Potentiometric Biosensors Based On Carbon Nanotubes And Graphene

In recent years,the most popular materials are carbon nanotube and graphene.Due to their novel properties such as exceptional thermal, mechanical properties, and high electrical conductivity, they have exhibited potential application in synthesizing nanocomposites and fabricating various electrical devices, such as battery, electromechanical resonators, nano-electronics biomedicine and biosensor. Due to their unique electronic properties and optics properties, they had developed a kind microenvironment for biological recognition and enzyme catalysis.Furthermore, there were some recent innovations in carbon material assisted biosensing technologies, such as DNA-hybridization, enzyme-binding, antibody-antigen. However, a vital issue had made the limitation of their application, because both carbon nanotube and graphene usually couldn’t disperse in water or other solvents during the experimental process very well.In my thesis, two different methods were studied, which used to immobility carbon nanotube and graphene.Then they were applied in the fabrication of potential immunosensor. The major contents in this thesis are described as follows:(1)Potential Immunosensor Based Multi-wall Carbon Nanotube Array ModifiedA novel potentiometric immunosensor for the detection of anti-sheep immunoglobulin G (IgG) has been developed by means of self-assembly to immobilize anti-sheep immunoglobulin G on a gold electrode based on nano gold (Au) and multi-wall carbon nanotube (MWCNTs) modified.Firstly, the mixture solution including4-amino thiolpheno (4-ATP) and thiolpheno (TP) were modified on the bare gold electrode through self-assembly, then the MWCNTs was covalent anchoring on electrode surfaces form highly-ordered by diazonium salt reactions, GNPs composite was directly electrochemically depositing via reduction HAuCl4. The sheep anti mouse immunoglobulin G (IgG) antibodies were conjugated with the GNPs through Au-NH2bond. At last the resulting electrode was incubated in BSA solution (0.25%,w/w) about30min in order to block possible remaining active sites and avoid the non-specific adsorption. Then the Au/MSAM/MWCNTs/GNPs/Ab immunosensor was obtained. The modified steps were characterized with cyclic voltammetry, electrochemical impedance spectroscopy, fourier transform infrared spectroscopy and scanning electron microscopy. Some experiment conditions were investigated,such as the temperature of the detect solution,the pH of the detect solution and the antibody solution.To optimize the experimental condition,the immunosensor exhibited a wide linear response to mouse IgG, rang from0.04～1.0×104ng/mL, the slope of the standard curve was-18.140mV/decade, the detection limit has been to0.03ng/mL, the correlation coefficient was0.9902. The4immunosensors showed good consistency.(2) Potential Immunosensor Based Graphene ModifiedA novel potentiometric immunosensor for the detection of anti-sheep immunoglobulin G (IgG) has been developed by means of self-assembly to immobilize anti-sheep immunoglobulin G on a gold electrode based on nano gold (Au) and graphene (RGO) modified. Preliminarily, the mixture solution including4-amino thiolpheno (4-ATP) and thiolpheno (TP) were modified on the bare gold electrode through self-assembly, then the RGO was covalent anchoring on electrode surfaces form highly-ordered by diazonium salt reactions, GNPs composite was directly electrochemically depositing via reduction HAuCL;. The sheep anti mouse immunoglobulin G antibodies were conjugated with the GNPs through Au-NH2bond. Tween-20to remove the physically absorbed biomolecules. At last the resulting electrode was incubated in BSA solution (0.25%, w/w) about30min in order to block possible remaining active sites and avoid the non-specific adsorption. Then the Au/MSAM/RGO/GNPs/Ab immunosensor was obtained. The modified steps were characterized with cyclic voltammetry and electrochemical impedance spectroscopy. Some experiment conditions were investigated, such as the temperature of the detect solution and the pH of the detect solution. To optimize the experimental condition, the immunosensor exhibited a wide linear response to mouse IgG, rang from1.0×10-3～4.0×102ng/mL, the slope of the standard curve was -13.554mV/decade, the detection limit has been to1.4×10-3ng/mL, the correlation coefficient was0.9925.The11immunosensors showed good consistency, all of them hold the same linear response, and almost the same detection limit, their relative standard deviation (RSD) was-2.6%.Its storage life was5days.(3)Potential Immunosensor Based on MWCNTs-GNPs-Chitosan ModifiedThe synthesis of a network of crosslinked multi-wall carbon nanotube-GNPs-chitosan (MWCNTs-GNPs-CS) nano composite on Au electrode and its use to fabricated immunosensor for the detection of anti-sheep immunoglobulin G (IgG). Preliminarily, the MWCNTs-GNPs-CS nano composite was dropped on the surface of bare gold electrode and dried in air. Then the GNPs composite was directly electrochemically depositing via reduction HAuCl4.The sheep anti mouse immunoglobulin G antibodies were conjugated with the GNPs through Au-NH2bond. Tween-20to remove the physically absorbed biomolecules. Tween-20to remove the physically absorbed biomolecules. At last the resulting electrode was incubated in BSA solution (0.25%, w/w) about30min in order to block possible remaining active sites and avoid the non-specific adsorption. Then the Au/MWCNTs-GNPs-CS/GNPs/Ab immunosensor was obtained. The modified steps were characterized with cyclic voltammetry and electrochemical impedance spectroscopy. The experiment conditions that the pH of the detect solution were investigated. To optimize the experimental condition, the immunosensor exhibited a wide linear response to mouse IgG, rang from2.0×10-51.0×103ng/mL, the slope of the standard curve was18.512mV/decade, the detection limit has been to2.0×10-5ng/mL, the correlation coefficient was0.9925. The11immunosensors showed good consistency, all of them hold the same linear response, and almost the same detection limit, their relative standard deviation (RSD) was2.11%. Its storage life was5days.