Development of a graphene oxide-SELEX derived aptamer and a lateral flow biosensor for on-site visual detection of...

Isofenphos-methyl (IFP) is a highly toxic organophosphorus pesticide that poses a significant risk to food safety due to its persistence and widespread use. High-affinity aptamers for IFP were selected via graphene oxide-SELEX, representing the novel report of aptamers specific to this pesticide. This yielded a 78-nt sequence (K_d=21.70±2.53 nM). A novel aptamer lateral flow strip biosensor was developed for rapid IFP detection. Polyethyleneimine was employed as a test line material to induce salt-dependent aggregation of unbound gold nanoparticles upon target-induced aptamer dissociation. The biosensor achieved broad detection range (20-300 nM) and low limit of detection (12.61 nM). Real-sample analysis of spiked vegetables demonstrated satisfactory recovery rates (90.67%-104.63%) and acceptable precision (RSD<5.29%). This study established a cost-effective and easy-to-operate test strip for rapid IFP detection. Successful detection in spiked vegetable samples with good recovery rates demonstrates its practical feasibility. Features such as visual semi-quantitative analysis and compliance with regulatory thresholds make it valuable for application in the field of agricultural safety monitoring.