Using Hydrothermal Method to Prepare Reduced Graphene-Hemin Electrochemical Biosensor for Tyrosine Detection
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Using Hydrothermal Method to Prepare Reduced Graphene-Hemin Electrochemical Biosensor for Tyrosine Detection Junhua Wei1 and Jenny Qiu1 1 Department of Mechanical Engineering, Texas Tech University, 2500 Broadway, Lubbock, TX, 79409-1021, U.S.A. ABSTRACT Hemin immobilized reduced graphene(HGN) has been investigated to be an outstanding enzymatic catalysis in detection important molecular recently. In this work, two "clean" methods to prepare HGN through π-π stack were charactered by UV-vis spectra, TEM images, and δpotential. The enzymatic catalysis of both materials was compared by catalytic hydrogen peroxide to oxidize pyrogallol. The colorimetric result shows HGN attached before reduction has stronger catalytic ability than the one after reduction. The optimized HGN was then used as an electrochemical biosensor to determine L-tyrosine levels. The cyclic voltammetry (CV) tests were carried out for the bare glass carbon electrode (GCE), and the optimized hemin-reduced graphene electrode (HGN1/GCE). The HGN1/GCE based biosensor exhibits a Tyrosine detection linear range from 5×10-7 M to 4×10-5 M with a detection limitation of 7.5×10-8 M at signal noise ratio (S/N) of 3. In comparison with other biosensor, electrochemical biosensors are easy-fabricated, easy-controlled, and cost-effective. Compared with other materials, the heminreduced graphene based biosensors demonstrate higher stability, a broader detection linear range, and better detection sensitivity. The study of oxidation scheme reveals that reduced graphene enhanced the electron transfer between electrode and hemin. Meanwhile, the hemin groups effectively electrocatalyzed the oxidation of tyrosine. This study contributes to a widespread clinical application of nanomaterial based biosensor devices with a broader detection linear range, improved stability, enhanced sensitivity, and reduced costs. INTRODUCTION Hemin (iron-containing porphyrin) is the active center for variety of protein such like cytochromes, peroxidase, myoglobin and hemoglobin. It has been used to detect important analytics because of its good electrocatalytic properties for the reversible redox of Fe(Ⅲ)/Fe(IV). This advantage makes Hemin a wide range applications in electrochemical reduction, including nitric oxide[1], neurotransmitters[2], hydrogen peroxide[3], nitrite[4] and oxygen[5, 6]. However the catalytic and electrochemical activity are usually limited because of the thermal ability and pH-sensitivity. Therefore hemin was investigated to immobilize onto a variety of solid substrates with large specific surface areas. Several materials were used in the past years, such as graphene oxide[7], carbon nanotube[8], and DNA[9]. As one of the candidates, reduced graphene has attracted enormous interest in recent years due to its exceptional electrical, chemical and mechanical properties. Graphene, a one-atom-thick two-dimensional graphite carbon nanostructure has emerged as a amazing material[10-14]. This unique nanostructure holds great promise for potential applications owing to its large
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