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 (V₀) 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.