The gold-coated magnetic nanoparticles (Au@MNPs) have been proposed to act as "dispersible electrodes" in sensing applications with the dual advantages of reduced detection time and increased sensitivity. As a sensor the Au@MNPs would be modified with ligands to capture the analyte, with exposure of a magnetic field bringing the nanoparticles back to a macroelectrode for electrochemical detection of the amount of analyte. In this paper, the potential of Au@MNPs as dispersible electrodes is assessed via (1) characterization of how they assemble onto a macroelectrode upon application of a magnetic field, (2) their electron transfer behaviour to redox species in solution and redox species attached to the Au@MNPs and (3) how low a detection limit is possible. Visualization with atomic force (AFM), scanning electron (SEM) and light microscopy showed the particles formed a coral-like structure on the electrode. Electron transfer kinetics of the Au@MNPs-modified electrode was shown to be similar to a bare electrode by both cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrochemistry of the Os(bpy)(2)(AMP) modified Au@MNPs enabled an estimation of the smallest number of redox molecules per Au@MNP that could be detected. It was estimated that as little as 0.144 +/- 0.007 redox molecules per nanoparticle could be detected with the lowest actual detected number being 0.79 +/- 0.11 molecule per nanoparticle. (C) 2011 Elsevier B.V. All rights reserved.