Showing papers on "Glutaraldehyde published in 2003"

Decolorization of reactive dyes by immobilized laccase

Abstract: Immobilization of laccase by Trametes versicolor on silica chemically modified with imidazol groups, amberlite IRA-400, glass–ceramic chemically modified with carbodiimide/glutaraldehyde and by aminoprolyltriethoxysilane/glutaraldehyde and montmorillonite modified by aminoprolyltriethoxysilane/glutaraldehyde were afforded. These supports were used in the decolorization of textile reactive dyes (Remazol Brilliant Blue R, Remazol Black B, Reactive Orange 122 and Reactive Red 251). One of the most efficient supports was studied in a more detailed way, silica modified by imidazole SiIm led us to obtain almost total immobilization of laccase at contact times lower than 45 min. The immobilized laccase showed high decolorization efficiency toward aqueous solutions of the dyes. In the first stages of the process, the decolorization is mainly due to adsorption of the dyes onto the support surface. However, when working in a successive dye addition system, the adsorption capacity of the supports decrease (saturation) and the enzymatic decolorization process is clearly evidenced. The use of a brief photochemical pre-treatment permitted a significantly increase on the efficiency of the enzymatic decolorization process.

Genipin-crosslinked gelatin microspheres as a drug carrier for intramuscular administration: in vitro and in vivo studies.

Abstract: Gelatin microspheres have been widely evaluated as a drug carrier. Nevertheless, gelatin dissolves rather rapidly in aqueous environments, making the use of the polymer difficult for the production of long-term delivery systems. This adverse aspect requires the use of a crosslinking agent in forming nonsoluble networks in microspheres. However, the use of crosslinking agents such as formaldehyde and glutaraldehyde can lead to toxic side effects owing to residual crosslinkers. In an attempt to overcome this problem, a naturally occurring crosslinking agent (genipin) was used to crosslink gelatin microspheres as a biodegradable drug-delivery system for intramuscular administration. Glutaraldehyde was used as a control. In the in vitro study, the morphology, dynamic swelling, and antienzymatic degradation of test microspheres were evaluated. In the in vivo study, the biocompatibility and degradability of test microspheres were implanted in the skeletal muscle of a rat model via intramuscular injection. The results obtained in the study suggested that crosslinking of gelatin microspheres with glutaraldehyde or genipin may produce distinct crosslinking structures. The water transport mechanism in both the glutaraldehyde- and genipin-crosslinked gelatin microspheres exhibit anomalous behavior ranging from Fickian to Case-II extremes. The increase of the swelling diameter for the genipin-crosslinked microspheres was significantly less than that observed for the glutaraldehyde-crosslinked microspheres. In the animal study, it was found that the degree in inflammatory reaction for tissues implanted with the genipin-crosslinked microspheres was significantly less than that implanted with the glutaraldehyde-crosslinked microspheres. Additionally, the degradation rate of the genipin-crosslinked microspheres was significantly slower than their glutaraldehyde-crosslinked counterparts. These results indicated that the genipin-crosslinked gelatin microspheres may be used as a long-acting drug carrier for intramuscular administration.

A genipin-crosslinked gelatin membrane as wound-dressing material: in vitro and in vivo studies

Abstract: A naturally occurring crosslinking agent (genipin) was used in this study to crosslink gelatin hydrogel to develop a wound-dressing membrane. The study was to investigate the in vitro characteristics of the genipin-crosslinked gelatin membrane. The glutaraldehyde-crosslinked counterpart, at a similar crosslinking degree, was used as control. Additionally, an in vivo experiment was undertaken to study the wound healings covered with the glutaraldehyde- and genipin-crosslinked dressings in a rat model. The in vitro results obtained suggested that crosslinking of gelatin membranes with glutaraldehyde or genipin may produce distinct crosslinking structures. The differences in crosslinking structure can significantly affect the mechanical property, water-vapor-transmission rate, swelling ratio, degradation against enzyme and cellular compatibility of the crosslinked membranes. In the in vivo study, it was found that the degree of inflammatory reaction for the wound treated with the genipin-crosslinked dressing was significantly less severe than that covered with the glutaraldehyde-crosslinked dressing throughout the entire course of the study. Additionally, the healing rate for the wound treated with the genipin-crosslinked dressing was notably faster than its glutaraldehyde-crosslinked counterpart.

