Enhanced Sensitivity of Dopamine Biosensors: An Electrochemical Approach Based on Nanocomposite Electrodes Comprising Polyaniline, Nitrogen-Doped Graphene, and DNA-Functionalized Carbon Nanotubes

A new, highly-exfoliated nitrogen-doped graphene is electrochemically synthesized, which enhances the catalytic activity of poly(anilineboronic acid) nanocomposite electrodes for dopamine detection in the presence of excess ascorbic acid. The sensing approach is made up of poly(anilineboronic acid) nanocomposites electrodeposited on the surface of a glassy carbon electrode via in-situ electrochemical polymerization of anilineboronic acid monomers using cyclic voltammetry. A thin layer of DNA-functionalized carbon nanotubes, and nitrogen-doped graphene is coated on the electrode surface prior to electro-polymerization. During the electro-polymerization the π-π stacking and electrostatic interactions between DNA-coated carbon nanostructures and monomers anchors anilineboronic acid monomers on the electrode surface. This molecular anchoring increases electrodeposition of the respective nanocomposites on electrode; thus, greatly enhances the density of boronic acid receptors for dopamine binding. The coordinate covalent bonds between nitrogen atoms of graphene and boron atoms of anilineboronic acid monomers further increase the density of boronic acid groups for target analyte detection. The developed highly-sensitive and highly-selective biosensor is capable of dopamine detection in a wide linear range from 0.02-1μM, along with a detection limit of 14nM, which is a very significant step forward for dopamine detection and paves the way for molecular diagnosis of neurological illnesses such as Parkinson's disease.