Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Alginates”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 1,531 records · Page 85Linked to original sources
PubMed2000

Immunization with DNA, adenovirus or both in biodegradable alginate microspheres: effect of route of inoculation on immune response.

To determine the potential for biodegradable alginate microspheres to be used as a delivery vehicle for DNA based vaccines, we constructed a plasmid, pMNe-gal-SV40, containing the bacterial beta-galactosidase (LacZ) gene under the control of the murine cytomegalovirus (MCMV) immediate-early promoter and the simian virus 40 (SV40) polyadenylation signal. The effect of the route of administration and co-administration of adenovirus on systemic and mucosal immune responses were investigated. Mice were inoculated orally, intranasally (i.n.), intramuscularly (i.m.), subcutaneously (s.c.) or intraperitoneally (i.p.) on days 0, 14 and 28 with microspheres containing plasmid DNA, bovine adenovirus type 3 (BAd3) or plasmid DNA + BAd3. Systemic routes of immunization (i.m., s.c. and i.p.) resulted in higher LacZ- or BAd3-specific IgG ELISA titers compared to those obtained by mucosal routes of inoculation (oral and i.n.). Mucosal immunization led to slightly higher titers of LacZ- or BAd3-specific IgA at mucosal sites compared to those obtained by the various systemic routes. All the routes of immunization induced LacZ-specific lymphoproliferation. Co-administration of BAd3 enhanced the LacZ-specific IgG response irrespective of the route of administration.

3T3 Cells↗
PubMed2002

Alginate-konjac glucomannan-chitosan beads as controlled release matrix.

Controlled release beads were prepared by using alginate (ALG), konjac glucomannan (KGM) and chitosan (CHI). Bovine serum albumin and insulin were used as model proteins for in vitro assessments. It was observed that KGM could be contained within beads, and faintness hydrogen binding and electrostatic interaction exist between ALG and KGM by infrared spectra. Clear dents were found on the surface of beads using KGM by scanning electron microscopy. Use of KGM could help increase the payload of drug. After beads were treated by 0.1 N HCl for 4 h and put into pH 7.4 buffers, protein was released from ALG-CHI beads within 1 h, while it was lost from ALG-KGM-CHI beads for 3 h. However, the leaking of protein from ALG-KGM-CHI beads was also increased in 0.1 N HCl solution. Concentration of gelling ion had great effect on release rate and gel structure. Studies of water of hydration had shown that swelling of ALG-KGM-CHI beads was higher than that of ALG-CHI beads in acidic solution, but the opposite result was obtained in alkali solution. The result indicated that the diffusion of protein was related to the viscosity and swelling properties of KGM.

Administration, Oral↗
PubMed2003

Oral sustained delivery of paracetamol from in situ-gelling gellan and sodium alginate formulations.

The purpose of this study was to evaluate the potential for the oral sustained delivery of paracetamol of two formulations with in situ gelling properties. Oral administration of aqueous solutions of either gellan gum (1.0%, w/v) or sodium alginate (1.5%, w/v) containing calcium ions in complexed form resulted in the formation of gel depots in rabbit and rat stomachs as a consequence of the release of the calcium ions in the acidic environment. In vitro studies demonstrated diffusion-controlled release of paracetamol from the gels over a period of 6h. The bioavailability of paracetamol from the gels formed in situ in the stomachs of rabbits following oral administration of the liquid formulations was similar to that of a commercially available suspension containing an identical dose of paracetamol.

Acetaminophen↗
PubMed2001

In-vitro release kinetics of cefadroxil-loaded sodium alginate interpenetrating network beads.

This paper reports the development of new interpenetrating polymeric networks of sodium alginate with gelatin or egg albumin cross-linked with a common cross-linking agent, glutaraldehyde, for the in-vitro release of cefadroxil. The beads formed were characterized by Fourier transform infra-red spectroscopy, scanning electron microscopy and differential scanning calorimetry. Swelling/drying experiments were performed to compute the diffusion coefficients and the molecular mass between cross-links of the beads. The release results were evaluated using an empirical equation to understand the transport mechanism. The extent of cross-linking was studied in terms of the size and release characteristics of the beads. The experimental and derived quantities have been used to study their dependencies on the nature of the polymeric beads, transport mechanism, encapsulation efficiency and drug diffusion, as well as the cross-linking abilities of the polymers.

