Preparation And Application Of Graphene Based Biosensing System

Graphene, a single layer of carbon atoms, is a novel and fascinating nanomaterial. Due to its large specific surface area, high mobility of charge carriers, excellent thermal and electric conductivity and good biocompatibility, graphene has attracted a great deal of interest in recent years. It has been used as transparent conducting films, sensors, supercapacitors, batteries and so on.In this paper, we prepare graphene, MoS2-RGO or GO-MoS2nanocomposites, and character the structure and morphology of the materials. We use the graphene based biosensor to measure the activity of kinase or detect the concentration of glucose and H2O2.Chapter1:IntroductionIn this part, we mainly introduce the structure, properties, synthesis procedures and application of graphene. Then the purpose and significance of the research was presented.Chapter2:Graphene based electrochemical biosensor for label-free measurement of the activity and inhibition of protein tyrosine kinaseIn this part, we report a simple, ultrasensitive and label-free method to evaluate the activity of protein tyrosine (Tyr) kinase based on the electrochemical signal of Tyr residues at a graphene modified glassy carbon electrode. It was found that graphene could enhance the electrochemical response of Tyr through electrocatalytic oxidation reaction. After phosphorylation by kinase, the phosphorylated Tyr (pTyr) is electro-inactive and the electrochemical signal is reduced. Therefore, the electrochemical response of Tyr residues in peptides can be used as a signal reporter to assay kinase activity. In this study, using Src-catalyzed Tyr-phosphorylation as a model, the activity of kinase can be evaluated with a linear range from0.26to33.79nM and an extraordinarily low detection limit of0.087nM. Moreover, this electrochemical biosensor can also be utilized for monitoring the inhibition of kinase using4-amino-5-(4-chlorophenyl)-7-(tert-butyl) pyrazolo [3,4-d] pyrimidine, a small molecule inhibitor. On the basis of the inhibitor concentration dependent Tyr oxidation signal, the IC50value was estimated to be99nM.Chapter3:Glucose electrochemical biosensor based on MoS2-RGO nanocompositeA novel glucose biosensor was developed based on the immobilization of glucose oxidase (GOx) at a MoS2-reduced graphene oxide nanocomposite (MoS2-RGO) modified glassy carbon electrode (GCE). MoS2-RGO was synthesizied via a simple and convenient hydrothermal route. The morphologies of MoS2-RGO were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM). A pair of well-defined redox couple was revealed in the cyclic voltammograms at the modified electrode, indicating the direct electron transfer between GOx and the electrode surface. The amperometric response of this proposed biosensor was linear with glucose concentration ranging from1to8mM at-0.45V, with a high sensitivity of14.5μA mM-1cm-2. This biosensor showed good stability, reproducibility and high selectivity, providing great potential in the practical applications.Chapter4:High peroxidase catalytic activity of GO/MoS2nanocompositeIn this part, we prepared graphene oxide-MoS2nanocomposites (GO-MoS2) by simple electrostatic adsorption. The morphologies of GO-MoS2were characterized by scanning electron microscope (SEM) and transmission electron microscopy (TEM). The nanocomposites were demonstrated to posess intrinsic peroxidase-like activity, they could quickly catalyze oxidation of the peroxidase substrate3,3,5,5-tetramethylbenzidine (TMB) in the presence of H2O2. Owing to the high activity, a simple and sensitive H2O2biosensor based on GO-MoS2could be constructed.