Showing papers on "Glutaraldehyde published in 1998"

Feasibility study of a natural crosslinking reagent for biological tissue fixation

Abstract: Bioprostheses derived from biological tissues must be chemically modified and subsequently sterilized before they can be implanted in humans. Various crosslinking reagents, including formaldehyde, glutaraldehyde, dialdehyde starch, and epoxy compound, have been used to chemically modify biological tissues. However, these synthetic crosslinking reagents are all highly (or relatively highly) cytotoxic. It is therefore desirable to provide a crosslinking reagent suitable for use in biomedical applications that is of low cytotoxicity and that forms stable and biocompatible crosslinked products. This study evaluates the feasibility of using a naturally occurring crosslinking reagent--genipin--to chemically modify biological tissues. Genipin and its related iridoid compounds, extracted from gardenia fruits, have been used in traditional Chinese medicine for the treatments of jaundice and various inflammatory and hepatic diseases. In this feasibility study, the cytotoxicity of genipin and the crosslinking characteristics of genipin-fixed biological tissues were investigated. Fresh porcine pericardia procured from a slaughterhouse were used as raw materials. Glutaraldehyde and an epoxy compound (ethylene glycol diglycidyl ether), which has been used extensively in developing bioprostheses, were used as controls. It was found that the cytotoxicity of genipin was significantly lower than that of glutaraldehyde and the epoxy compound. The amino acid residues in the porcine pericardium that may react with genipin were lysine, hydroxylysine, and arginine. Additionally, the genipin-fixed tissue had a mechanical strength and resistance against enzymatic degradation comparable to the glutaraldehyde-fixed tissue. This suggests that genipin can form stable crosslinked products. The results of this in vitro study demonstrate that genipin is an effective crosslinking reagent for biological tissue fixation.

Polyhemoglobin-superoxide dismutase-catalase as a blood substitute with antioxidant properties

Abstract: Polyhemoglobin-superoxide dismutase-catalase is designed to function as an oxygen carrier with antioxidant properties. This is based on cross-linking hemoglobin with superoxide dismutase and catalase (PolyHb-SOD-CAT). This study describes the structural and antioxidant properties of this solution. Our studies show that superoxide dismutase and catalase retain their enzymatic activity following glutaraldehyde polymerization with 8:1 and 16:1 glutaraldehyde:hemoglobin ratio. We have analyzed the optimal SOD/CAT ratios to prevent oxidation of hemoglobin in the presence of oxygen free radicals. The circulation half-life of crosslinked hemoglobin, SOD, and catalase in Sprague-Dawley rats correlates with the degree of polymerization as determined by high-performance molecular weight gel filtration. PolyHb-SOD-CAT decreases the formation of oxygen radicals compared with PolyHb in a rat intestinal ischemia-reperfusion model.

Biocompatibility study of a biological tissue fixed with a naturally occurring crosslinking reagent

Abstract: A recognized disadvantage of the currently available chemical reagents used to fix bioprostheses is the potential toxic effects a recipient may be exposed to from residues. It is therefore desirable to provide a crosslinking reagent that is of low cytotoxicity and can form stable and biocompatible crosslinked products. To achieve this goal, a naturally occurring crosslinking reagent-genipin-was used by our group to fix biological tissues. Genipin can be obtained from its parent compound geniposide, which can be isolated from the fruits of Gardenia jasminoides ELLIS. In our previous feasibility study, it was found that the cytotoxicity of genipin is significantly lower than both glutaraldehyde and an epoxy compound. Additionally, it was shown that genipin can form stable crosslinked products. The present study further investigates the biocompatibility of a genipin-fixed porcine pericardium implanted subcutaneously in a growing rat model. The fresh, glutaraldehyde-, and epoxy-fixed counterparts were used as controls. It was noted that the inflammatory reaction of the genipin-fixed tissue was significantly less than its glutaraldehyde- and epoxy-fixed counterparts. Also, the genipin-fixed tissue has tensile strength and resistance against in vivo degradation comparable to the glutaraldehyde-fixed tissue. Additionally, the calcium content of the genipin-fixed tissue measured throughout the entire course of the study was minimal. Nevertheless, further study in calcification for the genipin-fixed tissue should be conducted in a blood-contact environment. The results obtained in this subcutaneous study indicate that genipin is a promising crosslinking reagent for biological tissue fixation. However, further durability testing in vitro and in vivo are needed to determine the relative functional merits of this new crosslinker.

