Studies Of Fabrication And Biomedical Application Of Nitirc Oxide Sensor Based On Carbon Nanomaterials

Nitric oxide (NO) is a neurotransmitter and an important messenger molecule. It exists widely in human's organs and has strong biological activity. It also plays important roles in neural information transmitting, gastrointestinal protection, power control, cardiopulmonary, organ blood flow regulation, endocrine regulation, organism defense immune ability and apoptosis et al. Electrochemical methods have the merits of high sensitivity and quick response, and can realize the real time and online determination of NO; moreover, microelectrode and ultramicroelectrode are adequate for in vivo analysis and single cell analysis. So scientists have paid more attention to electrochemical methods. Electrochemical sensor depended on kinds of modified electrodes is one of the most important electrochemical methods. Therefore, looking for suitable electrode modifier that is molecular sensitive and energy transfer effective is essential for the excellent engineering of electrode interface, developing sensitive and selective NO electrochemical sensors and investigating the sensing mechanism of chemical and biological molecules.Carbon nano-materials are widely used as electrode modifier in fabricating electrochemical sensors due to their large surface area, good conductive ability, excellent electro-catalytic ability, strong adsorption ability, high surface activity and good biocompatibility. In this thesis, we combined carbon nano-materials with other function materials based on their high surface activity to fabricate some novel NO electrochemical sensors with good selectivity, sensitivity and biocompatibility. Moreover, the application of the NO electrochemical sensors in biomedicine had been investigated. The main results are summarized as follows:(1) A new noncovalent approach for the dissolution of MWCNTs in water by azocarmine B (ACB) was reported. Through a simple electropolymerization procedure, a novel electrochemical NO sensor based on water-soluble MWCNTs and polyazocarmine B (PACB) nanofilm electrode was prepared, which showed excellent electrocatalytic activity towards the oxidation of nitric oxide (NO). PACB-MWNTs composite film was characterized through many techniques and the NO detection conditions were optimized. The sensor has the merits of good stability, reproducibility, high sensitivity and selectivity, and it can be used to monitor NO released from rat liver cells effectively. (2) Carbon naofibers (CNFs) were functionalized by Alizarin Red (AR) through new noncovalent approach and could be dispersed in water stably. PAR-CNFs composite film modified carbon fiber miro-electrode (CFME) denoted as NO microsensor was fabricated through a simple in-situ electropolymerization. The electropolymerization mechanism of AR was studied with infrared spectrum and the surface morphology of PAR-CNFs composite film was characterized by scanning electron microscope. The PAR-CNFs composite film has loose structure with lots of nanopores which can improve the effect area and sensitivity of the NO micosensor. The NO microsensor was successfully used to detect the NO released from macrophage, which indicated its potential application in biomedicine.(3) A NO electrochemical sensor was fabricated through constant-potential electrodepositing Pt nanoparticles (PtNPs) onto the film of acetylene black (AB) modified glassy carbon electrode (GCE). Scanning electron microscopy (SEM), energy dispersive x-ray analysis (EDX) and electrochemical impedance spectroscopy (EIS) were used to characterize the PtNPs-AB. Electrochemical experiments revealed that the NO electrochemical sensor showed high electrocatalytic activity for the oxidation of nitric oxide. The linear range of the determination of nitric oxide was from 0.18μM to 120.0μM and the detection limit was low to 50 nM (S/N=3). This NO electrochemical sensor was applied to the determination of NO released from rat liver tissue and the result was satisfied.(4) We fabricated a novel carbon nanofiber paste microelectrode (CNFPME) and reported a sensitive NO microsensor based on cetyltrimethyl ammonium bromide (CTAB)-Nafion composite film modified CNFPME. The results from scanning electron microscope (SEM) and electrochemical technique showed that the CTAB-Nafion composite has large surface area and good conductive ability, which can improve the sensitivity of the NO microsensor. The NO microsensor also has good anti-interference ability because of the function of Nafion. The NO microsensor has good stability, reproducibility and low detection limit, and was successfully applied in the determination of NO released from rat liver cells.(5) We reported a simple method for the stable dispersion of multi-walled carbon nanotubes (MWNTs) in water by vanillin and controllable surface addition onto carbon fiber microelectrodes (CFME) via electropolymerization. We had characterized these polyvanillin-carbon nanotube (PVN-MWCNT) composite films, with techniques including scanning electron microscopy (SEM), infrared spectroscopy (IR) and voltammetry. These investigations showed that the film has a uniform porous nanostructure with a large surface area. This PVN-MWCNT composite-modified CFME (PVN-MWCNT/CFME) exhibited a sensitive response to the electrochemical oxidation of nitrite. We successfully applied the PVN-MWCNT/CFME system to the determination of nitrite from lake water. The efficient recovery of nitrite indicated that this electrode was able to detect nitrite in real samples.(6) In this work, Au-Ag alloy nanoparticles were biosynthesized by yeast cells and applied to fabricate a sensitive electrochemical vanillin sensor. Fluorescence microscopic and transmission electron microscopic characterizations indicated that the Au-Ag alloy nanoparticles were mainly synthesized via an extracellular approach and generally existed in the form of irregular polygonal nanoparticles. Electrochemical investigations revealed that the vanillin sensor based on Au-Ag alloy nanoparticles modified glassy carbon electrode was able to enhance the electrochemical response of vanillin for at least five times. This vanillin sensor was successfully applied to the determination of vanillin from vanilla bean and vanilla tea sample, suggesting that it may have practical applications in vanillin monitoring system.