Superoxide radical biosensor based on a nano-composite containing cytochrome c

Abstract

A biosensor for the quantification of superoxide radical (O₂˙⁻) was developed based on a nano-composite containing cytochrome c (Cyt c), carboxylated multi-walled carbon nanotubes and a room temperature ionic liquid (RTIL). The immobilized Cyt c was characterized by field emission scanning electron microscopy, electrochemical impedance spectroscopy and cyclic voltammetry. Using this biosensor a formal potential of −280 mV (vs.Ag/AgCl) and electron transfer rate constant of 1.24 was recorded for the immobilized Cyt c in 0.1 M phosphate buffer solution (pH 7.0). The biosensor showed a relatively high sensitivity (7.455 A M⁻¹ cm⁻²) and a long term stability (180 days) towards O₂˙⁻ in the concentration range from 0.05 to 8.1 μM with a detection limit of 0.03 μM. The selectivity of the biosensor to O₂˙⁻ was verified when its response was compared with those obtained by four potential interfering substances (ascorbic acid, uric acid, acetaminophen and hydrogen peroxide).