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PubMed1997

Differential expression of membrane-anchored proteoglycans in rabbit articular chondrocytes cultured in monolayers and in alginate beads. Effect of transforming growth factor-beta 1.

Cell-surface proteoglycans (PGs) were extracted with Triton X-100 from rabbit articular chondrocytes cultured in monolayers and in alginate beads. They were first purified on DEAE-Trisacryl columns and the proportion of hydrophobic PGs was determined by both Octyl-Sepharose chromatography and partitioning in Triton X-114. These two methods revealed that the proportion of hydrophobic PGs was higher in monolayer culture system as compared to alginate beads (24 and 15%, respectively). Characterization of the PGs by Sepharose CL 6B gel filtration followed by electrophoresis indicated that the PGs isolated from monolayers were composed of three chondroitin sulfate (CS) PGs (core proteins of 180, 100 and 50 kDa) and a heparan sulfate (HS) PG (core protein of 60 kDa). In the alginate system. CSPGs with core proteins of 180, 45 and 32 kDa were observed, but no HSPG was present. In parallel, the effect of TGF-beta on the distribution of membrane-associated PGs was studied. The results showed that the synthesis of cell-surface PGs was stimulated by TGF-beta in monolayers whereas it was inhibited in alginate beads, but the amount of hydrophobic PGs was not altered by the growth factor. These data clearly indicate that TGF-beta induces a differential expression of the PG families present at the cell surface. Taken together, the results reveal the complex regulation of cell-surface PG distribution, which obviously depends on the culture method used and suggest that rabbit articular chondrocytes may differentially respond to extracellular ligands according to their morphological state and environment.

Alginates↗
PubMed2001

Application of free and Ca-alginate-entrapped Glomus deserticola and Yarowia lipolytica in a soil-plant system.

This study was performed to investigate the applicability of microbial inoculants entrapped in alginate gel. Glomus deserticola (AM) was inoculated into soil microcosms, enriched with rock phosphate, as either free form or entrapped in calcium alginate alone or in combination with a P-solubilizing yeast culture (Yarowia lipolytica). Plant dry weight, soluble P acquisition, and mycorrhizal index were equal in treatments inoculated with free and alginate-entrapped AM. Dual inoculation with entrapped G. deserticola and free cells of Y. lipolytica significantly increased all analyzed variables. Highest rates of the latter were obtained when both fungal microorganisms were applied co-entrapped in the carrier. The yeast culture behaved as a 'mycorrhiza helper microorganism' enhancing mycorrhization of tomato roots. These results indicate that dual inoculation with an AM fungus and a P-solubilizing microorganism co-entrapped in alginate can be an efficient technique for plant establishment and growth in nutrient deficient soils.

Agriculture↗
PubMed2000

Oral sustained delivery of theophylline using in-situ gelation of sodium alginate.

Gels formed in situ following oral administration of aqueous solutions of sodium alginate (1.0-2.0%w/v) to rats were evaluated as sustained release vehicles for the delivery of theophylline. The liquid formulation contained calcium ions in complexed form, the release of which in the acidic environment of the stomach caused gelation of the alginate. Bioavailability of theophylline from alginate gels formed by in situ gelation in the rat stomach was increased by 1.3-2-fold in rats for alginate concentrations of 2.0 to 1.0%w/v respectively compared with that from a proprietary oral sustained release formulation containing an identical drug concentration. There was no significant difference in the mean residence times of theophylline when administered by these two vehicles.

Administration, Oral↗
PubMed2002

Time-programmed pulsatile release of dextran from calcium-alginate gel beads coated with carboxy-n-propylacrylamide copolymers.

Time-programmed release of macromolecular drugs was achieved by utilization of calcium-alginate gel beads modified with coated copolymer layers. Modified calcium-alginate gel beads coated with poly(carboxy-n-propylacrylamide-co-dimethylacrylamide) [poly(CNPAAm-co-DMAAm)] (22.7 mol% of CNPAAm) of varying coating thickness from 25 to 125 microm were developed as drug carriers. Model macromolecular drugs used were fluorescein isothiocyanate (FITC)-labeled dextrans with different molecular weights ranging from 9400 to 145000. FITC-dextran release was strongly dependent on both copolymer coating thicknesses and the dextran molecular weights. Release of FITC-dextran (MW 9400) followed Fickian diffusion according to t(1/2) dependence, indicating that the drug diffusion is the main driving force for release of dextran MW 9400. Release of higher molecular weight FITC-dextrans (71,00 and 145,00) exhibited a burst-effect preceded by a preset lag time. These release profiles were governed by the dissociation of calcium ions from polyguluronate sequences in alginate molecules along with the diffusion of sodium ions into the gel bead core. This created osmotic pressure inside the gel, inducing breakage of the coated copolymer layer and accelerated drug release. Burst release of macromolecular drugs thus occurred after a certain lag period. The lag time was regulated by the copolymer coat thickness. A pulsatile release of FITC-dextran was demonstrated by combining a series of modified alginate gel beads in a single batch.

