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PubMed2004

Chemotherapeutic potential of alginate-chitosan microspheres as anti-tubercular drug carriers.

OBJECTIVES: This study was designed to develop alginate-chitosan microspheres as drug carriers to reduce dose/dosing frequency in the management of tuberculosis (TB), which otherwise demands prolonged chemotherapy. METHODS: Alginate-chitosan microspheres encapsulating three frontline anti-tuberculous drugs (ATDs), rifampicin, isoniazid and pyrazinamide, were formulated. A therapeutic dose and a half-therapeutic dose of the microsphere-encapsulated ATDs were orally administered to guinea pigs for pharmacokinetic/chemotherapeutic evaluations, respectively. RESULTS: The drug encapsulation efficiency ranged from 65% to 85% with a loading of 220-280 mg of drug per gram microspheres. Administration of a single oral dose of the microspheres to guinea pigs resulted in sustained drug levels in the plasma for 7 days and in the organs for 9 days. The half-life and mean residence time of the drugs were increased 13- to 15-fold by microsphere encapsulation, along with an enhanced relative/absolute bioavailability. The sustained release and increase in bioavailability were also observed with a sub-therapeutic dose of the microspheres. In Mycobacterium tuberculosis H37Rv-infected guinea pigs, administration of a therapeutic dose of microspheres spaced 10 days apart produced a clearance of bacilli equivalent to conventional treatment for 6 weeks. The most important observation, however, was the documentation of therapeutic benefit with a half-therapeutic dose of the microspheres administered weekly. CONCLUSION: Alginate-chitosan microspheres hold promise as a potential natural polymer-based oral ATD carrier for better management of TB.

Alginates↗

PubMed2005

Use of a new alginate film test to study the bactericidal efficacy of the high-level disinfectant ortho-phthalaldehyde.

OBJECTIVES: To evaluate the merit of a new alginate efficacy film test to determine the bactericidal activity of the high-level disinfectant ortho-phthalaldehyde (OPA). METHODS: The efficacy of OPA was investigated using a new sodium alginate surface film test against Mycobacterium chelonae NCIMB 1474 and Epping, and Pseudomonas aeruginosa NCIMB 10421 under different test conditions. RESULTS: OPA was highly bactericidal against P. aeruginosa but its mycobactericidal efficacy was seriously reduced and produced >or=5 log reductions only at a concentration of 0.5% (w/v) within 30-60 min without organic load. CONCLUSIONS: The sodium alginate film efficacy was reproducible between repeats. Inactivation results depended upon the concentration of OPA, contact time, the presence of an organic load and the bacterial genera.

Alginates↗

PubMed2001

Evaluation of a combined calcium sodium alginate and bio-occlusive membrane dressing in the management of split-thickness skin graft donor sites.

The optimal treatment of the split-thickness skin graft (STSG) donor site remains an unresolved issue. This study was conducted to evaluate the combined use of calcium sodium alginate and a bio-occlusive membrane dressing in the management of STSG donor sites. This study was a prospective evaluation of all patients requiring an STSG over a 6-month period ending October 1998. There were 57 patients with a mean age of 61 years. All skin grafts were harvested with an electric dermatome from the anterior thigh and were 0.012 to 0.016 inches thick. Donor sites were dressed with calcium sodium alginate followed by a bio-occlusive dressing. Postoperatively, the skin graft donor site dressing was removed and replaced. The mean skin graft area was 114 cm2. The first dressing change occurred, on average, 3 days postoperatively. All dressings were taken down and the wounds reevaluated 7 days postoperatively. Fifty-two patients (91%) had achieved complete reepithelialization by this time. Five patients (9%) required an additional dressing. All wounds were healed completely by postoperative day 10. Donor site discomfort was minimal and limited to the time of dressing change. There were no wound-related complications. The average cost of dressing supplies was $48.00 per patient and $23.00 per dressing. This method of managing STSG donor sites allowed for unimpeded reepithelialization without wound complication. The bio-occlusive dressing eliminated the pain typically associated with fine mesh gauze dressings. The absorptive property of the calcium sodium alginate eliminated the problem of seroma formation and leakage seen routinely with the use of a bio-occlusive dressing alone. These results confirm that this technique is both efficacious and cost-effective.

Adult↗

PubMed2002

Reduced encephalopathy in pigs with ischemia-induced acute hepatic failure treated with a bioartificial liver containing alginate-entrapped hepatocytes.

