Development of ultra-sensitive and label-free ellipsometric aptasensor for the detection of residual fipronil

Abstract

Fipronil, an insecticide widely employed, poses risks to both the environment and human health. Existing detection methods for fipronil and its metabolites, such as GC-MS, are known; however, these methods are laborious and time-intensive. In this investigation, our aim was to devise a label-free aptasensor strategy for detecting fipronil in food-related scenarios. To achieve this objective, we developed ellipsometric-based aptasensors specifically tailored for fipronil detection. The advantage of ellipsometric sensors lies in their efficacy in analyzing thin and uniform films. Spectrophotometric ellipsometry (SE), utilized in this realm, is preferred due to its sensitivity to molecular accumulation at the substrate surface, as evidenced by the phase shift (Delta). The limit of detection (LOD) observed in the buffer solution for the two aptamers, Anti-FIP1 and Anti-FIP2, used in this study, with lengths of 80 and 73 bases respectively, showed promising results. Additionally, the specificity of these aptamers against bovine serum albumin and ethiprole in the SE sensor approached the reproducibility limit. This is attributed to the wide-ranging cocktail employed during the aptamer selection process. The LOD for Anti-FIP1 was 0.034 nM (33.7 pM), while for Anti-FIP2 it was 0.025 nM (24.9 pM). The limit of quantification (LOQ) was calculated as 0.1 nM (0.044 ng/mL) for Anti-FIP1 and 0.075 nM (0.033 ng/mL) for Anti-FIP2. Utilizing the spike method for fipronil detection by introducing egg and grain samples, the deviation observed was less than +/- 10 % for recovery. This study presents a dependable aptasensor platform for the testing of fipronil in food samples, employing aptamer-based SE.