| A method for the detection of biological toxins in foods has to be sensitive, rapid, and field-applicable since toxin detection is on the front line of food safety and food protection against bioterrorism. In this thesis a sensitive, rapid, and label-free electrochemical impedance spectroscopy (EIS) immunosensor was developed and its performance in real foods was demonstrated.;To improve the sensitive of EIS immunosensor, nanoporous aluminum was applied as the substrate of EIS immunosensor. Well ordered nanoporous aluminum having ∼30nm in pore diameter was obtained by anodizing food grade aluminum in 0.3M oxalic acid at 40V. EIS immunosensor for the detection of staphylococcal enterotoxin B (SEB) or ricin was developed by immobilizing anti-SEB or ricin on nanoporous aluminum using 3-aminopropyltriethoxysilane (APTES). Particularly efficient immobilization of antibody (Ab) was attained by silanization of aluminum in 2% APTES for 4hrs.;A time-resolved EIS of immunosensor was performed to investigate the effect of immunoreaction on impedimetric signal outputs. Immunoreaction between immobilized Ab and its target toxin resulted in gradual changes in the spectra of impedimetric signal outputs. The change by immunoreaction was significant especially in real part of impedance (Z') at the frequency region from 10kHz to 100kHz. The specific changes of Z' to immunoreaction also could be observed at pH 3.0 and pH 5.0. Using developed EIS immunosensor, it was possible to detect the presence of 10pg/ml of SEB in 15min without amplification of signal output such as labeling step. Moreover EIS immunosensor was applicable to real foods even to acidic foods. |
