Development of ultra-sensitive and label-free ellipsometric aptasensor for fipronil residues

Fipronil is a widely used insecticide that has an environmental and human health hazard. There are standard detection methods available for fipronil and its metabolites such as GC-MS. However, these methods are time-consuming and labor-intensive. In this study, we aimed to develop a label-free aptasensor approach for the detection of fipronil in food applications. For this purpose, ellipsometric-based aptasensors were developed for the detection of fipronil. Ellipsometric sensors are particularly advantageous in the analysis of thin and uniform films. Spectrophotometric ellipsometry used in this field is preferred because Δ (phase shift) is very sensitive to molecular accumulation at the substrate surface. Keywords: Aptamer, Aptasensor, Ellipsometry, Fipronil, Insecticide The limit of detection (LOD) in the buffer solution for the two aptamers of 80 and 73 bases (Anti-FIP1 and Anti-FIP2) used in the study was promising. Furthermore, the specificity of the aptamers against bovine serum albumin and ethiprole in the SE sensor was at the limit of reproducibility, since the research group that made the selection of aptamers used a wide-ranging cocktail in negative selection. The LOD for Anti-FIP1 is 0.034 nM (33.7 pM) and for Anti-FIP2 the LOD is 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. Spike method for the detection of fipronil by adding egg and grain samples resulted in a deviation of less than ± 10% for recovery. Here, a reliable aptasensor platform has been reported in real-sample testing of fipronil with aptamer-based SE.