Pectin-alginate systems

LM pectin/calcium systems Xanthan/carob and iota-carrageenan Xanthan/chromium Sodium alginates Gelatin. 

HM pectin/sucrose systems Schizophyllan/sorbitol Xanthan/aluminum Xanthan/carob gum mixtures Alginate/calcium Chitosan/acetic acid-water-propanediol... 

A slightly different approach is to deliver the active drug in a dry powder carrier system, for example microcrystalline cellulose, hydroxyethyl starch, cross-linked dextran, microcrystalline chitosan, carbomer, pectin, or alginic acid. The polymer absorbs water upon contact with the nasal mucosa and swells to become a viscous gel, often demonstrating bioadhesive properties. Such systems can remain in the nasal cavity for as long as six hours. For example, the bioavailability in rats of the somatostatin analogue, octreotide, was shown to be enhanced by the co-administration of alginic acid and cross-linked dextran as dry powders. 

Another system was based on a swelling core tablet and a surrounding coating consisting of a combination of hydrophobic and hydrophilic polymers. The insoluble hydrophilic polymer, such as calcium pectinate or calcium alginate, was dispersed in the coating and served as a channel-former in order to control the water penetration. The core contained a swelling, but... 

Pillay V, Danckwerts MP, Fassihi R. A crosslinked calcium-alginate-pectinate-cellulose acetophthalate gelisphere system for linear drug release. Drug Delivery 2002 9(2) 77-86. 

Algins and low-methoxyl pectins can form gels by slow precipitation, usually as the calcium salt, through the controlled release of calcium from sparingly water-soluble salts or chelated systems. These gels do not melt, but they can be dissolved after conversion into the monovalent-cation form. 

Toft, K, in "Prog. Food. Nutr. Sci. , 1982, 6, 89-96 Toft, K. "Gel Formation in Alginate-Pectin Systems Using Slow Acidifier" presented at the European Science Fundation Workshop on Specific Interactions in Polysaccharide Systems, Uppsala, Sweden, April 26-27, 1983. 

Calcium is a divalent cation that can be used to cross-link alginate or pectinate in the form of gel beads. These beads can be a suitable immobilization system for plant extracts or for pure polyphenolics like resveratrol, for controlled release after oral administration. 

Electrostatic polyelectrolyte complexes (PEC) are mentioned in the literature involving chitosan and synthetic or natural polymers such as PAA and CMC [155,156], xanthan, carrageenan, alginate [157-162], pectin [163,164], heparin, hyaluronan (HA) [165-169], sulfated cellulose, dextran sulfate, or N-acylated chitosan/chondroitin sulfate. Many systems were cited in the literature [2, 170]. The electrostatic interaction was discussed in relation with the stiffness of the backbone and the nature of the ionic groups involved. Especially, with alginate or HA, a pH-dependent complex is formed, whose stability depends on the ionic concentration. The complex formation was investigated in dilute solution by potentiometry (pH) and conductivity to determine the fraction of ion pairs (-COO + NH3 —) formed in dependence of the experimental conditions [164, 166]. 

Chitosan films exhibit low swelling in water, but membranes with diverse hydrophilic aptitudes can be prepared through the formation of mixtures or semi-interpenetrated and interpenetrated networks of chitosan with highly hydrophilic polymers like poly(vinyl alcohol), poly(vinylpyrrolidone) and gelatin [164]. PEC of chitosan with polyanions of natural origin like alginate, pectin or CMC or with synthetic ones, like poly(acrylic acid), have been investigated as matrices for controlled-release systems [165]. 

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