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PubMed2000

Parathyroid xenotransplantation without immunosuppression in experimental hypoparathyroidism: long-term in vivo function following microencapsulation with a clinically suitable alginate.

Permanent hypoparathyroidism is one of the most difficult of all endocrine disorders to treat medically. Because this deficiency syndrome rarely is a life-threatening condition, systemic immunosuppression for recipients of transgenic transplants is not justified. An alternative would be protecting the tissue to be transplanted from the immunologic response (immunoisolation) by coating it with a semipermeable membrane- microencapsulation. Unfortunately, prior to the first clinical use, further analysis of the coating substance (alginate) demonstrated that it has potential cancerogenic properties. Using a purified amitogenic alginate suitable for clinical use, we accomplished allotransplantation in a long-term animal model and reported the first clinical cases without postoperative immunosuppression recently. In view of the potential clinical use, we investigated the ability of the microencapsulation technology with the novel amitogenic alginate in experimental hypoparathyroidism (80 parathyroidectomized rats) to enable transgenic transplantation across the highest immunologic barrier (xenotransplantation: human to rat) to ensure intact transplant function without immunosuppression. In a controlled, long-term animal study, the effect of microencapsulation on xenotransplanted human parathyroid tissue was evaluated over a period of 30 weeks (microencapsulated and naked hyperplastic parathyroid tissue, respectively). Functionally, human parathyroid tissue was able to replace that of rats. More than 6 months after xenotransplantation 32 of 40 animals that had received microencapsulated transplants were normocalcemic. In contrast, serum calcium concentrations dropped to postparathyroidectomy levels within 3 weeks in the animals that had received naked tissue only. Correspondingly, normocalcemic animals showed vital parathyroid tissue inside the microcapsules, which were surrounded by a small rim of fibroblasts. When combining microencapsulation with an improved tissue culture method, xenotransplantation of human parathyroid tissue and maintenance of its physiologic function is reproducibly achieved over the highest transplantation barrier. Using the amitogenic alginate may be a crucial step toward the first clinical use of this technique for parathyroid xenotransplantation without immunosuppression.

Alginates↗

PubMed2004

Pharmacobezoar complicating treatment with sodium alginate.

We encountered a gastric bezoar that had developed in a 9-year-old girl treated with sodium alginate (Alloid G) for acute gastritis associated with systemic lupus erythematosus. A hard mass palpated in the left upper abdomen proved, upon gastric endoscopy, to be an intragastric foreign body. Sodium alginate was detected in an analysis of a sample from this bezoar. In an in vitro simulation, sodium alginate solidified when mixed with the patient's other medicines. The bezoar caused no complications, and disappeared spontaneously after discontinuation of the medications. This case indicates that this sodium alginate preparation, Alloid G, can be a cause of pharmacobezoar.

Alginates↗

PubMed2005

Extra thin alginate film: an efficient technique for protoplast culture.

This paper reports an efficient protoplast culture technique, the "extra thin alginate film" technique. The development of this improved method of protoplast culture was an outcome of an assessment of the efficiency and shortcomings of various protoplast culture techniques. The efficiency of this technique was evaluated with two model plant systems, viz., Nicotiana tabacum and Lotus corniculatus, and a comparison was made with the "thin alginate layer" technique, another efficient protoplast culture system. Results indicate that the culture technique with extra thin alginate film is as efficient as the technique with thin alginate layer, with many additional advantages. The present innovation overcomes most of the limitations of protoplast culture techniques described so far and can now be applied to a wide variety of crops to check its general applicability.

Alginates↗

PubMed2005

Effects of alginate encapsulation on mitochondrial activity.

The long-term objective of our research is to study the biochemical consequences of primary genetic defects of the Pyruvate Dehydrogenase Complex, a key mitochondrial enzyme complex, by NMR spectroscopy. An established method to obtain energetic and metabolic information from intact cells involves the use of 31P and 13C NMR spectroscopic techniques. NMR spectra from live and fully functional cells can be obtained from cells encapsulated within alginate beads and maintained in a perfusion bioreactor throughout the NMR experiment. However, before spectroscopic studies can commence, the effects of alginate encapsulation on the general metabolism and mitochondrial activity of fibroblasts need to be determined. in this study we report glucose consumption and flow cytometry measurements (with the fluorescent markers MitoTracker GreenFM and Nonyl-acridine Orange to determine the mitochondrial status and mass) of healthy human fibroblasts encapsulated in a mannuronic acid-rich alginate matrix. The results show that alginate encapsulation of fibroblasts does not affect the glucose consumption, the mitochondrial integrity, or the mitochondrial mass during 21 days of in vitro culture.

Alginates↗

PubMed2005

The crystallization of Hydroxyapatite in the presence of sodium alginate.

