Alginate network

Polyacrylic acid/sodium alginate network A Fungal resistance test [81]... 

For alginates, the copolymer composition (ratio of mannuronic to guluronic acid units) can influence the ultimate complex properties. These include elasticity as well as permeability and mechanical resistance of coacer-vates cast into 2D or spherical membrane structures. The type of polymer-polymer coacervate (precipitate, sol, network) will also often be highly molar mass dependent, with useful membranes formd within a narrow window. This often does not correspond to the molar mass range required for bioapplications, which is dictated by factors such as cell toxicity and biocompatability. 

Alginates are a family of polysaccharides mainly extracted by brown algae. Alginate hydrogels are able to store up to 100 times their weight of water, trapped in a network of hydrophilic fibrils. This property accounts for their natural occiurence as water reservoirs in plants of the tidal area [6]. 

Gelation of polyanionic or polycationic polymers by the addition of multi-valent counter-ions is a simple and common method of entrapment of enzymes and whole cells. In one common embodiment, whole cells or enzymes are entrapped by the drop-wise addition of an aqueous solution of sodium alginate and the biocatalyst to a concentrated solution of a Ca2+ salt. The cation acts as a cross-linking agent towards the alginate biopolymer and the droplets precipitate as beads with the biocatalysts entrapped within the network. Although the beads are relatively soft and unstable, this method has been one of the preferred methods for entrapment of whole cells. A... 

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