Isolation and characterization of the quinclorac-specific aptamer toward a colorimetric sensor for the visual detection of quinclorac in water and soil

Quinclorac is an herbicide widely used in rice production, and its residue in water and soil poses significant threats to aquatic organisms and subsequent crops. We herein isolated a group of aptamers with high binding affinity to quinclorac using library-immobilized SELEX. Notably, one of these aptamers (Apt.Q1) demonstrated excellent specificity and affinity to quinclorac, with dissociation constant (Kd) of 8.7 ± 2.4 µM and no interference from structurally similar pesticides. Molecular dynamics simulations identified the G-rich loop in Apt.Q1 as the potential binding domain, and circular dichroism analysis revealed the conformational transition from hairpin to G-triplex structure upon quinclorac interaction. Moreover, a one-step, label-free colorimetric biosensor was developed based on quinclorac-mediated displacement of Cy7 dye and Apt.Q1 for detecting quinclorac within 1 min with a detection limit of 237 nM and RSD<5%. Assessment of quinclorac residues in soil and river water using the biosensor demonstrated recoveries of 89–92%. The study not only provided a promising bio-receptor for developing various quinclorac biosensors but also provided a cost-effective tool for rapidly screening quinclorac in environment. Specifically, the investigation of the recognition mechanism between Apt.Q1 and quinclorac lays a theoretical foundation for designing more sensitive and reliable sensing platforms for quinclorac detection.