The effect of sodium alginate on the crystal growth of hydroxyapatite (HAP) was investigated at sustained supersaturation by the constant composition technique. Sodium alginate was found to inhibit HAP crystal growth at low concentrations and reduced the crystal growth rates by 42-86% for inhibitor concentrations of 2.1x10(-7)-12.6x10(-7) mol/l. The inhibition effect on the crystal growth rate may be explained possibly through adsorption onto the active growth sites. A detailed kinetics analysis suggested a Langmuir-type adsorption of the alginate on HAP surface and a value of 1.63x10(7) l/mol was obtained for the affinity constant of sodium alginate for the surface of HAP. The apparent order for the crystallization reaction was determined to be approximately 2, thus suggesting a surface diffusion controlled spiral growth mechanism.

Alginates↗

PubMed2005

Preparation and characterization of an electrodeposited calcium phosphate coating associated with a calcium alginate matrix.

A new way of optimizing osteoconduction of biomaterials is to bring to them biological properties. In this work, we associated a novel release system with an electrodeposited calcium phosphate (CaP) coated titanium alloy Ti6Al4V. The characterization of this material was performed by means of light microscopy, scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM) and X-ray energy dispersive spectroscopy (EDXS). The electrodeposited CaP coating was a tricalcium phosphate, and the release system was composed of microcapsules entrapped in an alginate film. We observed that the alginate matrix had a close contact with the coating. An intermediate layer containing calcium and phosphorus appeared at the interface between the alginate matrix and the CaP coating. These results allowed us to conclude that the association of two techniques, i.e. electrodeposition followed by deposition of a calcium alginate matrix, led to the elaboration of a new biomaterial.

Alginates↗

PubMed2006

Osteogenic behavior of alginate encapsulated bone marrow stromal cells: an in vitro study.

Sodium alginate is a useful polymer for the encapsulation and immobilization of a variety of cells in tissue engineering because it is biocompatible, biodegradable and easy to process into injectable microbeads. Despite these properties, little is known of the efficacy of calcium cross-linked alginate gel beads as a biodegradable scaffold for osteogenic cell proliferation and differentiation. In this study, we investigated the ability of rabbit derived bone marrow cells (BMCs) to proliferate and differentiate in alginate microbeads and compared them with BMCs cultured in poly-L-lysine (PLL) coated microbeads and on conventional 2D plastic surfaces. Results show that levels of proliferation and differentiation in microbeads and on tissue culture plastics were comparable. Cell proliferation in microbeads however diminished after fortification with a coating layer of PLL. Maximum cell numbers observed were, 3.32 x 10(5) +/- 1.72 x 103; 3.11 x 10(5) +/- 1.52 x 10(3) and 3.28 x 10(5) +/- 1.21 x 10(3 ) for the uncoated, PLL coated and plastic surface groups respectively. Alkaline phosphatase and protein expressions reflected the stage of cell differentiation. We conclude that calcium cross-linked alginate microbeads can act as a scaffold for BMC proliferation and osteogenic differentiation and has potential for use as 3D degradable scaffold.

Alginates↗

PubMed1979

A study of the reaction catalysed by alginate lyase VI from the sea mollusc, Littorina sp.

The molecular weight of polymeric alginic acid digested by alginate lyase (poly(1,4-beta-D-mannuronide) lyase, EC 4.2.2.3) was determined at various stages of the lysis. Low molecular weigh fragments were detected only after 60-100% lysis. Some high molecular weight fragments remained intact even after addition of a fresh aliquot of enzyme to the digest. The enzyme showed maximal activity at pH 5.6 in 0.05 M salt. Enzyme activity was stimulated by addition of 7.5 mM CaCl2 and 0.2 M NaCl, when the pH optimum was between 8 and 8.5. Only mannuronic acid was detected at the reducing end of fragments after exhausive enzymolysis, reduction and hydrolysis. On studying the reaction products by NMR, a double-bound signal (sigma = 5.98 ppm) was observed. A considerable decrease in intensity of the D-mannuronic acid residue signal was detected after hydrolysis of alginate lyase VI on poly-(ManUA-GulUA), but not poly(GulUA). The results suggest that alginate lyase VI may be an endoalginate lyase that splits glycoside bonds only between two mannuronic acid residues.

Alginates↗

PubMed1989

Calcium alginate dressing accelerates split skin graft donor site healing.

A prospective controlled trial of calcium alginate compared with traditional dressing of paraffin gauze on split skin graft (SSG) donor sites had to be abandoned after 15 patients as there was consistently better healing under the calcium alginate. The study was continued, on every patient requiring split skin grafting, to assess calcium alginate from the point of view of patient comfort, ease of dressing and quality of regenerated skin. In 107 patients with 130 SSG donor operations, there was a statistically highly significant decrease in average time to complete healing (from 10 down to 7 days), and also significantly better patient comfort. The alginate dressings were easy to use and the quality of the new skin significantly better than that seen under paraffin gauze dressings.

