Direct electron transfer of copper–zinc superoxide dismutase (SOD) on crystallographically oriented Au nanoparticles

The direct electron transfer (ET) of copper–zinc superoxide dismutase (SOD) has been realized, for the first time, at Au nanoparticles electrodeposited onto GC (nano-Au/GC) electrodes. Electrodeposition of Au nanoparticles in the presence of some additive (typically cysteine) resulted in the fabrication of Au nanoparticles with a high roughness morphology (enriched in the Au(1 0 0) orientation) and thus providing a favorable adsorption orientation of SOD (key–lock interaction) suitable for a facilitated direct ET without the use of mediators or so-called ET promoters. The redox reaction of the SOD confined on the nano-Au/GC electrode was found to have a formal potential of +0.02 V vs. Ag/AgCl/KCl(sat). Whereas, round-shape spherical plumbs of Au nanoparticles were electrodeposited in the presence of iodide ions (as additive) which lack for the favorable rough surface and consequently the suitable interaction with the SOD is missing and hence the ET is not realized at this surface.