Showing papers on "Glutaraldehyde published in 1995"

Glutaraldehyde as a crosslinking agent for collagen-based biomaterials

Abstract: The formation of Schiff bases during crosslinking of dermal sheep collagen (DSC) with glutaraldehyde (GA), their stability and their reactivity towards GA was studied. All available free amine groups had reacted with GA to form a Schiff base within 5 min after the start of the reaction under the conditions studied (0.5% (w/w) GA). Before crosslinks are formed the hydrolysable Schiff bases initially present were stabilized by further reaction with GA molecules. An increase in shrinkage temperature (Ts) from 56°C for non-crosslinked DSC (N-DSC) to 78°C for GA crosslinked DSC (G-DSC) was achieved after crosslinking for 1 h. From the relationship between the free amine group content and the Ts during crosslinking it was concluded that higher GA concentrations and longer reaction times will result in the introduction of pendant-GA-related molecules rather than crosslinks. After 24 h crosslinking an average uptake of 3 GA molecules per reacted amine group was found. No increase in the tensile strength of the materials was observed after crosslinking, which may be a result of formation of crosslinks within the fibres rather than in between fibres. Aligning of the fibres by applying a pre-strain to the samples and subsequent crosslinking yielded materials with an increased tensile strength.

Cross-linked chitosan microspheres as carriers for prolonged delivery of macromolecular drugs

Abstract: Bovine serum albumin (BSA) and diphtheria toxoid (DT) were loaded by passive absorption from aqueous solutions into preformed glutaraldehyde cross-linked chitosan microspheres. In vitro release of BSA under sink conditions at 37 degrees C showed that even though there was a large burst effect, there was a more or less steady increase with time thereafter for several days. Coating the BSA-loaded particles with paraffin oil or with a polymer, such as polylactic acid, modulated drug release. After the initial burst from PLA coated particles, the release rate increased with time for nearly 2 months. Preliminary immunogenicity studies on Wistar rats using DT loaded chitosan spheres showed that the antibody titres were fairly constant over a 5-month period, although very low compared to DT given on alum as control. Histological studies of placebo microspheres intramuscularly injected into rats demonstrated their tissue compatibility. Biodegradation was not complete in 6 months demonstrating the potential of cross-linked chitosan spheres as a long-acting drug delivery vehicle. The study demonstrated the possibility of incorporating biological macromolecules which are very sensitive to organic solvents, pH, temperature, ultrasound, etc. by a passive absorption technique to degradable biopolymer matrices thereby preserving their biological integrity. It is also shown that drugs passively absorbed into such matrices by taking advantage of their swelling behaviour need not necessarily be released completely in the initial 'burst' and a sustained release may be possible for macromolecules thus incorporated.

Biodegradable Packaging Made from Cottonseed Flour: Formation and Improvement by Chemical Treatments with Gossypol, Formaldehyde, and Glutaraldehyde

Abstract: Un procede de preparation de films proteiques et lipoproteiques a partir de farine de graines de coton avec ou sans gossypol est decrit. Des modifications chimiques des proteines des graines de coton avec le gossypol, le formaldehyde et le glutaraldehyde sont effectuees pour augmenter la force de rupture et diminuer la solubilite des films dans une optique d'emballage biodegradable. Des resultats prometteurs ont ete obtenus avec la farine de varietes de coton glandless. Le formaldehyde et le glutaraldehyde se sont reveles efficaces. Le gossypol peut egalement etre un agent utile

The effect of glutaraldehyde and microwave disinfection on some properties of acrylic denture resin.

Abstract: This study evaluated the effect of disinfection methods on the dimensional stability, flexural properties, and microhardness of a heat-polymerized denture acrylic resin A 1- and 12-hour immersion period in 2% alkaline glutaraldehyde, and 3- and 15-minutes exposure to microwaves were employed as disinfection or sterilization procedures Storage in water for 1 and 12 hours were used as the control For each procedure 10 specimens were used The results indicated that the linear changes observed were of no clinical importance The same conclusion can be drawn for flexural properties and microhardness The microwave method is a useful alternative to immersion disinfection

Investigation of pH‐sensitive drug delivery system of chitosan/gelatin hybrid polymer network

Abstract: A novel hydrogel based on a crosslinked chitosan/gelatin with glutaraldehyde hybrid polymer network was prepared. The gel swells in acidic medium and deswells in alkaline medium. A comparative study of the pH-dependent release of levamisole, cimetidine and chloramphenicol was carried out.