Albumins↗
PubMed2002

Behavior of alginate gel beads containing chitosan salt prepared with water-soluble vitamins.

Alginate gel beads were prepared which contained weak acid salts of chitosan (Alg-CS) and water-soluble vitamins (e.g. ascorbic acid (AS)) and the behavior of the beads, uptake of bile acids was investigated in vitro. The Alg-CS beads rapidly took up bile acid and this phenomenon was observed for both hydrogel beads and dried beads. About 120 micromol of taurocholic acid was taken up into Alg-CS (1 g) prepared with orotic acid. Dried Alg-CS is the granule which can be made easily, and keeps the ability of CS salt, and all elements can be taken as a food. Therefore, Alg-CS could serve as a useful dietary agent for the prevention of hyperlipidemia.

Alginates↗
PubMed1999

Preparation of alginate gel beads containing chitosan nicotinic acid salt and the functions.

Calcium-induced alginate gel beads containing chitosan salt (Alg-CS) was prepared using nicotinic acid (NA), a drug for hyperlipidemia, and investigated its two functions in gastrointestinal tract, (a) NA release from Alg-CS, (b) uptake of bile acids into Alg-CS. The amount of NA incorporated in Alg-CS increased according to increment of CS content. NA was rapidly released from Alg-CS in diluted HCl solution (pH 1.2) or physiological saline without disintegration of the beads. When Alg-CS was placed in bile acid solution it took bile acid into itself. About 80% of taurocholic acid dissolved in the medium was taken into Alg-CS. According to increment of bile acid concentration, the uptake amount increased and an approximately linear relationship existed among them.

Alginates↗
PubMed2001

Stimulation of various functions in murine peritoneal macrophages by high mannuronic acid-containing alginate (HMA) exposure in vivo.

High mannuronic acid-containing alginate (HMA) was tested to affect murine peritoneal macrophages. In the present study, we measured various functions of murine peritoneal macrophages that were isolated 20 h after intraperitoneal injection with HMA (25 and 100 mg/kg). HMA increased the number of peritoneal macrophages and phagocytosis. Macrophages from HMA-treated mice significantly inhibited growth of tumor cells compared to macrophages from control mice. In addition, supernatants from macrophages of HMA-treated mice contained nitric oxide (NO), hydrogen peroxide (H2O2) and TNF-alpha. The increased production of these cytotoxic molecules induced by HMA is consistent with tumoricidal activity of activated macrophages. Furthermore, HMA-induced tumoricidal activity was partially abrogated by anti-TNF-alpha, inhibitors of NO and the scavenger of reactive oxygen. Thus, the tumoricidal activity induced by HMA appeared to be mediated by the production of TNF-alpha, NO and H2O2. Taken together, these results suggest that HMA has the immunostimulating effect on macrophages after in vivo exposure of it.

Adjuvants, Immunologic↗
PubMed1989

Calcium alginate fibre (Kaltostat 2) for nasal packing after trimming of turbinates--a pilot study.

Following surgical trimming of the inferior turbinates, 32 nostrils were packed with Calcium alginate fibre (Kaltostat 2 gramme fibre packs 80:20 per cent calcium:sodium) for 36-48 hours to achieve haemostasis. There was no bleeding while the packs were in place or after they were removed. These results were compared with two retrospective groups of patients who had undergone the same surgical procedure but the nostrils had been packed with alternative materials.

Alginates↗
PubMed2003

Long-term viability and infectivity of intraradical forms of Glomus intraradices vesicles encapsulated in alginate beads.

Intraradical vesicles of Glomus intraradices were isolated, entrapped in alginate beads, and stored at 4 degrees C for periods from 2-74 months. The beads were used to inoculate leeks grown under standard conditions for 6 wk, then development of root colonization by G. intraradices was recorded. Colonization of leeks was high (mean > 50% in length) and did not vary markedly until five years of storage. After six years of storage, the inoculum proved infective and viable.

Alginates↗
PubMed2001

Molecular basis of C(2+)-induced gelation in alginates and pectins: the egg-box model revisited.

