In this paper an attempt was made to detect Staphylococcal enterotoxin B (SEB) both by electrochemical and fluorescence immunoassay methods using zinc sulphide (ZnS) QDs. Wet-chemical method was adopted for the preparation of fluorescent ZnS QDs (diameter ∼ 5-10 nm). These QDs were bioconjugated with monoclonal antibodies and then characterized by various method. A detection limit of 0.02 ng mL-1 by fluorescence assay and 1.0 ng mL-1 by electrochemical assay for SEB was achieved. While by sandwich ELISA it is possible to detect 0.24 ng mL-1 only. The sensitivity of all techniques is very good, since the LD50 of SEB is 20 ng kg-1. Electrochemical assay is faster, need low-cost instrument, independent to the size of QDs and found to be one of the best alternative methods as compared to the other existing methods studied herein. The presented method could be expanded to the development of electrochemical and fluorescence biosensors for various agents for field and laboratory use.
Keywords: ELISA; Electrochemical immunosensor; QDs-FLISA; Quantum dots; Square-wave voltammetry; Staphylococcal enterotoxin B.