Properties of fibers produced from soy protein isolate by extrusion and wet-spinning

Abstract: Fibers were produced from soy protein isolate by both wet-spinning and extrusion. In the wet-spinning process, aged, alkaline protein solution was forced through a spinnerette into an acid coagulating bath. In the extrusion process, a twinscrew extruder forced a protein isolate-water mixture through a die. The physical properties of the fibers were measured at various water activities. The fibers produced by both methods were brittle and lacked tensile strength (tenacity). The addition of glycerol reduced brittleness in extruded fibers. Zinc and calcium ions decreased the brittleness of wet-spun fibers. The tenacity of soy fibers was significantly improved by post-spinning treatments, including acetic anhydride, acetaldehyde, glyoxal, glutaraldehyde, a combination of glutaraldehyde and acetic anhydride, and stretching. The best extruded fibers were produced with a mixture of 45% soy protein, 15% glycerol, and 40% water, finished with a combination of glutaraldehyde and acetic anhydride and then stretched to 150% their original lengths. The best wet-spun fibers were produced with a 19.61% soy protein suspension at pH 12.1; coagulated in a 4% hydrochloric acid solution that contained 3.3% sodium chloride, 3.3% zinc chloride, and 3.3% calcium chloride; and followed by treatment with 25% glutaraldehyde and stretching to 170% their original lengths.

Methods for treating implantable biological tissues to mitigate the calcification thereof and bioprosthetic articles treated by such methods

Abstract: A method for treating fixed biological tissue inhibits calcification of the biological tissue following implantation thereof in a mammalian body. The method includes placing the biological tissue in contact with glutaraldehyde and then heating the glutaraldehyde. Alternatively, methods other than heating (e.g., chemical or mechanical means), for effecting polymerization of the glutaraldehyde may also be utilized. Alternatively, the tissue may be heat treated prior to fixing thereof. Alternatively, methods other than glutaraldehyde may also be used for fixing the tissue. The biological tissue may be so treated at any time prior to implantation thereof in a mammalian body.

Characterization of immobilized catalases and their application in pasteurization of milk with H2O2

Abstract: The catalase (fromAspergillus niger) has been immobilized by a chemical method on the pous SiO2 modified with γ-aminopropyltrietoxysilane, followed with glutaraldehyde and by a physical method in alginate and γ-carrageenan gel. Optimum support:enzyme ratios and pH values were determined for modified SiO2 in a series of immobilization reactions of catalase in the presence of the crosslinking agent glutaraldehyde, and for alginate and γ-carrageenan in the presence of hemoglobin and bovine serum albimine. pH and temperaturedependent activity variations and the stability properties of immobilized catalase preparations were investigated. Rate constants for H2O2 decomposition and catalase deactivation were determined. The decomposition rate of H2O2 used in the cold pasteurizatioan of milk were investigated in a discontinuous batch type reactor system. Activity half-lives of immobilized catalase were determined.

Activity of enzyme immobilized on silanized Co-Cr-Mo.

Abstract: The surface of an orthopedic biomaterial was modified by the covalent immobilization of biomolecules. Derivatization of Co-Cr-Mo samples with organic and aqueous solutions of gamma-aminopropyltriethoxysilane (APS) resulted in a concentration-dependent number of reactive NH2 groups on the surface available for coupling to protein. The enzyme trypsin was used as a model biomolecule to investigate the effect of immobilization on proteolytic activity. Trypsin was coupled to the silanized samples by formation of Schiff's base linkages via glutaraldehyde. The nature of the interaction between trypsin and biomaterial was then probed by treatment with concentrated guanidine hydrochloride (GuHCl) and urea. Residual activity (following treatment with chaotropic agents) of trypsin immobilized on silanized Co-Cr-Mo was dependent both on the nature of the silane solution and on the type of chaotropic agent. Organic silanization with APS required a minimum density of approximately 49 NH2 per nm2 of nominal surface area (> 0.021 M APS) for residual activity of immobilized trypsin. For aqueous silanization, approximately 5.4 NH2/nm2 (0.51 M APS) resulted in maximal residual trypsin activity. Treatment with GuHCl removed more trypsin activity from Co-Cr-Mo samples silanized with organic solutions of APS than did treatment with urea. On the contrary, with aqueous silanization the samples possessed greater residual activity following treatment with GuHCl than following urea. Compared to simple adsorption with protein onto Co-Cr-Mo, both methods of silanization with APS resulted in superior residual immobilized enzyme activity.