OBJECTIVE: To analyze the effects of an extracorporeal bioartificial liver containing alginate bead-entrapped hepatocytes on pigs with ischemia-induced acute hepatic failure. DESIGN: Prospective animal study. SETTING: University and INSERM laboratory. SUBJECTS: Fifteen Large White/Pietrin female pigs weighing 20-30 kg. INTERVENTIONS: Acute hepatic failure was induced by end-to-side portocaval shunt and ligature of the whole porta hepatitis. The bioartificial liver was in a thermostabilized column, containing a fluidized bed of alginate beads that embedded porcine hepatocytes, connected to a plasmapheresis system. Intracranial pressure; survival; ammonia, total bilirubin, aminotransferases, alkaline phosphatase, and lactate concentrations; and clotting factors were studied. The groups were pigs with acute hepatic failure (group 1, n = 4), pigs with acute hepatic failure treated with bioartificial liver containing empty beads (group 2, n = 4), or porcine hepatocytes (group 3, n = 5). MEASUREMENTS AND MAIN RESULTS: In group 1, survival of pigs averaged 10.9 +/- 1.0 hrs; intracranial pressure reached 32.3 +/- 3.8 mm Hg and was associated with coma and cerebral edema. After connection to the bioartificial liver, the survival of acute hepatic failure pigs was 12.1 +/- 1.4 hrs in group 2 and 14.8 +/- 2.5 hrs in group 3. In group 3, intracranial pressure and bilirubin concentrations were reduced significantly compared with both group 1 and group 2. Neither signs of encephalopathy nor cerebral edema was observed in any animal of group 3. In all animals, plasma ammonium, aminotransferases, alkaline phosphatase, and lactate concentrations increased and clotting factors decreased with no significant differences between the three groups. Autopsy revealed a total necrosis of the liver, which was histologically confirmed. CONCLUSIONS: The ischemia-induced model of acute hepatic failure in pigs is reproducible and provides measurable clinical and biological features. A bioartificial liver containing alginate bead-entrapped hepatocytes improves the signs of encephalopathy in pigs with ischemia-induced acute hepatic failure, suggesting that the bioartificial liver can clear out toxic compounds that are released from necrotic livers.

Alginates↗

PubMed1999

In vitro elution of antibiotic from antibiotic-impregnated biodegradable calcium alginate wound dressing.

OBJECTIVE: The authors investigated the calcium alginate dressing as a drug-delivery system for the treatment of various surgical infections. METHODS: Cytotoxicity of the calcium alginate dressing to fibroblasts and HeLa cells was evaluated by the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H tetrazolium bromide (MITT) colorimetric assay. The calcium alginate dressing was mixed with vancomycin, and lyophilized or not lyophilized to form two types of antibiotic dressings. The antibiotic dressings were placed in 2 mL of phosphate buffered saline (PBS) or in PBS containing 0.01% calcium ions, and incubated at 37 degrees C. The PBS was changed daily, and the removed solutions were stored at -70 degrees C until the antibiotic concentration in each sample was determined by high performance liquid chromatography assay. RESULTS: The results suggested that the antibiotic dressings present no obvious toxic risk to their use as a drug-delivery system. The concentration of vancomycin in each sample was well above the breakpoint sensitivity concentration (the antibiotic concentration at the transition point between bacterial kill. ing and resistance to the antibiotic) for more than 14 days. The release was most marked during the first 48 hours. The concentration of calcium ions in PBS and the lyophilization of the manufacture process of antibiotic dressings prolonged the antibiotic diffusion duration. The diameter of the sample inhibition zone ranged from 10 to 11 mm, and the relative activity of vancomycin ranged from 62.88% to 92.18%. CONCLUSION: All antibiotic dressings released bactericidal concentrations of the antibiotics in vitro for the period of time needed to treat surgical infections. This study offers a convenient method to meet the specific antibiotic requirement for different patients.

Alginates↗

PubMed2006

Six-month survival of microencapsulated pig islets and alginate biocompatibility in primates: proof of concept.

