Fluorescent Aptasensor Based on a Truncated Aptamer and DNase I-Assisted Amplification for the Determination of Chlorpyrifos in Agricultural Products

A highly sensitive and specific fluorescent aptasensor was constructed for the rapid detection of chlorpyrifos (CPF) residues in agricultural products. Through molecular docking simulation, a truncated CPF aptamer with enhanced affinity was screened and validated. The truncation strategy removed redundant sequences and improved folding efficiency, while essentially preserving the key functional regions responsible for target binding. On this basis, a fluorescent aptasensor integrated with deoxyribonuclease I (DNase I)-assisted signal amplification was constructed by combining the efficient fluorescence quenching effect of graphene oxide (GO) on fluorescently labeled aptamers and the high-specificity binding effect between the truncated aptamer and CPF. The constructed fluorescent aptasensor exhibited good linearity for CPF concentration detection within the range of 2.5–120 ng/mL, with a correlation determination (R2) of 0.996, and the limit of detection (LOD), which denotes the minimum target concentration distinguishable from blank background, was calculated to be 2.21 ng/mL. In practical application, the aptasensor was employed to determine CPF in spiked samples of celery, lettuce, cucumber, apple, and tomato, with an average recovery rate of 93.6%–105.4% and a relative standard deviation (RSD) ranging from 1.2% to 5.1%. The above results confirmed that the developed aptasensor enables the efficient and selective detection of CPF residues in complex matrices of agricultural products.