Functionalized ensembles of nanoelectrodes as affinity biosensors for DNA hybridization detection

A novel electrochemical biosensor for DNA hybridization detection based on nanoelectrode ensembles (NEEs) is presented. NEEs are prepared by electroless deposition of gold into the pores of a templating track-etched polycarbonate (PC) membrane. The wide surface of the templating membrane surrounding the nanoelectrodes is exploited to bind the capture DNA probes via amide coupling with the carboxylic groups present on the PC surface. The probes are then hybridized with the complementary target labelled with glucose oxidase (GO). The occurrence of the hybridization event is detected by adding, to the supporting electrolyte, excess glucose as the substrate and the (ferrocenylmethyl) trimethylammonium cation (FA) as suitable redox mediator. In the case of positive hybridization, an electrocatalytic current is detected. In the proposed sensor, the biorecognition event and signal transduction occur in different but neighbouring sites, i.e., the PC surface and the nanoelectrodes, respectively; these sites are separated albeit in close proximity on a nanometer scale. Finally, the possibility to activate the PC surface by treatment with permanganate is demonstrated and the analytical performances of biosensors prepared with KMnO4-treated NEEs and native NEEs are compared and critically evaluated. The proposed biosensor displays high selectivity and sensitivity, with the capability to detect few picomoles of target DNA.