Freeze-substitution protocols for improved visualization of membranes in high-pressure frozen samples.

Abstract: Specimen preparation methods based on high-pressure freezing and freeze-substitution have enabled significant advances in the quality of morphological preservation of biological samples for electron microscopy. However, visualization of a subset of cellular membranes, particularly the endoplasmic reticulum and cis Golgi, is often impaired by a lack of contrast. By contrast, some efforts to increase membrane staining may lead to excessively granular staining. No one freeze-substitution method has emerged that both overcomes these limitations and is suitable for all types of analysis. However, one or more of the following protocols, perhaps with minor modifications, should yield satisfactory results in most cases. Freeze-substitution in glutaraldehyde and uranyl acetate in acetone, followed by embedding in Lowicryl HM20, generates samples suitable for both immunolocalization and high-resolution structural studies. Membranes are typically lightly stained but very well defined. Initial freeze-substitution in tannic acid and glutaraldehyde in acetone prior to exposure to osmium tetroxide significantly enhanced contrast on mammalian cellular membranes. Finally, initial trials indicate that freeze-substitution in potassium permanganate in acetone can provide strong contrast on endoplasmic reticulum and Golgi as well as other membranes. The tendency of permanganate to degrade cytoskeletal elements and other proteins when employed in aqueous solutions at room temperature is apparently curtailed when it is used as a freeze-substitution reagent.

Poly (vinyl alcohol)-chitosan blends: preparation, mechanical and physical properties

Abstract: Poly (vinyl alcohol)-chitosan blend films were prepared by casting the respective polymer solutions. The glutaraldehyde was used as a cross-linking agent. A series of PVA-chitosan blends were prepared by varying the ratio of the constituents. Mechanical and physical properties of blended films such as tensile properties in the dry and wet states, water uptake, surface tension and contact angle were characterized. Blending PVA and chitosan improved strength and flexibility of the films in the dry and wet states. Cross-linking with glutaraldehyde improves tensile strength and decreases elongation of the films. PVA Content in the blends increases water uptake while cross-linking the films with glutaraldehyde causes less hydrophilicity. Water uptake in PVA-chitosan blends can be controlled by variation of their contents, cross-linking agent and the pH of solution. Blending of PVA and chitosan improves bulk and surface hydrophilicity of blended films.

Thermal dehydration treatment and glutaraldehyde cross-linking to increase the biostability of collagen–chitosan porous scaffolds used as dermal equivalent

Abstract: A biodegradable scaffold for skin-tissue engineering was designed using collagen and chitosan, which are common materials for biomedical application. The scaffolds containing different amounts of chitosan were prepared by mixing the collagen and chitosan solutions followed by removal of the solvent using a freeze-drying method. The cross-linking treatment of these scaffolds was performed using the dehydrothermal treatment (DHT) method or glutaraldehyde (GA) to increase their biostability. The effect of the chitosan concentration and the cross-linking methods on the morphology of these scaffolds was studied by SEM. The water retention and the biodegradability in vitro of various collagen-chitosan scaffolds were investigated. Finally the biocompatibility of the collagen-chitosan (10 wt% chitosan) scaffold treated with different cross-linking methods was evaluated using a in vivo animal test. A mild inflammatory reaction could be detected in the early stages, and GA treatment can decrease the inflammatory re...

