SEARCH · PubMed Health

Results for “Alginates”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 307 records · Page 17Linked to original sources

PubMedDate not supplied

Degradation of partially oxidized alginate and its potential application for tissue engineering.

Alginate has been widely used in a variety of biomedical applications including drug delivery and cell transplantation. However, alginate itself has a very slow degradation rate, and its gels degrade in an uncontrollable manner, releasing high molecular weight strands that may have difficulty being cleared from the body. We hypothesized that the periodate oxidation of alginate, which cleaves the carbon-carbon bond of the cis-diol group in the uronate residue and alters the chain conformation, would result in promoting the hydrolysis of alginate in aqueous solutions. Alginate, oxidized to a low extent (approximately 5%), degraded with a rate depending on the pH and temperature of the solution. This polymer was still capable of being ionically cross-linked with calcium ions to form gels, which degraded within 9 days in PBS solution. Finally, the use of these degradable alginate-derived hydrogels greatly improved cartilage-like tissue formation in vivo, as compared to alginate hydrogels.

Absorbable Implants↗

PubMedDate not supplied

Spherical alginate granules formulated for quick-release active subtilisin.

Novel attrition-resistant and spherical enzyme granules encapsulating active subtilisin were formed by emulsification of 2% alginate sol loaded with active enzyme, instantaneous gelation triggered through in situ release of Ca(2+) (internal gelation), particle separation, and finally acetone extractive drying. Granular subtilisin was highly active, readily dispersible, and mechanically robust. This technique serves as a new and attractive alternative to established enzyme granulation processes, such as fluid bed coating, extrusion followed by marumerization, drum granulation, or prilling, for use in industrial enzyme applications such as detergents, textile manufacturing, and food processing. The formulation and encapsulation conditions were optimized to maximize the resistance of the granule to compression and impact forces, consistent with enzyme release and particle dispersion in detergent solutions. Well characterized alginates, with specified guluronic/mannuronic acid (G/M) content and molecular weight, were used in the formulation. The characteristics of the resulting microspheres, including their size and distribution, morphology, shrinkage, compression resistance, impact strength, solubility and encapsulation yield, were examined. Spherical dry granules were formulated with a mean diameter of 500 microm with particle sizes ranging from 300 to 800 microm. Dry alginate granules were discrete, spherical, and glossy white and exhibited impact strength, compression resistance, and solubility difference dependent on composition. Reduced starch levels, high alginate concentration, low alginate molecular weight, and use of high guluronate alginates resulted in the lowest dust level and highest compression resistance. Subtilisin mass yields were approximately 50%, and specific activity yields ranged from 60% to 100%. A formulation consisting of 3% SG150 alginate, 10% starch, 10% TiO(2), and 1% CaCO(3) provided granules appropriate for use in detergent application.

Alginates↗

PubMed2000

Controlled release of carbofuran from an alginate-bentonite formulation: water release kinetics and soil mobility.

The insecticide-nematicide carbofuran was incorporated in alginate-based granules to obtain controlled-release (CR) properties. The basic formulation [sodium alginate (1.61%)-carbofuran (0. 59%)-water] was modified by addition of sorbents. The effect on carbofuran release rate, caused by the incorporation of natural and acid-treated bentonite (0.5 and 1.0 M H(2)SO(4)) in alginate formulation, was studied by immersion of the granules in water under shaking. The time taken for 50% of the active ingredient to be released into water, t(50), was longer for those formulations containing natural bentonite (6.1 h) or acid-treated bentonite (9.0 and 11.7 h for 0.5 and 1.0 M H(2)SO(4) treatments, respectively) than for the preparation without bentonite (4.7 h). It appears from the results that the release of carbofuran from the various formulations is controlled by a diffusion mechanism according to the n values obtained, which were close to 0.5 in all cases. The mobility of carbofuran from alginate-based CR formulations was investigated by using soil columns packed with a clay soil (53% clay and 0.08% organic matter). Two alginate-based CR formulations containing natural bentonite or acid-treated bentonite (0.5 M H(2)SO(4)) were compared to technical grade carbofuran. The use of alginate-based CR formulations resulted in a reduction of the leached amount of carbofuran compared with the total amount of pesticide leached using the technical product (50 and 75% for CR granules containing natural and acid-treated bentonite, respectively). Alginate-bentonite CR formulations might be efficient systems for reducing carbofuran leaching in clay soils, which would reduce the risk of groundwater pollution.