HMDC crosslinking of bovine pericardial tissue: a potential role of the solvent environment in the design of bioprosthetic materials

Abstract: The need for alternative crosslinking techniques in the processing of bioprosthetic materials is widely recognized. While glutaraldehyde remains the most commonly used crosslinking agent in biomaterial applications there is increasing concern as to its biocompatibility-principally due to its association with enhanced calcification, cytotoxicity, and undesirable changes in the mechanical properties of bioprosthetic materials. Hexamethylene diisocyanate (HMDC), like glutaraldehyde, is a bifunctional molecule which covalently bonds with amino groups of lysine residues to form covalent crosslinks. Evidence within the literature indicates HMDC-treated materials are less cytotoxic than glutaraldehyde-treated materials; however, there is limited characterization of the material properties of HMDC-treated tissue. This study uses a multi-disciplined approach to characterize the mechanical, thermal, and biochemical properties of HMDC-treated bovine pericardial tissue. Further, to facilitate stabilization of the HMDC reagent, non-aqueous solvent environments were investigated. HMDC treatment produced changes in mechanical properties, denaturation temperature, and enzymatic resistance consistent with crosslinking similar to that seen in glutaraldehyde treated tissue. The significantly lower extensibility and stiffness observed under low stresses may be attributed to the effect of the 2-propanol solvent environment during crosslinking. While the overall acceptability of HMDC as a crosslinking agent for biomaterial applications remains unclear, it appears to be an interesting alternative to glutaraldehyde with many similar features.

Fixation of whole eyes: the role of fixative osmolarity in the production of tissue artifact

Abstract: • Background: Whole eyes fixed in 4% buffered formaldehyde (10% neutral buffered formalin) demonstrate a variety of artifacts, including separation of the neurosensory retina from the retinal pigment epithelium. We postulate that the osmolarity of 4% buffered formaldehyde causes contraction of the internal compartments of the eye leading to several artifactual changes commonly observed in routine histologic sections. • Methods: In part I of the study, enucleated animal eyes were examined histologically after immersion in different concentrations of formaldehyde. The variables of fixation and processing were kept constant except for the concentration and osmolarity of formaldehyde. In part II, enucleated animal eyes were used to empirically determine the optimal mixture of formaldehyde and glutaraldehyde for fixation based on subjective assessment of histologic sections. • Results: In the first part of the study, the post-fixed volume of the anterior chamber and vitreous increased as the concentration (and osmolarity) of formaldehyde decreased. In part II of the study, fixation of whole eyes was optimal with a mixture of 1% buffered formaldehyde and 1.25% glutaraldehyde. The neurosensory retina was less likely to detach from the retinal pigment epithelium, and the anterior chamber retained a more normal shape with this fixative. • Conclusions: Volume contraction of whole eyes fixed in 4% buffered formaldehyde is caused by the relatively high osmolarity of the fixative. Immersion fixation of whole eyes for 36 h (or longer) in 1% buffered formaldehyde/1.25% glutaraldehyde reduces tissue distortion without compromising cellular preservation.

Role of glutaraldehyde in calcification of porcine heart valves: Comparing cusp and wall

Abstract: Experiments were performed to better understand the relationship between glutaraldehyde and calcification of bioprosthetic heart valves, using both the cusps and the wall of porcine aortic roots. The results of the first experiment, for which 3H-labeled glutaraldehyde solutions were used, indicated that binding of glutaraldehyde in cusps and wall is concentration-dependent, that the wall contains significantly less glutaraldehyde than the cusp, and that glutaraldehyde, which penetrates in the wall at similar rates from the intima and the adventitia, is homogeneously distributed throughout the wall after 7 days of fixation, except for the intima side, where it is significantly lower. The results of the second experiment, for which cusps and 1-cm2 pieces of wall from glutaraldehyde-fixed porcine aortic roots were implanted subdermally in young rats, indicated that for both types of tissue, calcification appears to first initiate predominantly in the cell nuclei before extending to the other structures. After 8 weeks of implantation, whereas the cusps were completely calcified, calcification of the wall was limited to two longitudinal bands 150-300 microns thick, located below the adventitia and intima surfaces. The results of the third experiment indicated that cusp calcification, which decreased significantly after a 12-month storage period, was reset to high levels by reexposing the valves to glutaraldehyde at the end of the 12-month storage period. Wall calcification remained constant under all tested conditions. The results suggest that the mechanism(s) of calcification in the wall and the cusp may be different, and that calcification may be related to a particular molecular configuration resulting from exposure to glutaraldehyde.

