respectively, in the presence of a reducing agent. The aldehyde gel support showed a higher immobilization efficiency relative to the amino gel. Of all reducing agents tested, the best results were obtained with a pyridine-borane complex. The other supports are based on an acrylamide gel activated with glutaraldehyde or a hydroxyalkyl-functionalized gel treated with mesyl chloride. The use of dimethylacrylamide instead of acrylamide allows subsequent gel modifications in organic solvents. All the immobilization methods are easy and simple to perform, give high and reproducible yields, allow long durations of storage of the activated support, and provide high stability of attachment and low non-specific binding. Although these gel supports have been developed for preparing oligonucleotide microchips, they may be used for other purposes as well.

Amide cross-linking: an alternative to glutaraldehyde fixation.

Abstract: Background and aims of the study A new fixation method for bioprosthetic tissues is being developed, which does not utilize the standard glutaraldehyde treatment. This method, referred to as Ultifix, uses a coupler and a coupling enhancer with or without one or more coupling agents. It fixes the tissue by linking the amine and the carboxyl moieties through amide bonds either directly, or indirectly when coupling agents form bridges. The amide bonds thus formed are more stable than the Schiff-base bonds formed by glutaraldehyde. All compounds used during the fixation process and their by-products are water-soluble, and are easily removed by washing. In addition, the by-products are not toxic, as opposed to glutaraldehyde, which induces toxic reactions after implantation. The tests described in the manuscript were specifically aimed at evaluating the cross-linking efficacy of the process on heart valve tissues, as well as their resistance to calcification in the rat model. Methods Porcine aortic roots and porcine pericardium were fixed using the coupling agents 1,6-hexane diamine (DIA) and suberic acid (SUA) in the presence of the coupler 1-ethyl-3(-3 dimethyl aminopropyl) carbodiimide hydrochloride (EDC) and the coupling enhancer N-hydroxysulfosuccinimide (sulfo-NHS). The tissues were then evaluated for their resistance to thermal denaturation, to enzymatic digestion, and to calcification when implanted subdermally in rats for two, four, eight and 16 weeks. Results The results demonstrate that the cusps and the wall of porcine aortic roots, and porcine pericardium, are as well stabilized and as cross-linked by Ultifix as they are by the standard glutaraldehyde method. In addition, the cusps of the porcine aortic root and the porcine pericardium, but not the wall of the porcine aortic root, calcify minimally and significantly less when implanted subdermally for up to 16 weeks in three week old rats than the control material fixed with glutaraldehyde. Conclusion The Ultifix process of cross-linking bioprosthetic heart valves may thus be a good alternative to the standard glutaraldehyde process of fixation, with increased durability and without toxic effects.

5-Fluorouracil-loaded chitosan microspheres: Preparation and release characteristics

Abstract: Cross-linked chitosan microspheres containing 5-Fluorouracil (S-FU) were prepared. Variables believed to be important for microsphere properties were examined; these included: drug and chitosan concentrations, cross-linking process, the type of oil, stirring rate and also additives. Initial 5-FU concentration, the type and concentration of chitosan, the viscosity of oil phase and glutaraldehyde concentration affected drug release from chitosan microspheres. 5-FU release from cross-linked chitosan microspheres is characterized by an initial rapid release of drug. Addition of substances such as alginic acid, chitin, agar, sodium caprylate and stearic acid changed the release properties of 5-FU microspheres.

Shrinkage temperature versus protein extraction as a measure of stabilization of photooxidized tissue.

Abstract: A rise in thermal denaturation temperature has been utilized as an indication of stabilization of collagen-containing materials such as pericardial tissue and porcine heart-valve leaflets following treatment with glutaraldehyde, Denacol™, or other chemical agents. In contrast, stabilization of bovine pericardial tissue by dye-mediated photooxidation does not result in a significant rise in shrinkage temperature comparable with these treated materials. It was therefore hypothesized that a rise in shrinkage temperature is not a necessary indication for tissue stabilization. A sensitive protein extraction assay has been developed which can be used to monitor the stabilization of pericardial tissue by a variety of treatment methods, including photooxidation. A reduction in extractable protein, as analyzed by polyacrylamide gel electrophoresis, is noted for pericardial tissue treated with photooxidation, glutaraldehyde, or Denacol™. Loss of extractable protein, as a function of treatment time, correlates well with a significant rise in shrinkage temperature for pericardium treated with glutaraldehyde or Denacol™ but not with photooxidation. This difference is attributed to the stabilization processes of glutaraldehyde and Denacol™, which involve extensive crosslinking and polymer formation within and in addition to the native pericardial matrix, leading to a rise in matrix complexity and thermal stability. In contrast, photooxidation is a catalytic process involving modification and crosslink formation within existing matrix components, resulting in a material with little added matrix complexity. © 1996 John Wiley & Sons, Inc.

