Electrochemiluminescence (ECL) is widely used in analytical chemistry and shows several advantages, such as high sensibility and selectivity. ECL is particularly well adapted to the biochip based on the immobilization of DNA probes onto a conducting polymer layer, such as the polypyrrole (Ppy). This bio-sensitive layer was electrogenerated on the electrode surface from pyrrole units and pyrrole monomer bearing DNA. The recognition between the DNA probes onto the Ppy and DNA targets present in an analyte could be achieved by ECL. The principle of this detection method is, as follow. Once the hybridization (DNA probes)/(DNA targets) is completed, the ECL marker was immobilized to the DNA targets thanks to the biotin-avidin interaction, for example. Then, the electrochemical generation of the ECL reaction is induced by polarization of the electrode coated with the DNA functionalized polypyrrole film. ECL combines the advantage of the straightforward monitoring of the electrical addressing with the sensitivity of the luminescence.
Various markers could be used as ABEI (luminol derivative) or Ru(bpy)32+ (bpy=2,2'-bipyridine). In a first step, the results shown in this communication concern the usefulness of the ECL reaction of ABEI in solution generated onto the surface of the electrode coated by a polypyrole film. Our results demonstrated that the potential value to activate the ECL reaction must be in a potentiel range where the polypyrrole matrix is or remains conducting for the time required for the ECL reaction to take place. In a second step, the detection of hybridization DNA probes/DNA targets from ECL of ABEI anchored to DNA targets was studied from a biochip format. The results achieved show that it is possible to discriminate the ECL emission generated from the duplex to this one corresponding to the background signal. In the last part, the ECL of Ru(bpy)32+ was studied onto polymers as polypyrrole and polythiophene showing that this marker could be used for the DNA recognition in a bio-sensitive layer of conducting polymer film as an underlayer.