Determination of the activity of superoxide dismutase using a glassy carbon electrode modified with ferrocene imidazolium salts and hydroxy-functionalized graphene

A glassy carbon electrode was modified with a composite consisting of ferrocene imidazolium salts and hydroxy-functionalized graphene in a Nafion matrix. The electrode is shown to facilitate the reduction of oxygen to form the superoxide anion radical. Atomic force microscopy and electrochemical impedance spectroscopy were used to characterize the electrode. The in-situ production of superoxide anion was then studied with an analogue of methyl-Cypridina luciferin (also referred to as Vargulin). As a result, an electrochemiluminescence (ECL) based assay was developed for the improved determination of the activity of the enzyme superoxide dismutase (SOD). Under optimized conditions, the ECL based calibration plot is linear in the 0.5 to 6.5 U·mL⁻¹ SOD activity range, with a 0.2 U·mL⁻¹ detection limit (at a signal-to-noise ratio of 3). (author)