Protein sensors based on reversible π-π stacking on basal plane HOPG electrodes

In this study, the modification of basal planes of highly oriented pyrolytic graphite (HOPG) electrodes with pyrene-functionalised biotin (PFB), via pi-pi stacking, and ethylene glycol antifouling molecules, via covalent bonding, for detection of streptavidin is presented. Biotin was first conjugated to the pyrene moieties by an esterification reaction in order to enable the self-assembly of biotin onto the surface of HOPG via non-covalent pi-pi stacking. The as-prepared biotinylated electrode was used as the sensing probe to analyze the concentration of streptavidin via the diminution in pyrene electrochemistry resulted from the desorption of pyrene from the surface that is mediated by the biotin-streptavidin recognition. X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), square wave voltammetry (SWV) measurements, and electrochemical impedance spectroscopy (EIS) were used to characterize the amount of surface bound pyrene modified biotin and the concentration of streptavidin. This simple strategy can be applied to the detection of other biomolecules via bio-recognition and the reversible pi-pi stacking process.