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

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 x 105 pM with the detection limit of 1.87 pM under optimization of the assay conditions.