Characterization of sodium alginate membrane crosslinked with glutaraldehyde in pervaporation separation

Abstract: Dense sodium alginate (SA) membranes crosslinked with glutaraldehyde (GA) have been prepared by the solution method, wherein a nonsolvent of SA (acetone) was used in a reaction solution instead of an aqueous salt solution. Through infrared radation, X-ray diffractometry, and the swelling measurement, the crosslinking reaction between the hydroxyl groups of SA and the aldehyde groups of GA was characterized. To investigate the selective sorption behavior of the crosslinked SA membranes, swelling measurements of the membranes in ethanol-water mixtures of 70–90 wt % ethanol contents were conducted by equipment that was able to measure precisely the concentration and amount of the liquid absorbed in the membranes. It was observed that the crosslinking could reduce both the solubility of water in the resulting membrane and the permselectivity of the membrane toward water at the expense of membrane stability against water. The pervaporation separation of a ethanol-water mixture was conducted with the membranes prepared at different GA contents in the reaction solution. When the membrane was prepared at a higher GA content, both flux and separation factor to water were found to be reduced, thus resulting from the more crosslinking structure in it. The pervaporation separations of ethanol-water mixtures were also performed at different feed compositions and temperatures ranging from 40 to 80°C. A decline in the pervaporative performance was observed due to the relaxation of polymeric chains taking place during pervaporation, depending on operating temperature and feed composition. The relaxational phenomena were also elucidated through an analysis on experimental data of the membrane performance measured by repeating the operation in the given temperature range. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 209–219, 1998

Cleaning and disinfection of equipment for gastrointestinal endoscopy. Report of a Working Party of the British Society of Gastroenterology Endoscopy Committee.

Abstract: Two per cent glutaraldehyde is the most commonly used disinfectant in endoscopy units within the UK. Unfortunately adverse reactions to glutaraldehyde are common among endoscopy personnel and the Health and Safety Commission has recommended substantial reductions in atmospheric levels of glutaraldehyde in order to comply with the Control of Substances Hazardous to Health Regulations, 1994. The Working Party addressed ways of eliminating or minimising exposure to glutaraldehyde in endoscopy units by reviewing alternative disinfectants and the use of automated washer/disinfectors. Alternatives to glutaraldehyde must be at least as microbicidal as glutaraldehyde, non-irritating and compatible with endoscope components and decontamination equipment. Peracetic acid is a highly effective disinfectant and may be a suitable alternative to glutaraldehyde. Peracetic acid has a vinegary-like odour and is claimed to be less irritating than glutaraldehyde. Experience with this agent remains relatively limited and the Working Party recommends that peracetic acid should be used in sealed or exhaust ventilated facilities until further experience is obtained. It is considerably more expensive than glutaraldehyde, is less stable and large volumes have to be stored. It causes cosmetic (but not functional) damage to endoscopes and is not compatible with some washer/ disinfectors. Chlorine dioxide is a powerful oxidising agent and highly effective as a disinfectant. Once activated it must be stored in sealed containers with little head space. Fumes cause irritation and sealed or exhaust ventilated facilities are necessary. The agent may damage some metallic and polymer components of endoscopes and automated washer/disinfectors and compatibility should be established with equipment manufacturers before the agent is used. Other disinfectants such as peroxygen compounds and quaternary ammonium derivatives are less suitable because of unsatisfactory mycobactericidal and/or virucidal activity, or incompatibility with endoscopes and automated washer/disinfectors. Alcohol is effective but, on prolonged contact, is damaging to lens cements. It is also flammable and therefore unsuitable for use in large quantities in automated systems. Superoxidised water (Sterilox) is an electrochemical solution (anolyte) containing a mixture of radicals with strong oxidising properties. It is highly microbicidal when freshly generated, provided items are thoroughly clean and strict generation criteria are met--that is, current, pH, redox potential. It seems to be safe for users and provided field trials substantiate laboratory efficacy tests, and the agent is non-damaging, it too may become an alternative to glutaraldehyde. When 2% glutaraldehyde is used for manual and automated disinfection, 10 minutes' immersion is recommended for endoscopes before the session and between patients. This will destroy vegetative bacteria and viruses (including hepatitis B virus (HBV) and HIV). A five minute contact period is recommended for 0.35% peracetic acid and for chlorine dioxide (1100 ppm av ClO2), but if immersed for 10 minutes sporicidal activity will also be achieved. At the end of each session 20 minutes' immersion in glutaraldehyde or five minutes in peracetic acid or chlorine dioxide is recommended. Microbiological studies show that 20 minutes of exposure to 2% glutaraldehyde destroys most organisms, including Mycobacterium tuberculosis. The Working Party concludes therefore that immersion of the endoscope in 2% glutaraldehyde for 20 minutes is sufficient for endoscopy involving patients with AIDS and other immunodeficiency states or pulmonary tuberculosis. Similarly, 20 minutes' immersion is recommended at the start of the list and between cases for endoscopic retrograde cholangiopancreatography (ERCP) when high level disinfection is required. Cleaning and disinfection of endoscopes should be undertaken by trained staff in a dedicated room. Thorough cleaning with detergent

