Enzyme-Modified Buckypaper for Bioelectrocatalysis

Direct bioelectrocatalysis was demonstrated with pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ–GDH) tethered to a range of carbon nanotube (CNT) materials, as evidenced by the generation of anodic current in the presence of glucose. Physical and electrochemical characterization of CNT paper (buckypaper) reveals marked differences attributed to changes in CNT dimensions, including conductivity, packing density, and electrochemically accessible surface area. By using single-walled CNTs as the electrode material, higher current densities per geometric area and lower electron transfer resistances were achieved. In comparison, electrodes made of oxidized CNTs enhanced in the physical adsorption of PQQ, but displayed voltage drops associated with activation losses. In addition, electrode longevity tests revealed that electrochemical activity was retained for two days but decreased by 50% on the third day. PQQ–GDH enzymatic electrodes show potential application as biological fuel cell anodes and will oxidize a range of mono- and disaccharide substrates.