Bioadhesive; preparation procedure and device for the application of a bioadhesive; and hardeners for a bioadhesive

Abstract: The present invention relates to a bioadhesive that includes at least two constituents that are intended to be combined, for simultaneous, separate, or time-shifted use, i.e.: 1) a semi-liquid constituent (A) that includes, at a minimum, gelatin in an aqueous solution; and 2) A constituent (B), in gel or non-gel form, that includes, at a minimum, an aldehyde, with the exception of non-gel solutions consisting of formaldehyde, glutaraldehyde, or glyceraldehyde. The invention also relates to the use of succinic dialdehyde and of aldehyde solution sin gel form as hardeners in a bioadhesive, and further relates to a procedure for the preparation of the said bioadhesives and to a device for the application of the said bioadhesives.

Method of use of compositions of biocides and fluorescent indicators to control microbial growth

Abstract: A concentration of microbiocides added to fluid systems is monitored by a fluorescence emission method which is based upon the measurement of the fluorescence intensity of an inert fluorescent additive which is added to the microbiocide composition prior to its introduction into the fluid system. Optionally, the fluorescent additive may be metered separately into the fluid system in direct proportion to the amount of industrial microbiocide added. Biocide compositions containing inert fluorescent additives are also disclosed. Preferably the fluid system is an industrial aqueous system. Preferred combinations of biocide and fluorescent additive are glutaraldehyde/1,5-naphthalene disulfonic acid, glutaraldehyde/1,3,6,8-pyrene tetrasulfonic acid, isothiazolone/1,5-naphthalene disulfonic acid, isothiazolone/1,3,6,8-pyrene tetrasulfonic acid, glutaraldehyde/fluorescein, alkyl-dimethylbenzyl ammonium chloride quaternary/2-naphthalene sulfonic acid and 2-(decylthio)-ethanamine/2-naphthalene sulfonic acid.

An experimental investigation of enzyme release from poly(vinyl alcohol) crosslinked microspheres.

Abstract: Crosslinked poly(vinyl alcohol) particles were prepared by the addition of glutaraldehyde into a PVA methanol/water solution in the presence of 0.2 N sulphuric acid. The polymer solution was dispersed in mineral oil in a jacketed vessel, with the aid of a six-blade impeller. Spherical crosslinked particles in the size range 30–80μm were obtained by varying the degree of agitation or/and the amount of suspending agent. The crosslinked particles, after washing and drying, were placed into a protease enzyme solution for loading. The enzyme-containing water-swollen particles were subsequently removed from the solution and the enzyme release kinetics determined by a UV spectrophotometer. The influence of the degree of crosslinking, ionic strength, pH, particle size, and degree of hydrophilicity of the polymer on the enzyme activity was retained during the adsorption-desorption studies. The release behaviour of enzymes from crosslinked PVA particles exhibited a biphasic kinetic model, with an initial fa...

Microwave fixation improves antigenicity of glutaraldehyde-sensitive antigens while preserving ultrastructural detail.

Abstract: Microwave fixation for electron microscopy has been used primarily for post-embedding immunocytochemistry. The present study examined the ability of microwave fixation to preserve the antigenicity of glutaraldehyde-sensitive antigens for pre-embedding immunocytochemistry. Five monoclonal antibodies (MAbs) directed against cell surface components of rat mast cells were tested. The MAbs failed to show any labeling of conventionally fixed rat bone marrow-derived mast cells even at glutaraldehyde concentrations as low as 0.1%. Strong staining of mast cell plasma membranes was seen when bone marrow was initially fixed with 2% formaldehyde and then refixed in 2% glutaraldehyde/2% formaldehyde after immunostaining. However, the ultrastructural preservation of the cells was poor. Antigenicity and morphological detail were both preserved when bone marrow was fixed in 0.05% glutaraldehyde/2% formaldehyde for 4 sec in a 550-W microwave oven. With this method, mast cells in various stages of maturation as well as cells that did not contain granules were immunoreactive. This method should prove useful with antigens from many different cell types that are sensitive to glutaraldehyde fixation.

