Phosphorothioated Oligonucleotides as Receptor Layers in Electrochemical Detection of Uranyl Cation

Abstract

The feasibility of using gold electrodes modified with phosphorothioated oligonucleotides (PTOs) for determination of uranyl cation is described. PTOs are able of anchoring to gold surface via phosphorothioate linkers, present in its backbone. This approach is advantageous due to lack of the necessity of chemical activation before use and low cost. It was shown that the sensor sensitivity highly dependents on the incubation time in the sample solution. The developed biosensor demonstrated high selectivity toward UO22+ ion with minor interferences from other metal ions. A linear relationship between the changes in current signal derived from methylene blue – used as a redox marker – and the uranyl ion concentration up to 100 nmol·L−1 was obtained, with a detection limit of 14.7 nmol·L−1. In order to characterize the morphology of gold surface modified with DNA-SH or PTO, atomic force microscopy (AFM) was used. Interactions between UO22+ and the receptor layer (PTO) were studied using square wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS).