Enhanced Direct Electron Transfer of a Multihemic Nitrite Reductase on Single-walled Carbon Nanotube Modified Electrodes

Single-walled carbon nanotubes (SWCNTs) deposits on glassy carbon and pyrolytic graphite electrodes have dramatically enhanced the direct electron transfer of the multihemic nitrite reductase from Desulfovibrio desulfuricans ATCC 27774, enabling a 10-fold increase in catalytic currents. At optimal conditions, the sensitivity to nitrite and the maximum current density were 2.4±0.1A Lmol^-1cm^-2 and 1500μA cm^-2, respectively. Since the biosensor performance decreased over time, laponite clay and electropolymerized amphiphilic pyrrole were tested as protecting layers. Both coating materials increased substantially the bioelectrode stability, which kept about 90% and 60 % of its initial sensitivity to nitrite after 20 and 248 days, respectively.