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

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 x 10(-7) M-1.6 x 10(-4) M), low detection limit (1.5 x 10(-7) M), high sensitivity (55.20 mu AmM-1 cm(-2)) and fast amperometric response (<25 s) at +0.70 V 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. (C) 2017 Elsevier B.V. All rights reserved.