Alginates↗

PubMed1997

Alteration of pharmacokinetics and nephrotoxicity of cisplatin by alginates.

This study was undertaken to demonstrate that alginates could form a complex with cisplatin and that the pharmacokinetics and nephrotoxicity of cisplatin could be altered by this complexation. The complexes were prepared with alginates of mean molecular weights of 10000 (AL-1) and 40000 (AL-2). The plasma clearances of cisplatin-alginate complexes were significantly reduced when compared with the drug alone. Urinary excretion of platinum (Pt) was increased when animals were dosed with the cisplatin-AL-1 complex, but not with the cisplatin-AL-2 complex. Renal clearance of cisplatin, when administered alone, was more rapid during the first 2 h than the rest of the study period (96 h) and was higher than its plasma clearance, which is consistent with irreversible binding of cisplatin to plasma protein. On the other hand, renal clearance of cisplatin-alginate complexes was not highly time dependent, and the values were more similar to those of plasma clearance. Complexation of cisplatin with alginates, especially AL-1, inhibited the accumulation of Pt in the kidneys and reduced blood urea nitrogen elevation by cisplatin. The in vitro antitumor activities against U937, P388, and cisplatin-resistant P388 (P388/cisplatin) cells were similar among cisplatin and its alginate complexes. These studies indicated that the pharmacokinetics and nephrotoxicity of cisplatin could be altered through complexation with alginate by (1) reducing cisplatin clearance, (2) inhibition of Pt accumulation of in the kidneys, and (3) reduction of apparent nephrotoxicity without decrease in in vitro antitumor activity.

Alginates↗

PubMed2006

Shape-controlled production of biodegradable calcium alginate gel microparticles using a novel microfluidic device.

In this paper we describe a novel method of manufacturing shape-controlled calcium alginate gel microparticles in a microfluidic device. Both manufacturing shape-controlled microparticles and synthesizing hydrogel microparticles could be performed simultaneously in the microfluidic device. The novel microfluidic device comprised of two individual flow-focusing channels and a synthesizing channel was successfully applied as a continuous microfluidic reactor to synthesize gel microparticles with size and shape control. By passive control based on the microchannel geometric confinement and liquid-phase flow rates, we succeeded in producing monodisperse sodium alginate microparticles with diverse shapes (such as plugs, disks, microspheres, rods, and threads) in the flow-focusing channels of the microfluidic device. The shape and size of the sodium alginate microparticles could be tuned by adjusting the flow rates of the various streams. Further stages of the chemical reaction could be initiated by mixing sodium alginate microparticles and calcium chloride (CaCl2) solution in the synthesizing channel. The shapes of the sodium alginate microparticles could be permanently preserved by the synthesis of calcium alginate gel microparticles. The preparation conditions of size- and shape-controlled calcium alginate microparticles and influence factors were studied.

Alginates↗

PubMed2000

Spray-dried lactose composite particles containing an ion complex of alginate-chitosan for designing a dry-coated tablet having a time-controlled releasing function.