For many ionic polysaccharides, the ability to form gels in the presence of divalent cations such as calcium is the key to biological functions and technological applications. This is particularly true for alginates and pectins, where the regular occurrence of respectively alpha-L-(1-4)-guluronate residues and alpha-D-galacturonate residues generates ordered templates for polymer chain associations that are involved in physical gels. The molecular basis responsible for the strength and the stereospecificity of calcium interactions for the two polysaccharides were investigated in a previous paper (Braccini; et al. Carbohydr. Res. 1999, 119). In the present work, a novel molecular modeling procedure has been developed; it involves a pairing procedure that evaluates all the possible associations of the ordered polyuronate chains with calcium ions to form dimers. Starting from the stable ordered forms of polygalacturonate and polyguluronate, all possible ways to form Ca(2+)-bridged dimers were computed; the parallel and antiparallel relative arrangements of the chains were also considered. Despite the structural analogy between polyguluronate and polygalacturonate chains, significant differences at the level of chain-chain associations are found. The popular "egg box model" can still be referred to in the case of polyguluronate. However, it cannot be used to describe a pectate junction zone as the unique feature of two consecutive chelation site per repeat, that provides a favorable entropic contribution to the interchain association is not reproduced by this pioneering model. The body of these results corroborates the two-stage process in the mechanism of calcium gelation, where the formation of strongly linked dimer associations is followed by the formation of weak inter-dimer associations mainly governed by electrostatic interactions.

Alginates↗
PubMedDate not supplied

Galactose-substituted alginate 2: conformational aspects.

Galactose moieties have been introduced on the uronic groups of alginates from different sources via an N-glycosidic bond, thus affecting the net charge on the polymer chain. The modified polymers have been analyzed by means of viscosity and of high-performance size-exclusion chromatography combined with refractive index multiple angle laser light scattering (HPSEC-RI-MALLS) measurements. The latter technique enabled us to determine the molecular weight of the modified polymers, proving that the synthetic procedure did not affect the chemical integrity of the chain. The intrinsic viscosity and the radius of gyration data showed that the hydrodynamic properties of the polymer chain varied with the degree and the pattern of substitution. In the presence of a relatively low galactose content (up to 19%), a decrease of the hydrodynamic dimensions of the coil was experienced, while on increasing the degree of substitution (especially on GG diads) a re-extension of the chain was discovered. Measurements of intrinsic viscosity at different values of the degree of dissociation have demonstrated that this effect cannot be solely explained by the reduction of the charge density of the polymer. Rather, it implies the occurrence of conformational changes of the chain that are specific to the chemical nature of the site of substitution. These data have been supported by the values of the persistence length of the natural and modified polymers obtained with the Doty-Benoit equation. The chiro-optical properties of the modified polymers studied by means of circular dichroism (CD) spectroscopy confirmed that conformational variations occurred to the polymeric chain upon introduction of galactose residues.

Alginates↗
PubMedDate not supplied

Rheological and structural properties of aqueous alginate during gelation via the Ugi multicomponent condensation reaction.

Turbidity, structure, and rheological features during gelation via the Ugi multicomponent condensation reaction of semidilute solutions of alginate have been investigated at different polymer and cross-linker concentrations and reaction temperatures. The gelation time of the system decreased with increasing polymer and cross-linker concentrations, and a temperature rise resulted in a faster gelation. At the gel point, a power law frequency dependence of the dynamic storage modulus (G' proportional, variant omega(n)(')) and loss modulus (G' ' proportional, variant omega(n)(' ')) was observed for all gelling systems with n' = n' ' = n. By varying the cross-linker density at a fixed polymer concentration (2.2 wt %), the power law exponent is consistent with that predicted (0.7) from the percolation model. The value of n decreases with increasing polymer concentration, whereas higher temperatures give rise to higher values of n. The elastic properties of the gels continue to grow over a long time in the postgel region, and at later stages in the gelation process, a solidlike response is observed. The turbidity of the gelling system increases as the gel evolves, and this effect is more pronounced at higher cross-linker concentration. The small-angle neutron scattering results reveal large-scale inhomogeneities of the gels, and this effect is enhanced as the cross-linker density increases. The structural, turbidity, and rheological features were found to change over an extended time after the formation of the incipient gel. It was demonstrated that temperature, polymer, and cross-linker concentrations could be utilized to tune the physical properties of the Ugi gels such as structure, transparency, and viscoelasticity.

Alginates↗
PubMedDate not supplied

Study of the release mechanism of diltiazem hydrochloride from matrices based on chitosan-alginate and chitosan-carrageenan mixtures.

