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PubMed1997

Stimulation of human keratinocyte growth by alginate oligosaccharides, a possible co-factor for epidermal growth factor in cell culture.

Oligosaccharides, involved in regulation of plant developmental and defensive processes, were tested to determine their ability to enhance proliferation of human keratinocytes. A mixture of alginate oligosaccharides remarkably stimulated keratinocyte growth and [3H]thymidine uptake in the presence of epidermal growth factor (EGF). The activity was comparable to bovine pituitary extract, a common complement in keratinocyte culture, and additive on BPE-induced stimulation. The most effective oligosaccharide in the mixture was identified and its chemical structure was determined. These findings demonstrate a novel activity of alginate oligosaccharide(s) in keratinocyte growth and suggest a possible co-factor for EGF-dependent stimulation in medium for keratinocytes.

Alginates↗
PubMed1976

Chromatographic behaviour of alkaloids on thin layers of cation exchangers. II. Alginic acid, Rexyn 102, Dowex 50-X4 and CMCNa.

The chromatographic behaviour of 48 alkaloids on cation exchangers with cellulose, paraffin and polystyrene matrices in both the acid and sodium salt forms has been investigated. Water-organic solvent mixtures, aqueous buffer solutions and organic and mineral acid solutions in both water and in aqueous-organic solvents have been used as eluents. The retention mechanisms of these compounds on alginic acid, Rexyn 102 (Hplus) and Dowex 50-X4 (Hplus) thin layers are discussed. Interesting separations of the alkaloids were carried out on alginic acid and Rexyn 102 (Hplus).

Alginates↗
PubMed1997

Effects of long-term storage on properties of an alginate impression material.

STATEMENT OF PROBLEM: Storage stability is a critical characteristic for perishable dental materials. PURPOSE: The purpose of this shelf-life study was to document changes in the properties of an alginate impression material on exposure to various environmental conditions for more than 78 months. MATERIAL AND METHODS: Properties measured included recovery from deformation, strain in compression, compressive strength, tear strength, working time, and creep compliance. RESULTS: Results revealed increases in strength and working time and a decrease in recovery from deformation at 30 to 50 months: strength and recovery then remained constant past 6 years, whereas working time and creep compliance decreased. Only the most stressful environmental conditions (heat and humidity) caused spontaneous failure of the material to set. CONCLUSIONS: We concluded that, under most storage conditions, properties of the alginate material tested remain within ADA specification limits well past manufacturer's designated shelf life. ADA specifications should require manufacturers to verify that the shelf life of each perishable material is based on valid data. An accelerated aging test was developed to simulate real time property changes and to assist in evaluating similar materials.

Alginates↗
PubMedDate not supplied

Proteoglycan metabolism of equine articular chondrocytes cultured in alginate beads.

Equine chondrocytes were cultured in vitro for 30 days in ionically gelled alginate beads. The alginate polymerises into a stable gel in the presence of divalent cations (calcium), and rapid depolymerisation in the presence of a calcium chelator releases the viable chondrocytes. The chondrocytes maintained a spherical appearance for 30 days in culture, in marked contrast to monolayer cultures, which develop a dedifferentiated fibroblastic morphology. The major proteoglycan molecule produced by the encapsulated chondrocytes was aggrecan, of similar hydrodynamic size to aggrecan molecules present in the matrix of the articular cartilage from which the cells were harvested. Link protein, keratan sulphate and chondroitin sulphate were also synthesised by the chondrocytes, as demonstrated by immunohistochemistry. The proteoglycan secreted by the chondrocytes consisted of at least two pools, one remaining adjacent to the cell and forming a dense, cell-associated matrix, and another migrating more peripherally into the intercellular compartment. Newly synthesised proteoglycans extracted from the pericellular matrix and the intercellular matrix were similar in hydrodynamic size and aggregated in the presence of exogenous hyaluronan.

Alginates↗
PubMed2003

13C-NMR study of the interaction of bacterial alginate with bivalent cations.