Equilibrium swelling properties of a novel ethylenediaminetetraacetic dianhydride (EDTAD)‐modified soy protein hydrogel

Abstract: A novel pH and ionic strength-sensitive protein-based hydrogel was synthesized via cross-linking ethylenediaminetetraacetic dianhydride-modified soy protein isolate (EDTAD–SPI) with glutaraldehyde. Incorporation of ionizable carboxyl groups into soy proteins increased the net negative charge of the protein and caused extensive unfolding of the protein structure. The EDTAD–SPI hydrogel was capable of imbibing 80-300 g water per g dry gel after centrifuging at 214g, depending on the extent of modification, protein structure, crosslinking density, protein concentration during the crosslinking step, gel particle size, and environ-mental conditions, such as temperature, pH, and ionic strength. The protein concentration used during the crosslinking step was found to be the most important factor affecting the water uptake of the gel. The lower the protein concentration, the higher was the water uptake at 214g. The hydrogel was highly sensitive to pH and exhibited reversible swelling when sequentially exposed to water and 0.15M NaCl. © 1996 John Wiley & Sons, Inc.

Solvent environment modulates effects of glutaraldehyde crosslinking on tissue-derived biomaterials.

Abstract: Bioprosthetic materials utilized in the construction of heart valves and vascular grafts possess limited performance and viability in vivo This is due (in part) to the failure of these materials to mimic the mechanical properties of the host tissue they replace If bioprosthetic materials could be engineered to meet the mechanical performance required in vivo, the functional lifetime of implants would be increased In this study, glutaraldehyde/solvent solutions of decreasing dielectric constant (polarity) were utilized to modify the properties of crosslinked collagen in whole bovine pericardial tissue Solvents included phosphate buffer, methanol, 95% (w/w) ethanol, n-propanol, and n-butanol Exogenous crosslinking was verified in collagen by thermal denaturation tests and amino acid analyses Tensile mechanical behavior of collagenous pericardial samples was found to depend upon the dielectric constant (polarity) of the glutaraldehyde/solvent solutions employed; however, treatment in the solvents alone had little, if any, effect As the dielectric constant of the solvents decreased, three mechanical properties were systematically altered: plastic strain fell from a mean of 89 +/- 15% (buffer) to 16 +/- 04% (n-butanol); strain at fracture increased from 322 +/- 26% (buffer) to 556 +/- 46% (n-butanol); and percent stress remaining after 1000-s stress relaxation from an 80-g initial load fell from 863 +/- 11% (buffer) to 769 +/- 10% (n-butanol) Crosslinking using a glutaraldehyde/n-butanol solution produced materials with tensile mechanical behavior that was very close to that of fresh tissue; however, the flexural properties of the treated tissue were different from those of fresh tissue This decoupling of the flexural and tensile mechanical behaviors of crosslinked bioprosthetic materials is unique to this form of treatment The observed phenomena may be the results of conformational changes in collagen facilitated by polar/nonpolar interactions with the solvent that are "locked in" by the action of glutaraldehyde This technique may aid in the "customized" design of mechanical properties in tissue-derived biomaterials

Chemical crosslinking of hydroxypropyl cellulose and chitosan blends

Abstract: Two liquid crystal forming polysaccharides, hydroxypropyl cellulose and chitosan, were blended in aqueous acetic acid solutions and were crosslinked with dialdehydes (glyoxal and glutaraldehyde) as crosslinker and hydrochloric acid as catalyzer The crosslinkability, morphology, solubility, and tensile properties of the cross linked blend films are determined and the dependence of those properties on the blend composition and on crosslinker species are discussed The crosslinked blend films cast from the aqueous acetic acid solutions were amorphous The solubility, Young's modulus, and tensile strength of the crosslinked blend films greatly depended on blend composition; those properties appeared to exhibit a maximum and a minimum around given blend compositions The solubility for the crosslinked blend film cast from glyoxal system was greater than that from glutaraldehyde one © 1996 John Wiley & Sons, Inc

L-DOPA production from tyrosinase immobilized on nylon 6,6.

