Copper, zinc superoxide dismutase and nitrate reductase coimmobilized bienzymatic biosensor for the simultaneous determination of nitrite and nitrate
2014
Madasamy, Thangamuthu | Pandiaraj, Manickam | Balamurugan, Murugesan | Bhargava, Kalpana | Sethy, Niroj Kumar | Karunakaran, Chandran
This work presents a novel bienzymatic biosensor for the simultaneous determination of nitrite (NO2−) and nitrate (NO3−) ions using copper, zinc superoxide dismutase (SOD1) and nitrate reductase (NaR) coimmobilized on carbon nanotubes (CNT)–polypyrrole (PPy) nanocomposite modified platinum electrode. Morphological changes of the PPy and CNT modified electrodes were investigated using scanning electron microscopy. The electrochemical behavior of the bienzymatic electrode (NaR–SOD1–CNT–PPy–Pt) was characterized by cyclic voltammetry exhibiting quasi-reversible redox peak at +0.06V and reversible redox peaks at −0.76 and −0.62V vs. Ag/AgCl, for the immobilized SOD1 and NaR respectively. The electrocatalytic activity of SOD1 towards NO2− oxidation observed at +0.8V was linear from 100nM to 1mM with a detection limit of 50nM and sensitivity of 98.5±1.7nAµM−1cm−2. Similarly, the coimmobilized NaR showed its electrocatalytic activity towards NO3− reduction at −0.76V exhibiting linear response from 500nM to 10mM NO3− with a detection limit of 200nM and sensitivity of 84.5±1.56nAµM−1cm−2. Further, the present bienzymatic biosensor coated with cellulose acetate membrane for the removal of non-specific proteins was used for the sensitive and selective determinations of NO2− and NO3− present in human plasma, whole blood and saliva samples.
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