PURPOSE: The properties of novel spray-dried lactose composite particles suitable for the coating filler of a dry-coated tablet having a long induction period in drug release were investigated. METHODS: To prepare spray-dried composite particles containing alginate-chitosan complex (SD(L/AL-CS)), an aqueous solution of lactose and sodium alginate and the acetic acid solution of chitosan were concomitantly fed into the rotary atomizer of a spray-dryer. The formation of the alginate-chitosan complex was confirmed by measuring the weight of insoluble portion in the mixture of sodium alginate and chitosan solutions. The dissolution properties of the dry-coated tablet were measured with the JP specified paddle method. RESULTS: The micromeritic properties of SD(L/AL-CS) were compared to those of the SD composite particles of lactose-sodium alginate, having a good compacting property. The drug release profiles of dry-coated tablet with SD(L/AL-CS) contained a long induction period followed by a rapid drug release phase in the artificial intestinal fluid. The induction period for drug release to occur was increased with an increase in the degree of deacetylation of chitosan and in the amount of chitosan in the formulation. The prolongation of induction period was attributed to the formation of an insoluble ion complex between sodium alginate and chitosan in the composite particles, which could form a rigid gel structure on the tablet surface. CONCLUSIONS: A time-controlled release tablet was designed with the composite particles of lactose containing the alginate-chitosan ion complex. The induction period of the dry-coated tablet could be prolonged in order to deliver the drug to the colon by controlling the type and amount of chitosan formulated in the composite particles.

Alginates↗

PubMed2003

Alginate as a new biomaterial for the growth of porcine retinal pigment epithelium.

OBJECTIVE: Determine the effect of a 3-dimensional alginate matrix on the growth and differentiation of cells isolated from porcine retinal pigment epithelium (RPE). PROCEDURES: Porcine RPE cells were harvested from enucleated eyecups, isolated by differential gravity sedimentation and cultured in either alginate alone (Group 1) or on plastic tissue culture plates followed by alginate (Group 2). Group 1 cells were cultured in alginate to evaluate the efficacy of the matrix as a culture medium. Group 2 cells were initially cultured on plastic to induce dedifferentiation. The cells were then harvested, suspended in alginate beads, and incubated for a second culture period to determine if the induced dedifferentiation was reversible. RESULTS: The number of Group 1 cells was significantly greater (P < or = 0.01) at the end of the culture period. The amount of pigment and cell morphology of Group 1 cells at the end of the culture period was similar to that seen at initial cell isolation. The initial culture of Group 2 cells on plastic showed characteristic features of dedifferentiation marked by the loss of pigment and alterations in microscopic appearance. Secondary culture of dedifferentiated Group 2 cells in alginate beads resulted in a return to pigmentation and characteristic morphology for a majority of the cultured cells. CONCLUSIONS: Porcine RPE cells can be propagated in alginate culture with a significant increase in cell numbers while maintaining normal morphology. Under the conditions described in the present study, the dedifferentiation of porcine RPE induced by standard in vitro culture methods is reversible.

Alginates↗

PubMed2004

New approaches to the visualization, quantification and explanation of acid-induced water loss from Ca-alginate hydrogel beads.

The water loss of Ca-alginate hydrogels at pHs below 4.0 was visualized with 1HNMR-imaging by covering a single alginate bead with cyclohexane-d12 in a specially equipped NMR-tube and adding propionic acid at defined concentrations. The exact amount of water expelled from the beads was calculated from their weight loss and correlated with the acid concentrations and pHs within the hydrogel matrix. The maximum water loss of 52% (w/w) occurred at pH 1.0, while only 5% (w/w) of the initial water content were lost at pH 3.6. The analysis of the water collected from several alginate beads for Ca2+ -ions and free polysaccharides led to the assumption that, due to the acid-induced protonation of the carboxyl functions, the ionotropic network is gradually converted to an alginic acid gel structured by H-bonds. This contradicts existing theories explaining the pH-induced water loss by a lower solubility of the alginate chains and decreased repulsion between protonated carboxyl functions, but explains previously reported pH-dependent alterations of mass transport and drug retention of Ca-alginate gels. Thus, the presented experiments enable a more precise and complete view of the acid-induced process within Ca-alginate hydrogels. The transfer to the characterization of other hydrogels is possible and should be advantageous, especially if a calibration of the NMR-measurement could be achieved.

Alginates↗

PubMed2005

Development and evaluation of polyethyleneimine-treated calcium alginate beads for sustained release of diltiazem.

