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PubMed2004

[Tolerance of a new calcium-alginate-insert for controlled medication therapy of the eye].

PURPOSE: For an effective pharmaceutical treatment it is necessary in some cases to maintain a constant drug level over a certain period. This cannot be achieved by conventional eye drop application. Therefore, a new insert basically consisting of alginates with a different hydroxyethylcellulose (HEC) content was developed. The aim of this study was to evaluate the tolerance of these inserts applied to the conjunctival cul de sac. METHODS: 24 healthy volunteers received the insert containing different concentrations of hydroxyethylcellulose (0%, 5%, 30%) for 1 up to 5 days. The eyes have been examined several times (including visual acuity, ocular surface morphology, break-up-time, Schirmer-Tear-Test). Subjective parameters were pain sensations or daily life disturbance. RESULTS: After an initial conjunctival hyperemia and a mild foreign body sensation, the insert was well tolerated. No variations concerning the tolerance between the different concentrations of hydroxyethylcellulose were observed. CONCLUSION: This study showed good tolerance of the new calcium-alginate-insert applied to the ocular surface for controlled drug release.

Alginates↗
PubMedDate not supplied

Alginate oligosaccharides modulate cell morphology, cell proliferation and collagen expression in human skin fibroblasts in vitro.

Effects of alginate oligosaccharides on cell proliferation and expression of collagen in cultured skin fibroblasts were studied. The oligosaccharides were found to suppress fibroblast proliferation to half the level in control cultures at a dose of 10 mg/ml during a period of 5 days. The inhibition was accompanied by a change in cell shape. The inhibition of cell proliferation was reversible, since depletion of these oligosaccharides led to a recovery of cell motility. Treatment of confluent cells with 10 mg/ml oligosaccharides for 5 days resulted in a reduction in collagen synthesis to one half of that in control cultures and inhibition of steady state levels of alpha1(I), alpha2(I), alpha1(III) and alpha1(VI) collagen mRNAs. These results suggest that alginate oligosaccharides are potential modulators of dermal fibroblasts and may provide a useful tool for the treatment of disorders related to abnormal collagen metabolism.

Alginates↗
PubMed2002

Contamination level of alginate impressions arriving at a dental laboratory.

The contamination level of alginate impressions delivered to a large dental laboratory in Sweden was determined. One hundred and seven consecutive alginate impressions were included during 7 days. Samples were taken and transferred into sterile physiological saline and analysed microbiologically for colony-forming units (cfu) as well as nonhemolytic, alpha-hemolytic, and beta-hemolytic colonies. After sampling, the clinics were contacted and asked to fill in simple questionnaires about their routines of disinfecting impressions. The questionnaire study revealed that about half of the clinics had some kind of disinfection routine, while the others rinsed in running water only. Seventy-two percent of the impressions yielded growth of bacteria, with a median number of 1.3x10(2) cfu. Thirteen per cent of the samples yielded >10(3) cfu, with a maximum number of 3.4x10(4) cfu. The majority of isolates were non- and alpha-hemolytic bacteria. Growth was recorded in 61.3% of disinfected impressions, and the numbers of bacteria in disinfected and nondisinfected impressions were similar. These findings raise the question of whether impressions need to be disinfected or if proper handling and hygienic procedures are sufficient to block the possible route of infection.

Alginates↗
PubMed2004

Influence of immobilization parameters on growth and lactic acid production by Streptococcus thermophilus and Lactobacillus bulgaricus co-immobilized in calcium alginate gel beads.

Streptococcus thermophilus and Lactobacillus bulgaricus were co-immobilized in different systems with varying calcium (0.1-1.5 M) and alginate (1-2%, w/v) concentrations. Highest lactic acid production was 35 g l(-1) when both bacteria were in high viscosity beads (1%, w/v alginate) hardened in 0.1 M CaCl2 . The gel bead composition affected size and distribution of entrapped lactic acid bacteria.

