(624e) Impedimetric Immunosensor for Ricin Detection in Low pH Foods

Low pH foods have not been able to be applied since the antibody loses its stability in low pH condition. The purpose of this study is to develop an impedimetric immunosensor, based on electrochemical impedance spectroscopy (EIS) technique to measure ricin toxin in low pH condition. We developed a ricin immunosensor, based on EIS. To improve the sensitivity, the immunosensor's substrate was fabricated into nano-structure. The applicability of the immunosensor was evaluated by comparing the impedimetric responses of Ab/Ag reaction on the immunosensor's surface in different pH (pH 3.0, 5.0, 7.0). The presence of 1 µg/ml of ricin at pH 7.0 was distinguished by EIS analysis of ricin immunosensor at specific sinusoidal frequency (10 kHz). Although abnormal changes of impedance were observed at pH 3.0 and 5.0, Ab/Ag specific increase of impedance at 10 kHz could be seen in 10 minutes even in low pH. It is seemed that the denaturation of antibody at low pH cannot be avoided even if antibody is associated on solid surface. However, the rate of Ab/Ag reaction on immunosensor's surface may be faster than the rate of denaturation in low pH so immunoreaction on immunosensor's surface can give immunoreaction specific change in impedance. It is expected that an immunosensor, based on EIS for low pH foods can be developed by the further studies of time functional characteristics of antibody denaturation and Ab/Ag reaction.