2007 NSTI Nanotechnology Conference and Trade Show - Nanotech 2007 - 10th Annual

Covalently immobilized cytochrome c on self-assembled monolayers on ultrananocrystalline diamond electrodes

S.Q. Lud, F. Spirkl, M. Niedermeier, P. Bruno, D.M. Gruen, P. Feulner, J.A. Garrido and M. Stutzmann
TU Munich, DE

Keywords:
diamond enzyme immobilization electron transfer

Abstract:
We report on a direct immobilization of horse heart cytochrome c on amino-terminated benzene monolayers on nitrogen-doped ultrananocrystalline diamond (UNCD) electrodes and have investigated its electron-transfer and ligand binding properties. Cyclic voltammetry, atomic force microscopy, and X-ray photoelectron spectroscopy were used to characterize the spontaneous grafting of the self-assembled diazonium monolayer onto the diamond surface. The results confirm the presence of a very stable, homogeneous and dense self-assembled monolayer on the hydrogenated UNCD. For protein attachment, electrochemical reduction of the functional NO2 group to NH2 was induced within the grafted layer. Upon immobilization onto this functionalized diamond surface, the protein retains its conformation, as suggested by the recorded redox potential of 75 mV vs Ag/AgCl for the Fe(III) / Fe(II) transition of the protein heme group. Furthermore, cyclic voltammetry experiments indicated that the immobilized cytochrome c retained its electrocatalytic activity to the reduction of H2O2. The integrated charge transfer of linear sweep voltammograms in physiological electrolyte solutions equivalents a high protein surface coverage of approximately 45 % of a highly dense protein monolayer. With our promising strategy to immobilize proteins an excellent spatial specificity by electro-addressed switching of nitro to amino groups becomes available.

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