Alginates↗
PubMed2005

In vitro study of alginate-chitosan microcapsules: an alternative to liver cell transplants for the treatment of liver failure.

The application of alginate-chitosan (AC) microcapsules to liver cell transplantation has not been previously investigated. In the current in vitro study, we have investigated the potential of AC microcapsules for the encapsulation of liver cells and show that the AC membrane supports the survival, proliferation and protein secretion by entrapped hepatocytes. The AC membrane provides cell immuno-isolation and has the potential for cell cryopreservation. The AC microcapsule has several advantages compared to more widely used alginate-poly-L-lysine (APA) microcapsules for the application of cell therapy.

Alginates↗
PubMed2005

Increased erythromycin production by alginate as a medium ingredient or immobilization support in cultures of Saccharopolyspora erythraea.

Erythromycin production by Saccharopolyspora erythraea immobilized in 2% (w/v) calcium alginate or grown in medium containing 20 g sodium alginate/l inoculated with free cells was almost twice more than that of the control. S. erythraea did not consume alginate, agar, dextran, silicon antifoaming agent or cyclodextrin as a carbon source, although, all of these increased the production of erythromycin. Highest titer of erythromycin (2.3 times more than that of the control) was achieved in medium containing 1 g agar/l.

Agar↗
PubMedDate not supplied

A comparison of calcium alginate and scarlet red dressings in the healing of split thickness skin graft donor sites.

Forty-six patients had split thickness skin grafts harvested from the upper inner thigh. Calcium alginate (Kaltostat) and scarlet red dressings were applied to each half of the wound. Dressings were changed after 10 days and healing of the donor site was assessed. Seventy-two per cent of wounds dressed with calcium alginate and 84% of wounds dressed with scarlet red were healed at 10 days. Scarlet red was shown to be significantly better than Kaltostat in the healing of split thickness skin graft donor sites when assessed at 10 days (p less than 0.04).

Adolescent↗
PubMed1994

Modulation of systemic cytokine levels by implantation of alginate encapsulated cells.

The availability of cell lines that are transfected with IL-4, IL-5 and IFN-gamma cytokine genes permits the prolonged in vivo delivery of functional cytokines in relatively large doses for the modulation of specific immune responses. Often the transfected cells are xenogeneic or allogeneic to the experimental animal and have to be encapsulated in such a way that no cellular response by the host will be induced. Alginate has proven to be a simple matrix for encapsulating cells under mild conditions suitable for in vivo implantation. Encapsulated cells express the transfected IL-4 gene for at least 14 days after in vivo implantation and were shown to be functional during that period by modulating ongoing IgE responses. The application of adherent growing transfected cells permits dose-response titrations and provides an easy method for local and systemic cytokine delivery. Alternatively, hybridoma cells can be encapsulated and the secreted antibody monitored in the serum. It was found that no host immune response was triggered by alginate encapsulated cells. The efficiency of treatment by encapsulated hybridoma cells was shown to be equivalent to that of injecting purified antibodies.

Alginates↗
PubMed1990

Effective diffusion coefficient of sucrose in calcium alginate gel.

The effective diffusion coefficient of sucrose in 5% calcium alginate gel containing 41.6 g.d.c. l-1. Saccharomyces cerevisiae was investigated. Both free and immobilized S. cerevisiae in 0.175 cm and 0.3 cm diameter particles were used and the reactions were achieved in a medium containing 100 g l-1 sucrose and 0.05 M CaCl2. With the assumption that the microorganisms did not grow or die in this medium, the results were analyzed according to Michaelis-Menten kinetics and the values of the parameters were determined as: Vm = 0.256 g ml-1 gel h-1, Km0 = 0.097 g ml-1, Km1 = 0.125 g ml-1, and Km2 = 0.165 g ml-1. Using these values, effectiveness factors were calculated as eta 1 = 0.89 and eta 2 = 0.76, and effective diffusion coefficients for sucrose in calcium alginate gel were determined as De1 = 4.1 X 10(-6) cm2 s-1 and De2 = 4.0 X 10(-6) cm2 s-1, for the particle size involved.

