A new methodology for the preparation of addressed DNA matrices is described. The process includes an electrochemically directed copolymerization of pyrrole and oligonucleotides bearing on their 5' end a pyrrole moiety introduced by phosphoramidite chemistry. The electro-controlled synthesis of the copolymer (poly-pyrrole) gives, in one step, a solid conducting film deposited on the surface of an electrode. The resulting polymer consists of pyrrole chains bearing covalently linked oligonucleotide. The polymer growth is limited to the electrode surface, so that it is possible to prepare a DNA matrix on a multiple electrode device by successive copolymerizations. A support bearing four oligonucleotides was used to detect three ras mutations on a synthetic DNA fragment.

We describe in this paper a methodology to quantify multispot parallel DNA hybridizations and denaturations on gold surfaces by using, on one hand, a polypyrrole-based surface functionalization based on an electrospotting process and, on the other hand, surface plasmon resonance imaging allowing real-time measurements on several DNA spots at a time. Two characterization steps were performed in order to optimize the immobilization of oligonucleotide probes and, thus, to increase the signal-to-noise ratio of monitored hybridization signals: the first step consisted of characterizing the signal dependence upon the density of immobilized 15-mer probes, and, the second step, in analyzing the hybridization response versus spot thickness. We further demonstrated that a surface density of polypyrrole/DNA probes of approximately 130 fmol/ mm2 (590 pg/mm2) optimizes the hybridization signal that can be detected directly. Optimal thickness of the spot was found to be close to 11 nm. Specificity and regeneration steps on each spot have also been demonstrated successfully, showing this method to be very competitive and convenient in use.