REVIEW Analysis of the evolution of the detection limits of electrochemical DNA biosensors Mathieu Lazerges & Fethi Bedioui Received: 7 September 2012 / Revised: 4 December 2012 / Accepted: 18 December 2012 / Published online: 22 January 2013 # Springer-Verlag Berlin Heidelberg 2013 Abstract In this paper we critically review detection limits of electrochemical DNA biosensors enabling DNA detec- tion without target labelling. The review includes transduc- tion principles and latest breakthroughs. To compare the efficiency of each type of electrochemical DNA biosensor, a simple DNA biosensors classification is established on the basis of the nature of the bio-electrochemical transduction. Keywords Biosensor . DNA . Electrochemical . Label-free Introduction DNA biosensing is a major challenge in gene diagnosis. Electrochemical DNA biosensors designed during the last three decades have two major advantages over fluorimetric analysis—they are label-free and the transduction is more direct than for other techniques, because the biochemical process is transduced in an electrical response. The most severe limitation of electrochemical DNA biosensors is the detection limit, which is far below that of fluorimetric assays. Nevertheless, recent work focusing on enhancing the detection limit of electrochemical biosensors has reported analysis of DNA at femtomolar and attomolar levels. This review focuses on the evolution of label-free electrochemical biosensors comprising DNA or PNA (pep- tide nucleic acid) probes grafted on to a solid substrate and direct hybridization with an unlabelled DNA target, with electrochemical transduction during hybridization matched with, or without, a redox indicator. Biosensors using redox enzymes are not reported herein, because proteins are less resilient than chemical redox probes. The classification of biosensors presented herein is based on the nature of the bio-electrochemical transduction. Only biosensors involved in detection limit breakthroughs, with the two lowest detec- tion limits obtained, are reported in the main text of the manuscript. The detection limits are estimated as the stan- dard deviation, σ, of the blank: for most of the articles reviewed herein, the detection limit is reached when the signal is equal to 3σ. A full listing of biosensor detection limits is given in the electronic supplementary material. Biosensors based on direct DNA oxidation Direct electrochemical oxidation of guanine can be used to prepare DNA biosensors [1–10], because the faradic charge required for guanine oxidation is higher after hybridization. These biosensors are classically prepared by electrochemi- cal adsorption of the DNA probe (i.e. stripping) on to electrode surface. Such biosensors can be prepared with Published in the topical collection Bioelectroanalysis with guest editors Nicolas Plumeré, Magdalena Gebala, and Wolfgang Schuhmann. Electronic supplementary material The online version of this article (doi:10.1007/s00216-012-6672-5) contains supplementary material, which is available to authorized users. M. Lazerges (*) : F. Bedioui (*) Unité de Pharmacologie Chimique et Génétique et Imagerie, Chimie ParisTech, Ecole Nationale Supérieure de Chimie de Paris, Paris, France e-mail: mathieu.lazerges@parisdescartes.fr e-mail: fethi-bedioui@chimie-paristech.fr M. Lazerges : F. Bedioui Unité de Pharmacologie Chimique et Génétique et Imagerie UMR 8151, CNRS, Paris, France M. Lazerges : F. Bedioui Unité de Pharmacologie Chimique et Génétique et Imagerie, Université Paris Descartes, Paris, France M. Lazerges : F. Bedioui Unité de Pharmacologie Chimique et Génétique et Imagerie (N° 1022), INSERM, Paris, France Anal Bioanal Chem (2013) 405:3705–3714 DOI 10.1007/s00216-012-6672-5