A novel label-free electrochemical microRNA biosensor using Pd nanoparticles as enhancer and linker

Abstract

In this paper, a novel, label-free amperometric biosensor for the detection of microRNA-155 based on the conductive self-assembled multilayer comprised of Nafion, thionine (Thi) and Pd nanoparticles was successfully prepared. Nafion was firstly dropped on to a bare glass carbon electrode. Then Thi was absorbed by the cation exchanger Nafion. Furthermore, a Pd nanoparticles layer which was used to immobilize target biomolecules was constructed by the amino group of Thi as linker. Moreover, the proposed biosensor showed excellent electrocatalytic activity towards H₂O₂ and enhanced the current response of the biosensor. Cyclic voltammetry was used for the characterization and electrochemical properties of the stepwise self-assembly process of the biosensor, and scanning electron microscopy was used for observing the microstructure of the modified film. Using microRNA-155 as a model, the resulting biosensor presented high sensitivity, good stability and a broad linear response from 5.6 to 5.6 × 10⁵ pM with the detection limit of 1.87 pM under optimization of the assay conditions.