The effect of bivalent cations on solutions of extracellular polymeric substances (EPS) isolated from Pseudomonas aeruginosa was monitored by means of solid-state nuclear magnetic resonance. In particular, the binding of Ca2+ and Mg2+ to the alginate in aqueous solution was studied by determining the spin-lattice relaxation rates, line widths and line shapes of 13C nuclei under variation of the ion concentration. Both cations differ strongly in their affinity towards bacterial alginate. Spectral data indicate that the strong binding capacity of calcium is connected to the formation of a chelate complex, in which binding occurs particularly with the monomer units in alternating mannuronate-guluronate blocks. In contrast to this, binding of magnesium ions was found to be much weaker and non-specific.

Alginates↗
PubMed2000

Magnetic nanostructured composites using alginates of different M/G ratios as polymeric matrix.

Alginate extracted from Sargassum fluitans and Macrocystis pyrifera with different molecular weights and mannuronic/guluronic ratios, M/G, were used as gel matrixes in order to obtain magnetic nanostructured composites. Magnetic nanocrystalline particles of iron oxides were formed inside the alginate matrix by in situ alkaline oxidation of ferrous ions. The magnetic materials obtained were subjected to several oxidative cycles and the increment in iron content was determined after each cycle. X-ray diffraction, magnetometry and Mössbauer spectroscopy were used to examine the materials. The high magnetic response, the absence of hysteresis, and the centered paramagnetic doublet in the Mössbauer spectra indicate the presence of nanocrystalline particles with a superparamagnetic behavior. X-ray diffractograms show peaks that correspond to maghemite. After the first cycle, Sargassum had four times the magnetic response of Macrocystis, which had more than twice the M/G ratio.

Alginates↗
PubMed2002

Effects of aldehydes and methods of cross-linking on properties of calcium alginate microspheres prepared by emulsification.

Calcium alginate microspheres were prepared by an emulsification method and cross-linked with various aldehydes using different methods. Methanal and pentanedial produced low aggregation of microspheres while octanal and octadecanal produced the opposite effect. The latter two aldehydes displaced very little calcium ions from the alginate microspheres, indicating that the aggregation was due to the tackiness imparted by the aldehydes to the microsphere surface. Higuchi's model was not applicable to the drug release from microspheres in this study. The microspheres treated with methanal or pentanedial showed comparable dissolution T75% values which were significantly higher than that of the control. In contrast, octanal and octadecanal produced microspheres with lower dissolution T75% values. The drug contents of the microspheres treated with aldehydes were significantly lower than that of the control. There was insignificant interaction between the aldehydes and the drug. However, the aldehydes were found to impart acidity to the aqueous solution to varying extents, resulting in varying drug loss from the microspheres. The properties of the microspheres were also markedly affected by the method of incorporating the aldehyde. Soaking the microspheres in methanal solution produced microspheres with marked aggregation and low drug content.

Aldehydes↗
PubMed2002

Tailoring the pore architecture in 3-D alginate scaffolds by controlling the freezing regime during fabrication.

The pore architecture in 3-D polymeric scaffoldings plays a critical role in tissue engineering as it provides the framework for the seeded cells to organize into a functioning tissue. In the present paper, we investigate the effect of freezing regime on the pore microstructure in 3-D alginate scaffolds, fabricated by the freeze-dry method. The scaffolds have shown isotropic pore structure, when the calcium crosslinked alginate solutions were slowly frozen at -20 degrees C, in a nearly homogenous cold atmosphere; the pores were spherical and interconnected. In contrast, when the cooling process was performed in liquid nitrogen or oil bath, where a temperature gradient was formed along the freezing solution, two main regions of pore structure were noted; at the interface with the cooling medium, small spherical pores were seen and above them a region with elongated pores. The different pore shape affected the compressibility of the scaffolds, while it had no effect on albumin diffusion. Rat hepatocytes seeded within the scaffolds were arranged according to the their pore shape. In scaffolds with elongated pores, the cells were lining along the pores, thus forming lines of interacting cells. In the scaffolds with the isotropic spherical pores, the hepatocytes clustered into spheroid-like aggregates. Thus, it appears that pore shape can modulate hepatocyte morphogenesis.