Acrylic Resins↗
PubMed1999

Effect of Ca2+-alginate gel dissolution on release of dextran with different molecular weights.

Release of macromolecular drug from calcium-alginate gel beads was investigated. Fluorescein isothiocyanate-labeled dextrans with molecular weight ranging from 9400 to 145000 were used as a model macromolecular drug. Dextran release was observed to be molecular weight-dependent, with the release pattern changing from pseudo first-order for dextran with 9400 molecular weight to sigmoidal for dextran with molecular weight of 145000. Release of a lower molecular weight dextran is mainly governed by the drug diffusion through the calcium-alginate gel matrix. With increasing dextran molecular weights, dextran release was strongly influenced by the dissolution of alginate matrix through the exchange of Ca2+ ions which act as a cross-linker. Rapid and complete release was achieved for dextran with 145000 molecular weight in a "burst" fashion showing a initial lag time. Minimal dextran release was observed in pseudo-gastric fluid at pH 1.2, while rapid dextran release within a narrow time range was achieved in simulated intestinal fluid at pH 6. 8. These results strongly suggest that calcium-alginate gel is a useful vehicle for pulsatile release of macromolecular drugs in oral drug delivery.

Alginates↗
PubMed2001

Human hepatocyte cell lines proliferating as cohesive spheroid colonies in alginate markedly upregulate both synthetic and detoxificatory liver function.

BACKGROUND/AIMS: Bio-artificial liver support systems for treatment of hepatic failure require maintained expression of hepatocyte function in vitro. We studied cultures of human hepatocyte cell-lines proliferating within alginate beads, investigating the hypothesis that 3-dimensional cohesive colonies of hepatocyte cell-lines would achieve polarity and cell-to-cell contact resulting in upregulation of function. METHODS: HepG2 and HHY41 human cell lines in alginate beads were cultured for >20 days. RESULTS: Proliferation was maintained for 20 days. Production of albumin, prothrombin, fibrinogen, alpha-1-acid glycoprotein and alpha-1-antitrypsin was maintained throughout, maximal at days 8-10, when upregulation was 300-1100% compared with monolayer cultures at similar cell number per unit volume. Detoxificatory functions: ethoxyresorufin deethylase activity, androstenedione metabolism, and urea synthesis from arginine was also increased several-fold. Function returned to pre-freezing levels within 18 h of thawing after cryopreservation of cells in alginate. Electron microscopy revealed spherical colonies of cells of cuboidal shape, with cell-to-cell contact via desmosomes and junctional complexes, abundant microvilli, and cytoplasmic appearances suggesting transcriptionally active hepatocytes. CONCLUSION: Hepatocyte cell-lines, proliferating in alginate express a range of liver-specific functions at levels approaching those found in vivo, relevant to their use in liver support systems.

Alginates↗
PubMed2003

Role of humic acid entrapped calcium alginate beads in removal of heavy metals.

Most of the available techniques for removal of heavy metals from solution such as leachates from waste sites are very expensive. The technique described in this paper is designed to study the removal of humic acid by alginate beads and the subsequent binding of the metals within the beads thus decreasing the leachability of heavy metals from a hazardous waste site. The entry of 500 mg/l humic acid into 3% calcium alginate beads in 24 h showed a distinct fluorescence as compared to the fluorescence shown by the entry of 100 and 250 mg/l of humic acid into alginate beads. Further, on treatment of calcium alginate beads containing 500 mg/l humic acid with metals such as Cu, Mn, Zn, Cr and Fe, quenching of fluorescence was noticed, which was maximum with Cu and minimum with Fe.

Alginates↗
PubMed2000

Amoxycillin release from a floating dosage form based on alginates.