BACKGROUND: Pig islets xenotransplantation remains associated with a strong humoral and cellular xenogeneic immune responses. The aim of this study was to assess the long-term biocompatibility of alginate encapsulated pig islets after transplantation in primates. METHODS: Adult pig islets encapsulated in alginate under optimal conditions (n=7) or not (n=5) were transplanted under the kidney capsule of nondiabetic Cynomolgus maccacus. Additional primates received empty capsules (n=1) and nonencapsulated pig islets (n=2) as controls. Capsule integrity, cellular overgrowth, pig islet survival, porcine C-peptide and anti-pig IgM/IgG antibodies were examined up to 6 months after implantation. RESULTS: Nonencapsulated islets and islets encapsulated in nonoptimal capsules were rapidly destroyed. In seven primates receiving perfectly encapsulated pig islets, part of the islets survived up to 6 months after implantation without immunosuppression. Porcine C-peptide was detected after 1 month in 71% of the animals. The majority of grafts (86%) were intact and completely free of cellular overgrowth or capsule fibrosis. Explanted capsules, after 135 (n=2/2) and 180 (n=2/3) days, demonstrated residual insulin content and responses to glucose challenge (stimulation index of 2.2). Partial islet survival was obtained despite an elicited anti-pig IgG humoral response. CONCLUSIONS: Optimal alginate encapsulation significantly prolonged adult pig islet survival into primates for up to 6 months, even in the presence of antibody response.

Alginates↗

PubMed1977

An alginate lysate from Azotobacter vinelandii phage.

The alginate depolymerase associated with bacteriophage infection of Azotobacter vinelandii has been used in the analysis of sodium alginate. The enzyme degraded the polysaccharide to a series of oligouronides each containing a terminal 4-deoxy-alpha-L-erythro-hex-4-enopyranuronosyl residue. Analysis of these oligouronides, together with kinetic information, indicated that the enzyme was specific for mannuronic acid-containing regions of the polyuronide. The specificity of the enzyme made it possible to determine the primary structure of the macro-molecule. The phage-induced enzyme was shown to be distinct from the alginate lyase elaborated by the host organisms by its pH optimum, molecular weight, Michaelis constant and stability.

Alginates↗

PubMed1990

The influence of calcium alginate haemostatic swabs upon operative blood loss in adenotonsillectomy.

Although adenotonsillectomy is regarded as a minor procedure, it has been shown that 18% of patients may experience an operative blood loss of 10-20% of the total blood volume. The aim of this study was to determine whether calcium alginate haemostatic swabs reduce operative blood loss in adenotonsillectomy. Seventy-two patients (ages 2-12 years) entered a prospective trial in which the operation was performed either with normal gauze swabs or calcium alginate swabs. Thirty-six children were randomized to each group. The mean blood loss was found to be 34.9 ml (2.07% of total blood volume) and 47.8 ml (2.97% of total blood volume) respectively. Although there was no significant reduction in operative blood loss using calcium alginate, in both groups the blood loss was much smaller than that stated by the majority of previous workers.

Adenoidectomy↗

PubMed1990

Pulmonary dehydration and infection in cystic fibrosis: evidence that ethanol activates alginate gene expression and induction of mucoidy in Pseudomonas aeruginosa.

Mortality among cystic fibrosis (CF) patients is most commonly attributed to pulmonary infection by mucoid, alginate-producing Pseudomonas aeruginosa. The initial infecting P. aeruginosa are typically non-mucoid; however, upon continued exposure to the CF lung environment, they become highly mucoid. The CF lung is an osmotically high environment because of the presence of substantial concentrations of electrolytes and dehydrated mucus. In this report we demonstrate that ethanol (a commonly used dehydrating agent) activates transcription from a critical alginate promoter, algD, and show that prolonged exposure to ethanol allows switching to the mucoid form. This activation appears to be dependent on DNA gyrase. Analysis of alginate gene activation, and the subsequent reversal of the activation process by bacterial DNA gyrase inhibitors, should aid the development of treatment strategies for CF patients infected with this organism.

Alginates↗

PubMed1992

Pseudomonas aeruginosa AlgB, which modulates the expression of alginate, is a member of the NtrC subclass of prokaryotic regulators.

The Pseudomonas aeruginosa exopolysaccharide alginate is an important virulence factor in chronic pulmonary infections of cystic fibrosis patients. We determined the nucleotide sequence of the gene, algB, which regulates the level of exopolysaccharide produced by mucoid P. aeruginosa. The predicted amino acid sequence of AlgB revealed a high degree of similarity to the regulatory proteins in the NtrC subclass of 'two-component regulatory systems'. AlgB expression in Escherichia coli minicells showed a molecular weight of approximately 50,000 Da, comparable to that of the inferred amino acid sequence (49,318 Da). We show that algB is transcriptionally active in mucoid strains of P. aeruginosa and regulates the expression of the alginate biosynthetic gene, algD, thereby resulting in increased expression of alginate in mucoid P. aeruginosa.

