A label-free bioelectronic detection of aptamer-thrombin interaction based on electrochemical impedance spectroscopy (EIS) technique is reported. Multiwalled carbon nanotubes (MWCNTs) were used as modifiers of screen-printed carbon electrotransducers (SPCEs), showing improved characteristics compared to the bare SPCEs. 5'amino linked aptamer sequence was immobilized onto the modified SPCEs and then the binding of thrombin to aptamer sequence was monitored by EIS transduction of the resistance to charge transfer (Rct) in the presence of 5 mM [Fe(CN)(6)](3-/4-), obtaining a detection limit of 105 pM. This study represents an alternative electrochemical biosensor for the detection of proteins with interest for future applications. (C) 2010 Elsevier B.V. All rights reserved.