3.2. Label-free impedance immunosensor using gold nanoparticles for characterization of Brucella melitensis
The impedance method is one more quick and cheap substition for those methods using label-free biosensors (Wu et al., 2013). Most of these sensors are label-dependent that require labeling of bio-molecules to convert the antibody/antigen interaction into detectable electrochemical signals. In contrast, label-free impedance immunosensors show outstanding advantages such as speed, cheapness and ease of operation (Varshney, Li, Srinivasan, & Tung, 2007).
Wu et al. designed a label-free impedance immunosensor based on the gold nanoparticles with modified screen-printed carbon electrodes (GNP-SPCEs) for rapid detection of Brucella melitensis. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were utilized to characterize interaction of the Brucella melitensis antigens on the surface of GNP-SPCEs against antibody molecules. This designed biosensor was able to detect 1 × 104 and 4 × 105 CFU/mL of Brucella melitensis in pure culture and milk samples in less than 1.5 h, respectively (Wu et al., 2013).