Albumins↗
PubMed2003

Scanning electron microscopic examination of bacterial immobilisation in a carboxymethyl cellulose (AQUACEL) and alginate dressings.

Dressings have been applied to open wounds for centuries. Traditionally they have been absorbent, permeable materials, i.e. gauze that could adhere to desiccated wound surfaces, inducing trauma on removal. With the advent of modern wound care products many dressings are now capable of absorbing large volumes of exudate whilst still continuing to provide a moist wound healing environment. Equally important is their ability to lock exudate in the dressing (i.e. bacterial retention within the dressing matrix) such that upon removal from a wound surface bacterial dispersion is minimised. In these studies detailed scanning electron microscopy techniques have demonstrated the fluid controlling properties of alginate wound dressings and a carboxymethylated cellulose wound dressing (AQUACEL) Hydrofiber) dressing (CMCH)). It was demonstrated that following hydration of the latter wound dressing, the subsequent formation of a cohesive gel was effective in encapsulating large populations of potentially pathogenic bacteria such as Psuedomonas aeruginosa and Staphylococcus aureus under the gelled surface, as well as being immobilised within the swollen fibres. In contrast, hydrated alginate wound dressings did not form a uniform, cohesive gel structure, with the result that fewer bacteria were immobilised within the gel matrix. Many bacteria were trapped on individual, non-hydrated fibres. The unique absorbent gelling properties of the CMCH dressing appears to provide an ideal environment for immobilising bacteria.

Alginates↗
PubMed2001

Induction of systemic and mucosal immune response in cattle by intranasal administration of pig serum albumin in alginate microparticles.

Biodegradable microparticles are an efficient mucosal delivery system that protect antigens from the harsh mucosal environment and facilitate their uptake by M cells at the epithelium of mucosal-associated lymphoid tissue. In this study, we determined the systemic and mucosal immune response in calves following intranasal and oral immunization with pig serum albumin (PSA) encapsulated in alginate microparticles. The size of the particles ranged from 1 to 50 microm in diameter, with 95% of the particles being smaller than 5 microm. High levels of anti-PSA IgG1 antibodies were found in the serum, nasal secretions, and to a less extent in saliva of calves vaccinated intranasally, but not orally, with PSA-microparticles. There was no significant increase of PSA-specific IgA. A weak lymphocyte proliferative immune response was observed in peripheral blood mononuclear cells (PBMCs), and few anti-PSA antibody-secreting cells (ASC) were detected in the blood of calves immunized intranasally. The combined systemic and mucosal response observed in intranasally immunized animals may be attributed to the wide variation in the size of the alginate microparticles, with smaller particles translocating to regional lymph nodes and inducing a systemic immune response, and larger particles being retained in the NALT and inducing a mucosal immune response. The procedure presented here may be useful as an intranasal vaccine against respiratory diseases in cattle.

Administration, Intranasal↗
PubMed2003

Reproducing shake flasks performance in stirred fermentors: production of alginates by Azotobacter vinelandii.

Keeping equal the initial power drawn (0.27 W l(-1)) in shake flasks and in a stirred fermentor did not reproduce the behaviour of alginate production by Azotobacter vinelandii. A lower mean molecular weight (1.1x10(6) Da) of the polymer was obtained in the bioreactor as compared to that obtained in shake flasks (1.9x10(6) Da). The reasons for this can reside in the fact that the evolution of the power drawn in the shake flasks could be considerably different to that observed in the stirred bioreactor. A drastic drop in the specific power drawn is expected in the shake flasks as a consequence of the increased viscosity, which caused the liquid not following the movement of the shaker. This was supported by the fact that cultures developed in the fermentor at lower initial power drawn (as low as 0.027-0.056 W l(-1)) or in a culture in which the power drawn was deliberately reduced along cultivation, produced alginates with similar molecular characteristics as that obtained in shake flasks.

Alginates↗
PubMed2002

Immunization of rabbits against a bacterial pathogen with an alginate microparticle vaccine.

