Fabrication of Redox‐Mediator Supported Potentiometric Nitrate Biosensor with Nitrate Reductase

Abstract

Fabrication of a more superior nitrate potentiometric biosensor than previously achieved with NaR and NADH has been accomplished by co-entrapment of redox mediators and NaR into polypyrrole (PPy) film during galvanostatic polymerization of pyrrole. The replacement of NADH with redox mediators such as thionin acetate (ThAc), safranin (Saf), and azure A (AzA) gave more sensitive potentiometric responses, better minimum detectable concentration, linear concentration range and response time for nitrate than possible with NADH. The co-entrapment of ThAc, Saf, AzA and methyl viologen (MV) with NaR into PPy films also improved the Nernstian behavior of the electrode process beyond the capability of the PPy-NaR-NADH biosensor. Substantial reduction in volume and quantity of cofactor/mediator and, hence cost, was achieved by the replacement of NADH with a redox mediator. Only 50 mM of AzA was required to form a PPy-NaR-AzA biosensor which gave the most sensitive potentiometric response for nitrate, achieving a minimum detectable concentration of 10 mM, a linear concentration range of 50 -5000 mM and a response time of 2 -4 s.

Reduced graphene oxide/polypyrrole/nitrate reductase deposited glassy carbon electrode (GCE/RGO/PPy/NR): biosensor for the detection of nitrate in wastewater

“…Incorporation of metal nanoparticles (Sohail and Adeloju 2016), colloidal dirt (Barbier et al 2004) and redox polymers is the state-of-the-art technology in the development of biosensors. Another idea that the vast majority of the earlier workmanship concentrates on is screen printing/thick film microfabrication innovation (Sohail and Adeloju 2009). Thick film methods are appropriate for large-scale manufacturing of the enzyme electrodes to be employed in the application of nitrate biosensors.…”

Composite Material Based on Macroporous Polyaniline and Osmium Redox Complex for Biosensor Development

“…6.1024.300, Metrohm, Switzerland) of 3 mm diameter modified as described below, an Ag|AgCl reference electrode and a glassy carbon rod as counter electrode. Before each experiment the GC electrode was subjected to a thorough cleaning procedure 40, which consists of a series of treatments: firstly, a process of mechanical cleaning by diamond paste and alumina (0.1 µm) subsequently removed by sonication (10 min) and abundant washing using deionized water and finally electrochemical cleaning by performing several cyclic scans between − 1.2 V and 1.5 V at 100 mV/s in a 0.2 M H 2 SO 4 solution. The electrochemical measurements were carried out in a 5 mL thermostatted electrochemical cell (Model 6.1415.150, Metrohm, Switzerland) filled with 0.01 M phosphate buffer pH 7.2 ( I =0.1 M, with KCl) under a nitrogen stream.…”

Biosensors on Enzymes, Tissues, and Cells

“…97 Nitrate biosensors based on NaR usually employ a cofactor or mediator, such as NADH and Azure A, by either adding to the measurement solution or immobilizing. 98,99 Based on this sensing mechanism, nitrate biosensors can detect as low as 0.2 μM. 100 The nitrate biosensor from the Nitrate Elimination Company, Inc. (NECi) is one of those commercially available biosensors for environmental applications.…”