Split aptamers immobilized array microelectrodes for detection of chlorpyrifos pesticide using electrochemical impedance spectroscopy

Pesticide contamination in foods and its high persistence in environments are major serious issues globally. Chlorpyrifos (CPS), a broad-spectrum organophosphate insecticide, is commonly used as an active ingredient for pest control in agricultures and industries, and eventually it is found in high prevalence of contamination in food chains. Unfortunately, CPS exerts several adverse effects, especially as a neurotoxic agent, that cause severe health implications on humans and animals. To prevent the overexposure of pesticide residues in contaminated foods and environments, a label-free impedimetric aptamer-based biosensor for CPS determination was developed. The split aptamers for CPS were designed from its parent sequence to encounter nonspecific binding, and were immobilized onto the array microelectrodes consisting of four gold (Au) working microelectrodes, a platinum (Pt) counter microelectrode, and two Ag/AgCl reference microelectrodes. The aptasensor showed a good linear EIS response with CPS concentration ranging from 0.01 to 1 μg/mL with a detection limit (LOD) of 0.01 μg/mL. Moreover, the aptamer-immobilized Au multi-microelectrodes provided excellent selectivity to CPS over high level of other interferences, yet it also revealed good reproducibility. The sensitivity of CPS was successfully determined with acceptable recoveries in the range of 75–128% in spiked coriander, orange juice, and tap water. Therefore, the split aptamer-functionalized microchip could be a potential biosensor for monitoring CPS contamination in fruits, vegetables, and environments to improve human health and well-being.