Abstract: A novel colorimetric aptamer sensor (aptasensor) was developed for rapid identification of fluoronitrile in egg samples. The assay was based on highly selective aptamer binding to its targets combined with the dual-amplification effect of the EnVision? polymerase chelate (EV) labeled with gold nanoparticles (AuNPs). This method could specifically and sensitively detect ultra-trace amounts of fluoronitrile in egg. EV contained approximately 100 urease molecules which could effectively catalyze decomposition of urea to enrich copper ions to produce basic copper carbonate. Color change of the chromogenic agent of acid copper ion could be generated by basic copper carbonate. In addition, gold nanoparticles could catalyze the deposition of basic copper carbonate to a certain extent. Thus, a dual-amplification effect could be achieved by using the proposed method. The amount of fluoronitrile in samples could be calculated by measuring the change in the absorbance of chromogenic agent-copper ion complex. The results indicated that under optimal conditions, the limit of detection was identified as 0.072 μg/kg and good linearity was observed within the concentration range of 0.1 μg/kg–50 mg/kg with a correlation coefficient of 0.998. This assay was successfully used to analyze fluoronitrile concentrations in egg samples with results consistent with those obtained by a conventional ELISA method.

Key words: colorimetric aptasensor; gold nanoparticles; fluoronitrile