Quaternary Ammonium Based Carboxyl Functionalized Ionic Liquid for Covalent Immobilization of Horseradish Peroxidase and Development of Electrochemical Hydrogen Peroxide Biosensor

Abstract

AbstractA novel electrochemical biosensor was developed using a judiciously designed platform for the rapid and accurate determination of hydrogen peroxide (H2O2). The horseradish peroxidase (HRP) based biosensor was constructed by covalent anchoring of the enzyme to a newly synthesized quaternary ammonium‐based carboxyl functionalized ionic liquid (TBA−COOH−IL) immobilized on a multiwalled carbon nanotube deposited glassy carbon electrode (MWCNT/GCE). A stable amide bond is formed between HRP enzyme and IL by utilizing the terminal −NH2 of HRP and −COOH groups of TBA−COOH−IL, while the pi‐pi stacking holds the TBA−COOH−IL firmly on the MWCNT/GCE and forms HRP/TBA−COOH−IL/MWCNT/GCE. Thus fabricated HRP/TBA−COOH−IL/MWCNT/GCE displayed a well‐resolved redox peak at a formal potential (E°’) of −0.32 V, which corresponds to the concealed FeIII/FeII redox centre of the immobilized HRP enzyme. Further, the developed biosensor was employed for the electrocatalytic determination of H2O2 in static and dynamic conditions, which showed a wide linear range from 0.02 to 4.30 mM with a high sensitivity and low detection limit of 160.6 μA mM−1 cm−2 and 6 μM, respectively. The excellent performance of the fabricated biosensor is attributed to the stable covalent anchoring of freely water‐soluble enzyme on the newly designed, highly conducting and biocompatible platform. Furthermore, the fabricated biosensor exhibited good reproducibility with an extended long‐term stability.