Biocompatibility of collagen membranes crosslinked with glutaraldehyde or diphenylphosphoryl azide: An in vitro study

Abstract: Crosslinking of collagen biomaterials increases their resistance to degradation in vivo. Glutaraldehyde (GA) is normally used to crosslink collagen biomaterial, but is often cytotoxic. Diphenylphosphoryl azide (DPPA) has recently been proposed as reagent, but little is known about its effects on cell behavior. In this study, we determined which collagen membrane was the most biocompatible: Paroguide which is crosslinked with DPPA and contains chondroitin sulfate; Opocrin which is crosslinked with DPPA; Biomed Extend which is crosslinked with GA; and Bio-Gide which is left untreated. Cell proliferation and extracellular matrix macromolecule deposition were evaluated in human fibroblasts cultured on the membranes. The GA-crosslinked Biomed Extend membrane and the not-crosslinked Bio-Gide membrane reduced cell growth and collagen secretion compared with DPPA-crosslinked biomembranes. When Paroguide and Opocrin were compared, better results were obtained with Paroguide. The greatest amount of transforming growth factor beta1, a growth factor involved in extracellular matrix macromolecule accumulation and in tissue regeneration, was produced by cells cultured on Paroguide, with Opocrin second. Our data suggest that the DPPA method is more biocompatible than the GA for crosslinking collagen biomaterials and that membranes made of collagen plus chondroitin sulfate are better than membranes made of pure collagen.

Synthesis and characterization of modified chitosan microspheres: Effect of the grafting ratio on the controlled release of nifedipine through microspheres

Abstract: The grafting of acrylamide onto a chitosan backbone was carried out at three acrylamide concentrations (polymer/monomer ratio = 1:1, 1:2, and 1:3). The synthesis of the grafted polymer was achieved by K2S2O8-induced free-radical polymerization. Microspheres of polyacrylamide-g-chitosan crosslinked with glutaraldehyde were prepared to encapsulate nifedipine (NFD), a calcium channel blocker and an antihypertensive drug. The microspheres of polyacrylamide-g-chitosan were produced by a water-in-oil emulsion technique with three different concentrations of glutaraldehyde as the crosslinking agent. Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC) were used to characterize the grafted copolymers, and the microspheres were prepared from them. FTIR and DSC were also used to analyze the extent of crosslinking. The microspheres were characterized by the particle size; the water transport into these microspheres, as well as the equilibrium water uptake, were studied. Scanning electron microscopy confirmed the spherical nature of the particles, which had a mean particle size of 450 μm. Individual particle dynamic swelling experiments suggested that with an increase in crosslinking, the transport became case II. The release of NFD depended on the crosslinking of the network and on the amount of drug loading. Calculating the drug diffusion coefficients with the initial time and later time approximation method further supported this. The drug release in all 27 formulations followed case II transport, and this suggested that the time dependence of the NFD release followed zero-order kinetics. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2940–2949, 2003

Preserving the structure of adsorbed protein films for time-of-flight secondary ion mass spectrometry analysis.

Abstract: The characterization of adsorbed protein films with ultrahigh vacuum (UHV) surface analysis techniques requires dehydration of the samples, which can cause significant alterations in protein structure. It is desirable to preserve the structure of adsorbed protein films during drying, so UHV analysis could be done in a state that is more representative of proteins' actual structure in the aqueous environment. In this study, two methods, trehalose protection and glutaraldehyde fixation, were explored for their feasibility in preserving adsorbed protein structure for a powerful UHV surface analysis technique, time-of-flight secondary ion mass spectrometry (ToF-SIMS). Trehalose protection had shown some promise for ToF-SIMS analysis in our previous study and was further examined with the model protein fibrinogen in this study. Using the combination of principal component analysis (PCA) and static ToF-SIMS analysis, we found that trehalose protection could reduce the conformation change of fibrinogen upon drying, and prevent it from unfolding and exposing hydrophobic domains. Moreover, when the adsorbed protein film became more densely packed, the drying-induced changes in protein structure were reduced. Thus, the protection afforded by trehalose coating was more significant at lower protein surface concentrations. The other method, glutaraldehyde fixation, was used in ToF-SIMS analysis for the first time. The ϵ-amino group of lysine was identified as the major reactive group in the protein structure toward glutaraldehyde fixation. Structural differences observed between fibrinogen films that were glutaraldehyde fixed before drying and after drying were similar to those observed between trehalose-protected and-unprotected dried fibrinogen films. Glutaraldehyde fixation was found to be a viable, alternative stabilizing method to trehalose protection for ToF-SIMS analysis. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 179–190, 2003

