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. (C) 2013 Elsevier B.V. All rights reserved.