Azure A Mediated Polypyrrole-Based Amperometric Nitrate Biosensor

Authors

  • Samuel B. Adeloju,

    Corresponding author
    1. Nanoscience and Sensor Technology Research Group, School of Applied Sciences and Engineering, Monash University, Gippsland Campus, Churchill 3842, Victoria Australia tel: +61 3 9902 6250; fax: +61 3 9902 6738
    • Nanoscience and Sensor Technology Research Group, School of Applied Sciences and Engineering, Monash University, Gippsland Campus, Churchill 3842, Victoria Australia tel: +61 3 9902 6250; fax: +61 3 9902 6738
    Search for more papers by this author
  • Manzar Sohail

    1. Nanoscience and Sensor Technology Research Group, School of Applied Sciences and Engineering, Monash University, Gippsland Campus, Churchill 3842, Victoria Australia tel: +61 3 9902 6250; fax: +61 3 9902 6738
    2. Current address: Nanochemistry Research Institute, Curtin University of Technology, Perth, Western Australia 6845
    Search for more papers by this author

Abstract

The co-entrapment of Aspergillus niger-nitrate reductase (NaR) and azure A (AzA), as a redox mediator has been investigated for fabrication of a polypyrrole (PPy)-based electron mediated amperometric nitrate biosensor. Optimum formation of PPy-NaR-AzA film was achieved in a monomer solution which contained 0.3 M Py, 0.1 M KCl, 1U/mL NaR, 50 µM AzA with an applied current density of 0.5 mA/cm2 for 240 s. The optimum applied potential of −0.25 V for amperometric detection of nitrate with PPy-NaR-AzA biosensor was 50, 100 and 150 mV more positive than those achieved with the use of safranin O (Saf), methyl viologen (MV) and bromophenol blue (BrB) or red (BrR), respectively, as mediators. Similar optimum applied of −0.25 V was achieved with thionin acetate (ThAc) which was in the same phenothiazine group of mediators as AzA. The electron mediated amperometric detection of nitrate with the PPy-NaR-AzA biosensor also gave the best performance with a sensitivity of 40.8 nA µM−1 cm−2, detection limit of 0.5 µM, a response time of 18–20 s and a linear concentration range of 20–500 µM.

Ancillary