Treatment of bioprosthetic tissues to mitigate post implantation calcification

Abstract: Bioprosthetic tissues are treated by immersing or otherwise contacting fixed, unfixed or partially fixed tissue with a glutaraldehyde solution that has previously been heat-treated or pH adjusted prior to its contact with the tissue. The prior heat treating or pH adjustment of the glutaraldehyde solution causes its free aldehyde concentration to decrease by about 25% or more, preferably by as much as 50%, and allows a “stabilized” glutaraldehyde solution to be obtained at the desired concentration and pH for an optimal fixation of the tissue at high or low temperature. This treatment results in a decrease in the tissue's propensity to calcify after being implanted within the body of a human or animal patient.

Fixation method for bioprostheses

Abstract: An improved fixative for tissue useful for bioprosthetic heart valves is provided. The tissue can have an elastin content and the elastin can be chemically fixed using a phenolic tannin, for example, tannic acid. The fixed elastin component provides greater mechanical durability and improved resistance to biological degradation following implantation. The tannic acid fixation protocol allows for biological material having a high elastin content, for example, about 30% or more. When used in combination with a glutaraldehyde fixative an additive effect can be seen in increased cross-link density and increased resistance to degradation and calcification.

A New Polyphenol Oxidase Biosensor Mediated by Azure B in Laponite Clay Matrix

Abstract: Amperometric biosensor based on the entrapment of polyphenol oxidase within a laponite clay coating and cross-linked by glutaraldehyde is described for catechol detection Laponite provides a hydrophilic enzyme surrounding increasing the long term stability of the biosensor compared to the corresponding biosensors obtained by chemical cross-linking of PPO with glutaraldehyde Azure B, a cationic dye exchanged within the clay matrix, is used as an electron shuttle allowing the mediated detection of phenol derivatives at −005 V The detection limits obtained with the optimized biosensor configuration for catechol, p-cresol and phenol are 1, 1 and 17 nM, respectively

Gelatin blends with alginate: gels for lipase immobilization and purification.

Abstract: Blends of natural polysaccharide sodium alginate (5%) with gelatin (3%) cross-linked with glutaraldehyde provide beads with excellent compressive strength (8 x 10(4) Pa) and regular structure on treatment with calcium chloride. Lipases from porcine pancreas, Pseudomonas cepacia, and Candida rugosa were immobilized in such a blend with excellent efficiency. The immobilized enzymes were stable and were reused several times without significant loss of enzyme activity both in aqueous and reverse micellar media. The beads were functionalized with succinic anhydride to obtain beads with extra carboxylic acid groups. These functionalized beads were then successfully used for 7.4-fold purification of crude porcine pancreatic lipase in a simple operation of protein binding at pH 5 and release at pH 8.5.

Glutaraldehyde-treated bovine pericardium: effects of lyophilization on cytotoxicity and residual aldehydes.

Abstract: This work assesses the effect of lyophilization on the cytotoxicity and residual aldehyde concentra- tion of glutaraldehyde-treated and lyophilized bovine pericardium (group A), comparing it to conventional glutaraldehyde-treated bovine pericardium (group B). Cytotoxicity was measured by incubating a pericardium sample from each group in saline and assessing the eluant's influence on cellular growth. Residual aldehydes were measured by HPLC. Although both groups' eluants exhib- ited some cytotoxicity, the eluant from group A was less cytotoxic, with a cytotoxicity index (IC50(%)) of 41%. Group B eluants all had marked cytotoxic effects; cell growth was 24.15% of the negative control at the most dilute eluant concentration (6.25%). The mean residual glutaraldehyde level was less in group A than in group B (2.36 ± 0.11 and 9.90 ± 3.70 g/l, respectively; n = 3, P < 0.05), but residual formaldehyde levels did not differ. These results demon- strate that compared with conventional glutaraldehyde- treated bovine pericardium, lyophilized pericardium is less cytotoxic, with fewer glutaraldehyde residues. Key Words: Biocompatibility—Cytotoxicity—Bioprosthesis— Bovine pericardium—Glutaraldehyde.