The objective of this investigation is to develop a multi-unit sustained release dosage form of a water soluble drug from a completely aqueous environment avoiding the use of any organic solvent. The drug was complexed with resin and calcium alginate or polyethyleneimine-treated calcium alginate beads loaded with the resinate were prepared by a ionic/polyelectrolyte complexation method. The effect of different formulation variables on the characteristics of the beads was investigated. Although the drug release from spherical and smooth-surfaced calcium alginate beads in both acidic and alkaline dissolution media were slower than those obtained from plain resinate, none of the variables were found to prolong the drug release considerably due to rapid swelling and disintegration of calcium alginate beads in alkaline medium. On the other hand, drug release from polyethyleneimine-treated calcium alginate beads in acidic medium did not increase appreciably following a burst release. However, in alkaline medium, the drug release was found to increase gradually and extend over a different period of time depending on the intensity of polyethyleneimine treatment. Scanning electron micrographs revealed the formation of a dense membrane around the resinate-loaded calcium alginate matrix. The membrane appeared to be responsible for reduced swelling and protracted disintegration of the beads resulting in slow release of the drug. The results indicate that sustained release of a water soluble drug from polyethyleneimine-treated calcium alginate beads could be achieved by adjusting the formulation variables.

Alginates↗

PubMed2002

Repair of facial nerve with alginate sponge without suturing: an experimental study in cats.

A bioabsorbable material, alginate, was used to repair a defect in the facial nerve. In five cats a 5-mm gap was created in the dorsal ramus of the facial nerve on one side selected at random, which was repaired by implantation of alginate sponge without suturing. In the control group, two cats had a similar nerve injury but without implantation of alginate. Behavioural, electrophysiological, and histological examinations were made over a period of 16 weeks postoperatively. Movement of the upper eyelids and electrophysiological function were restored 12 weeks postoperatively, and many myelinated axons were observed both in the gap of facial nerve and its branches 16 weeks after operation, whereas no alginate residue was detected remaining within gap. In the control group, no movement or electrophysiological restoration was recorded, and there were few regenerated axons accompanied by a large amount of scar tissue. The nerve repaired with alginate showed remarkable regeneration. These results suggest that alginate is a promising material for facial nerve repair, and sutureless repair with alginate is a possible option for treating defects in the facial nerve.

Alginates↗

PubMed2000

Temperature- and moisture-induced crystallization of amorphous lactose in composite particles with sodium alginate prepared by spray-drying.

The purpose of this study was to investigate the temperature- and moisture-induced crystallization of amorphous lactose in the composite particles prepared by spray-drying an aqueous solution of crystalline lactose and sodium alginate. The temperature-induced crystallization of amorphous lactose in the composite particles was suppressed by increasing the amount of sodium alginate in the particles. The stabilizing effect of sodium alginate on amorphous lactose in the composite particles was greater than that in physical mixtures having the same formulating ratios. The improved stability of amorphous lactose in the composite particles was attributed to an increase in the glass transition temperature (Tg) of the mixture. Moisture-induced crystallization of amorphous lactose was also retarded by increasing the amount of sodium alginate in composite particles. Although the Tg of the mixture was reduced by increasing the water content of the particles, the values were higher than that of 100% amorphous lactose when particles of the same water content were compared. The change in the Tg of the composite particles with increasing water content was interpreted as involving three components of the Gordon-Taylor equation. In the amorphous lactose-sodium alginate systems, the Tg values of the composite particles containing sodium alginate were higher than the theoretical line predicted by two components of the Gordon-Taylor equation. These results suggested that there was a specific interaction between the sodium alginate and lactose molecules. This specific interaction was suggested by the fact that only very little amorphous lactose was measured in the spray-dried composite particles stored under humid conditions using differential scanning calorimetry. This molecular interaction may also be partly responsible for the suppression of both the temperature- and moisture-induced crystallization of amorphous lactose in the composite particles.

Alginates↗

PubMed2005

Nonmucoid Pseudomonas aeruginosa expresses alginate in the lungs of patients with cystic fibrosis and in a mouse model.