Floating alginate beads have been prepared from alginate solutions containing either dissolved or suspended amoxycillin. The beads were produced by the dropwise addition of the alginate into calcium chloride solution, followed by removal of the gel beads and freeze drying. Drug release studies showed that beads prepared with the drug in solution provided some sustained release characteristics and that these could be improved by the addition of amylose. In all cases, the drug release was consistent with release of a dissolved solute from a granular or porous matrix. The beads retained their buoyancy when amylose and amoxycillin were incorporated, exhibiting resultant weight values greater than zero after 20 h. Preparation of the beads from alginate solutions containing the drug in suspension allowed higher drug loadings, at the expense of faster release and lower buoyancy.

Alginates↗
PubMed2002

Production of alginate microspheres by internal gelation using an emulsification method.

Alginate is a natural polysaccharide found in brown algae. Alginates are widely used in the food and pharmaceutical industries and have been employed as a matrix for the entrapment of drugs, macromolecules and biological cells. Alginate microspheres can be produced by the external or internal gelation method using calcium salts. The addition of calcium chloride solution in the final phase of production of microspheres by external gelation method using an emulsification technique causes the disruption of the equilibrium of the system being stirred, resulting in a significant degree of clumping of microspheres. Therefore, in this study, production of alginate microspheres by the internal gelation method using a modified emulsification technique was explored. The influence of calcium salt, added in varying amounts and at different stages, on the morphology of the microspheres was investigated. The effects of other hardening agents and different drying methods were also studied.

Alginates↗
PubMed1999

Microencapsulation of lipophilic drugs in chitosan-coated alginate microspheres.

Chitosan-coated alginate microspheres containing a lipophilic marker dissolved in an edible oil, were prepared by emulsification/internal gelation and the potential use as an oral controlled release system investigated. Microsphere formation involved dispersing a lipophilic marker dissolved in soybean oil into an alginate solution containing insoluble calcium carbonate microcrystals. The dispersion was then emulsified in silicone oil to form an O/W/O multiple phase emulsion. Addition of an oil soluble acid released calcium from carbonate complex for gelation of the alginate. Chitosan was then applied as a membrane coat to increase the mechanical strength and stabilize the microspheres in simulated intestinal media. Parameters studied included encapsulation yield, alginate concentration, chitosan molecular weight and membrane formation time. Mean diameters ranging from 500 to 800 micron and encapsulation yields ranging from 60 to 80% were obtained. Minimal marker release was observed under simulated gastric conditions, and rapid release was triggered by transfer into simulated intestinal fluid. Higher overall levels of release were obtained with uncoated microspheres, possibly due to binding of marker to the chitosan membrane coat. However the slower rate of release from coated microspheres was felt better suited as a delivery vehicle for oil soluble drugs.

Alginates↗
PubMed1998

Formulation and investigation of nicardipine HCl-alginate gel beads with factorial design-based studies.

The release rate of nicardipine HCl from various alginate gel bead formulations was investigated. The formulations were prepared by utilizing 23 factorial design. The effect of drug:polymer weight ratio, CaCl2 and sodium-alginate concentration on the time for 50% of the drug to be released (t50%) and the drug entrapment efficiency were evaluated with analysis of variance. The mean particle size and the swelling ratio of the beads were determined. The in vitro release studies were carried out by flow-through cell apparatus in different media (pH 1.2, 2.5, 4.5, 7 and 7.5 buffer solutions). Drug:polymer weight ratio and the interaction of drug:polymer weight ratio and CaCl2 concentration had a significant effect on the drug entrapment efficiency. The release of nicardipine was extended with the alginate gel beads, which were prepared in a ratio of 1:1 (drug:polymer). The release of drug from alginate gel beads took place both by diffusion through the swollen matrix and relaxation of the polymer at pH 1.2-4.5. However, the release was due to the diffusion and erosion mechanism at pH 7-7.5.

Alginates↗
PubMed1992

Synthesis and turnover of proteoglycans by human and bovine adult articular chondrocytes cultured in alginate beads.