Abstract: The production of L-DOPA immobilized on chemically modified nylon 6,6 membranes was studied in a batch reactor. Tyrosinase was immobilized on nylon using glutaraldehyde as a crosslinking agent. The effects of membrane pore size and glutaraldehyde concentration upon enzyme uptake and L-DOPA production were investigated. Enzyme uptake was unaffected by glutaraldehyde concentration; approximately 70% uptake was observed when 25% w/v (group 1), 5% (group 2), and 3% (group 3) glutaraldehyde were used, indicating that glutaraldehyde was in excess. Similarly, uptake was the same for membranes with 0.20 and 10 μm pore sizes. Membranes produced using different levels of glutaraldehyde exhibited dramatically different capacities for L-DOPA production, despite the fact that enzyme uptake was equivalent. Membranes from groups 2 and 3 (5% and 3% glutaraldehyde) produced L-DOPA at a rate of 1.70 mg L−1 h−1 over 170 h in a 500-mL batch reactor. However, no free L-DOPA was detected when group 1 membranes were used. Experimental evidence suggests that L-DOPA was produced, but remained bound to these membranes via excess glutaraldehyde left over from the immobilization process. Membrane pore size also effected L-DOPA production; less production was observed when 10-μm membranes were used, despite equivalent enzyme uptake. The observed difference in production may be due to differences in the pore density on the two types of membranes which could affect the access of the substrate to the immobilized enzyme. The results of these studies indicate that tyrosinase can be effectively immobilized on nylon 6,6. L-DOPA production was optimal when 0.20-μm-pore-size membranes were activated with 3–5% glutaraldehyde. Stability studies indicated a 20% reduction in activity over 14 days when the immobilized enzyme was used under turnover conditions. © 1996 John Wiley & Sons, Inc.

The Effect of Glutaraldehyde Adulteration of Urine Specimens on Syva EMIT II Drugs-of-Abuse Assays

Abstract: The effect of glutaraldehyde (the active component of "UrinAid") on Syva EMIT II drugs-of-abuse screening assays was studied. It was found that, dependent on the assay involved, concentrations of between 0.75 and 2.00% (v/v) of glutaraldehyde in urine could give rise to false-negative screening results. A simple method for identifying urine specimens that have been adulterated with glutaraldehyde, based on final absorbance rate readings (dA/min), is proposed.

Bioartificial materials based on collagen: 1. Collagen cross-linking with gaseous glutaraldehyde

Abstract: The effect of exposure time of thin films of soluble collagen to glutaraldehyde (GTA) vapour was studied at 37 degrees C, and was evaluated by examining the thermal and biological stability and the swelling ratio. It was found that the collagen films treated with GTA vapour for 18 h showed the highest denaturation temperature, the lowest swelling ratio, and an enhanced proteolytic stability. This study shows that soluble collagen can be effectively cross-linked with GTA vapour and that the degree of cross-linking can be controlled by varying the exposure time.

A new method for the controlled immobilization of enzyme in inorganic gels (laponite) for amperometric glucose biosensing

Abstract: The feasibility of an amperometric glucose biosensor based on immobilization of glucose oxidase (GOD) in inorganic gels (laponite) is investigated. The gels modified with enzyme were deposited onto platinum electrodes and then were exposed to glutaraldehyde vapor. The effects of different parameters (glutaraldehyde crosslinking and time of drying) on the performances of the biosensor have been studied. For optimum conditions, remarkably good characteristics were obtained: larger dynamic range (0.1–4 mM of glucose), higher i max , higher sensitivity (threefold better than this obtained through immobilization of enzymes in laponite films). The main advantage of the biosensor reported here is its long stability. The biosensor was kept for several weeks in a buffer solution at 4°C. About 450 measurements were done without any loss of the linearity in the range (0.1–4 mM). The possibility of an increase in the amount of enzyme in the biofilm which has been demonstrated, allows us to obtain more sensitive devices.

