Imidacloprid quantification directly in human urine with aptamer-functionalized nanopipettes

The widespread use of the neonicotinoid pesticide imidacloprid presents an emerging human health risk, necessitating rapid, high-sensitivity tools for exposure monitoring. Herein, we report a novel aptamer-functionalized nanopipette sensor for the selective quantification of imidacloprid with a limit of detection (LOD) as low as 3 pM. We demonstrate that the sensor's performance is profoundly enhanced through a simple yet highly effective "dip-modification" strategy. By exploiting capillary forces to localize aptamer immobilization exclusively at the nanopipette tip, we achieve superior sensitivity compared to conventional, uniform backfilling approaches. We also show that tuning the probe loading density allows for control over the sensor's LOD and working range. Finally, we validate the sensor's practical utility by directly quantifying imidacloprid contamination in urine samples from pet owners in the Republic of Ireland who were exposed to imidacloprid through their pet’s flea treatments, achieving detection without any sample preparation. By achieving robust detection in a complex biological matrix without any sample pre-treatment, this work establishes a powerful new methodology for rapid pesticide monitoring.