Human and bovine adult articular chondrocytes cultured in alginate beads or agarose gel retain their spherical shape and typical chondrocytic appearance for at least 5 weeks. Aggrecan is always the major population of proteoglycans (PGs) synthesized; its size varies depending upon the age of the cartilage from which the cells are derived but it is not influenced by the culture system used. Studies of human chondrocytes cultured in alginate showed that the majority of the newly-synthesized aggrecan molecules are rapidly incorporated into aggregates which can be extracted from the gel in their native form. About one-third of the aggregates formed during a 4-hour period of incubation in the presence of [35S]-sulfate are packed at high concentration in the cell-associated matrix; the remainder is present in areas of the gel further removed from the cells. Aggrecan appears to be turned over more slowly by human than by bovine cells in both culture systems; in both species, the rate of turnover is slower in alginate than in agarose. Decorin is also synthesized in small amounts but it is rapidly lost from the agarose or alginate gel.

Adolescent↗
PubMed2001

Studies on the suitability of alginate-entrapped Chlamydomonas reinhardtii cells for sustaining nitrate consumption processes.

Some aspects of the suitability of alginate beads entrapping Chlamydomonas reinhardtii cells for nitrate consumption from nitrate-containing waters were studied and discussed. Among 14 different metal cations tested as gel bead stabilizing agents, only calcium and barium formed beads showing nitrate-consuming activity. Pure calcium alginate cell entrapment resulted in the most suitable method for active cell immobilization compared to alginate-composite-gel beads based on poly-vinylcaprolactam (PVCL) and poly-vinylpyrrolidone (PVP). To perform a continuous nitrate consumption process, calcium alginate-entrapped cells were first grown in a 2.5 l airlift-loop reactor. A cell loading of about 150 microg Chl. g(-1) gel was achieved. Afterwards, five days nitrate consumption processes were performed and three different dilution rates were applied: (i) D < mu; (ii) D = mu; (iii) D > mu, where mu is the specific growth rate (h(-1)). The maximum consumption rates calculated for each dilution rate were: (i) 3.8, (ii) 6.4 and (iii) 7.2 mg nitrate mg(-1) Chl. h(-1). For low dilution rates (D < mu) some nitrite (< 300 microM) was excreted into the culture medium. However, this concentration of nitrite was not high enough to inhibit nitrate consumption.

Alginates↗
PubMed2000

Kinetics of release of heparin from alginate hydrogel.

PURPOSE: Injected sodium alginate may be a useful perivascular drug delivery vehicle. This study was performed to determine the release rates of heparin from sodium alginate hydrogels cross-linked with varying amounts of calcium gluconate. MATERIALS AND METHODS: Six hydrogels, composed of 0.16 mEq sodium alginate and 4,000 units unfractionated heparin, were cross-linked with calcium gluconate to yield ion equivalence (IE) ratios (calcium:alginate) of 0.2, 0.4, 0.58, 0.8, 1.0, or 1.2. Two milliliters of normal saline was placed on top of each gel and allowed to remain in contact for up to 10 days. At set time intervals, the amount of heparin in the eluent was determined with use of high-performance liquid chromatography. RESULTS: Gels with 0.2 and 0.4 IE were partially liquid at 24 hours; the other gels solidified within 10 minutes. The 0.58 IE gel was slowest to solidify but immobilized the most heparin and released heparin slowest over 10 days. At 10 days, between 5.5% and 9.8% of the heparin immobilized was retained in the gel. CONCLUSION: This hydrogel shows promise as a vehicle for in vivo perivascular heparin delivery. The 0.58:1 IE ratio hydrogel has slowest release rate and the greatest immobilization despite its longer cross-linking time.

Alginates↗
PubMed1998

Proteoglycan synthesis by fibroblasts from different regions of bovine tendon cultured in alginate beads.

The ability of cell shape to modulate proteoglycan synthesis in tendon fibroblasts was investigated by placing freshly isolated tendon fibroblasts and chondrocytes into primary culture either as adherent cells on a polystyrene substratum or as rounded cells in alginate beads. Chondrocytes and cells from the compressed region of adult tendon synthesized predominantly large proteoglycan when maintained either as dense monolayers, where actin stress fibers in the cytoskeleton were prominent, or in alginate beads, where actin fibers could not be detected. After three rounds of proliferation as elongated adherent cells the synthesis of large proteoglycan was greatly reduced, i.e. the chondrocytic cells underwent 'dedifferentiation'. Cells from the tensional region of adult tendon synthesized predominantly small proteoglycan when in primary culture as a monolayer, after proliferation on a flat substratum, or as round cells in alginate beads. Fibroblasts from the tensional region of newborn tendon showed no tendency toward increased synthesis of large proteoglycan when maintained as round cells in alginate beads for 7 weeks. In tendon there appears to be a mechanically induced developmental transition from fibroblastic to chondrocytic cells. However, neither the change to a rounded cell shape nor the lack of organized cytoskeletal actin fibers was sufficient to induce chondrocyte-like proteoglycan synthesis in differentiated tendon fibroblasts in culture.