Prevention of calcification of glutaraldehyde-crosslinked porcine aortic cusps by ethanol preincubation: mechanistic studies of protein structure and water-biomaterial relationships.

Abstract: Clinical usage of bioprosthetic heart valves (BPHVs) fabricated from glutaraldehyde-pretreated porcine aortic valves is restricted due to calcification-related failure. We previously reported a highly efficacious ethanol pretreatment of BPHVs for the prevention of cuspal calcification. The aim of the present study is to extend our understanding of the material changes brought about by ethanol and the relationship of these material effects to the ethanol pretreatment anticalcification mechanism. Glutaraldehyde-crosslinked porcine aortic valve cusps (control and ethanol-pretreated) were studied for the effects of ethanol on tissue water content and for spin-lattice relaxation times (T1) using solid state proton NMR. Cusp samples were studied for protein conformational changes due to ethanol by ATR-FTIR spectroscopy. The changes in cuspal tissue-cholesterol (in vitro) interactions also were studied. Cusp material stability was assessed in terms of residual glutaraldehyde content and collagenase degradation. Water content of the cusp samples was decreased significantly due to ethanol pretreatment. The cuspal collagen conformational changes (per infrared spectroscopy) brought about by ethanol pretreatment were persistent even after rat subdermal implantation of cusp samples for 7 days. In vitro cholesterol uptake by cusps was greatly reduced as a result of ethanol pretreatment. Ethanol pretreatment of cusps also resulted in increased resistance to collagenase digestion. Cuspal glutaraldehyde content was not changed by ethanol pretreatment. We conclude that ethanol pretreatment of bioprosthetic heart valve cusps causes multi-component effects on the tissue/material and macromolecular characteristics, which partly may explain the ethanol-pretreatment anticalcification mechanism.

Influence of physicochemical and structural characteristics of chitosan flakes on molybdate sorption

Abstract: This study investigates the effect of deacetylation degree and molecular weight of chitosan on molybdate sorption on both raw and glutaraldehyde crosslinked samples. It appears that the physicochemical parameters affect the crystallinity of the samples: a high crystallinity reduces the accessibility of both water and metal ions to the amine binding sites. Both equilibrium and kinetic performances are thus influenced. The crosslinking by glutaraldehyde decreases sorption performances for large size particles while it does not influence sorption for the smallest. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 571–580, 1998

Non-calcific biomaterial by glutaraldehyde followed by oxidative fixation

Abstract: This invention relates to tanning biomaterial to obtain calcification resistant biomaterial with good mechanical properties for bioprosthetic applications. The biomaterial of the invention is obtained by tanning tissue by any method except by oxidation, and then at a later time tanning the tissue by any of the oxidative fixation methods. The process was shown to provide beneficial results with the most frequently used fixation process, which involves fixating tissue with glutaraldehyde. Tissue fixated with glutaraldehyde and then by oxidative fixation has a lower calcification potential than does glutaraldehyde-only tanned tissue and has mechanical properties more similar to glutaraldehyde tanned tissue than to oxidative stabilized tissue. In particular, a process is described where tissue is fixed with glutaraldehyde followed by photoxidation.

