Rationally designed naphthyl substituted amine functionalized ionic liquid platform for covalent immobilization and direct electrochemistry of hemoglobin.

Herein, we have designed and demonstrated a facile and effective platform for the covalent anchoring of a tetrameric hemoprotein, hemoglobin (Hb). The platform comprises of naphthyl substituted amine functionalized gel type hydrophobic ionic liquid (NpNH2-IL) through which the heme protein was covalently attached over a glassy carbon electrode (Hb-NpNH2-IL/GCE). UV-vis and FT-IR spectral results confirmed that the Hb on NpNH2-IL retains its native structure, even after being covalently immobilized on NpNH2-IL platform. The direct electron transfer of redox protein could be realized at Hb-NpNH2-IL/GCE modified electrode and a well resolved redox peak with a formal potential of -0.30 V and peak separation of 65 mV was observed. This is due to the covalent attachment of highly conducting NpNH2-IL to the Hb, which facilitates rapid shuttling of electrons between the redox site of protein and the electrode. Further, the fabricated biosensor favoured the electrochemical reduction of bromate in neutral pH with linearity ranging from 12 to 228 µM and 0.228 to 4.42 mM with a detection limit and sensitivities of 3 µM, 430.7 µA mM-1 cm-2 and 148.4 µA mM-1 cm-2 respectively. Notably, the fabricated biosensor showed good operational stability under static and dynamic conditions with high selectivity and reproducibility.