A Disposable Aptasensor for Sensitive Detection of Okadaic Acid in Shellfish

Based on the specific combination between aptamer and its target analyte, a disposable aptasensor was built for the sensitive detection of okadaic acid ( OA ) ( a main constituent of diarrhetic shellfish poisoning) in shellfish. The aptamer was employed as the probe and screen-printed gold electrodes ( SPGE ) as the support. Electrochemical impedance spectroscopy ( EIS) was performed to test the change of electron transfer resistances ( R-ct) of SPGE before and after binding with OA and OA in shellfish samples could be thus quantified. In order to improve the sensitivity of the method, Fe3O4@Au was introduced into the fabrication of SPGE since it could enhance the gold working electrode's surface areas. Compared with antibody, the use of aptamer was cheaper, and SPGE avoided the polish step which was needed of traditional electrodes. The change of Ret was linearly correlated with the natural logarithm of concentration of OA from 1 mu g/kg to 800 mu g/kg. The limit of detection was 1 mu g/kg. Recoveries in diarrhetic shellfish at different spiked levels were in the range of 92.0% -118. 6%, and relative standard deviations ( RSDs) were less than 12%. The proposed disposable aptasensor was efficient and sensitive with good repeatability, and was suitable for screening and quantification of shellfish samples.