In recent years, entrapment of cells within spheres of Ca 2+ alginate has become the most widely used technique for immobilizing living cells. This versatile method includes applications ranging from immobilization of living or dead cells in bioreactors, immobilization of plant protoplasts for micropropagation and immobilization of hybridoma cells for production of monoclonal antibodies, to entrapment of animal cells for implantation of artificial organs. This review evaluates the potential of this method on the basis of the current knowledge of structural and functional relationships in alginate gels.

Many different techniques for immobilizing ceils have been proposedL Recently, use of polysaccharides for gel entrapment or encapsulation has developed into a challenging method 1 and the use of alginate gel beads stands out as the most promising and versatile method yet a-3. This immobilization procedure can be carried out in a single-step process under very mild conditions and is therefore compatible with most living cells. The cell suspension is mixed with an Na+ alginate solution, and the mixture dripped into a solution containing multivalent cations (usually Ca2+). The droplets form gel spheres instantaneously, entrapping the cells in a threedimensional lattice of ionically cross-linked alginate (Fig. 1). Most