Adolescent↗

PubMed1991

A comparative investigation of re-epithelialisation of split skin graft donor areas after application of hydrocolloid and alginate dressings.

The performances of hydrocolloid and alginate dressing materials have been compared in a study of 65 split skin graft donor areas. The donor areas were randomised between the two dressing materials. The rates of epithelialisation, the discomfort experienced by the patients and the convenience of the dressings in clinical use were compared. At the time of the first dressing change 87% of the donor areas dressed with the hydrocolloid and 86% of the donor areas dressed with the alginate were found to be more than 90% healed. The mean time from operation to the observation of complete healing was 10.0 days for the donor areas dressed with the hydrocolloid and 15.5 days for the donor areas dressed with the alginate: this difference was found to be statistically significant. The discomfort experienced by the two groups of patients was comparable. The rapid healing associated with the hydrocolloid dressing was thought to be of greatest benefit to inpatients; alginate dressings were thought to be more suitable for outpatients, as they proved to be simpler to use.

Alginates↗

PubMed1990

Kinetics and specificity of alginate lyases: Part I, A case study.

Purified preparations of alginate lyase from Klebsiella aerogenes and Haliotis sp. were investigated for activity and degradation patterns with alginate and alginate fragments having different compositions and sequences. With fragments approaching homopolymers of guluronate and mannuronate, Michaelis-Menten kinetics were obeyed and kinetic parameters could be obtained. Degradation of alginates containing all four possible linkages in various proportions, followed by isolation of the fragments and identification of the end groups by n.m.r. spectroscopy, indicated that the enzyme preparations can attack more than one type of linkage. The results are discussed with reference to the concept of specificity for enzymes with copolymeric substrates having non-regular distributions of units.

Alginates↗

PubMed1992

Microbial contamination in two antimicrobial and four control brands of alginate impression material.

Previous investigations have revealed commercial alginate impression material to be contaminated with viable microorganisms. Some manufacturers are now producing alginate materials that contain antimicrobial agents. The purpose of this study was to test and compare two antimicrobial and four control brands without antimicrobial agents of commercial dental alginate impression material for the presence of viable microorganisms. Forty-eight or 96 measured samples of each brand were taken from previously unopened containers using a sterile technique. The samples were placed on chocolate agar plates and in thioglycolate broth tubes and were incubated along with appropriate parallel controls. After incubation, colonies were enumerated, gram-stained, and identified using standard microbiologic methods. The two antimicrobial brands contained viable organisms in 12.5% of the samples incubated on agar media and also contained such organisms from 0% to 16.7% of the samples incubated in thioglycolate media. The four control brands contained viable organisms in from 29.2% to 100% of the samples incubated on agar media and also contained these organisms in from 25% to 79.2% of the samples incubated in thioglycolate media. There was a statistically significant difference (p less than 0.05) in contamination frequencies among some brands. Contamination frequencies of the top and middle portions of the containers did not differ significantly. The concentration of organisms in contaminated samples was 2.8 colony-formed units (CFUs) per gram for the antimicrobial alginates, and from 9 to 161.1 CFUs per gram for the control brands.(ABSTRACT TRUNCATED AT 250 WORDS)

Actinomyces↗

PubMed1994

Alginate fiber dressing for oral mucosal wounds.

The aim of this study was to evaluate the effect on hemostasis and wound healing of a proprietary alginate fiber dressing when applied to a wound of the buccal mucosa of approximately 2 mm depth. The study showed a significant reduction in the number of residual bleeding points in shallow wounds when the alginate fiber dressing was applied for 5 minutes as compared with the use of non-alginate-impregnated surgical gauze. There was no significant difference in the rate of epithelial repair of the test and control sites nor in the area of the resulting mucosal scar. In addition, there was no significant difference in the numbers of tissue components in the submucosa. It is concluded that the alginate fiber dressing material evaluated in this study may be effective as a hemostatic mucosal dressing in shallow wounds, but it does not accelerate mucosal wound healing.

Alginates↗

PubMed1987

Diffusion characteristics of alginate membranes.

The diffusive properties of alginate membranes prepared by the interfacial reaction of sodium alginate solution with gypsum substrates were studied. The penetrants of primary importance for the above study were methyl methacrylate (MMA) and water, since alginate membranes are used as mould release agents, during the casting of poly(methyl methacrylate) (PMMA) in gypsum moulds in a water bath. Vapour sorption measurements were carried out at various temperatures. The effect of temperature and the combined action of water and MMA on the swelling behaviour of the membrane was also investigated. The results indicate that the water sorption of alginate membranes is non-Fickian, in spite of the linearity of the curves obtained by plotting Mt/M infinity versus t 1/2, at least for a short time period. The membrane treatment with methyl methacrylate, leads to considerably lower equilibrium sorption, possibly because of the formation of a thin film of poly(methyl methacrylate) on the membrane surface.

