In this short review, our objective was to describe few new applications of a natural polysaccharide extracted from algae, the alginates. Firstly, the chemical composition is recalled and the main techniques used for characterization are cited. The role of guluronic acid blocks (GG blocks) is particularly important for gel mechanical properties in presence of calcium counterions. Then, the main applications in food and biomedicine are briefly mentioned followed by tentative applications in packaging, paper, textil and wound dressing which are described. Especially, fine fibers are produced now industrially under mixed sodium/calcium ionic form.

En esta corta revisión, nuestro objetivo fue describir algunas nuevas aplicaciones de un polisacárido natural extraído de algas: el alginato. Primeramente, la composición química es revisada, además de citar las principales técnicas utilizadas para su caracterización. El papel de los bloques de ácido gulurónico (bloques GG) es particularmente importante para las propiedades mecánicas del gel en presencia de Ca como contraión. Después, se mencionan brevemente las principales aplicaciones en el área de alimentos y biomedicina, seguida de aplicaciones experimentales en embalaje, papel, textiles, y vendajes de heridas, las cuales son descritas. Especialmente, fibras finas de alginato son ahora producidas industrialmente en una forma iónica mixta de sodio/calcio.

Abstract This paper describes the rheological and thermal behaviour of alkylated chitosan and hyaluronan derivatives and methylcellulose, Their behaviour is characterized by the formation of hydrophobic domains which may be considered as crosslinked points. Then, depending on the thermodynamic conditions (temperature, salt concentration), an aqueous solution transforms to a 3D-physical network formed on the basis of hydrophobic cooperative interactions.

Resumen Este trabajo describe el comportamiento reológico y térmico de quitosano y hialuronano alquilados y de metilcelulosa. Dicho comportamiento está caracterizado por la formación de dominios hidrofóbicos que pueden considerarse como puntos de entrecruzamiento. Por tanto, en dependencia de las condiciones termodinámicas (temperatura, salinidad), las disoluciones acuosas pueden transformarse en una red física tridimensional basada en interacciones cooperativas de carácter hidrofóbico.

Chitosan is a natural polysaccharide constituted by D-glucosamine units beta-(1 4) linked. In the present work new phosphorylated derivatives of chitosan were synthesized. The heterogeneous reaction was carried out using diethyl chlorophosphate as phosphorylating agent. The relation of the degree of substitution with the molar ratio used to obtain the derivatives was studied and a DS 1.0 was achieved. Chitosan diethyl phosphate obtained was characterized by FTIR, elemental analysis, ¹H, 31P and 13C NMR to confirm its structure. The elemental analysis revealed up to 10.5% P was incorporated to this polysaccharide

Among the biodegradable polymers, the polysaccharides have been found to be promising carriers for bioactive molecules. From a general standpoint, they present several reactive groups, such as hydroxyl, carboxyl and amine, that can be modified in a number of ways, giving rise to suitable devices for controlled release. In this paper, agarose was submitted to O-acetylation reactions under heterogeneous conditions, using acetic anhydride and pyridine, aiming to observe the effect of acetyl groups on the agarose properties. The products were characterized by Infrared and ¹H NMR spectroscopies. In the range of average acetylation degrees (DA) 0.07-0.48, the polymers presented partial solubility in boiling water and in common organic solvents. The ¹H NMR spectra presented evidences of non-homogeneous acetyl group distribution along the chains, as concluded from the solubility of only one of the fractions with DA<0.09, in boiling water .