Alginates↗
PubMed1992

Determination of glucose and ethanol effective diffusion coefficients in Ca-alginate gel.

Glucose and ethanol diffusion coefficients in 2% Ca-alginate gel were measured using the experimental technique based on solute diffusion into or out of gel beads in a well-stirred solution. The aim of the study was to make the measurements under typical conditions found in alcoholic fermentations, such as the concentrations of glucose (100 g l-1) and ethanol (50 g l-1), the simultaneous counter-diffusion of glucose and ethanol, and the presence of cells in the gel beads at a level of 10(9) cells g-1 of beads. Previously, an evaluation of the error associated with the methodology used indicated how the experimental procedure would minimize the error. The individual measurement of glucose and ethanol coefficients in 2% Ca-alginate with no cells gave values of 5.1 and 9.6 x 10(-6) cm2 s-1, respectively, which are lower than those in water. When the effect of counter-diffusion was investigated, both coefficients decreased: glucose by 14% and ethanol by 28%. When cells were incorporated into the beads, only the ethanol coefficient decreased significantly, while the glucose coefficient apparently increased its value to 6.9 10(-6) cm2 s-1.

Alginates↗
PubMed1993

Production of intracellular enzyme by Corynebacterium glutamicum T6-13 protoplasts immobilized in Ca-alginate gels.

The glutamate dehydrogenase (GDH) (EC 1.4.1.4) productivity of the immobilized Corynebacterium glutamicum T6-13 protoplasts in Ca-alginate gels was investigated. GDH in Corynebacterium glutamicum T6-13 cells is an intracellular enzyme. The cells pretreated with 0.5 U/l-1 penicillin G were used for the preparation of protoplasts. Protoplasts were prepared by treating these cells with lysozyme at 30 degrees C for 14 h in 0.5 M NaCl solution and separating the protoplasts. Protoplasts were directly immobilized in 3% Ca-alginate gels (method I). The immobilized protoplasts could be also prepared by treating the immobilized whole cells with lysozyme (method II); this method was more convenient than method I. The GDH productivity of the immobilized protoplasts amounted to 205% of that of the free cells (intracellular). The immobilized protoplasts could be repeatedly used for at least 6 batches (18 days) and had good storage stability.

Alginates↗
PubMed1994

11 alpha-Hydroxylation of progesterone in biphasic media using alginate-entrapped Aspergillus ochraceus gel beads coated with polyurea.

A novel cell-immobilization technique was developed in this study for increasing substrate partition to the gel matrix by coating a polyurea thin layer on the surface of Ca-alginate beads. The proposed method was simple and could be performed under mild conditions. The bioconversion of progesterone to 11 alpha-hydroxyprogesterone with these polyurea-coating alginate-entrapped Aspergillus ochraceus cells was investigated using different organic solvents in biphasic media. The reaction medium of ethyl acetate could markedly enhance the bioconversion rate with the existence of a hydrophobic layer, most likely resulting from the increasing partition of substrate to gel matrix. Bioconversion with higher substrate concentration was possible using an ethyl acetate-water medium. The conversion rate increased almost linearly with increasing substrate concentration from 10 to 80 g l-1. The rate with 80 g l-1 progesterone increased up to six times greater than the rate with the immobilized cells without coating, and also exhibited a much higher rate than that reported in the literature.

Alginates↗
PubMed1985

Stability of some soluble alginate solutions.

The stability of some water alginates against bacterial degradation was studied. The study was based on viscosity and pH measurements of some typical alginate solutions, containing suitable additives during an extended time period (222 days).

Alginates↗
PubMed1992

Poly(ethylene oxide)-graft-poly(L-lysine) copolymers to enhance the biocompatibility of poly(L-lysine)-alginate microcapsule membranes.

