Electrochemical Sensors Based On Graphene For Bioanalysis Applications

Graphene is a kind of two-dimensional carbon material with special structure,which has gained tremendous attention in electrochemical sensing field due to itsexcellent properties. The latest electrochemical researches on graphene mainly usedthe reduced graphene oxide （rGO）, because of its better electrochemical signalenlargement effect and the excellent dispersibility in solution. The design of a simpleand reliable modification method of graphene-based electrode or an assembly methodfor functionalized graphene-based electrode is the key to the electrochemicalapplication of graphene. In this thesis, based on the simple electrodepositon method,an rGO-modified electrode and a nanoparticles-functionalized graphene modifiedelectrode were prepared, and the two electrochemical sensors were applied to theanalysis of biomarker glutathione （GSH） and cancer cells. The main points of thisthesis are listed as follows:1. An rGO-modified glassy carbon electrode （GCE） was prepared throughone-step electrochemical deposition method, and anodic stripping voltammetry （ASV）technology was employed to the electrochemical detection of GSH. This sensor ownshigh sensitivity, stability and repeatability. On the one hand, the rGO material has anenhancement effect to the electrochemical signal; on the other hand, based on theextreme high binding affinity between GSH and mercury ion, the highly sensitiveASV method was utilized to gain the signal of GSH, which vastly increased thedetection sensitivity and solved the problem of high oxidation overvoltage of GSH. Inthis work, the modification condition of rGO was optimized and scanning electronmicroscopy （SEM） was used to characterize the morphology. The ASV detectionparameters were optimized as well. Finally, we could detect GSH as low as1.0×10^-10M, with a broad linearity range (1×10^-101×10^-5M).2. By using a simple electrochemical reduction method and self-assemblytechnique to prepare the graphene-gold nanoparticles interface functionalized with alayer of4-mercaptophenylboronic acid （MPBA）, we successfully constructed areusable electrochemical impedance cell sensor. This cytosensor could be used tosensitively detect Jurkat cells and to evaluate apoptosis. Without special labeling ofcells, the cytosensor had a wide linearity range between5.0×10³¹.0×10⁷cellsmL1and could detect cells as low as3.6×10³cells mL^-1. The MPBA functional group endowed the sensor with a merit of reusability in capturing cells, and thereactivity of MPBA was controllable and easy to preserve. The simple preparationprocess, the broad detection range as well as the wide applicability, made theMPBA-Au-rGO interface potential for the detection of sugars on cell surface and theanalysis of sialidase.