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

A 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 -NH(2)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 degrees') of -0.32 V, which corresponds to the concealed Fe-III/Fe(II)redox centre of the immobilized HRP enzyme. Further, the developed biosensor was employed for the electrocatalytic determination of H(2)O(2)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 mu A mM(-1) cm(-2)and 6 mu M, 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.