Amperometric Detection and Quantification of Nitrate Ions Using a Highly Sensitive Nanostructured Membrane Electrocodeposited Biosensor Array

In the past few decades, there has been a steady rise in the release of nitrate (NO3-), a prominent water soluble contaminant associated with the increasing use of nitrate based fertilizers. In this study, we suggest the use of a highly sensitive, enzymatic biosensor capable of quantifying minute concentrations of nitrate. The disposable nitrate biosensor consists of a sensing element in the form of nitrate reductase which is immobilized within a conductive polymer matrix to generate a quantifiable amperometric response. In this work, nanoarrays of co-immobilized nitrate reductase and poly(3,4-ethylenedioxythiophene) (PEDOT), were grown using a template assisted electropolymerization route. The performance of the biosensor is a strong function of electropolymerization conditions and the morphology of the PEDOT nanostructures. The electropolymerized biosensor displays excellent specificity w.r.t other interfering ions as evidenced from the initial rate kinetics. With a response time of a few seconds, limit of detection (LOD) as low as 0.16 ppm and sensitivity of about 92 mu A/mM, the one-step electropolymerized nanostructured nitrate biosensor developed in this study shows improved performance compared to similar electrochemical sensors reported in literature. The PEDOT/nitrate reductase nanowire sensor developed in this work shows superior attributes compared to a flat 2D nitrate reductase-co-immobilized PEDOT film grown using similar electropolymerization conditions. This combined with easy and fast fabrication technique opens up exciting opportunities for developing high accuracy PEDOT based nanobiosensors for field testing of nitrate contaminants in the future.