Nanocomposites, gold nanoparticles on Orange II functionalized graphene (AuNPs/O-GNs), were developed to modify the electrode surface for anchoring an insulin binding aptamer. The nanocomposites integrate the high electrical conductivity of graphene, and the easily functionalized surface chemistry of AuNPs along with excellent biocompatibility. The characterization using UV-vis absorption spectroscopy, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) revealed the successful synthesis of AuNPs/O-GNs. The determination of insulin by electrochemistry indicated the electrochemical aptamer sensor has good selectivity and high sensitivity at physiological conditions. The linear range was from 1.0 × 10−14 to 5.0 × 10−10 mol L−1 with a low detection limit of 6.0 × 10−15 mol L−1 (S/N = 3). The recovery of insulin in human blood serum samples was from 102.3% to 104.7%. The aptamer sensor provided a promising strategy for insulin detection in clinical diagnostics.
