Development of a chimeric aptamer and an AuNPs aptasensor for highly sensitive and specific identification of Aflatoxin B1

Abstract In this study, a bivalent anti-Aflatoxin B1 (AFB1) chimeric aptamer (B72) was firstly engineered by a rational truncation and splicing-based post-selection strategy. Compared with that of the originally-selected anti-AFB1 aptamer (B50), a 188-fold enhanced affinity of B72 was revealed by microscale thermophoresis (MST) assay. In addition, isothermal titration calorimetry (ITC) research and molecular docking simulation affirmed consistently that B72 possessed dual binding sites for AFB1. A gold nanoparticles (AuNPs) aptasensor was developed to further validate the real-world applicability of the chimeric aptamer by colorimetric assay of AFB1 based on the peroxidase-like activity of AuNPs to catalyze 3,3,5,5-tetramethylbenzidine (TMB) with the assistance of H2O2. The aptasensor could identify AFB1 in corn oil with a limit of detection (LOD) of 1.96 nM and a linear range of 5 to 5120 nM, respectively. Moreover, good recovery rates from 91.5 to 117.7% and low relative standard deviations below 9% were obtained, suggesting the good accuracy of the developed aptasensor. The study could thus be referred as a universal post-selection strategy for engineering high affinity aptamers and constructing novel aptamer-based biosensing platforms for highly sensitive and specific analysis of other targets.