An Electrochemical Genosensor for a Fragment of Apolipoprotein E gene based on Reduced Graphene and Cerium Oxide Nanocomposite

A genosensor was fabricated for detecting a fragment of Apolipoprotein E gene (ApoE). The sensor was made of a nanocomposite of reduced graphene oxide (rGO) and cerium oxide (CeO2) nanoparticles. For this purpose, surface of a glassy carbon electrode was first modified by polyaniline (PANI) and then rGO-CeO2 nanocomposite. It was next characterized through scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. A 23-base oligonucleotide sequences previously reported as a fragment of Apolipoprotein E gene (ApoE) which has a point mutation occurred in the progression of Alzheimer’s disease was selected as a target molecule. Its ssDNA probe was immobilized on the modified surface via a strong interactions between CeO2 nanoparticles and the phosphate groups in the ssDNA. Detection of the biosensor signal was performed by square wave voltammetry (SWV) and Ru(bpy)3]2+/3+ as an electrochemical probe. In presence and absence of the target sequence, the electrochemical probe showed a different behaviour on the electrode surface. The developed genosensor could detect the ApoE gene sequence high selectively and sensitively, with in a good linear range of 10 fM to 10 nM.