Design of a new electrogenerated polyquinone film substituted with glutathione. Towards direct electrochemical biosensors.

We developed a method to graft a tripeptide (glutathione) onto 5-hydroxy-1,4-naphthoquinone, an electropolymerizable molecule. The resulting thin conducting polymer presents a well-defined and stable electroactivity in neutral buffered solution, due to the embedded quinone group, and is able to covalently graft amino-modified DNA probe strands. It is shown that the bioelectrode presents positive current change following DNA hybridization. This makes a "signal-on" direct electrochemical DNA sensor. The results were obtained with low target concentration (50nM) and the selectivity is excellent as a single-mismatch sequence can be discriminated from the full-complementary target.