A highly sensitive and stable electrochemical nitrate biosensor

We report an electrochemical nitrate biosensor incorporating the enzyme nitrate reductase (NR) from the fungus Neurospora crassa entrapped within a polymeric chitosan matrix on a glassy carbon (GC) electrode. The artificial electron mediator anthraquinone sulfonate (AQ) is utilized as an electron transfer partner (co-substrate) for NR. The NR enzyme was effectively immobilized within the chitosan matrix without the need for a dialysis membrane, and exhibited high sensitivity and selectivity for nitrate using either rotating disk cyclic voltammetry or constant potential amperometry methods. A particular feature was the longevity of the biosensor which retained more than 70% activity over a period of 3 months. The practical application of the biosensor was demonstrated by the determination of nitrate concentrations in lake and river water samples without any pre-treatment, and the results were validated with a reliable spectroscopic assay. (c) 2021 Elsevier Ltd. All rights reserved.

Automated summary

The electrochemical nitrate biosensor utilizes nitrate reductase from Neurospora crassa, entrapped within a polymeric chitosan matrix on a glassy carbon electrode, with the electron mediator anthraquinone sulfonate. The sensor shows high sensitivity, selectivity, and long-term stability, and is successfully applied for nitrate detection in lake and river water samples.