Actins↗
PubMed1991

Combined study to assess the role of calcium alginate swabs and ligation of the inferior tonsillar pole in the control of intra-operative blood loss during tonsillectomy.

Bleeding is the major source of morbidity and mortality of tonsillectomy and most operative time is spent securing haemostasis. Calcium alginate reduces experimental wound blood loss. This study assessed the efficacy of alginate swabs during tonsillectomy and inferior tonsillar pole ligation in the control of blood loss during tonsillectomy. Ninety-nine tonsillectomy patients were randomized to gauze or alginate swab use. A haemoglobinometer measured blood losses collected by suction during dissection and by swab until haemostasis was secured. Operative time, complications and healing were also assessed. Mean total blood losses and operative times were similar for the two groups. Swab blood loss was significantly lower for surgeons who ligated the lower tonsillar pole, compared with surgeons who used a snare. This finding was independent of swab type. Independent assessment showed no difference in the healing rate. Alginate swabs offer no advantage over gauze in terms of blood loss, operative time or complications of tonsillectomy. The results show that routine lower pole ligation significantly reduces post-dissection blood loss. We suggest that this technique should be more widely adopted.

Adolescent↗
PubMedDate not supplied

Combined physical and chemical immobilization of glucose oxidase in alginate microspheres improves stability of encapsulation and activity.

Chemical sensors utilizing immobilized enzymes and proteins are important for monitoring chemical processes and biological systems. In this study, calcium-cross-linked alginate hydrogel microspheres were fabricated as enzyme carriers by an emulsification technique. Glucose oxidase (GOx) was encapsulated in alginate microspheres using three different methods: physical entrapment (emulsion), chemical conjugation (conjugation), and a combination of physical entrapment and chemical conjugation (emulsion-conjugation). Nano-organized coatings were applied on alginate/GOx microspheres using the layer-by-layer self-assembly technique in order to stabilize the hydrogel/enzyme system under biological environment. The encapsulation of GOx and formation of nanofilm coating on alginate microspheres were verified with FTIR spectral analysis, zeta-potential analysis, and confocal laser scanning microscopy. To compare both the immobilization properties of enzyme encapsulation techniques and the influence of nanofilms with uncoated microspheres, the relationship between enzyme loading, release, and effective GOx activity (enzyme activity per unit protein loading) were studied over a period of four weeks. The results produced four key findings: (1) the emulsion-conjugation technique improved the stability of GOx in alginate microspheres compared to the emulsion technique, reducing the GOx leaching from microsphere from 50% to 17%; (2) the polyelectrolyte nanofilm coatings increased the GOx stability over time, but also reduced the effective GOx activity; (3) the effective GOx activity for the emulsion-conjugation technique (about 3.5 x 10(-)(5) AU microg(-)(1) s(-)(1)) was higher than that for other methods, and did not change significantly over four weeks; and (4) the GOx concentration, when compared after one week for microspheres with three bilayers of poly(allylamine hydrochloride)/sodium poly(styrene sulfonate) ({PAH/PSS}) coating, was highest for the emulsion-conjugation technique. As a result, the comparison of these three techniques showed the emulsion-conjugation technique to be a potentially effective and practical way to fabricate alginate/GOx microspheres for implantable glucose biosensor application.

Alginates↗
PubMedDate not supplied

Riboflavin-photosensitized changes in aqueous solutions of alginate. Rheological studies.

Interactions between photoexcited riboflavin (RF), promoted by irradiation in the range of 310-800 nm, and alginate have been studied in air equilibrated aqueous solutions with the aid of rheological methods. Light irradiation of RF causes under aerobic conditions fragmentation of alginate and a decrease in the shear viscosity and other rheological parameters of its solutions. The decrease is most pronounced in concentrated polymer solutions. The photochemical degradation of alginate is inhibited in the presence of the quenchers/scavengers d-mannitol, glutathione, potassium iodide, and sodium azide and in excess oxygen. The addition of thiourea to alginate-RF solutions leads to enhanced degradation of the polymer. Significant shear-thinning effects and deviations from the Cox-Merz rule are observed at higher polymer concentrations.

Alginates↗