Alginates↗

PubMed1992

FT-IR measurement of emulsified cationic DMAEMA-MMA adsorption to calcium alginate.

The rate of adsorption of aqueous emulsions of DMAEMA-MMA copolymers to calcium alginate substrates was examined using ATR FT-IR spectroscopy. This work was undertaken as part of the development of a hybrid artificial pancreas. Aqueous DMAEMA-MMA copolymer emulsions containing < 25 mol% DMAEMA were slowly adsorbed to calcium alginate substrates; emulsions of 50 mol% DMAEMA-MMA copolymer were adsorbed rapidly to calcium alginate gels. The adsorption of 50 mol% DMAEMA-MMA copolymer emulsions to calcium alginate gels was attributed to electrostatic rather than simple van der Waals' attractive forces.

Adsorption↗

PubMed1996

Alginate polycation microcapsules. II. Some functional properties.

The main cause of alginate polycation capsule breakage under physiological conditions is probably the osmotic swelling of the alginate core owing to the Donnan equilibrium set up by the negative charges of the carboxyl groups not involved in cooperative binding of counterions in the junction zones of the network. In the present paper we show how capsules can be stabilized extensively by reducing their swelling capacity in various ways. Alginate polycation capsules with good chemical and mechanical stability have been made by controlling their swelling behaviour through selection of capsule material according to chemical structure and molecular weight, as well as by controlling the kinetics of the capsule formation. Stable capsules have been made either by increasing the strength of the polyanion-polycation membrane, or by keeping a low-swelling gel network in the core. The latter capsules are made from an alginate rich in guluronic acid both in the core and in an outer coating, and with anisotropic distribution of the polymer material in the core where the concentration at the surface is higher than that in the centre of the capsule. Some functional properties of these capsules, such as porosity, have also been studied.

Alginates↗

PubMed1983

Microencapsulation of erythrocytes in Eudragit-RL-coated calcium alginate.

Human erythrocytes have been encapsulated in calcium alginate gel beads (approx. 2 mm diameter) which were subsequently coated with a water-insoluble cationic polyacrylate, Eudragit RL. Stained histological sections as well as scanning and transmission electron micrographs clearly showed the presence of a dense capsule wall, approx. 60 micron thick after 60 min of exposure to an aqueous emulsion of Eudragit, surrounding a sponge-like alginate core. Eudragit beads could withstand greater compressive forces before mechanical failure than uncoated beads. The effect of alginate concentration, coating time and ionic strength on the compressive load at failure, indicated the likelihood that coating involved ionic interactions between the polycationic Eudragit and the polyanionic alginate. Encapsulated erythrocytes continued to consume glucose but at a rate one-third higher than normal which attributed to an under estimate in the number of immobilized cells or to an actual increase in cell metabolism due to immobilization. Alginate/Eudragit encapsulated erythrocytes also continued to reversibly bind oxygen even after 21 days storage at 4 degrees C. Although in vivo stability and biocompatibility remain at question, this system is a model of that required to encapsulate pancreatic islets for the treatment of insulin-dependent diabetes.

Alginates↗

PubMed1995

Genetic linkage in Pseudomonas aeruginosa of algT and nadB: mutation in nadB does not affect NAD biosynthesis or alginate production.

The 68-min region of the chromosome of Pseudomonas aeruginosa (Pa) contains the gene algT, encoding a putative alternate sigma factor similar to sigma E in Escherichia coli, that is required for the expression of several genes in the alginate biosynthetic regulon. Sequences immediately upstream from algT were found to contain a divergently expressed open reading frame encoding a 60-kDa protein with 64 and 36% identity to the nadB gene products of E. coli and Bacillus subtilis, respectively. The nadB gene encodes L-aspartate oxidase and has been shown in several bacteria to be essential for de novo nicotinamide-adenine dinucleotide (NAD) biosynthesis. Pa nadB complemented the growth requirement for nicotinic acid in a nadB mutant strain of E. coli, suggesting that this gene encodes a functional homologue of L-aspartate oxidase. A nadB::Tn501 mutant was constructed by gene replacement in the alginate-producing strain, Pa FRD. This NadB- mutant still produced alginate and appeared normal with respect to the regulation of alginate synthesis. Interestingly, the NadB- mutant did not have an auxotrophic phenotype for nicotinic acid, indicating that this nadB was not essential for NAD biosynthesis in Pa. These results suggest the possibility that Pa has an alternate mechanism for de novo NAD biosynthesis.

Alginates↗