Electrostatically Immobilized Hemoglobin on Silica-Coated Magnetic Nanoparticles for Simultaneous Determination of Dopamine, Uric Acid, and Folic Acid

This work describes the development of a novel biosensor for simultaneous determination of dopamine, uric acid, and folic acid by carbon paste electrode modified by hemoglobin which is electrostatically immobilized on silica- coated magnetic nanoparticles and multi- walled carbon nanotubes. Peroxidase properties of hemoglobin nominate this protein as an abundant and inexpensive alternative for costly peroxidase enzymes in dopamine biosensor fabrication. Silica- coated nanoparticles of Fe3O4 as a suitable support for hemoglobin immobilization can enhance the loading and stability of hemoglobin. Magnetic nanoparticles were synthesized via a simple co- precipitation method and then were coated with silica to immobilize hemoglobin electrostatically on them. All synthesis andmodification steps were characterized by different techniques and then the conditions of hemoglobin immobilization onmagnetic nanoparticles were optimized. Multi- walled carbon nanotubes were used as an additional modifier of carbon paste electrode because of their high electroactive surface area and interesting electrocatalytic properties. The modified carbon paste electrode provided a sensitive and stable biosensor for simultaneous determination of dopamine, uric acid, and folic acid whose performance is much better than those of many previously reported sensors. The detection limits were calculated to be about 12 nM, 14 nM and 18 nM and the linear range for determination of DA, UA and FA are 1-30.6 mu M, 1- 286 mu M and 1- 369 mu M, for dopamine, uric acid, and folic acid, respectively. Finally, the applicability of the proposed biosensor was verified by dopamine evaluation in serum samples. (C) 2016 The Electrochemical Society.