Glutaraldehyde-induced and formaldehyde-induced allergic contact dermatitis among dental hygienists and assistants

Abstract: Background Research has found that among health care workers, dental personnel are especially likely to have reactions to glutaraldehyde and formaldehyde. Methods The authors conducted patch test evaluations with a voluntary cohort of randomly recruited, healthy dental hygienists, or DHs, and dental assistants, or DAs, and nondental professionals to determine the incidence of glutaraldehyde-induced and formaldehyde-induced allergic contact dermatitis, or ACD; the potential for coreactivity between glutaraldehyde and formaldehyde; and the correlation between training methods in safe handling of sterilizing solutions and the sensitivity to glutaraldehyde and formaldehyde among DHs and DAs. Results The researchers enrolled 101 DHs and DAs and 51 nondental professionals in the study. All except one DH/DA subject were female. The dental subjects' mean age was 34.3 ± standard deviation of 10.7 years; the nondental subjects', 33.8 ± 11.0 years. DHs and DAs had worked in their profession for a mean of 11.0 ± 9.3 years. Among the dental professionals, 80 (79.2 percent) had had a known exposure to cold sterilizing solutions, while the remainder were unable to provide a known history of exposure. Eleven (10.9 percent) dental professionals had clear reactions to glutaraldehyde, four (4.0 percent) were questionably allergic to glutaraldehyde, and two (2 percent) were definitively allergic to formaldehyde. One (2 percent) control subject had a reaction to glutaraldehyde, and one other (2 percent) had a reaction to formaldehyde. Conclusions and Clinical Implications The authors found a statistically significant disparity in the rates of glutaraldehyde sensitivity among healthy DHs and DAs versus healthy control subjects (10.9 percent versus 2 percent reactively; P = .02). They found no evidence of cross-reactivity between glutaraldehyde and formaldehyde. The preponderance of reactions among the DHs and DAs suggests that their present safety practices are largely ineffective in protecting against sensitization to glutaraldehyde in sterilizing solutions.

Comparison of chemical treatments on the chain dynamics and thermal stability of bovine pericardium collagen

Abstract: A new approach for the replacement of heart valves consists of obtaining an acellular matrix from animal aortic valves that performs mechanically, is nonantigenic, and is free from calcification and fibroblast proliferation. Novel biochemical treatments must be developed for this purpose. In this work, we focus on the characterization of collagen in acellular bovine cardiovascular tissues, fresh or glutaraldehyde treated, and stored in different solutions [phosphate-buffered saline (PBS), ethanol, octanol, and glutaraldehyde], to determine whether the resulting fibrous material is structurally preserved. The preservation of the triple helical structure of collagen is checked by differential scanning calorimetry (DSC), which is a well suited technique to analyze thermal transitions in proteins, such as denaturation. To get insight into the molecular dynamics of collagen in the nanometric range, we used thermally stimulated currents, a dielectric technique running at low frequency, that measure the dipolar reorientations in proteins submitted to a static electrical field. The combined use of these two techniques allowed us to evaluate the physical structure and conformation of collagen after the different chemical treatments. We have found that the glutaraldehyde treatment followed by octanol storage preserves the triple helical conformation of the polypeptidic chains of collagen, contrary to the ethanol and PBS storage that induce drastic changes in the thermal and dielectric behavior of the protein. Moreover, this particular chemical treatment stabilizes the collagen structure (shift toward high temperature of the collagen denaturation and stiffening of the chains by a cross-linking action) when compared to the control sample, and so could provide interesting fibrous material for the conception of bioprosthetic heart valve.