Ultrasensitive electrochemical immunosensor for zeranol detection based on signal amplification strategy of nanoporous gold films and nano-montmorillonite as labels

Nano-montmorillonites belong to aluminosilicate clay minerals with innocuity, high specific surface area, ion exchange, and favorable adsorption property. Due to the excellent properties, montmorillonites can be used as labels for the electrochemical immunosensors. In this study, nano-montmorillonites were converted to sodium montmorillonites (Na-Mont) and further utilized for the immobilization of thionine (TH), horseradish peroxidase (HRP) and the secondary anti-zeranol antibody (Ab(2)). The modified particles, Na-Mont-TH-HRP-Ab(2) were used as labels for immunosensors to detect zeranol. This protocol was used to prepare the immunosensor with the primary antibody (Ab(1)) immobilized onto the nanoporous gold films (NPG) modified glassy carbon electrode (GCE) surface. Within zeranol concentration range (0.01-12 ng mL(-1)), a linear calibration plot (Y=0.4326 + 8.713 X, r=0.9996) was obtained with a detection limit of 3 pg mL(-1) under optimal conditions. The proposed immunosensor showed good reproducibility, selectivity, and stability. This new type of immunosensors with montmorillonites and NPG as labels may provide potential applications for the detection of zeranol. (C) 2012 Elsevier B.V. All rights reserved.