Investigation of electrochemical micropatterning using a dually electroactive molecule

Abstract

Electrochemical patterning of biomolecules on surfaces has recently received a considerable attention because of the large variety of its potential applications such as biochips and molecular electronic devices. In this study we report a new electrochemical method for the micropatterning of protein on indium-tin-oxide (ITO) coated glass via an electrochemical deposition process of a dually electroactive molecule, MUAHQ (11,11``dithiobis(undecanoic acid hydroquinone monoester)). One end of this molecule comprises electropolymerizable unit like a phenol group, and the other is disulfide unit that can be reducible to thiol one. For the patterning, individually addressable ITO-microelectrode arrays were prepared by a simple microfabrication. Electropolymerized thin films of MUAHQ were formed on selected electrodes by successive addressings of anodic potential. The resulting array surface was chemically treated with TCEP (Tris(2-carboxyethyl)phosphine hydrochloride), which reduces disulfide group in the films to a free thiol form. These reduced electrodes were selectively oxidized to disulfide surfaces by second electrochemical addressings. The whole array was immersed in the solution with maleimide-biotin conjugate. While thiol-formed surface can be an active site for the attachment of maleimide functional group, a disulfide surface is inactive. The resulting array was disclosed to the buffer solution of labeled streptavidin with a quantum dot. Highly contrasted patterning images observed by a fluorescence microscope demonstrate that electrochemical control of thiol and disulfide inter-conversion might be nicely used for a protein patterning.