Alginates↗

PubMed1995

A family of modular type mannuronan C-5-epimerase genes controls alginate structure in Azotobacter vinelandii.

The L-guluronic acid residues in the Azotobacter vinelandii polysaccharide alginate originate from a post-polymerization reaction catalysed by the enzyme mannuronan C-5-epimerase (ME). We have previously reported the cloning and expression of an A. vinelandii gene encoding this enzyme, and we show here that the organism encodes at least four other ME genes originating from a common ancestor gene by a complex rearrangement process. The biological function of the corresponding enzymes is probably to catalyse the formation of alginates with a variety of physical properties. This model may explain the origin of the structural variability found in alginates isolated both from prokaryotic and eukaryotic organisms. The A. vinelandii enzymes may also potentially be useful for certain medical and biotechnological applications of this commercially important polysaccharide.

Alginates↗

PubMed1996

Genetic analysis of the transcriptional arrangement of Azotobacter vinelandii alginate biosynthetic genes: identification of two independent promoters.

The study of alginate biosynthesis, the exopolysaccharide produced by Azotobacter vinelandii and Pseudomonas aeruginosa, might lead to different biotechnological applications. Here we report the cloning of A. vinelandii algA, the gene coding for the bifunctional enzyme phosphomannose isomerase-guanosine diphospho-o-mannose pyrophosphorylase (PMI-GMP). This gene was selected by the complementation for xanthan gum production of Xanthomonas campestris pv. campestris xanB-mutants, which lack this enzymatic activity. The complementing cosmid clones selected, besides containing algA, presented a gene coding for an alginate lyase activity (algL), and some of them also contained algD which codes for GDP-mannose dehydrogenase. We present here the characterization of the A. vinelandii chromosomal region comprising algD and its promoter region, algA and algL, showing that, as previously reported for P. aeruginosa, A. vinelandii has a cluster of the biosynthetic alginate genes. We provide evidence for the presence of an algD-independent promoter in this region which transcribes at least algL and algA, and which is regulated in a manner that differs from that of the algD promoter.

Alginates↗

PubMed1983

The use of alginate ester films on solid supports in the preparation of water-insoluble immunoadsorbents for purification of antigens.

A novel method developed for the preparation of immunoadsorbents is based on the technique of coating potential column supports with a propylene glycol alginate ester film created by emulsion polymerisation. The cross-linking of the film with 1,2-diaminoethane in alkaline solution resulted in a water-permeable but water-insoluble film which was stable at high pH. Sheep anti-(human IgG) was subsequently coupled to the cyanogen-bromide-activated film and the resultant immunoadsorbents were used to purify IgG from whole human serum. The production of the film-coated supports, chemical coupling of antibody and the chromatographic characteristics of four alginate-film-coated supports are described. With the use of Sepharose--alginate-ester--sheep-anti-(human IgG) immunoadsorbent the overall yield for IgG from five serial adsorption-elution cycles was 94% of the adsorbed IgG. This immunoadsorbent proved to be of high binding capacity and allowed the elution of specific antigen in almost 100% yield and high purity with minimal non-specific interference from other serum proteins.

Alginates↗

PubMed1998

Immobilization of urease from pigeonpea (Cajanus cajan L.) in polyacrylamide gels and calcium alginate beads.

Urease from pigeonpea was entrapped in polyacrylamide gel with 50% immobilization at 10% total monomer (containing 5% cross-linker) with high mechanical stability of the gel. Approximately 0.61 mg of protein could be loaded per 5 ml of gel. The immobilized enzyme had a t1/2 of approx. 200 days when stored in 0.1 M Tris/acetate buffer, pH 6.5, at 4 degrees C. The gel strips were used 4-5 times for urea assay over a period of 6 h with less than 2% loss of activity. Approximately 50% immobilization of urease in calcium alginate was observed at 3% alginate with 0.12 mg protein/ml alginate. The resultant enzyme beads showed a t1/2 of approx. 75 days when stored in 0.1 M Tris/acetate buffer, pH 6.5, at 4 degrees C. The beads were used 4-5 times for urea assay over a period of 6 h with about 40% loss of activity. In both cases, the enzyme activity was directly proportional to the amount of immobilized enzyme. There was practically no leaching of the entrapped enzyme over a period of 48 h from either of the polymers. Both the immobilized enzyme preparations were used to analyse the blood urea of some clinical samples from the University hospital. The results obtained compared favourably with those obtained by the usual method employed in the clinical pathology laboratory.

