Amperometric l-lysine biosensor based on carboxylated multiwalled carbon nanotubes-SnO2 nanoparticles-graphene composite

Abstract

A novel matrix, carboxylated multiwalled carbon nanotubes–tin oxide nanoparticles–graphene–chitosan (c-MWCNTs–SnO2–GR–CS) composite, was prepared for biosensor construction. Lysine oxidase (LOx) enzyme was immobilized covalently on the surface of c-MWCNTs–GR–SnO2–CS composite modified glassy carbon electrode (GCE) using N-ethyl-N′-(3-dimethyaminopropyl) carbodiimide (EDC) and N-hydroxyl succinimide (NHS). Effects of electrode composition and buffer pH on biosensor response were investigated to optimize the working conditions. The biosensor exhibited wide linear range (9.9×10−7M–1.6×10−4M), low detection limit (1.5×10−7M), high sensitivity (55.20μAmM−1cm−2) and fast amperometric response (<25s) at +0.70V vs. Ag/AgCl. With good repeatability and long–term stability, the c-MWCNTs–SnO2–GR–CS based biosensor offered an alternative for l-lysine biosensing. The practical applicability of the biosensor in two dietary supplements has also been addressed.