Pasteurella multocida is an important bacterial pathogen of domestic rabbits. To evaluate the ability of a thiocyanate extract (PTE) of P. multocida to stimulate an immune response and protect against infection with P. multocida, rabbits were immunized subcutaneously or intranasally on Days 7, 21 and 35. Cholera toxin, a potent mucosal adjuvant, was included in one treatment group. Rabbits immunized subcutaneously (SC) or intranasally (IN) had significant increases in serum anti-PTE IgG but not IgA. In contrast, only rabbits immunized IN with PTE developed significant titers of nasal lavage anti-PTE IgA and cholera toxin significantly enhanced this response. In a second study rabbits were immunized via the drinking water with PTE incorporated into alginate microparticles on Days 7, 14 and 21. Mild increases in serum IgG were noted in rabbits immunized with PTE in microparticles, with or without cholera toxin, and this increase was significant (P<or=0.05) on Day 21 for rabbits receiving PTE and cholera toxin. Nasal lavage anti-PTE IgA was significantly (P<or=0.05) increased in rabbits immunized orally with PTE, with or without cholera toxin, in microparticles. This effect was not enhanced by cholera toxin. Rabbits orally immunized with PTE in microparticles had significantly fewer colony forming units of homologous P. multocida recovered from the lungs and nasopharynx following an intranasal challenge. These results demonstrate that PTE incorporated into alginate microparticles and administered orally is immunogenic and confers protective immunity.

Alginates↗
PubMed1999

Evaluation of parameters involved in preparation and release of drug loaded in crosslinked matrices of alginate.

Parameters affecting the characteristics of the drug loaded crosslinked sodium alginate matrix films and the release of metoclopramide hydrochloride and cisapride from these matrices were studied. It was shown that the release rate is influenced by the crosslinking technique of the matrix film, crosslinker type and concentration, drug physico-chemical properties especially solubility and the molecular weight, acidity of the release medium, concentration and the loaded quantity of the drug in the matrix. The crosslinking process of the matrix film was shown to be an interfacial phenomenon and the nature of crosslinking depends on the crosslinker type and concentration. This work also showed that crosslinked alginate in a matrix form has limitation in practical use due to the effect of acidic medium on the crosslinking of the matrix film and hence, the rate of drug release.

Alginates↗
PubMed1994

A new method for the 3-D in vitro growth of human RT112 bladder carcinoma cells using the alginate culture technique.

We studied the response to different in vitro culture conditions and the ability for polarization in three-dimensional (3-D) and two-dimensional (2-D) cell culture systems of the commonly used human bladder carcinoma cell line RT112. In the case of 2-D culture the cells were grown on glass or plastic coverslips, filter membranes, or bovine lens capsules. The alginate culture technique (ACT) was used to test the effects of 3-D cell culture on the polarization of the RT112 epithelial cells. Our studies show clear differences in the arrangement of the cells depending on the cultivation procedure. The RT112 cells cultured on glass and plastic supports were irregular and flattened in shape whereas the cells grown on filters or on lens capsules developed into 2-3 layers consisting of markedly polarized cells. However, ACT was superior to cell culture on either artificial supports or even on lens capsule. During the 3-D cultivation the transformed epithelial cells regenerated multicellular spheroids which maintained a tissue-like, geometrically well-ordered and highly prismatic organization. This ACT-induced morphogenesis is novel and distinct from that reported with conventional culture conditions. Microscopic investigations showed that RT112 cells grown in alginate were both much more tightly packed and more regularly organized compared to 2-D cultures. In addition, the spheroidal organized cells exhibited well developed cell-cell contacts, a distinct endoplasmatic reticulum, and a marked Golgi apparatus. In summary, ACT can be used for 3-D in vitro growth of the transformed human epithelial cell line RT112 that offers substantial advantages over conventional cell culture methods.

Alginates↗
PubMed1999

Oral vaccination of animals with antigens encapsulated in alginate microspheres.

