RESEARCH PAPER Mediated bioelectrochemical system for biosensing the cell viability of Staphylococcus aureus Rabeay Y. A. Hassan 1,2 & Ulla Wollenberger 1 Received: 31 July 2015 /Revised: 13 September 2015 /Accepted: 19 October 2015 # Springer-Verlag Berlin Heidelberg 2015 Abstract Staphylococcus aureus is one of the most danger- ous human pathogens and is the cause of numerous illnesses ranging from moderate skin infections to life-threatening diseases. Despite advances made in identifying micro- organisms, rapid detection methods for the viability of bacteria are still missing. Here, we report a rapid electro- chemical assay for cell viability combining the use of double redox mediators and multiwall carbon nanotubes-screen printed electrodes (MWCNTs-SPE), ferricyanide (FCN) and 2,6-dichlorophenolindophenol (DCIP), which served as elec- tron shuttle to enable the bacterial-electrode communications. The current originating from the metabolically active cells was recorded for probing the activity of the intracellular redox centers. Blocking of the respiratory chain pathways with elec- tron transfer inhibitors demonstrated the involvement of the electron transport chain in the reaction. A good correlation between the number of the metabolically active cells and the current was obtained. The proposed assay has been exploited for monitoring cell proliferation of S. aureus during the growth. The sensitivity of the detection method reached 0.1 OD 600 . Therefore, the technique described is promising for estimating the cell number, measuring the cell viability, and probing intracellular redox center(s). Keywords Microbial electrochemistry . Pathogenic detection . Probing living Staphylococcus aureus . CNTs-based screen printed electrodes Introduction Invasive infections caused by Staphylococcus aureus, the ma- jor human pathogen that infects every organ and tissue in the human body, have become extremely difficult to be treated [1, 2]. An early and rapid diagnosis that identifies pathogenic organisms and their susceptibilities to antibiotics will reduce the risk of severe complications and death. Thus, there is a need to develop new diagnostic methods [3, 4]. Detection systems for microorganisms have to be optimized with respect to simplicity, specificity, and sensitivity. The available diagnostic tools mainly relied on complicated microbiologic assays, such as cell counting, selective growth, and microscopic examination [5–7]. The problem is that the procedure of such tests is time-consuming and the results are difficult to interpret. Modern molecular diagnostic techniques such as PCR-based tests [ 8] and ELISA assays [9] are used with high sensitivity and specificity for identification of microbes but are unable to differentiate between viable cells and dead cells. This may lead to the infection risk being overestimated [3, 10]. Redox compounds such as tetrazolium salts [11, 12], resazurin (Alamar blue) [13], and various quinoid compounds [14] were used in colorimetric assays to assess viability and/or cell proliferation. Nevertheless, these assays are not suitable for fast routine analysis use due to the long incubation time of the redox mediators in the microbial culture and their interfer- ence with the optical density measurement. Measuring the Electronic supplementary material The online version of this article (doi:10.1007/s00216-015-9134-z) contains supplementary material, which is available to authorized users. * Rabeay Y. A. Hassan rabeayy@yahoo.com 1 Institute of Biochemistry and Biology, University of Potsdam, Karl-Liebknechtstrasse 24-25, 14476 Potsdam-Golm, Germany 2 Microanalysis Lab, Applied Organic Chemistry Department, National Research Centre (NRC), El Bohouth St., Dokki, 12622 Giza, Egypt Anal Bioanal Chem DOI 10.1007/s00216-015-9134-z