▎ 摘　　要

A sensitive amperometric method is reported for the determination of lactate. A platinum electrode was modified with a composite prepared from reduced graphene oxide (rGO), carbon nanotubes (CNTs) and gold nanoparticles. The composite was synthesized by the in-situ reduction of gold(III) ions on the GO-CNT hybrid. Triple composite components showed synergistic effects on the enzyme loading, electrocatalytic activity and electron transfer between receptor and electrode surface. The amperometric lactate sensor was obtained by immobilization of lactate oxidase (LOx) on the modified electrode. LOx catalyzes the conversion of lactate into pyruvate and hydrogen peroxide. The generated hydrogen peroxide is simultaneously involved in the oxidation reaction, which is associated with the electron production. These electrons act as amperometric signal generators. At the low potential of 0.2 V, the nanobiosensor shows a relatively wide linear analytical range (i.e., 0.05-100 mM of lactate) with high electrochemical sensitivity (35.3 mu A mM(-1) cm(-2)) and limit of detection of 2.3 mu M. The sensor is stable, repeatable and reproducible. It is a highly sensitive tool for the detection of lactate in biological samples under both normoxic and hypoxic conditions. Graphical abstract Schematic representation of an electrochemical biosensor for sensitive detection of lactate in biological and food samples based on reduced graphene oxide-carbon nanotube-gold nanocomposite, as a surface modifier, and lactate oxidase, as a bioreceptor.