Ultrasensitive label-free immunoassay for diethylstilbestrol based on Au nanoparticles on mesoporous silica and amino-functionalized graphene

Abstract

A novel label-free electrochemical immunosensor was developed for sensitive and selective determination of diethylstilbestrol (DES). An amino-functionalized graphene sheet dispersed with chitosan (NH₂-GS-Chit) and Au nanoparticles onto mesoporous silica (Au@SBA-15) was used to modify screen-printed electrodes (SPEs). NH₂-GS-Chit with prominent conductivity as well as a large number of –NH₂ binding groups was explored to amplify electrochemical signals. Au nanoparticles (AuNPs) acting as an electroactive material could efficiently enhance the interfacial electron transfer. While the amino-functionalized mesoporous silica (NH₂-SBA-15) offered more binding sites for loading the DES antibody (Ab) and AuNPs due to the large surface area of the mesoporous structure, the synergistic effect of AuNPs and NH₂-SBA-15 enhances the electrochemical signal for highly sensitive assay of the target. Under optimal conditions, the electrochemical immunoassay exhibited a wide linear range of 0.01–20 ng mL⁻¹ with a low detection limit of 3.4 pg mL⁻¹ for DES. The performance of the fabricated immunosensor was evaluated with fresh milk spiked with DES. The satisfactory results indicate that this convenient and sensitive technique offers great promise for the detection of DES in animal derived foods.