Fenitrothion is an insecticide belonging to the organophosphate family of pesticides that is widely used around the world in agriculture and living environments. Today, it is one of the most hazardous chemicals that causes severe environmental pollution. However, detection of fenitrothion residues in the environment is considered a significant challenge due to the small molecule nature of the insecticide and lack of molecular recognition elements that can detect it with high specificity. We performed in vitro selection experiments using the SELEX process to isolate the DNA aptamers that can bind to fenitrothion. We found that newly discovered DNA aptamers have a strong ability to distinguish fenitrothion from other organophosphate insecticides (non-specific targets). Furthermore, we identified a fenitrothion-specific aptamer; FenA2, that can interact with Thioflavin T (ThT) to produce a label-free detection mode with a Kd of 33.57 nM (9.30 ppb) and LOD of 14 nM (3.88 ppb). Additionally, the FenA2 aptamer exhibited very low cross-reactivity with non-specific targets. This is the first report showing an aptamer sensor with a G4-quadruplex-like structure to detect fenitrothion. Moreover, these aptamers have the potential to be further developed into analytical tools for real-time detection of fenitrothion from a wide range of samples.
Keywords: SELEX; aptamer; fenitrothion; fluorescence; insecticide; thioflavin T.