This paper describes the investigation of two aspects which play a fundamental role in the development of an enzyme-linked electrochemical genosensor: the labelling step and the electrode surface. Biotinylated locked nucleic acid (LNA) signalling probes were investigated in order to design a sandwich hybridisation format able to detect PCR amplified samples with high specificity. After labelling the biotinylated hybrid with a streptavidin-enzyme conjugate, the electrochemical detection of the enzymatic product was performed onto the surface of disposable carbon nanotube-modified electrode. In this way, the sensor coupled the high stability and specificity of LNA with the unique electrical properties of carbon nanotubes (high surface area, fast heterogeneous electron transfer, chemical stability, and ease of miniaturisation). After characterisation, the sensor was applied to the detection of PCR amplicons related to a region of the CB2 cannabinoid receptor gene (CNR2), which is relevant for the study of a mutation suspected to account for altered receptor activity. To our knowledge, this is the first example of recognition of this particular gene in real samples, using a LNA-based electrochemical genosensor. A linear response was obtained over a wide concentration range (0-100 nmol/L) and a detection limit of 0.4 nmol/L was achieved (RDS = 9%). (C) 2011 Elsevier B.V. All rights reserved.