Modification of electrodes with dicarboxylate self-assembled monolayers for attachment and detection of nucleic acids

Self-assembled monolayers of dodecanedicarboxylic acid (DDCA) were formed on indium tin oxide (ITO) electrodes using the known affinity of carboxylate for metal-oxide surfaces. The electrodes were modified and derivatized with DNA through a reaction of the pendant carboxylate with amines of nucleobases. The electrochemistry of Ru(bpy)32+ was unaffected by the monolayer formation but attachment of the DNA to the electrode led to catalytic enhancement due to guanine oxidation. This arrangement can be used to detect hybridization of poly[G] to an electrode. The carboxylate-ITO interface is compatible with the electrochemistry of Ru(bpy)32+ which would not be the case in gold-thiol monolayers.