DNA biosensor for detection of Helicobacter pylori using phen-dione as the electrochemically active ligand in osmium complexes

A surface-based method for the study of the interactions of DNA with redox-active 1,10-phenantroline-5,6-dione (phen-dione) osmium complexes is described. The study was carried out using gold electrodes modified with DNA via adsorption and [Os(bpy)2(phe-dione)]3+/2+ (bpy = 2,2‘-bipyridyl) or [Os(phen)2(phen-dione)]3+/2+ (phen = 1,10-phenantroline) as electrochemical reported molecules. The method, which is simple and reagent-saving, allows the accumulation of osmium complexes within the DNA layer. The amount of osmium complex bound by the adsorbed layer of DNA was determined from the voltammetric charge associated with the osmium redox process of the immobilized metal complex. The quinone moiety of the phen-dione ligand was useful as an indicator for electrochemical DNA sensing because of its redox response at low potentials. A thiol-linked single-stranded Helicobacter pylori DNA probe was immobilized, through S−Au bonds on to a gold electrode (density of modification 86 pmol/cm2). Following hybridization...