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 ( NH 3 ) 6 3 + .