L-glutamate is one of the 20 standard amino acids used by all organisms. It plays an important role in clinical applications and in food processing and well known as a flavor enhancer commonly found in various foods. The excessive intake of this flavor enhancer can cause toxic effect to the human health. Therefore, development of sensors or biosensors for the determination of glutamate has been of great interest over the past two decades owing to its importance in food and biomedical industries^1-4.

In this work, a sensitive and enzymeless glutamate sensor has been constructed using highly dispersed NiO nanoparticle modified glassy carbon electrode (NiO/GCE). The NiO nanoparticle is synthesized using sol-gel method and has been characterized using scanning electron microscope (SEM), transmission electron microscope (TEM), Raman spectroscopy and X-ray diffraction (XRD). Electron microscopy analysis showed that the particles have an average diameter of 40 nm (Fig. 1(a-c)) and the selected area diffraction analysis confirmed the particles are polycrystalline (Fig. 1(d)). Cyclic voltammetry (CV) and amperometry were used to investigate the electrochemical behavior and catalytic properties of the assembled sensor for glutamate electro-oxidation in alkaline media. Nanoparticle modified electrode showed high electrocatalytic activity towards the oxidation of glutamate in 0.1 M NaOH solution. At an applied potential of +0.55 V, it gives a fast response time (<5 s) and a linear dependency (R = 0.997) for the glutamate concentration from 1.0 to 8.0 mM with a high sensitivity of 11 µA/mM/cm² and a detection limit of 272 μM. Compared to glutamate, the interference study for the ascorbic acid, uric acid and glucose on the NiO/GCE yielded current response ranging from 6-13%. It allows a sensitive, simple and fast amperometric sensing of glutamate, which is promising for the development of a non-enzymatic glutamate sensor.

Acknowledgment

Authors acknowledge financial supports from the Ministry of Science & Technology, Bangladesh funded project “FACSens” under the special allocation to science & technology activity programme; and Science Foundation Ireland funded project “SweatSens” under the grant agreement No. 14/TIDA/2455.

Corresponding authors email addresses: mamun.jamal@chem.kuet.ac.bd and kafil.mahmood@tyndall.ie

Reference

1. M. Jamal, M. Hasan, A. Mathewson, and K. M. Razeeb, Biosens. and Bioelectron., 40, 213 (2013).

2. G. Hughes, R. M. Pemberton, P. R. Fielden, and J. P. Hart, Trends in Anal. Chem., 79, 106 (2016).

3. R. E. Özel, C. I, M. Ganesana, J. C. Leiter, S. Andreescu, Biosens. Bioelectron., 52, 397 (2014).

4. B. Batra, and C. S. Pundir, Biosens. Bioelectron., 47, 496 (2013).

Figure 1. (a, b) SEM images of NiO nanoparticles at different magnifications; (c) TEM images of NiO nanoparticles, (d) corresponding selected area electron diffraction (SAED) pattern.