A nano-structured Ni (II)/ACDA (2-amino-1-cyclopentene-1-dithiocarboxylic acid) film was electrodeposited on a gold nanoparticle-cysteine-gold electrode. The formation of Ni (II)/ACDA film and electrocatalytic oxidation of tryptophan on the surface of the modified electrode were investigated with cyclic voltammetric and chronoamperometric techniques. The hydrodynamic amperometry at rotating modified electrode was used for determination of tryptophan in the range of 0.085-43.0 mu mol l(-1). The detection limit was found to be 23 nmol l(-1). The rate constant, transfer coefficient for the catalytic reaction and the diffusion coefficient of tryptophan in the solution were found to be 9.1 x 10(2) M-1 S-1. 0.52 and 1.09 x 10(-5) cm(2) s(-1) respectively. It is worth noting that the as formed matrix in our work possesses a 3D porous network structure with a large effective surface area and high catalytic activity and behaves like microelectrode ensembles. The modified electrode indicated reproducible behavior and a high level stability during the experiments, making it particularly suitable for the analytical purposes. (C) 2011 Elsevier Ltd. All rights reserved.