Optimization of protease immobilization by covalent binding using glutaraldehyde

Abstract: Immobilization of a protease, Flavourzyme, by covalent binding on various carriers was investigated. Lewatit R258-K, activated with glutaraldehyde, was selected among the tested carriers, because of the highest immobilized enzyme activity. The optimization of activation and immobilization conditions was performed to obtain high recovery yield. The activity recovery decreased with increasing carrier loading over an optimal value, indicating the inactivation of enzymes by their reaction with uncoupled aldehyde groups of carriers. The buffer concentrations for carrier activation and enzyme immobilization were optimally selected as 500 and 50 mM, respectively. With increasing enzyme loading, the immobilized enzyme activity increased, but activity recovery decreased. Immobilization with a highly concentrated enzyme solution was advantageous for both the immobilized enzyme activity and activity recovery. Consequently, the optimum enzyme and carrier loadings for the immobilization of Flavourzyme were determined as 1.8 mg enzyme/mL and 0.6 g resin/mL, respectively.

Immobilization of glucose oxidase on poly‐(L‐lysine)‐modified polycarbonate membrane

Abstract: The paper describes the immobilization of glucose oxidase on a polycarbonate membrane modified by a urethane coupling with poly-(L-lysine) and activated with glutaraldehyde The enzymic properties of the immobilized enzyme were investigated and compared with the those of native glucose oxidase The thermal stability and pH stability of the immobilized glucose oxidase were greater than those of the native enzyme The membrane was applied as a glucose sensor

Detoxification process for glutaraldehyde-treated bovine pericardium: biological, chemical and mechanical characterization

Abstract: Background and aims of the study Glutaraldehyde cross-linked bovine pericardium was post-treated with homocysteic acid in order to bond unreacted glutaraldehyde groups, and preserved in aldehyde-free solution to reduce the toxicity and calcification potential of the tanned tissue. The study aim was to verify the efficacy and preservation of chemical and mechanical properties of pericardial tissue treated in this way. Methods Detoxification efficacy was tested by measuring free aldehyde groups and by in vitro cultivation of human endothelial cells on pericardial samples. Material stability tests included mechanical characterization, shrink temperature measurement, pronase digestion resistance and amino acid analysis after acid hydrolysis. The effect of treatment on fatigue resistance was evaluated by monitoring changes in permeability and compliance caused by 15 x 10(6) cycles of pulsatile stress. Results Detoxified samples showed negligible glutaraldehyde residues and significantly improved endothelial cell proliferation compared with conventionally treated samples. Chemical and mechanical properties were similar in detoxified and glutaraldehyde-treated samples. Tissue fatigue behavior was not modified by homocysteic acid treatment. Conclusion Homocysteic acid treatment effectively reduces toxicity but does not affect the stability of glutaraldehyde cross-linked pericardium.

Preparation and evaluation of microspheres prepared from whey protein isolate

Abstract: Whey protein (WPI) microspheres were successfully produced containing hydrochlorothiazide, eosin, patent blue violet and sodium salicylate using a w/o emulsification method with glutaraldehyde cross linking. The release of these compounds from WPI microspheres occurred rapidly, with at least 70% of the incorporated material released for all systems within the first 20min. Release of microsphere payload was essentially complete within 1 h. The degree of glutaraldehyde cross-linking was found to have no effect on the release profile for durations of cross-linking up to 24 h. Of a range of release equations examined, the experimental release data was best described by a biexponential equation and this agrees with the work of Tomlinson et al. (1984) for the release of drugs from albumin microspheres. Swelling of the microsphere systems was examined as this may contribute to the rapid release of drug from these systems.

