Mediator-less highly sensitive voltammetric detection of glutamate using glutamate dehydrogenase/vertically aligned CNTs grown on silicon substrate

Abstract

A sensitive glutamate biosensor is prepared based on glutamate dehydrogenase/vertically aligned carbon nanotubes (GLDH, VACNTs). Vertically aligned carbon nanotubes were grown on a silicon substrate by direct current plasma enhanced chemical vapor deposition (DC-PECVD) method. The electrochemical behavior of the synthesized VACNTs was investigated by cyclic voltammetry and electrochemical impedance spectroscopic methods. Glutamate dehydrogenase covalently attached on tip of VACNTs. The electrochemical performance of the electrode for detection of glutamate was investigated by cyclic and differential pulse voltammetry. Differential pulse voltammetric determinations of glutamate are performed in mediator-less condition and also, in the presence of 1 and 5μM thionine as electron mediator. The linear calibration curve of the concentration of glutamate versus peak current is investigated in a wide range of 0.1–500μM. The mediator-less biosensor has a low detection limit of 57nM and two linear ranges of 0.1–20μM with a sensitivity of 0.976mAmM−1cm−2 and 20–300μM with a sensitivity of 0.182mAmM−1cm−2. In the presence of 1μM thionine as an electron mediator, the prepared biosensor shows a low detection limit of 68nM and two linear ranges of 0.1–20 with a calibration sensitivity of 1.17mAmM−1cm−2 and 20–500μM with a sensitivity of 0.153mAmM−1cm−2. The effects of the other biological compounds on the voltammetric behavior of the prepared biosensor and its response stability are investigated. The results are demonstrated that the GLDH/VACNTs electrode even without electron mediator is a suitable basic electrode for detection of glutamate.