Cross-linking process of carboxylated polysaccharides

A process for the preparation of cross-linked polysaccharides wherein the cross-linking occurs only through amide bonds between carboxy groups of the starting polysaccharides and amino groups of a polyamine in which the polysaccharide is selected from the group consisting of hyaluronic acids, carboxymethyldextran, carboxymethylcellulose, carboxymethylstarch, alginic acids, cellulose acid, N-carboxy-methyl or butyl glucans or chitosans, heparins with different molecular weights, optionally desulphated and succinylated, dermatan sulphate, chondroitin sulphates and heparan sulphates comprising (a) activating the caboxy groups of the polysaccharide in an aqueous aprotic solvent using a suitable carboxy activating agent;

• (b) reacting the carboxy activated polysaccharide with a polyamine selected from the group having the formula R1—NH—A—NH—R2 wherein R1 and R2, which may be the same or different, are hydrogen, C 1-C6 alkyl, phenyl or benzyl groups;
• A is a C2-C10 alkylene chain;
• a polyoxyalkylene chain of the formula [(CH2)n—O—CH2)n]m wherein n is 2 or 3 and m is an integer from 2 to 10;
• a C5-C7 cycloalkyl group or an aryl or heteroaryl group;
• and (c) recovering the resultant cross-linked polysaccharide.