Graphene-based lysozyme binding aptamer nanocomposite for label-free and sensitive lysozyme sensing

This work presents a facile route to fabricate a highly sensitive platform for the recognition of lysozyme. Graphene oxide was coated on the surface of a glassy carbon electrode (GCE) followed by reduction with hydrazine to obtain a graphene (GR) coated GCE. After activation of GR-GCE with EDC and NHS, lysozyme binding aptamer (LBA) was molecularly tethered onto GR to obtain a highly sensitive platform named as LBA-GR-GCE. Results show that GR greatly promotes the electron transfer at electrode/electrolyte interface due to its excellent electrical conductivity. LBA-GR-GCE is able to quantitatively detect the analyte of lysozyme in real samples of human saliva and chicken egg white with high selectivity, with a linear range of 0.01-0.5 pmol L−1 and detection limit of 6 fmol L−1 (S/N = 3). Furthermore, the surface feature of the functionalized electrode was investigated to determine its effect on charge transfer resistance with two different electrochemical probes of [Fe(CN)6]3−/4− and Ru(NH3)63+.