Real-time monitoring of fenitrothion in water samples using a silicon nanophotonic biosensor

Highlights: • An immunosensor for fenitrothion using monoclonal antibodies is described. • It relies on a label-free, silicon photonics interferometric biosensor. • A robust, accurate and sensitive method (LOD of 0.29 μg L-1) has been achieved. • Tap water can be directly analyzed after a 1:1 dilution, with no sample extraction. Due to the large quantities of pesticides extensively used and their impact on the environment and human health, a prompt and reliable sensing technique could constitute an excellent tool for in-situ monitoring. With this aim, we have applied a highly sensitive photonic biosensor based on a bimodal waveguide interferometer (BiMW) for the rapid, label-free, and specific quantification of fenitrothion (FN) directly in tap water samples. After an optimization protocol, the biosensor achieved a limit of detection (LOD) of 0.29 ng mL⁻¹ (1.05 nM) and a half-maximal inhibitory concentration (IC₅₀) of 1.71 ng mL⁻¹ (6.09 nM) using a competitive immunoassay and employing diluted tap water. Moreover, the biosensor was successfully employed to determine FN concentration in blind tap water samples obtaining excellent recovery percentages with a time-to-result of only 20 min without any sample pre-treatment. The features of the biosensor suggest its potential application for real time, fast and sensitive screening of FN in water samples as an analytical tool for the monitoring of the water quality.