Occupational allergy to aldehydes in health care workers. Clinical observations. Experiments.

Abstract: The incidence of allergy to aldehydes (formaldehyde, glutaraldehyde, glyoxal) was examined in 280 health care workers suffering from skin lesions. Allergy was diagnosed in 64 (22.8%) patients. The majority of them (85.9%) were sensitive only to 1 aldehyde. Formaldehyde caused allergy slightly more frequently (13.9%) than glutaraldehyde (12.4%). Only 5 (1.9%) patients were sensitive to glyoxal. The irritant effect of aldehydes to the rabbit eye and skin was tested by the Draize and OECD methods. Formaldehyde and glutaraldehyde showed stronger irritant effect than glyoxal. The sensitizing activity of aldehydes was also confirmed in guinea pigs (using the Maximization Test and the OECD methods). Formaldehyde showed the strongest and most persistent reactions. Significantly higher eosinophil and basophil counts were found in the blood samples of the sensitized guinea pigs. Cytotoxicity of glutaraldehyde and glyoxal was tested on mouse 3T3-L1 fibroblasts by the Neutral Red Uptake and MTT Reduction Assay. It was shown that both aldehydes were cytotoxic, and that the cytotoxic effect of glutaraldehyde was stronger than that of glyoxal.

Detoxified glutaraldehyde cross-linked pericardium: tissue preservation and mineralization mitigation in a subcutaneous rat model.

Abstract: Background and aim of the study Glutaraldehyde is considered a promoter of calcification by the action of toxic aldehyde group residuals from cross-linking. Post-fixation treatment with homocysteic acid (HA), besides bonding aldehyde groups and neutralizing toxicity, should enhance biocompatibility due to the strongly electronegative sulfonic group. The aim of this investigation was to evaluate HA efficacy on tissue preservation and dystrophic calcification mitigation in glutaraldehyde cross-linked bovine pericardium (BP) using a subcutaneous rat model. Methods Four samples of BP, two with glutaraldehyde-HA and two with glutaraldehyde treatment, were implanted in each of 24 male Sprague-Dawley rats. Three rats were killed at 14 days, eight at 28 days, eight at 56 days and five at 84 days. Unimplanted glutaraldehyde-HA- and glutaraldehyde-treated samples served as controls. All samples were studied by gross examination, mammography, light transmission and scanning electron microscopy, and atomic absorption spectroscopy. The nature of mineralization was investigated by coupling techniques of scanning electron microscopy, electron microprobe analysis and X-ray powder diffraction. Results No histological and ultrastructural differences were found between glutaraldehyde-HA- and glutaraldehyde-treated BP, whether implanted or unimplanted. In both groups, calcification progressed with time, but significantly less after glutaraldehyde-HA treatment than after glutaraldehyde alone and at all time intervals (14.63 +/- 21.34 versus 43.17 +/- 15.99 at 28 days, p = 0.003; 56.42 +/- 40.20 versus 90.59 +/- 32.90 at 56 days, p = 0.008; 91.68 +/- 67.68 versus 156.23 +/- 17.85 at 84 days, p = 0.01). Differences were evident by mammography and histology (von Kossa stain). Electron microprobe analysis in both groups showed the composition of calcified nuclei to be calcium phosphate, stoichiometrically close to apatite (Ca5(PO4)3(OH)). The occurrence of crystallized apatite was supported by X-ray powder diffraction findings, the amount of crystallized apatite being higher in glutaraldehyde-treated samples. Conclusions Post-fixation treatment with HA preserves BP structural properties and significantly mitigates mineralization of long-term subcutaneous implants.

