Fabrication of flexible interdigitated μ-electrodes (FIDμEs) for the development of a conductimetric immunosensor for atrazine detection based on antibodies labelled with gold nanoparticles

The present paper describes a simple and low-cost method for the fabrication of mechanically flexible interdigitated μ-electrodes (FIDμEs) and its application as immunosensor. FIDμEs consist of two coplanar non-passivated interdigitated metallic μ-electrodes supported on a flexible transparent substrate, polyethylene naphthalate (PEN). Bioreagents deposition on PEN substrates becomes possible by depositing SiO₂ on the electrodes surface (fingers and inter-digits space). These FIDμEs were successfully applied for the development of a selective conductimetric immunosensor for the quantification of atrazine residues. The immunosensor has been demonstrated for detection of small amounts of atrazine, thanks to the use of immunoreagents specifically developed to detect this pesticide. The detection method applied is based on the use of antibodies labelled with gold nanoparticles. The presence of these particles amplifies the conductive signal; hence the immunosensor response was quantified using simple and inexpensive DC measurements. Immunochemical detection of the concentrations of atrazine is achieved by a competitive reaction which occurs before the inclusion of the labelled antibodies. The immunosensor shows limits of detection in the order of 2-3 μg L^-1, far below the maximum residue level (50 μg kg^-1) established by EU for residues of atrazine as herbicide in the wine grapes and other foodstuff products.