Sensors and Actuators B 138 (2009) 214–220 Contents lists available at ScienceDirect Sensors and Actuators B: Chemical journal homepage: www.elsevier.com/locate/snb Impedimetric aflatoxin M 1 immunosensor based on colloidal gold and silver electrodeposition Attila Vig a,b , Antonio Radoi b,∗ , Xavier Mu ˜ noz-Berbel b , Gyongyi Gyemant c , Jean-Louis Marty b a Department of Biochemistry, College of Károly Eszterházy, Leányka u. 6, 3300 Eger, Hungary b IMAGES EA 4218, University of Perpignan, 52 Av. Paul Alduy, 66860 Perpignan, France c Department of Biochemistry, University of Debrecen, Egyetem tér, 4032 Debrecen, Hungary article info Article history: Received 2 November 2008 Received in revised form 9 December 2008 Accepted 12 December 2008 Available online 25 December 2008 Keywords: Immunosensor AFM1 Impedance Silver electrodeposition abstract An impedimetric immunosensor based on colloidal gold and silver electrodeposition for the detection of aflatoxin M 1 (AFM 1 ) herein is reported. An indirect like competitive ELISA procedure was performed on screen-printed electrodes (SPEs) in presence of anti-AFM 1 gold-labelled antibodies. Silver was chronoam- perometrically electrodeposited at a fixed applied potential and for a determined period of time to amplify the signal. The calculated charge transfer resistance (R ct ) was found to correlate well with the concen- tration of AFM 1 . The linear working range of the described AFM 1 immunosensor ranged between 15 and 1000 ng/L with a limit of detection (LoD) equal to 15 ng/L (R.S.D. = 20%). Impedimetric results were confronted with linear sweep voltametry (LSV) and corresponded well to this technique. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Mycotoxins (AFM 1 , AFB 1 , AFG, OTA, etc.) usually can be found in agricultural commodities [1] and animal foodstuff [2,3]. Aflatoxin M 1 (AFM 1 ) is the hydroxylated metabolite of aflatoxin B 1 (AFB 1 ) and may be found in milk or dairy products obtained from live- stock that have ingested Aspergillus flavus or Aspergillus parasiticus contaminated animal foodstuff [4]. Aflatoxins are potent liver carcinogens and DNA-damaging agents. In 1987, the World Health Organization (WHO) classified these toxins as Group 1 carcinogens and they are still subject of recent regulations [5], the European Community legislation limit- ing the concentration of aflatoxin M 1 , in milk and dried or processed milk products intended for adults, at 0.050 ppb (g/kg) [6] and at 0.025 ppb (g/kg) for milk intended for infants or for baby-food pro- duction [7]. Analysis of aflatoxins is generally performed by using thin layer chromatography (TLC) [8], liquid chromatography (LC) [8], high-performance liquid chromatography (HPLC) [9] and con- ventional immunoassays such as enzyme linked immunosorbent assay (ELISA) [10]. However, these methods have several limi- tations in terms of sensitivity and detection limit [11], so that novel and improved methods are currently under development, mainly based on immunoassay techniques [12,13]. Recently the new requirements for food quality and safety regulations induced ∗ Corresponding author. Tel.: +33 4 68 66 22 57. E-mail address: radoiantonio@yahoo.com (A. Radoi). to new type, reliable analysis methods for analytical investigation. Since electrochemical impedance spectroscopy (EIS) analyses the changes of conductive and semi-conductive surfaces, and it is a non-destructive steady-state technique, it can be used to detect the dynamics of bio-molecular interactions [14]. The electrical prop- erties of the electrode–solution interface are modified when an antibody reacts with the antigen of interest, thus among other immunosensor techniques like surface plasmon resonance (SPR) [15] and quartz crystal microbalance (QCM) [16], EIS is suitable to monitor adsorption and charge transfer processes [17–19]. Self- assembled monolayers with gold nanoparticles were already used to improve the sensitivity of an impedimetric sensor [20]. The detection of aflatoxin B 1 has been reported by monitoring the charge transfer resistance changes (R ct ) by EIS on the surface of an electropolimerized conductive polymer [21]. In another reported research paper nanogold hollow balls modified with anti-AFB 1 anti- bodies were used in detection of AFB 1 by QCM technique [22]. Through a precipitation reaction, good sensitivity was reached with alkaline phosphatase-labelled immunosensor based on SPR using mouse-IgG [23]. In another reported paper, a conjugate consisting of aflatoxin B 1 -bovine serum albumin (AFB 1 -BSA) was immobilized on dextran gel and competition reaction was monitored by SPR technique [24]. The purpose of the present study was the development of a new procedure for the detection of aflatoxin M 1 in milk. The proposed impedimetric immunosensor is based on screen-printed electrode technology [25,26]. The aflatoxin M 1 -BSA conjugate was adsorbed on the surface of a graphite screen-printed working electrode, and 0925-4005/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.snb.2008.12.033