Electrocatalytic oxidation and determination of insulin at CNT-nickel–cobalt oxide modified electrode

CNT-nickel–cobalt oxide/Nafion composites were prepared by combining the nickel–cobalt oxide powder with CNT directly into the Nafion solution used as a binder and deposited on screen-printed electrodes substrates. Their electrochemical behaviour was investigated by means of cyclic voltammetry and amperometry techniques in NaOH and phosphate buffer solutions. The electrocatalytic activity of these sensors was evaluated in terms of sensitivity, detection limit and stability towards insulin detection. CNT-nickel–cobalt oxide/Nafion electrodes enable the oxidative detection of insulin in aqueous solution at physiological pH, with a good sensitivity (22.57 μA × mg−1 × mL−1). An electrochemical activation step of the sensor in alkaline solution has been shown to be necessary for a three times more sensitive response of CNT-nickel–cobalt oxide-composite electrode toward insulin detection.