Fabrication of a label-free electrochemical immunosensor by functionalized nanofiber membrane for the ultrasensitive detection of quinalphos

The accumulation of quinalphos pesticide in agricultural products have detrimental effects to human body and environment, hence, an efficient and sensitive detection approach is desirable. In this study, a label-free electrochemical immunosensor based on the directly immobilizing nanobody onto functionalized polyvinyl alcohol/gelatin-gold nanoparticles nanofiber membrane (PVA/G-AuNPs NFM) was fabricated. First, a homogeneous PVA/G-AuNPs NFM with multiple-porosity structure and appropriate hydrophilicity was prepared. Then, the electrochemical immunosensor was assembled and under the optimized conditions, the prepared biosensor exhibited good detection performance towards quinalphos with the linear range and limit of detection being 0.06–1000 ng/mL and 50.74 pg/mL (S/N = 3), respectively. Moreover, the sensor presented good specificity, regenerability and stability, maintaining more than 90% activity after 5 times of regeneration and about 90% activity after 6 weeks of storage. Finally, the average recoveries of quinalphos from food samples were 89.68%–110.88% with the coefficient of variation being 1.65%–7.81%, showing good correlation with UPLC-MS/MS (R 2  = 0.9859), indicating the accuracy of the proposed electrochemical immunosensor assay. Overall, the label-free electrochemical immunosensor presents a novel approach for the rapid and sensitive detection of quinalphos and other pesticide residues.