Glucose Biosensors Based On Novel Nanostructure Materials

Nano materials, which are nano-size in at least one of three-dimensional space or are consist of nano structures, have got more and more attention of experts and researchers in many science fields due to their distinctive characteristics in chemistry, mechanism, electric, magnetic and optic etc. Since the end of 20th century, the nano materials have become one of the most popular research subjects.With rapid development of nano technique, people find that it's necessary to focus on not only single nanoparticle' feature but also the total action of the material consisted of nanoparticles in actually application. A lot of researches indicate that all macro materials' characteristics result in the interaction of the material units, and in a complex system, we could observe some characteristics which couldn't see in a single unit. So, the next development of nano materials is preparation and assembling of nano structures or nano devices. Nano structures are new systems constructed in defined rules with nano-size substances as basic units. The basic units of nano structures include nanoparticles, nanolines, nanorods and nanowires etc, and these nano-size units bring special characteristics that differ from macro materials for nano structures, which will provide new choices for designing new devices with special photic, electrical and catalyzed characteristics.The analysis and detection of the active materials in vivo are important to the achievement of chemical and biological information during the vital process. They are also important to explaining the living activities mechanism and diagnosing diseases. With the continuous development of life science, the bound of human study are ranging to cell and single molecule degree. What we need is to realize the biological molecules detections in situ and in vivo at a more microscopic scale. Many conventional and traditional biological and analytical methods and way are facing huge challenges. For their special surface effects, macro quanta tunnel effects and quanta size effects etc, nano materials usually exhibit excellent electrical, magnetic, photic characteristics, which were not occurred in macro materials. If the nano material is used in preparing of biological sensors, due to its size effect, surface effect etc, the modified electrodes will exhibit high electro-catalyze, reduce the over-potential and the possible interference of the background. If the nano material can be assembled or developed according to defined rule and improved inbiocompatibility, it is possible to generate micro environments with high biological active and stability satisfying identification process of biological molecules. With further research in creating connection between biological molecules and nanoparticles, it is possible to obtain new nano biosensors and realize identifying and inspecting of the goal molecules.The main work of this paper is focus on one of the most active field where nano technique combines with electroanalytical chemistry: developing and fabrication novel modified electrodes based on nano structure materials. The emphasis of this paper is to construct some new nanostructure materials as well as research the advantages of these materials modified electrodes in glucose molecules' detection. Besides, the other emphasis of this paper is to apply these new nano structure materials modified electrodes to realize the detection of glucose in actual samples, which may provide new analytical methods for the life science and relative fields. What we have done is to try our best to combine the nano technique, life science with electroanalytical chemistry firmly. The details are listed below:1.Nanoelectrode ensembles based on conductive polyaniline/poly(acrylic acid) using porous Sol-Gel film as templateFor conductive polymers, due to their special structures and excellent physical and chemical characteristics, they have extensive application foreground in energy source, photoelectron apparatus, information, sensor, molecule lead and molecule apparatus etc. Polyaniline (PAn), acting as one of excellent delegate of polymers, because of its high conductivity, high stability of adulterated and unadulterated, easily fabrication, low cost of monomer, has been considered one of polymers with the highest actual application value.In this paper, we have been exploring the idea of using the porosity of inorganic sol-gel films (PSG) as a template for electropolymerization of polyaniline / poly (acrylic acid) (PAn/PAAC) nanocomposites to get a sequence of PAn/PAA nano array in PSG. The conductive polymer "wires"of PAn/PAA formation in PSG matrix can behave as an ensemble of closely-spaced but isolated nanoelectrodes. Moreover, the nanoelectrode ensembles based on conductive PAn/PAA for glucose biosensing are fabricated by immobilization of glucose oxidase (GOx) and Nafion onto the surface of conductive polymer. Owing to the biocompatibility of PSG and electro-activity ofPAn/PAA at neutral pH regions, the glucose biosensor shows excellent characteristics and performance.2.Template synthesis of Au nanotubes by coalescence of Au nanoparticales and its application in glucose biosensorSince carbon nanotube was found by Iijima, kinds of nano tabular materials, for their special characteristics, obtained more and more attention. In all means of preparing nanotubes, the template method created by C.R. Martin is the most effective method to fabricate metal nanotubes. In this paper, Au nanotubes (AuNTs) were synthesized by coalescence of Au nanoparticals (AuNPs) in amino-derivatived nanoporous alumina membrane. The structures and morphologies of these AuNTs were characterized using scanning electron microscopy (SEM). A novel glucose biosensor was developed by immobilizing glucose oxidize (GOD) on AuNTs modified glass carbon electrode. Because of AuNTs excellent catalysis, special tabular structure and biological compatibility, the glucose biosensor could reduce over potential largely, enhance current responses, increase enzymatic loading and improve the enzymatic activity.3. Template synthesis of Au nanoporous and its application in glucose biosensorAu colloid, because of its mature preparation method, stability and excellent catalytic character, has been applied in many fields, such as fabricating micro electro-device, preparing kinds of novel nano materials, etc. In the field of electroanalytical chemistry, based on Au collide's huge surface area, high activity of surface reaction, more surface activity center, strong adsorb ability, and better stability, it is often adsorbed on the surface of the electrodes to design self-assembled electrode and to prepare all kinds of chemical sensors with special functions. In this paper, we assembled Au and Ag nanoparticles alternately using L-Cys as difunction molecule to get (Au/Ag)n/Au multi-films, and then selectively dissolve Ag nanoparticals to get NPAu. After immobilized with GOD on the surface of NPAu modified electrode, we obtained glucose biosensor. The results of the experiments indicate that because of NPAu's porosity and excellent biocompatibility, the modified electrodes could improve enzymatic stability and biological activity and realize direct electrons transport between GOD and electrodes.