Covalently cross-linked copolymers are described herein. More specifically, polysaccharide-polyamine copolymeric matrices or structures and cationic copolymeric matrices are described herein. The polysaccharide-polyamine copolymers, when protonated, can form cationic copolymeric matrices having exceptionally high densities of cationic sites. In one form, the covalently cross-linked copolymers provide a three-dimensional structure, especially when hydrated.