Acrylic Resins↗

PubMed1994

Complement activation by alginate-polylysine microcapsules used for islet transplantation.

A foreign body reaction is frequently observed around implanted microcapsules of alginate-polylysine. Since complement activation can play a role in this reaction, we checked in vitro the ability of empty alginate-polylysine microcapsules to activate complement. Human serum was incubated with microcapsules, and complement activation was evaluated by two methods: the complement hemolytic activity (CH50) and the assay of the C3adesArg fragment. The occurrence of complement activation in the presence of microcapsules was suggested both by a CH50 decrease and by high C3adesArg levels despite C3adesArg adsorption to the capsule membrane. Capsule membrane protection against the cytotoxic effects of complement was also tested. No hemolysis occurred when microencapsulated sensitized sheep erythrocytes were incubated with activated complement. In conclusion, the microcapsule membrane can protect cells against activated complement fragments. Nevertheless, alginate-polylysine microcapsules do activate complement, and this effect must be considered for its use as an implant.

Alginates↗

PubMed1995

High gene expression in Escherichia coli of recombinant alginate lyase as a fused protein with beta-galactosidase alpha-peptide.

Escherichia coli LE392 (pAL28) was previously isolated as a positive clone harboring the alginate lyase gene (aly) from an alginate-degrading strain, Pseudomonas sp. OS-ALG-9. The plasmid pAL205, one of the constructs obtained after successive subcloning of pAL28, gave the highest expression of aly in E. coli cells. A 8-fold increase in the alginate lyase (Aly) activity in E. coli JM109 (pAL205) was induced with isopropyl-beta-D-thiogalactoside, which was 210 times higher than that in E. coli LE392 (pAL28). The highly significant increase in the expression of the Aly enzyme with pAL205 was investigated through the nucleotide sequence around the 5' region of aly as well as the N-terminal sequence of the purified enzyme. It was found that the Aly expressed in E. coli (pAL205) was a fused protein containing 7 residues from the N-terminus of beta-galactosidase alpha-peptide and the mature protein found in the Pseudomonas sp. except for three residues in the N-terminal.

Alginates↗

PubMed1997

Implication of neutral polysaccharides associated to alginate in inhibition of murine macrophage response to Pseudomonas aeruginosa.

There is evidence that exopolysaccharides (EPS) contribute to the persistence of Pseudomonas aeruginosa in cystic fibrosis lung. However, the relationship between the chemical composition of EPS and the modulation of phagocytic cells is poorly understood. In order to evaluate the role of the chemical composition of EPS in macrophage behavior changes, we pretreated macrophages with characterized EPS and assessed P. aeruginosa phagocytosis and reactive oxygen intermediate (ROI) production. The results showed that alginate and neutral polysaccharides are involved in phagocytic impairment of P. aeruginosa. Moreover, alginates were able to prime macrophages for increased P. aeruginosa-induced macrophage oxidative burst as determined by chemiluminescence. In contrast, neutral polysaccharides are responsible for the decrease of ROI by a scavenging effect evaluated by the xanthine-xanthine oxidase system. This study showed that the content of P. aeruginosa EPS in alginate, but also in neutral polysaccharides, influences the behavior of strains towards phagocytosis and macrophage oxidative burst.

Alginates↗

PubMed1989

Accuracy of alginate and elastomeric impression materials.

The accuracy of three alginates and seven elastomeric impression materials was determined. Impressions were taken of a truncated cone and poured with stone die. A steel ring fitting the steel cone was placed on the dies, and the discrepancy between the top surface of the ring and the die was measured. From these measurements the deviation between the base diameter of the die and that of the cone was calculated and used to express the accuracy of an impression material. All impressions showed a net shrinkage, resulting in too large a die stone and incomplete seating of the steel ring. The inaccuracy of the alginates varied between 44 and 188 microns. Blueprint regular was found to be significantly more accurate than the two other alginates investigated, and had a degree of accuracy comparable with that of the more accurate elastomeric impression materials. Within this group of materials the inaccuracy varied between 39 and 130 microns. Generally, the addition-curing silicones were more accurate than the polyethers. Baysilex and President regular body had the highest degree of accuracy of the elastomeric impression materials.

Alginates↗