Electrocatalytic determination of traces of insulin using a novel silica nanoparticles-Nafion modified glassy carbon electrode

• Design of a voltammetric insulin-selective sensor based on SiO2NPs-Nafion/GCE.
• Morphological and electrochemical characterization of modified electrode by SEM, EIS and CV.
• Insulin determination at neutral pH over a linear range of 10–50 nM with a limit of detection and of 2.8 nM.
• Method development and validation for assay of insulin in Bovine insulin injection and skin sweat samples.

A novel electrochemical sensor for the detection of insulin was proposed based on immobilizing silica nanoparticles/Nafion on glassy carbon electrode. Transmission electron microscopy, electrochemical impedance spectroscopy, cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to confirm the successful stepwise assembly procedure of the sensor. The electrocatalytical behaviors of the sensor were also investigated by CV and DPV. Results showed that nano-SiO2 exhibited a remarkable electrocatalytic activity for the oxidation of insulin under optimal conditions. The electrocatalytic response of the sensor was proportional to the insulin concentration in the range of 10–50 nM with a limit of detection and sensitivity of 3.1 nM and 300 pAnM−1, respectively. The modified electrode show many advantages such as simple preparation without using any special electron transfer mediator or specific reagent, high sensitivity, excellent catalytic activity at physiological pH values, short response time, and remarkable antifouling property toward insulin and its oxidation product.