Applications Of Graphene In Electrochemical Biosensors

Electrochemical biosensor is one of the most important branches of chemical sensors.Graphene, a new carbon material with unique properties, is widely used in electrochemicalbiosensor and has attracted much interest. In this paper, graphene and its functionalnanocomposite were prepared, which were used to modify the electrode for the construction ofelectrochemical biosensors. Using graphene and its nanocomposites, a glucose nonenzymaticelectrochemical sensor was fabricated to detect glucose; a DNA sensor and an aptamer sensorwere used to identify specific DNA strand and thrombin protein, respectively. This dissertationincludes the following three aspects:1. A simple electrodeposition method was used to prepare the CuO nanocubes-graphenenanocomposites modified glassy carbon electrode and a nonenzymatic amperometric glucosebiosensor was fabricated. Experimental conditions of Cu deposition time, the pH value andapplication potential were optimized. Under the optimal conditions, a high sensitivity up to1360μA mM–1cm–2(R2=0.997), a low limit of detection (LOD) as low as0.7μM and a wide linearrange from0.02to4.0mM were obtained.The proposed glucose sensor had long-term stability,good reproducibility and anti-interference ability. Moreover, satisfactory results were obtained bythe developed sensor in the determination of glucose content in the serum samples.2.Thionine-graphene nanocomposite was prepared to modify gold electrode and was used toimmobilize amino-substituted probe ssDNA. A DNA electrochemical biosensor based onthionine-graphene was proposed. The oxidation peak current of daunomycin at+0.31V, whichwas the indicator signal of the DNA concentration was monitored. Factors affecting the sensorwere investigated and optimized. The hybridization temperature, hybridization time, theintercalation time and K+concentration were optimized. In the optimal conditions, the range of thetarget ssDNA from1.0×10–12to1.0×10–7M, with the linear correlation coefficient (R2=0.9976), LOD of1.26×10–13M were obtained. In addition, the DNA sensor could identify one ortwo base mismatched DNA strands.3. A sensitive thrombin aptamer electrochemical biosensors based on goldnanoparticles/thionine-graphene modified glassy carbon electrode was prepared. The sensor wascharacterized by cyclic voltammetry and AC impedance. The decreases of current signal of thethionine oxidation caused by the reaction between thrombin and thrombin binding aptamer weremonitored to indicate the thrombin concentration. The effects of reaction temperature, reactiontime and pH value were optimized. Under the optimized conditions, the aptamer sensor showedthe linear range from0.5to40nM (R2=0.9953), with the LOD of0.093nM. Aptamer sensor hadgood selectivity and the feasibility of the determination in the blood samples. In addition, the apta mer sensor also showed good reproducibi lity, stabilit y and other advantages.