Sodium Alginate Polymer Research Articles

Strategies to Overcome pH-Dependent Solubility of Weakly Basic Drugs by Using Different Types of Alginates

Weakly basic drugs demonstrate higher solubility at lower pH, thus often leading to faster drug release at lower pH. The objective of this study was to achieve pH-independent release of weakly basic drugs from extended release formulations based on the naturally occurring polymer sodium alginate. Three approaches to overcome the pH-dependent solubility of the weakly basic model drug verapamil hydrochloride were investigated. First, matrix tablets were prepared by direct compression of drug substance with different types of sodium alginate only. Second, pH-modifiers were added to the drug/alginate matrix systems. Third, press-coated tablets consisting of an inner pH-modifier tablet core and an outer drug/sodium alginate coat were prepared. pH-Independent drug release was achieved from matrix tablets consisting of selected alginates and drug substance only. Alginates are better soluble at higher pH. Therefore, they are able to compensate the poor solubility of weakly basic drugs at higher pH as the matrix of the tablets dissolves faster. This approach was successful when using alginates that demonstrated fast hydration and erosion at higher pH. The approach failed for alginates with less-pronounced erosion at higher pH. The addition of fumaric acid to drug/alginate-based matrix systems decreased the microenvironmental pH within the tablets thus increasing the solubility of the weakly basic drug at higher pH. Therefore, pH-independent drug release was achieved irrespective of the type of alginate used. Drug release from press-coated tablets did not provide any further advantages as compound release remained pH-dependent.

Mucoadhesive bilayer tablets of propranolol hydrochloride

The purpose of this research was to study mucoadhesive bilayer buccal tablets of propranolol hydrochloride using the bioadhesive polymers sodium alginate (Na-alginate) and Carbopol 934P (CP) along with ethyl cellulose as an impermeable backing layer. The tablets were evaluated for weight variation, thickness, hardness, friability, surface pH, mucoadhesive strength, swelling index, in vitro drug release, ex vivo drug permeation, ex vivo mucoadhesion, and in vivo pharmacodynamics in rabbits. Tablets containing Na-alginate and CP in the ratio of 5:1 (F2) had the maximum percentage of in vitro drug release without disintegration in 12 hours. The swelling index was proportional to Na-alginate content and inversely proportional to CP content. The surface pH of all tablets was found to be satisfactory (7.0 +/- 1.5), close to neutral pH; hence, buccal cavity irritation should not occur with these tablets. The mechanism of drug release was found to be non-Fickian diffusion and followed zero-order kinetics. The formulation F4 was optimized based on good bioadhesive strength (28.9 +/- 0.99 g) and sustained in vitro drug permeation (68.65% +/- 3.69% for 12 hours). The behavior of formulation F4 was examined in human saliva, and both the drug and the buccal tablet were found to be stable. The formulation F4 was applied to rabbit oral mucosa for in vivo studies. The formulation inhibited isoprenaline-induced tachycardia. The studies conducted in rabbits confirmed the sustained release as compared with intravenous administration.

Preparation and properties of waterborne polyurethane‐urea/sodium alginate blends for high water vapor permeable coating materials

AbstractTo improve the water vapor permeability of coating materials, aqueous sodium alginate (SA) solution was blended with waterborne polyurethane‐urea (WBPU) dispersions synthesized by prepolymer mixing process. The content of SA for stable WBPU/SA dispersions was found to be below 30 wt %. As the SA content increased, the number and density of total micropores (tunnel‐like micropores/isolated micropores) formed after dissolution of SA in water increased, and the water vapor permeability of coated Nylon fabric also increased remarkably. These results clearly demonstrate that utilizing WBPU/water soluble polymer SA blends as coating materials and then dissolving SA in water surely facilitate obtaining prominent breathable fabrics. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

Novel alginate–acrylic polymers as a platform for drug delivery

The aim of the present work was to develop a family of novel materials based on a combination of sodium alginate and acrylic polymers and to evaluate their potential in drug delivery applications. In the presence of sodium alginate, acrylic chains with acidic as well as basic moieties were polymerized to create an interpolymer complex based on electrostatic interactions that are able to modulate the release rate of low molecular weight drugs. The synthesized materials were used to prepare hydrophilic matrices for drug delivery and tested for their adhesion properties to glass, used as a model substrate for mucoadhesion.

Calcium Alginate Barrier Films Modified by Montmorillonite Clay

The goal of decreasing the permeation of small molecules through calcium alginate films is addressed by incorporating small amounts of montmorillonite clay into the polymer. Incorporation is achieved by (i) blending up to 3 wt% pre‐exfoliated montmorillonite into sodium alginate polymer solutions, (ii) casting thin films, (iii) cross‐linking the chains with calcium chloride solution into insoluble calcium alginate, and (iv) drying the resulting cross‐linked materials. Exfoliation and dispersion of the montmorillonite platelets is assessed by light scattering and small‐angle X‐ray scattering. The barrier properties of the impregnated films were gauged by permeation of benzaldehyde using a Hanson‐Research diffusion cell. Decreased permeability is found at clay loadings below 3 wt%. Dedicated to Professor John L. Stanford on the occasion of his 60th birthday.