Efficient immunodetection of various protein antigens in glutaraldehyde-fixed brain tissue

Abstract: Optimal ultrastructural preservation of brain tissue for electron microscopy is best achieved with fixatives containing high concentrations of glutaraldehyde, which is generally considered detrimental to the immunogenicity of most protein antigens. We tested seventeen mono- or polyclonal antibodies against peptide or protein antigens, including a majority for which immunoreactivity had previously been reported to be sensitive to glutaraldehyde fixation. Forebrain sections of rats or mice fixed by perfusion with 3.5% glutaraldehyde were processed for pre-embedding immunocytochemistry by the avidin-biotin method. The resulting immunostaining was in most cases at least similar to that obtained in sections fixed with paraformaldehyde. Immunoreactivity against the mouse or human neurofilament protein NF-L was even improved, being similar to that previously reported for unfixed brain tissue. Of all antigens tested, only choline acetyltransferase, phenylethanolamine-N-methyl transferase, and neuropeptide Y were detected with lower sensitivity than after paraformaldehyde fixation, which was attributed to a rather restricted penetration of the primary antibody into glutaraldehyde-fixed tissue sections. These results indicate that glutaraldehyde may be envisaged as a possible fixative for optimal immunocytochemical detection of any tissue antigen at the electron microscopic level, including antigens which, on the basis of results obtained after fixation with paraformaldehyde-glutaraldehyde mixtures, were considered highly sensitive to glutaraldehyde fixation.

Impact of glutaraldehyde versus glutaraldehyde-formaldehyde fixative on cell organization in fish corneal epithelium.

Abstract: The purpose of this study was to examine the impact of a low osmolality glutaraldehyde fixative and a high osmolality glutaraldehyde-formaldehyde fixative on the structural organization of a tissue that could be exposed to low and high osmolality environments. The corneas of freshwater trout were prepared for transmission and scanning electron microscopy using either a fixative of 2% glutaraldehyde in 60 mM cacodylate buffer (pH 7.8, 260 mOsm/l) or a fixative prepared by adding 2.5% glutaraldehyde to a solution of 1% formaldehyde and buffering the solution with 0.1 M cacodylate (pH 7.6, 850 mOsm/l; Karnovsky-type fixative). The corneal epithelial cell layer thickness was greater after glutaraldehyde compared to glutaraldehyde-formaldehyde fixation (67 vs 55 μm), as was the thickness of the superficial cells (5.1 vs 3.4 μm) and basal cells (43 vs 38 μm). The intermediate (wing) cells of the epithelium were, however, less thick after glutaraldehyde fixation (15 vs 18 μm). The width of the squamous, intermediate and basal cells was greater following glutaraldehyde fixation with the effect being greatest in the superficial layers and insignificant at the level of the basal cells. The results show that chemical fixatives with extremes of osmolality cannot only produce different cell sizes in a tissue but also determine the overall organization of the cells in a positional-dependent fashion.

A simple technique for staining of cell membranes with imidazole and osmium tetroxide.

Abstract: We describe a simple new technique based on the affinity of imidazole and osmium tetroxide for unsaturated lipids Organs (eg, kidney, liver, intestine) were perfused in vivo with a glutaraldehyde solution Tissue fragments were then immersed in a solution containing imidazole and OsO4 and are further stained with a double lead and copper citrate solution Ultra-thin (006 microns) or thick (01-03 microns) sections were observed with transmission electron microscopy (80-100 kV) The method presented permits excellent visualization of cell membranes (eg, endoplasmic reticulum, endocytotic apparatus) because it favors good resin penetration and the alkaline pH preserves cell volume A better stereomicroscopic analysis of the relationship between cell organelles can be carried out with thick sections The imidazole/osmium can be used routinely because the technical steps are easy and simple to follow Furthermore, it can complement other cytochemical methods