Electrochemical studies of single-wall carbon nanotubes as nanometer-sized activators in enzyme-catalyzed reaction

Chronoamperometry based on the "controlling-diffusion layer" concept of the convective system was used to assay the activity of lactate dehydrogenase (LDH) on a bare glassy carbon (GC) electrode and a GC electrode modified by a single-wall carbon nanotube (SWNT) film. The effects of lanthanum ion, oxalic acid, and nicotine on the LDH activity were monitored. Analysis of the experimental results revealed that the single-wall carbon nanotubes could markedly increase the activity of LDH. The activation and inhibition were characterized by three quantities: the real initial reaction rate (V-0) and the maximum reaction rate (V-max) of the enzyme-catalyzed reaction and the Michaelis-Menten constant (K-m). Tapping mode atomic force microscopy (AFM) images and the Raman spectra unambiguously demonstrated that the single-wall carbon nanotubes could interact with the enzyme LDH while the SWNT-modified electrode was under the potential control. In this case, the activation of SWNT was attributed to the interaction of SWNTs with the enzyme. (C) 2004 Elsevier B.V. All rights reserved.