Preparation and Photo-catalyst Properties of the α-Fe_2O_3-TiO_2 Films on Sodium Alginate Polymer

Preparation and Photo-catalyst Properties of the α-Fe_2O_3-TiO_2 Films on Sodium Alginate Polymer

Preparation and release characteristics of polymer-coated and blended alginate microspheres

To prevent a rapid drug release from alginate microspheres in simulated intestinal media, alginate microspheres were coated or blended with polymers. Three polymers were selected and evaluated such as HPMC, Eudragit RS 30D and chitosan, as both coating materials and additive polymers for controlling the drug release. This study focused on the release characteristics of polymer-coated and blended alginate microspheres, varying the type of polymer and its concentration. The alginate microspheres were prepared by dropping the mixture of drug and sodium alginate into CaCl(2) solution using a spray-gun. Polymer-coated microspheres were prepared by adding alginate microspheres into polymer solution with mild stirring. Polymer-blended microspheres were prepared by dropping the mixture of drug, sodium alginate and additive polymer with plasticizer into CaCl(2) solution. In vitro release test was carried out to investigate the release profiles in 500 ml of phosphate buffered saline (PBS, pH 7.4). As the amount of polymer in sodium alginate or coating solution increase, the drug release generally decreased. HPMC-blended microspheres swelled but withstood the disintegration, showing an ideal linear release profiles. Chitosan-coated microspheres showed smooth and round surface and extended the release of drug. In comparison with chitosan-coated microspheres, HPMC-blended alginate microspheres can be easily made and used for controlled drug delivery systems due to convenient process and controlled drug release.

Preparation and release characteristics of polymer-coated and blended alginate microspheres

To prevent a rapid drug release from alginate microspheres in simulated intestinal media, alginate microspheres were coated or blended with polymers. Three polymers were selected and evaluated such as HPMC, Eudragit RS 30D and chitosan, as both coating materials and additive polymers for controlling the drug release. This study focused on the release characteristics of polymer-coated and blended alginate microspheres, varying the type of polymer and its concentration. The alginate microspheres were prepared by dropping the mixture of drug and sodium alginate into CaCl2 solution using a spray-gun. Polymer-coated microspheres were prepared by adding alginate microspheres into polymer solution with mild stirring. Polymer-blended microspheres were prepared by dropping the mixture of drug, sodium alginate and additive polymer with plasticizer into CaCl2 solution. In vitro release test was carried out to investigate the release profiles in 500 ml of phosphate buffered saline (PBS, pH 7.4). As the amount of polymer in sodium alginate or coating solution increase, the drug release generally decreased. HPMC-blended microspheres swelled but withstood the disintegration, showing an ideal linear release profiles. Chitosan-coated microspheres showed smooth and round surface and extended the release of drug. In comparison with chitosan-coated microspheres. HPMC-blended alginate microspheres can be easily made and used for controlled drug delivery systems due to convenient process and controlled drug release.

In-Vitro Release of Acetaminophen from Sodium Alginate Controlled Release Pellets

The production of spheres loaded with acetaminophen by the cross linking technique was achieved. The hydrophilic polymer sodium alginate which gels in presence of a cross linking ion was used as a matrix for the spheres production. Two processing variables were studied. The drug load in the formula which varied from 5% w/v to 20% w/v, and the cross linking agents used; calcium chloride, calcium acetate, and aluminum sulfate. Also the effects of the dissolution medium and the rotational speed of the dissolution apparatus on drug release were investigated. Spheres were compacted into 450 mg tablets without the aid of excipients. The drug release from spheres containing 20% w/v drug was 90% after 6 hours, while the drug release from compacts of these spheres was 90% after 12 hours. The mechanism of drug release from spheres and compacts containing 20% w/v drug and prepared with 5% w/v cross linking material

Sedimentary carbonate mineralsF. Lippmann, 1973. Springer, Berlin/Heidelberg/New York, VI + 228 pp., U.S. $21.50

In this study, a selective depressant sodium alginate (SA) was used to improve the flotation performance of separating apatite from dolomite. The flotation results show that SA can completely depress dolomite with a slight effect on apatite flotation in pH 8–11. The contact angle tests and adsorption tests indicate that depressant SA absorbed onto both apatite and dolomite surfaces and the adsorption intensity of the latter was greater than that of the former. The FTIR and XPS analysis indicate that SA absorbed onto apatite surface mainly through hydrogen bonding between hydroxyl groups on apatite surface and hydroxyl and carboxyl groups on polymer SA, while onto dolomite surface mainly through chemical chelating between Ca on dolomite surface and hydroxyl and carboxyl groups on polymer SA. Therefore, the adsorption of SA on dolomite was stronger than on apatite, which resulted in a selective depression for dolomite

The effects of sodium alginate and other untested polymers on radiostrontium retention in the rat.

At levels of 1, 5, and 10%, sodium alginate, guar gum, carboxymethyl guar gum, and Questran were tested in diets fed to rats to determine their effects on radiostrontium skeletal retention. Alginate was the only effective agent against radiostrontium retention, approaching, at the 10% level, 70% less 89Sr skeletally retained than radio-control animals and a 3-fold improvement over natural biological strontium-calcium discrimination. The strontium-binding ability shown by alginate was probably clue to its functional carboxyl groups.

A New Alginate Adjuvant

Studies with a new, low polymer sodium alginate adjuvant are described using soluble, as well as particulate, antigens. Comparative data in experimental animals for the titres elaborated using the sodium alginate as an adjuvant were, in most cases, as good as, or superior to, antibody titres procured with Freund's adjuvant. The alginate adjuvant is miscible with water and can be used as a liquid sodium salt prior to injection, after which it forms an insoluble gel as the calcium alginate which is gradually absorbed from the site of the inoculation.