BACKGROUND: In patients with cystic fibrosis (CF), lung infection with mucoid Pseudomonas aeruginosa strains overexpressing the exopolysaccaride alginate is preceded by colonization with nonmucoid strains. We investigated the kinetics, impact of environmental signals, and genetics of P. aeruginosa alginate expression in a mouse model and in patients with CF. METHODS: Using indirect immunofluorescence, microarray technology and real-time reverse-transcription polymerase chain reaction, we assessed alginate gene expression during aerobic and anaerobic growth of the nonmucoid strain PAO1 in vitro, in a mouse lung-infection model and in sputum specimens from patients with CF infected with nonmucoid or mucoid P. aeruginosa strains. RESULTS: Anaerobic conditions increased the transcription of alginate genes in vitro and in murine lungs within 24 h. Alginate production by PAO1 in murine lungs and by nonmucoid P. aeruginosa strains in patients with CF was reversible after in vitro culture under aerobic conditions. A subpopulation of P. aeruginosa clones revealing stable alginate production was detected in murine lungs 2 weeks after infection. CONCLUSIONS: Anaerobiosis and lung infection rapidly induce alginate production by gene regulation in nonmucoid P. aeruginosa. This trait may contribute to early persistence, leading to chronic P. aeruginosa infection once stable mucoid strains are generated.

Alginates↗

PubMed2005

Encapsulation of recombinant cells with a novel magnetized alginate for magnetic resonance imaging.

Implanting recombinant cells encapsulated in alginate microcapsules to express therapeutic proteins has been proven effective in treating several mouse models of human diseases (neurological disorders, dwarfism, hemophilia, lysosomal storage disease, and cancer). In anticipation of clinical application, we have reported the synthesis and characterization of a magnetized ferrofluid alginate that potentially allows tracking of these microcapsules in vivo by magnetic resonance imaging (MRI). We now report the properties of these ferrofluid microcapsules important for applications in gene therapy. When a mouse myoblast cell line was encapsulated in these microcapsules, it showed similar viability as in regular unmodified alginate capsules, both in vitro and in vivo, in mice. The permeability of these magnetized microcapsules, a critical parameter for immunoisolation devices, was comparable to that of classic alginate in the transit of various recombinant molecules of various molecular masses (human factor IX, 65 kDa; murine IgG, 150 kDa; and beta-glucuronidase, 300 kDa). When followed by MRI in vitro and in vivo, the ferrofluid microcapsules remained intact and visible for extended periods, allowing quantitative monitoring of microcapsules. At autopsy, the ferrofluid microcapsules were mostly free within the intraperitoneal cavities, with no overt inflammatory response. Serological analyses demonstrated a high level of biocompatibility comparable to that of unmodified alginate. In conclusion, ferrofluid-enhanced alginate microcapsules are comparable to classic alginate microcapsules in permeability and biocompatibility. Their visibility and stability to MRI monitoring permitted qualitative and quantitative tracking of the implanted microcapsules without invasive surgery. These properties are important advantages for the application of immunoisolation devices in human gene therapy.

Alginates↗

PubMed1992

Cloning hybridomas in a reversible three-dimensional alginate matrix.

Alginate is a transparent polymer of guluronic and mannuronic acids that provide a favorable microenvironment for cell growth. Alginate gelation is calcium dependent and temperature independent. To facilitate the isolation of stable and productive antibody-producing hybridomas, we have developed a technique of cloning hybridomas in the three-dimensional alginate matrix. To provide cavities for hybridoma growth, we encorporated 10-15% (v/v) gelatin into the alginate prior to gelation. We have cloned more than 90 monoclonal antibody-producing hybridomas using the alginate matrix. The alginate matrix is readily reversible with the addition of a calcium chelator. The alginate matrix permits efficient cloning in limited incubator space, without the use of a feeder layer, and with minimal amount of medium. The transparent matrix also permits easy screening for clonality and growth.

