SYNTHESIS OF N-(AMINOALKYL)CHITOSAN FOR MICROCAPSULES

Chitosan was chemically modified by alkylation with N-(2-bromoethyl) phthalimide, N-(3-bromopropyl)phthalimide, and N-(4-bromobutyl)phthalimide. The resulting N-(phthalidimidoalkyl) chitosans were treated with hydrazine to remove the phthalidimido group resulting in the final N-(aminoalkyl) chitosan products. For comparison purposes, poly(vinyl alcohol) (PVA) was alkylated with N-(3-bromopropyl)phthalimide, then treated with hydrazine to give the N-(3-aminopropyl) PVA product. All alkylation products were characterized by solution H-1- and C-13-NMR and by solid-state CP-MAS C-13-NMR. The above synthetic polymer derivatives, as well as chitosan, polyallyl amine, and polyethylenimine, were used to form membrane coatings around calcium alginate beads in which blue dextran of molecular weight 7.08 X 10(4) or 26.6 X 10(4) was entrapped. These microcapsules were prepared by extrusion of a solution of blue dextran in sodium alginate into a solution containing calcium chloride and the membrane polymer. Membrane integrity and permeability were assessed by measuring the elution of the blue dextran from the capsules, spectrophotometrically. (C) 1993 John Wiley & Sons, Inc.