Bienzyme HRP-GOx-modified gold nanoelectrodes for the sensitive amperometric detection of glucose at low overpotentials

Gold nanotubular electrode ensembles were prepared by using electroless deposition of the metal within the pores of polycarbonate track-etched membranes. Mono-enzyme (GOx) and monolayer/bilayer bienzyme (GOx/HRP) bioelectrodes were prepared by immobilizing the enzymes onto gold nanotubes surfaces modified with mercaptoethylamine. Batch amperometric responses to glucose for the different bioelectrodes were determined and compared. The response of the two geometries (monolayer and bilayer) of the bienzyme electrodes was shown to vary with regard to sensitivity at detection potentials above 0 V. On the contrary, at detection potentials below 0 V, no noticeable influence of the configuration of the bienzyme on the response intensity was observed. The mono-enzyme (650 muA mM(-1) in benzoquinone (BQ) at -0.8 V versus Ag/AgCl) and the two bienzyme bioelectrodes (+/-400 muA mM(-1) in hydroquinone (H(2)Q) at -0.2 V versus Ag/AlCl) display remark-able sensitivities compared to a classical GOx-modified gold macroelectrode (13 muA mM(-1) in BQ at -0.8 V versus Ag/AgCl). A remark-able feature of the bienzyme electrodes is the possibility to detect glucose at very low applied potentials where the noise level and interferences from other electro-oxidizable compounds are minimal. Another important characteristic of the monolayer bienzyme electrode is the possible existence of a direct electronic communication between HRP and the transducer surface. (C) 2004 Elsevier B.V. All rights reserved.