Factors influencing the loss of bacteria in preserved seawater samples

Abstract: Several time course storage experiments with preserved seawater samples were conducted to study the loss of bacterial cells as a function of storage time The number of bacteria decreased by 24 to 50'% within 7 to 29 d i n samples preserved with 2.5";* glutaraldehyde [final conc.). A comparison between epifluorescence and electron microscope counts showed that the decrease was not due to filtration artefacts. Only 0.4 to 0.6% of the bacterial cells were found to be attached to the walls of the sample containers after 1 yr of storage. There was no positive correlation between the frequency of virus-infected cells at the start of the storage experiments and the loss of bacteria as a function of storage time. Numbers of bacteria declined by only 5 % the first 9 d in samples preserved in glutaraldehyde and stored at -20°C. By adding phenolmethylsulfonylfluoride (PMSF), a protease inhibitor, prior to the addition of glutaraldehyde, the loss of bacterial cells only 17 to 18' over a 30 to 35 d period. Our study shows that protease activity may be a inajor cause of bacterial loss in glutaraldehyde preserved samples.

The use of biocides to control sulphate‐reducing bacteria in biofilms on mild steel surfaces

Abstract: Three different types of biocides, viz. formaldehyde (FM), glutaraldehyde (GA) and isothiozolone (ITZ) were used to control planktonic and sessile populations of two marine isolates of sulphate‐reducing bacteria (SRB). The influence of these biocides on the initial attachment of cells to mild steel surfaces, on subsequent biofilm formation and on the activity of hydrogenase enzymes within developed biofilms was evaluated. In the presence of biocides the rate and degree of colonization of mild steel by SRB depended on incubation time, bacterial isolate and the type of biocide used. Although SRB differed in their susceptibility to biocides, for all isolates the biofilm population was more resistant to the treatment than the planktonic population. GA showed highest efficiency in controlling planktonic and sessile SRB compared with the other two biocides. The activity of the enzyme hydrogenase measured in SRB biofilms varied between isolates and with the biocide treatment. No correlation was found between the...

Inactivation of glutaraldehyde by reaction with sodium bisulfite.

Abstract: The microbiocidal activity of glutaraldehyde was inactivated by reaction with sodium bisulfite via formation of a proposed glutaraldehyde-bisulfite complex. High-performance liquid chromatography (HPLC) analysis of 2% (0.2 M) alkaline glutaraldehyde indicated complete loss of glutaraldehyde at a 2.2:1 molar ratio of sodium bisulfite to glutaraldehyde. Neither 1.7% (0.17 M) sodium bisulfite alone nor the glutaraldehyde-bisulfite complex was microbiocidal when tested against Escherichia coli, Pseudomonas aeruginosa, Enterobacter aerogenes, and Polybac Polyseed BOD seed inoculum. Bacterial inhibition tests indicated that the glutaraldehyde-sodium bisulfite complex had no effect on the growth of sewage microorganisms at concentrations as high as 50-100 ppm (5 10-4-1 10-3M), with an IC50 of 230-440 ppm (2.3 10-3-4.4 10-3 M), based on glutaraldehyde concentration. A28-d closed bottle test showed a 5-d biodegradation of 48% and 51%, and a 15-d biodegradation of 57% and 63% for 3:1 and 2.2:1 bisulfite to glutaral...

Development of Drug Delivery Systems from Vegetal Proteins: Legumin Nanoparticles

Abstract: Legumin (storage protein from Pisum sativum L.) nanoparticles of about 250 nm were prepared by means of a pH-coacervation method and chemical cross-linking with glutaraldehyde. This preparative method enabled to avoid the use of organic solvents but only yielded about 27% of protein added as nanoparticles. No significant differences in size, percentage yield, and surface charge were obtained between legumin nanoparticles cross-linked with different glutaraldehyde concentrations. Legumin nanoparticles were quite stable in phosphate-buffered saline (PBS). They follow a zero-order degradation, and by increasing glutaraldehyde concentration, a longer half-life (t50) was obtained. The amount of methylene blue (MB), used as a model of hydrophilic drug, loaded was about 6.2% of the initial dye. Its release from the nanoparticles consisted of a rapid initial phase followed by a slower second period. The rates in this second phase were inversely related to the degree of cross-linking.