Electrode coatings based on chitosan scaffolds

Thin films of a biopolymer chitosan (CHIT) were cast on glassy carbon electrodes, modified by grafting Lucifer Yellow VS dye (LYVS) onto chitosan chains, and cross-linked with glutaric dialdehyde (GDI). The ion-transport and ion-exchange properties of such polymeric structures (CHIT, CHIT-LYVS, CHIT-LYVS-GDI) were studied using cyclic voltammetry, rotating disk electrode, and flow injection analysis. The results showed that the chitosan matrix supported a fast ion transport as demonstrated by aqueous-like values of the apparent diffusion coefficients of Ru(NH3)6(3)+ and dopamine in the films. Anionic LYVS dye introduced a permselectivity against anions (e.g., Fe(CN)6(4)-, ascorbate) into the CHIT-LYVS films. The cross-linking of such films with GDI further increased their permselectivity as well as their stability. A unique combination of high permselectivity and fast ion transport in the CHIT-LYVS-GDI films is discussed in terms of the mixed-transport mechanism involving both pore and membrane diffusion in a highly hydrated chitosan matrix. The results indicate that the chemically modified chitosan is an attractive new coating for the development of fast, selective, and reversible sensors.