Most infectious diseases begin at a mucosal surface. Prevention of infection must therefore consider ways to enhance local immunity to prevent the attachment and invasion of microbes. Despite this understanding, most vaccines depend on parenterally administered vaccines that induce a circulating immune response that often does not cross to mucosal sites. Administration of vaccines to mucosal sites induces local immunity. To be effective requires that antigen be administered often. This is not always practical depending on the site where protection is needed, nor comfortable to the patient. Not all mucosal sites have inductive lymphoid tissue present as well. Oral administration is easy to do, is well accepted by humans and animals and targets the largest inductive lymphoid tissue in the body in the intestine. Oral administration of antigen requires protection of antigen from the enzymes and pH of the stomach. Polymeric delivery systems are under investigation to deliver vaccines to the intestine while protecting them from adverse conditions that could adversely affect the antigens. They also can enhance delivery of antigen specifically to the inductive lymphoid tissue. Sodium alginate is a readily available, inexpensive polymer that can be used to encapsulate a wide variety of antigens under mild conditions. Orally administered alginate microspheres containing antigen have successfully induced immunity in mice to enteric (rotavirus) pathogens and in the respiratory tract in cattle with a model antigen (ovalbumin). This delivery system offers a safe, effective means of orally vaccinating large numbers of animals (and perhaps humans) to a variety of infectious agents.

Administration, Oral↗
PubMed2002

[Efficacy and tolerance of Algosteril (calcium alginate) versus Jelonet (paraffin gauze) in the treatment of scalp graft donor sites in children. Results of a randomized study].

Split skin graft is frequently needed in the treatment of burned patients. Scalp is often free of burns. Due to its good skin quality and important surface, scalp is a very interesting skin donor site, specially in case of children. A controlled, randomised clinical trial was carried out in 10 French Plastic Surgery or Burns Units. It assessed the efficacy and the acceptability of calcium alginate dressing (Algosteril) versus paraffin gauze dressing (Jelonet) in the treatment of scalp donor sites in children. 67 children (mean age 54 months) entered the study, 34 in the alginate group and 33 in the control group. Follow-up visits were on day 2/d3, d5/d6, Day complete healing, d30 and d60 after surgery. The two groups were comparable on inclusion (demographic characteristics, burn nature and surface, donor site surface and thickness of split skin graft). The mean healing time was 10 and 11 days for Algosteril and Jelonet group respectively (ns). The quality of the newly formed tissue was estimated to permit a sooner skin reharvesting in the Algosteril group than in the control group (p = 0.003). Bleeding through dressing was significantly less important in the Algosteril group (p = 0.02). Changes were considered by investigators less painful with Algosteril on day complete healing (p = 0.0096). Hair growth is homogenous in both groups on day 30 and day 60 (ns). These results showed that scalp is a very interesting skin donor site and that Algosteril is of a real interest in donor site treatment.

Alginates↗
PubMed1999

Cat peripheral nerve regeneration across 50 mm gap repaired with a novel nerve guide composed of freeze-dried alginate gel.

We have developed a novel artificial nerve guide composed of biodegradable freeze-dried alginate gel covered by polyglycolic acid mesh, and evaluated its effect on peripheral nerve regeneration, using a 50-mm gap cat sciatic nerve model. Functional reinnervation of motor and sensory nerves occurred 13 weeks after implantation, as demonstrated by recovery of compound muscle action potential (CMAP) and somatosensory evoked potential (SEP). For histologic evaluation, samples of tissue were harvested from the grafted material segment 7 months after operation. Many newly developed nerve fasciculi were found, and the implanted nerve guidance material had completely disappeared with little inflammation. These results indicate that freeze-dried alginate gel allows the nerve to regenerate across longer gaps than described in previous literature.

Alginates↗
PubMed2000

Unusual donor site reactions to calcium alginate dressings.

Calcium alginate dressings have been used as the standard dressing for split skin donor sites at the Women's and Children's Hospital burn unit for the last 12 yr. This method has proven satisfactory with good haemostasis, reliable healing, low infection rate and is well accepted by the children and nursing staff. We have recently had 5 cases with the unusual and unexplained phenomenon of dermal calcification in the donor site following the use of two new varieties of calcium alginate dressing.

Alginates↗