Redox-active thionine-graphene oxide hybrid nanosheet: One-pot, rapid synthesis, and application as a sensing platform for uric acid

In this paper, we fabricate a sensitive and stable amperometric UA amperometric biosensor using nanobiocomposite derived from thionine modified graphene oxide in this study. A simple wet-chemical strategy for synthesis of thionine-graphene oxide hybrid nanosheets (T-GOs) through pi-pi stacking has been demonstrated. Various techniques, such as UV-vis absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), atomic force microscopy (AFM) and electrochemistry have been utilized to characterize the formation of the T-GOs. Due to the synergistic effect between thionine and graphene oxide, the nanosheets exhibited excellent performance toward H2O2 reduction. The incorporation of thionine onto graphene oxide surface resulted in more than a twice increase in the amperometric response to H2O2 of the thionine modified electrode. The as-formed T-GOs also served as a biocompatible matrix for enzyme assembly and a mediator to facilitate the electron transfer between the enzyme and the electrode. Using UOx as a model system, we have developed a simple and effective sensing platform for assay of uric acid at physiological levels. UA has been successfully detected at -0.1 V without any interference due to other electroactive compounds at physiological levels of glucose (5 mM), ascorbic acid (0.1 mM), noradrenalin (0.1 mM), and dopamine (0.1 mM). The response displays a good linear range from 0.02 to 4.5 mM with detection limit 7 mu M. The application of this modified electrode in blood and urine UA exhibited a good performance. The robust and advanced hybrid materials might hold great promise in biosensing, energy conversion, and biomedical and electronic systems. (C) 2012 Elsevier B.V. All rights reserved.