The aim of this work was to establish the diltiazem hydrochloride release mechanism from the chitosan-alginate matrix tablet (MCB/AS) and chitosan-carrageenan matrix tablet (MCS/CSI). The weight loss for MCS/CSI is mainly due to the weight loss of the matrix while for MCB/AS it is mainly due to the diltiazem hydrochloride released from the tablet. Using the Peppa's model the release order for MCS/CSI was n = 1.07 +/- 0.13 and for MCB/AS was n = 0.76 +/- 0.02. Thus, MCS/CSI has a transport mechanism, and for MCB/AS the drug release mechanism is a combined process of diffusion and relaxation. MCB/AS has an elastic modulus (G' = 10(5) Pa) one order of magnitude higher than MCS/CSI (G' = 10(4) Pa). MCB/AS is able to uptake solvent without disrupting the microstructure due to its high elastic modulus. Instead MCS/CSI showed a quick erosion process, which conducted to the tablet disintegration due to a fast solvent uptake process.

Alginates↗
PubMed2006

Combined rheological and ultrasonic study of alginate and pectin gels near the sol-gel transition.

The sol-gel transition of biopolymer mixtures has been investigated by rheological and ultrasonic measurements. A scaling analysis of the data was performed for both types of measurements. A gel time was determined from rheology for the pure pectin samples, and the data could be fitted to a universal scaling form near the transition point. Its critical exponents are in good agreement with the predictions of scalar percolation theory. In addition, the ultrasonic signal of the pectin samples close to the transition was analyzed in terms of a high-frequency scaling approach for the attenuation and the velocity. For the alginate samples and the mixtures, for which the gel point cannot be determined reliably from rheology, the ultrasonic measurements were analyzed using the same scaling form as for the pectin sample, thus providing a method for estimating the gel point, even in the absence of rheological data.

Alginates↗
PubMed2007

Conformational changes and aggregation of alginic acid as determined by fluorescence correlation spectroscopy.

Insight into the conformations and aggregation of alginic acid was gained by measuring its diffusion coefficient at very dilute concentrations using fluorescence correlation spectroscopy. Both the pH and ionic strength (I) had an important influence on the diffusion coefficient of the polysaccharide. For pH, three effects were isolated: (i) below pH 4, the charge density decreased causing increased aggregation; (ii) between pH 4 and 8, a molecular expansion was observed with increasing pH, whereas (iii) above pH 8 some dissociation of the polymer was observed. Increasing I from 0.001 to 0.1 M resulted in a ca. 20% increase in the diffusion coefficient. By coupling these measurements to molar mass determinations obtained by size exclusion chromatography and monomer size estimations determined from ab initio calculations, it was possible to determine the radii of gyration via de Gennes renormalization theory. From diffusion coefficients and radii of gyration obtained as a function of ionic strength, persistence lengths (total, electrostatic, and intrinsic) were calculated from the Benoit-Doty relationship.

Alginates↗
PubMedDate not supplied

Gelatin blends with alginate: gels for lipase immobilization and purification.

Blends of natural polysaccharide sodium alginate (5%) with gelatin (3%) cross-linked with glutaraldehyde provide beads with excellent compressive strength (8 x 10(4) Pa) and regular structure on treatment with calcium chloride. Lipases from porcine pancreas, Pseudomonas cepacia, and Candida rugosa were immobilized in such a blend with excellent efficiency. The immobilized enzymes were stable and were reused several times without significant loss of enzyme activity both in aqueous and reverse micellar media. The beads were functionalized with succinic anhydride to obtain beads with extra carboxylic acid groups. These functionalized beads were then successfully used for 7.4-fold purification of crude porcine pancreatic lipase in a simple operation of protein binding at pH 5 and release at pH 8.5.

Alginates↗
PubMedDate not supplied

Macroaffinity ligand-facilitated three-phase partitioning (MLFTPP) of alpha-amylases using a modified alginate.

The crude extracts of alpha-amylases when mixed with alginate, tert-butyl alcohol, and ammonium sulfate resulted in an interfacial precipitate containing polymer-bound amylase. The precipitate was dissolved in 1 M maltose to recover alpha-amylase activity. The recovery of alpha-amylases were 74%, 77%, and 92% in the case of Bacillus amyloliquefaciens, wheat germ, and porcine pancreas, respectively. All purified preparations showed a single band on SDS-PAGE.

Adsorption↗