Alginates↗

PubMed1994

Alginate, small bowel sterol excretion, and absorption of nutrients in ileostomy subjects.

The effect of alginate on ileostomy excretion of sterols and nutrients was investigated in six ileostomy subjects fed a constant low-fiber diet with or without supplementation with 7.5 g sodium alginate. A mean of 95% of uronic acids derived from the sodium alginate was recovered in the ileostomy contents. Supplementation with alginate increased fat excretion by 140% and decreased bile acids excretion by 12%. Sodium and potassium excretion were significantly increased whereas starch and nitrogen excretion were unchanged. Five of six subjects showed a decreased apparent absorption of iron and manganese with alginate, which, however, was not statistically significant. Absorption of phosphorus, calcium, magnesium, and zinc were unchanged. Almost no digestion of sodium alginate occurs in the stomach and small intestine. The increased fatty acids excretion may be explained by the binding or trapping of fatty acids in the gel matrix formed by alginate, which may also cause a reduced bile flow.

Adolescent↗

PubMed1988

Antibiotic interaction and diffusion through alginate and exopolysaccharide of cystic fibrosis-derived Pseudomonas aeruginosa.

The interaction of five anti-pseudomonas antibiotics with both commercial and pseudomonas alginates was studied by investigation of their binding and diffusion characteristics. The two sources of alginate were qualitatively but not quantitatively similar in these respects. Unlike the beta-lactams, gentamicin and tobramycin bound avidly to both sources of alginate and, when the alginate gel to antibiotic ratio was high, the aminoglycosides exhibited diffusion coefficients which were approximately 20% of the beta-lactam values. At much lower ratios of alginate to antibiotic the aminoglycosides caused precipitation in the alginate with apparent disruption of the gel structure, and ultimately penetrated the gel at a faster rate than the beta-lactams. The strong aminoglycoside binding to alginate was reduced, but not eliminated by the presence of physiological concentrations of salts.

Alginates↗

PubMed2003

Alginate-based oral drug delivery system for tuberculosis: pharmacokinetics and therapeutic effects.

Alginate microparticles were developed as oral sustained delivery carriers for antitubercular drugs in order to improve patient compliance. In the present study, pharmacokinetics and therapeutic effects of alginate microparticle encapsulated antitubercular drugs, i.e. isoniazid, rifampicin and pyrazinamide were examined in guinea pigs. Alginate microparticles containing antitubercular drugs were evaluated for in vitro and in vivo release profiles. These microparticles exhibited sustained release of isoniazid, rifampicin and pyrazinamide for 3-5 days in plasma and up to 9 days in organs. Peak plasma concentration (Cmax), Tmax, elimination half-life (t1/2e) and AUC0- infinity of alginate drugs were significantly higher than those of free drugs. The encapsulation of drug in alginate microparticles resulted in up to a nine-fold increase in relative bioavailability compared with free drugs. Chemotherapeutic efficacy of alginate drug microspheres against experimental tuberculosis showed no detectable cfu values at 1:100 and 1:1000 dilutions of spleen and lung homogenates. Histopathological studies further substantiated these observations, thus suggesting that application of alginate-encapsulated drugs could be useful in the effective treatment of tuberculosis.

Administration, Oral↗

PubMed1991

Induction of cytokine production from human monocytes stimulated with alginate.

Alginates are polysaccharides with gel-forming properties composed of 1,4-linked beta-D-mannuronic acid (M), alpha-L-guluronic acid (G), and alternating (MG) blocks. Alginate can be used as a matrix for implanted cells in vivo. In this study, we have examined the ability of alginates and their components to stimulate human monocytes to produce tumor necrosis factor-alpha, interleukin-6, and interleukin-1. Alginates stimulated the monocytes to produce high levels of all three cytokines. Low G alginates were approximately 10 times more potent in inducing cytokine production compared with high G alginates. The M-blocks and the MG-blocks, but not the G-blocks, stimulated the cytokine production. The results demonstrate that the mannuronic acid residues are the active cytokine inducers in alginates.

Alginates↗