Implementation of electroconducting conjugated polymer, ECP, based sensitive layers to build up (bio)sensors, appears to offer a number of advantages over other technologies: (i) ease of construction, (ii) various routes of functionalisation of surfaces, (iii) chemoelectronic properties, i.e. ability to transduce a (bio)chemical recognition event into an electrical signal.
1. ECPs as a matrix for specific immobilisation of receptors
(i) The synthesis of films onto electrode surfaces by electropolymerization of monomers in solution is easily obtained. The thickness of the deposit is directly related to the amount of electricity passed during the electropolymerization reaction. This easy electrodeposition on an electrode surface opens the route to miniaturization since the deposit cover exactly the surface of the metallic dot; (ii) a versatile functionalization by biological moieties either by grafting or doping, that allows the assembly of a myriad of (bio)receptors at the surface of electrodes enabling one to perform selective recognition.
2. ECPs as sensitive components
The redox state (doping level), ionic transport and electronic transfer properties of ECP films are collective properties, which are sensitive to minor (bio)chemical interactions. These (bio)chemical perturbations result in transducible responses such as changes in electronic conductivity, UV-vis absorption spectrum, voltamperometric curve or photocurrent signal.
The potentialities of ECPs as passive supports or structural materials to provide a stable environment to the receptor have been exploited in the construction of various electrochemical biosensors such as enzymatic sensors and immunosensors. The electrochemical addressing is a key point for constructing sensor arrays and allows an easy miniaturisation since semiconductor microfabrication techniques can be easily used to create multielectrode devices. This will be illustrated by the presentation of our methodology for the preparation of addressed DNA matrices (DNAchips) . Electrospotting involving a moving electrochemical cell tip has been proven to be fruitful for the creation of an ECP pattern on a unique gold electrode and allows multiparametric imaging by Surface Plasmon Resonance technique .
Enzyme, single stranded DNA sequence or peptide  immobilisation's onto or into ECP films will illustrate one-step functionalisation or post-functionalisation. The need for versatile processes for the immobilisation of biological species onto surface led us to develop a more general grafting based on affinity interactions between a biotinylated polypyrrole substrate and the biological probe. A surface renewable DNA sensor  has been developed. Taking into account the availability of a wide variety of avidin or biotin conjugates, this new approach enables the study of biosensing behaviour of many commercial biomolecules.
The ECP matrix may act as a mediator for the electrical wiring of enzymes. Literature results and our recent data on electrochemiluminescence detection on polypyrrole will be presented
Interfacing ECP materials with biology appears to be a very promising area leading to miniaturised and multiparametric sensors based on a wide panel range of analyte-receptor interactions.
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