A graft copolymer having poly(L-lysine) (PLL) as the backbone and monomethoxy poly(ethylene glycol) (MPEG) as pendent chains was synthesized. This polycationic copolymer was used to form microcapsules with sodium alginate, a polyanion. Microcapsules and model surfaces formed with PLL-graft-MPEG demonstrated reduced protein adsorption, complement binding and cell adhesion in vitro compared to materials with unmodified PLL. Microcapsules with PLL-g-MPEG on the surface were seen to be much more biocompatible than the widely used alginate/PLL/alginate microcapsule in a mouse intraperitoneal implant model. The graft copolymers demonstrated a lower affinity for alginate and increased microcapsule permeability more than PLL. To correct this, pentalayered alginate/PLL/alginate/PLL-g-MPEG/alginate microcapsules were fabricated, and these demonstrated both appropriate permselectivity and enhanced biocompatibility.

Adsorption↗
PubMed1993

Interfacial photopolymerization of poly(ethylene glycol)-based hydrogels upon alginate-poly(l-lysine) microcapsules for enhanced biocompatibility.

The biocompatibility of microcapsules made by the co-acervation of alginate and poly(l-lysine) (PLL) was enhanced by coating the surface of these microcapsules with a poly(ethylene glycol) (PEG)-based hydrogel. The hydrogel was formed by an interfacial photopolymerization technique using visible light from an argon ion laser. The light absorbing chromophore, eosin Y, was immobilized on the microcapsule surface. This restricted the formation of the PEG hydrogel to the surface of the microcapsule. The presence of the PEG gel on the surface was confirmed by fluorescent dextran entrapment, by direct visualization after dissolution of the underlying membrane and by electron spectroscopy for chemical analysis. The biological response of such microcapsules was evaluated by intraperitoneal implantation in mice. The PEG-coated microcapsules were found to be less inflammatory and were seen not to elicit a fibrotic response, as was the case with alginate-PLL microcapsules.

Alginates↗
PubMed1995

Encapsulation of urease enzyme in xanthan-alginate spheres.

Urease-containing xanthan-alginate spheres were prepared by a two-step process which involved the Ca2+ coupling of the polysaccharides, followed by gentle glutaraldehyde cross-linking with amine groups of gelatin present in the initial mixture. This second step caused a slight decrease in the enzymatic activity but increased the stability. The water content and size distribution of the spheres were examined together with the sphere morphology. The effect of polymer ratio and enzyme loading on urease activity was investigated. An increase in xanthan content was found to affect the water uptake of the spheres. Temperature and pH stability of encapsulated urease was found to be higher than the free form. The xanthan-alginate spheres showed 75% of maximum urease activity even after 20 repeated uses under optimal conditions.

Alginates↗
PubMed1990

Alginate as immobilization matrix for cells.

In recent years, entrapment of cells within spheres of Ca2+ alginate has become the most widely used technique for immobilizing living cells. This versatile method includes applications ranging from immobilization of living or dead cells in bioreactors, immobilization of plant protoplasts for micropropagation and immobilization of hybridoma cells for production of monoclonal antibodies, to entrapment of animal cells for implantation of artificial organs. This review evaluates the potential of this method on the basis of the current knowledge of structural and functional relationships in alginate gels.

Alginates↗
PubMed1996

Heat resistance of Bacillus stearothermophilus spores in alginate-mushroom puree mixture.

Thermal resistance of Bacillus stearothermophilus spores has been established inoculating spores in alginate-mushroom puree mixture (ungelled) and in alginate-mushroom puree mixture set in calcium chloride (gelled). Data are compared with those obtained suspending the spores in distilled water, mushroom extract and in calcium chloride. Results indicated that, in general, D values obtained in gelled mixture were higher than D values obtained in distilled water, mushroom extract or in ungelled mixture, while the D value in the ungelled mixture was similar to that obtained in distilled water. D121 value in gelled mixture was close to that obtained in 2% (w/v) calcium chloride.

Alginates↗