A label-free electrochemical impedance immunosensor based on AuNPs/PAMAM-MWCNT-Chi nanocomposite modified glassy carbon electrode for detection of Salmonella typhimurium in milk
2013
Dong, Jing | Zhao, Han | Xu, Minrong | Ma, Qiang | Ai, Shiyun
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 electron-transfer resistance (Ret), which was directly measured with EIS using [Fe(CN)6]3−/4− as a redox probe. A linear relationship of Ret and Salmonella concentration was obtained in the Salmonella concentration range of 1.0×103 to 1.0×107CFUmL−1 with a detection limit of 5.0×102CFUmL−1. Additionally, the proposed method was successfully applied to determine S. typhimurium content in milk samples with satisfactory results.
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