Electrochemical Analysis On Neurontransmitter Compound And Electrochemical Study On The Interaction Of The Boronic Acid System With Saccharides

Catecholamine is a kind of the neurotransmitters, including dopamine (DA), epinephrine (EP) and norepinephrine. If the levels of catecholamine change among the blood plasma, the organism shall put up different morbidity. Therefore, the determination of catecholamine makes a very realistic significance. In recent years, a significant advance has been made in carbohydrate research, the knowledge of the structure and function of carbohydrates has been gradually obtained, and the importance of saccharides to the life, not just as a kind of simple energy substances, has also been realized. The researches of saccharides will become the emphases of life sciences. Saccharides are not only the main energy substances, but also as molecules with the function of carrying information, participate in many physiological and pathological processes. There are a lot of diseases tightly related to saccharides; thus, the analysis of saccharides is very important. In this work, one principal reaearch is about the application of NADH and chitosan congo red-polysaccharide hybrid modified electrode in the field of analysis of catecholamine, and the other is about the boronic acid system for the recognition of saccharides.The primary reaearch work is as follows:1. A novel sensor of NADH immobilized on poly-o-phenylenediamine film self-assembled nano gold and its application for the determination of epinephrineThe preparation of NADH-poly-o-phenylenediamine film-nano gold chemically modified glassy carbon electrode was studied, and the cyclic voltammetric behavior of epinephrine (EP) on this modified electrode was investigated. It was found that EP showed a well oxidation peak on the modified electrode in a phosphate buffer solution of pH 7.2. The linear range of EP was 3.0×10^-6-5.0×10^-5mol/L and the detection limit was 5.0×10^-7mol/L. This method was applied to the measurement of EP in epinephrine hydrochloride injection samples with satisfaction results. 2. Application of chitosan congo red-polysaccharide hybrid modified electrode in the field of simultaneous analysis of dopamine and uric acidChitosan and congon red polysaccharide hybrid can be modified onto the surface of glassy carbon electrode through daubing technique. The modified electrode shows an obvious electrochemical activity for the dopamine and uric acid. The reaction conditions were optimized carefully by differential pulse voltammetry. The modified electrode was applied to the determination in practical samples with satisfaction results.3. 3-Aminophenylboronic acid self-assembled layer based on chitosan films for recognition of monosaccharideChitosan film has been successfully deposited at gold electrodes from an acidic solution and 3-aminophenylboronic acid (APBA) has been covalently bound to the chitosan film with glutaraldehyde (GD) linkage. The boronic acid groups of the APBA film could form covalent-bond with different sugars, which can change the dielectric characteristics of the APBA film. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetric (CV) were used to characterize the change of the dielectric characteristic. The CV peak current of Fe(CN)₆^3-/4- ion decreased and the EIS impedance increased with an increase in sugar concentration. Glucose and mannose have been detected with the CV and EIS methods. The EIS method had higher sensitivity compared with the CV method.4. 3-Thiopheneboronic acid self-Assembled gold naoparticles monolayer-modified electrodes sensitive to saccharideThe glassy carbon electrode modified with nano-gold was prepared by the electrodeposition. Afterward the surface of nano-gold film was modified with a self-assembled monolayer (SAMs) of 3-thiopheneboronic acid (TBA). TBA can form well-packed monomolecular layers on the nano-gold modified glassy carbon electrode through a sulfur-Au bond. The boronic acids group of the TBA films can form covalent-bond with different sugars. Electrochemical impedance spectroscopy was used to display response to sugars in the presence of Fe(CN)₆^3-/4- ion. The dielectric characteristics of the TBA film can change with type and concentration of sugars. Three kinds of sugars have been studied by this method and good linear relationship and high sensitivity were obtained.