An amperometric glutamate biosensor based on immobilization of glutamate oxidase onto carboxylated multiwalled carbon nanotubes/gold nanoparticles/chitosan composite film modified Au electrode

•Constructed a cMWCNT/AuNPs/CHIT hybrid film.•Fabricated an improved amperometric glutamate biosensor based on this film.•Biosensor had a detection limit of 1.6 μM and linear range 5–500 μM.•Employed for glutamate determination in different serum samples.•It also showed improved storage stability and reusability.

A method is described for the construction of a novel amperometric glutamate biosensor based on covalent immobilization of glutamate oxidase (GluOx) onto, carboxylated multi walled carbon nanotubes (cMWCNT), gold nanoparticles (AuNPs) and chitosan (CHIT) composite film electrodeposited on the surface of a Au electrode. The GluOx/cMWCNT/AuNP/CHIT modified Au electrode was characterized by scanning electron microscopy (SEM), fourier transform infra-red (FTIR) spectroscopy, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The biosensor measured current due to electrons generated at 0.135 V against Ag/AgCl from H2O2, which is produced from glutamate by immobilized GluOx. The biosensor showed optimum response within 2 s at pH 7.5 and 35 °C. A linear relationship was obtained between a wide glutamate concentration range (5–500 μM) and current (μA) under optimum conditions. The biosensor showed high sensitivity (155 nA/μM/cm2), low detection limit (1.6 μM) and good storage stability. The biosensor was unaffected by a number of serum substances at their physiological concentrations. The biosensor was evaluated and employed for determination of glutamate in sera from apparently healthy subjects and persons suffering from epilepsy.