Graphene Electrochemical Biosensors Are Used For The Detection Of Enzyme And DNA Oxidative Damage

Electrochemical biosensors have valuable applications in chemistry, environmental science, food industry, clinical medicine and screening of new drugs because of its excellent selectivity, rapid analysis, high sensitivity, low cost and easy to be miniaturized. Nanomaterials are attractive in the development of biosensors due to their large specific surface area, good conductivity, special catalytic properties and excellent biocompatibility. The performance of the resulting biosensors could be improved greatly with the application of nanomaterials. In the thesis, a novel electrochemical biosensor based on graphene-doped nano-titanium dioxide was developed and applied for detection of enzyme and oxidative DNA damage. The main results of this thesis are as following:(1) The fabrication of 3DOM GR-TiO2 modified electrode and direct electrochemical behavior of catalaseA novel three-dimensionally ordered macroporous (3 DOM) graphene-doped nano-titanium dioxide (GR-TiO2) modified electrode (3DOM GR-TiO2) was fabricated by the colloidal crystal template technique. The direct electron transfer and electrocatalysis of catalase immobilized on this electrode have been investigated. The results indicated that the enzyme electrode has good electrocatalytic activity to the reduction of H2O2, the reduction peak current of enzyme electrode in the range of 3.0×10-6mol/L?3.6×10-3mol/L showed linear correlation with concentration of H2O2 which could be used to determine the concentration of H2O2 in the solution.(2) The electrochemical studies of 8-hydroxydeoxyguanosine (8-OHdG) in chitosan/ graphene modified GC electrodeDNA oxidative damage can be obtained through the detection of 8-OHdG, which is the important biomarker of oxidative DNA damage. The chitosan and graphene modified glass carbon electrode (Chi/GR/GCE) was fabricated by adsorption and electrochemical behavior of 8-OHdG in the modified electrode was studied. A linear relationship between the oxidative peak current and the concentration of 8-OHdG was detected in the range of 3.5×10-7mol/L?1.4×10-4mol/L with a detection limit of 6.4×10-8mol/L. Moreover, electrochemical methods for the detection of 8-OHdG and DNA oxidative damage and influence factors were discussed on the modified electrode.(3) The application of 3DOM GR-TiO2 modified electrode for detection of DNA oxidative damageThe oxidative damage experiments of DNA were conducted with Fenton's reagent. The oxidative damage DNA was immobilized on the surface of 3DOM GR-TiO2 modified electrode, and electrochemical signals of before and after DNA damage were detected by using methylene blue (MB) as an electrochemical indicator. The electrochemical signal of MB was observed to increase significantly when DNA was oxidative damaged, which could be used to detect DNA damage. The high-performance liquid chromatography with mass spectrometry (HPLC-MS/MS) experiments further confirmed that 8-OHdG is a product of oxidative damage DNA.