A label-free electrochemical impedance immunosensor based on AuNPs/PAMAM-MWCNT-Chi nanocomposite modified glassy carbon electrode for detection of Salmonella typhimurium in milk

A sensitive and stable label-free electrochemical impedance immunosensor for the detection of Salmonella typhimurium was developed by immobilising anti-Salmonella antibodies onto the gold nanoparticles and poly(amidoamine)-multiwalled carbon nanotubes-chitosan nanocomposite film modified glassy carbon electrode (AuNPs/PAMAM-MWCNT-Chi/GCE). Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were used to verify the stepwise assembly of the immunosensor. Co-addition of MWCNT, PAMAM and AuNPs greatly enhanced the sensitivity of the immunosensor. The immobilisation of antibodies and the binding of Salmonella cells to the modified electrode increased the electrontransfer resistance (R), which was directly measured with EIS using [Fe(CN)(6)](3-14)- as a redox probe. A linear relationship of Re, and Salmonella concentration was obtained in the Salmonella concentration range of 1.0 x 10(3) to 1.0 x 10(7) CFU mL(-1) with a detection limit of 5.0 x 10(2) CFU mL(-1). Additionally, the proposed method was successfully applied to determine S. typhimurium content in milk samples with satisfactory results. (C) 2013 Elsevier Ltd. All rights reserved.