Electropolymerisable pyrrole-oligonucleotide: synthesis and analysis of ODN hybridisation by fluorescence and QCM

Conducting polymer films, such as polypyrrole, appear particularly attractive for the immobilisation of biological molecules by entrapment or covalent grafting. We describe here a new pyrrole phosphorarnidite building block allowing the synthesis of oligonucleotide (ODN) bearing a pyrrole moiety. The electropolymerisable pyrrole moiety was then introduced on the 5' end of the oligonucleotide. The electrosynthesis of a copolymer, from solutions containing pyrrole and pyrrole-ODN, gives in one step strongly adhesive films containing ODN probes at electrode surfaces. In this contribution, we have used such a methodology to verify its feasibility for the modification of quartz crystal microbalance (QCM) electrodes. The obtained biosensors enable the detection of DNA hybridisation in real time by micro-gravimetric transduction. Finally, as DNA targets were previously modified by biotin, we have used the affinity between biotin and avidin to validate the effectiveness of QCM transduction by fluorescence microscopy and to amplify the recorded micro-gravimetric signal.