Ferrocene-bra:ached chitosan derivatives (CHIT-Fc) are synthesized by reductive N-alkylation of chitosan with ferrocenecarboxaldehyde. The structures of the products are determined by H-1 NAAR and FT-IR spectra. CHIT-Fc is used as a functionalized matrix to immobilize GOD on glassy carbon electrodes. Ferrocenyls in CHIT-Fc exhibit an excellent redox activity and establish efficient electrical communication between GOD and the electrodes for the oxidation of glucose. The development of a reagentless glucose biosensor is described.