A novel electrochemical sensor for bisphenol A detection based on nontarget-induced extension of aptamer length and formation of a physical barrier

In this study, a novel electrochemical sensing strategy was developed based on nontarget-induced bridge assembly and aptamer (Apt) extension reaction triggered by terminal deoxynucleotidyl transferase (TdT). Bisphenol A (BPA) was chosen as the target analyte to study the analytical performance of the designed aptasensor. This sensing system takes advantages of electrochemical sensing platforms and detection of an ultra-low level of BPA, due to the formation of bridge on the surface of electrode in the absence of BPA. In the presence of BPA, Apt/BPA complex is formed and inhibits the access of TdT to the 3′-end of Apt, resulting in the lack of bridge assembly and high access of [Fe(CN)6]3-/4- as redox agent to the electrode surface. Thus, a strong redox peak is observed. This aptasensor enabled the selective detection of BPA with the wide linear range of 0.08-15 nM and detection limit as low as 15 pM. Furthermore, the presented sensing platform was successfully applied for the detection of BPA in tap water and grape juice samples.