Glutaraldehyde-fixed bioprostheses

Abstract: Methods for treating glutaraldehyde-fixed collagenous tissues to mitigate there propensity for subsequent calcification and to improve durability. Collagenous tissues which have been harvested and cross-linked by glutaraldehyde are exposed to a carboxyl activating agent to convert the free carboxyl (COOH) groups of the collagen molecules to activated carboxyl moieties (e.g., o-acylisourea). Thereafter, the collagenous tissue is exposed to a compound capable of reacting with the activated carboxyl moieties (e.g., o-acylisourea) to form non-carboxyl side groups. Monofunctional and multifunctional amines are examples of compounds which may be utilized to react with the activated carboxyl moieties to form such non-carboxyl side groups. Thereafter, the collagenous tissue is again exposed to glutaraldehyde. If the non-carboxyl side groups have functional amino groups (NH 2 ), such additional exposure to glutaraldehyde will result in additional glutaraldehyde cross-linking of the collagen molecules and resultant improvement of durability.

Poly(EGDMA/AAm) copolymer beads: a novel carrier for enzyme immobilization

Abstract: In this study, we evaluated a new carrier (i.e., the poly(EGDMA/AAm copolymer beads) for enzyme immobilization. Two different types of copolymer beads with different swellabilities with an average diameter of about 200 μm were produced by suspension copolymerization of the respective comonomers, with or without using toluene. BPO and PVA were used as the initiator and the stabilizer. The copolymer beads produced without toluene were nonporous and nonswellable. While porous and swellable (swelling ratio: 14.28%) beads were obtained in which toluene was used as the diluent. Both type of beads were modified by using glutaraldehyde and hexamethylene diamine as the coupling agent and the spacer-arm, respectively. Immobilization of a model enzyme (i.e., glucose oxidase) was studied to show the feasibility of using these beads as an enzyme carrier. More enzyme, but with very low activities, were immobilized on the beads with relatively lower swellabilities. While much higher activities were observed on the beads with relatively higher swellabilities prepared with toluene. Incorporation of the spacer-arm (i.e., hexamethylene diamine) increased the apparent activity of the immobilized enzyme. The optimal glutaraldehyde concentrations to achieve the highest immobilized enzyme activities for the swellable and nonswellable beads were 23.1 and 4.8% (v/v), respectively, while the optimal hexamethylene diamine concentrations to achieve the highest immobilized enzyme activities for these beads were 0.10 and 0.16 mmol/ml, respectively.

Laboratory and Hospital Evaluation of Four Personal Monitoring Methods for Glutaraldehyde in Ambient Air

Abstract: Four industrial hygiene monitoring methods were studied in the laboratory and in a hospital to evaluate their effectiveness in measuring glutaraldehyde concentrations in ambient air. The sampling devices evaluated included a silica gel tube, a direct reading handheld glutaraldehyde meter, a DNPH- (2,4-dinitrophenylhydrazine) impregnated passive diffusion badge, and a DNPH-impregnated filter cassette. The accuracy and precision of the different methods were determined in the laboratory. The methods were evaluated using dynamically generated glutaraldehyde air concentrations over the range of 0.05–0.4 ppm. The badge, silica gel tube, and filter cassette methods were found to be accurate under controlled laboratory conditions. The handheld meter did not respond to the glutaraldehyde test atmospheres. The methods were compared in a hospital environment. During the hospital study the performance of the handheld meter could not be demonstrated because the concentrations of glutaraldehyde were below or only slig...

The Chemical Protecting Group Concept Applied in Crosslinking of Natural Tissues with Glutaraldehyde Acetals

Abstract: This work describes the results of the controlled crosslinking of collagen matrices by glutaraldehyde based on a double protection strategy, glutaraldehyde acetals and lysine protonation due to the acidic conditions of acetal formation. Materials crosslinked by this approach were characterized by thermal stability comparable to those obtained by conventional procedures with mechanical properties expected for bioprosthesis manufacture and with a higher stability toward collagenase hydrolysis. The integrity of the microfibrillar structure was confirmed by optical and scanning electronic microscopy. The results indicate that the glutaraldehyde acetals procedure may be of potential use for the crosslinking of bovine pericardium used in the manufacture of bioprosthetic devices. Advantages may be related to the production of materials with homogeneous crosslinking distributions, associated with better definition in the nature of the chemical link that they introduce, due to a better distribution of glutaraldehyde within the tissue matrix before the crosslinking reaction is allowed to occur. As a result, materials with improved biological and mechanical properties are expected.