Synthesis Of Several New Nanocomposites And Their Application In Electrochemical Glucose Biosensors

The determination of glucose has vital significance in many areas. Modern electrochemical glucose biosensor perfectly combines the nano-materials with electrochemical detection technologies, which produced a series of electrochemical glucose biosensor with excellent performance. This article focuses on the study and synthesis of novel nanocomposite and constructs several distinctive glucose sensors employing electrochemical as well as electro-chemiluminescence detection techniques. This paper consists of six parts.Chapter one:In this chapter, the basic principles and classification of biosensors, electrochemical biosensor as well as the definition and characteristics of nanomaterials are introduced. In addition, several aspects are briefly summarized including applications of common nanomaterials in biosensors, development of electro-chemical glucose biosensors, the application of nanomaterials in development of the glucose biosensor and ECL glucose biosensors.Chapter two:Introduction of nanomaterials brings new opportunities for the direct electrochemistry of glucose biosensor. Glucose biosensors based on various nanomaterials to realize the direct electron transfer of glucose oxidase have become hot research now. However, most of the nanomaterials are easy to leak from the electrode surface, which makes the measured electrochemical signal unstable, thus reducing the performance of the sensor. Glucose biosensor constructed by nanomaterials with good performance can not only overcome the problem of leakage of nanomaterials, but also achieve direct electron transfer between the redox-active center of the enzyme and the electrode surface, thus improved the response time and the sensitivity. Therefore, in this chapter, firstly, the Chitosan/Prussian blue/graphene nanocomposite (CS-PB-GR) was synthesized based on the electroactive species including Prussian blue, graphene and chitosan. The application of chitosan for building chitosan/Prussian blue/graphene nanocomposites not only enhanced the biocompatibility of the complex but also effectively avoided the leakage of poly Prussian blue nanoparticles, which strongly improved the performance of composite nanomaterials. The CS-PB-GR nanocomposites, nano-Au and half sword bean globulin a (Con A) were applied to construct the GOD/Con A/GOD/nano-Au/CS-PB-GR/glassy carbon electrode. The advantages of this method were summarized as follows: The introduction of nano-Au and Con A effectively improved the amount of glucose oxidation. A pseudobienzymatic system was formed with PB nanoparticles and GOD to enhance the esponse signal. The electron transfer rate between the activity center (FAD) of enzyme and electrode surface was significantly accelerated by the application of grapheme and PB nanoparticles. The biosensor exhibits good electrocatalytic behavior towards detection of glucose with fast response, high sensitivity and selectivity and realized the direct electron transfer.Chapter three:With further research on the carbon materials, fullerenes, as a biomaterial, began to be applied in glucose biosensor. C60molecule has a large conjugated delocalizedπbond and behaves strong electron affinity, which can be used as the electron acceptor. The characters mentioned above endow C60special physical and chemical properties, which prompt such material present potential application prospects. C60is soluble in non-polar organic solvent such as toluene, benzene, paraffin, and carbon disulfide. However, C60has poor water soluble and conductivity, which limited its application in biosensor. In order to overcome this shortcoming of C60, we synthesized platinum wrapped C60nanowires. The synthesized Pt@C60nanowires, glucose oxidase and CS were dropped onto the electrode surface to prepare a glucose sensor. Results showed that the enzyme biosensor based on Pt@C60nanowires behaved good catalytic performance towards glucose, due to the introduction of platinum nanomaterials with good electrical conductivity, high catalytic performance and good biocompatibility. Besides, the sensor exhibited short response time, good selectivity and good stability.Chapter four:As an amphiphilic molecule, the surface active agent containing polar and non-polar functional groups can strongly adsorb on the solid-liquid interface. The application of surfactant solution could form an orderly double biomimetic membrane, which can speed up the exchange rate of electrons between the enzyme and the electrode. To overcome the water-insoluble and poor conductivity of C60, Au@C60core-shell nanoparticles were synthesized with cationic surfactants tetraoctylammonium bromide (TOAB) as a stabilizing agent and phase transfer reagent. Furthermore, the glucose enzyme biosensor was fabricated based on glucose oxidase/Au@C60. The utility of nano-Au enhanced the electronic affinity of C60, which ensured the effective immobilization of glucose oxydase by Au@C60. Simultaneously, the positive charged TOAB also increased the enzyme loading amount. Moreover, the obtained Au@C60nanoparticles can promote the direct electron transfer between the active center of glucose oxydase and the electrode surface. The fabrication process of the sensor was simple, and the sensor exhibited short response time, good selectivity and excellent stability.Chapter five:In order to expand the application of C60nanoparticles in biosensors, a new type of Palladium Nanoparticles (Pd@Cys-C60) were synthesizes employing C60and potassium tetrachloropalladate. The nanoparticles were modified onto the glassy carbon electrode surface to construct non-enzymatic glucose sensor. Pd@Cys-C60nanoparticles behaved excellent catalysis to glucose due to the synergetic effect of Pd nanoparticles and C60. The non-enzymatic glucose sensor can be saved under common conditions and are free of influence by the deactivation of the enzyme variability. Moreover the stability and reproducibility of this non-enzyme sensor are better than the ordinary enzyme biosensor.Chapter six:ECL is a new testing technology combining electro-chemistry and chemiluminescence, which not only obtains the advantages of electrochemical analysis, but also exhibits many characteristics of chemiluminescence analysis. Luminol is most commonly used reagent in the luminescent ECL. The ECL intensity of luminol-H2O2is directly proportional to the quantity of H2O2. GOD can produce H2O2during their substrate-specific enzymatic reaction and the intensity of the ECL signal is directly proportional to the concentration of H2O2which was generated by enzymatical catalysis. Therefore, a sensitive ECL glucose biosensor could be designed for measure of glucose by detecting H2O2indirectly. Gold nanoparticles can enhance the ECL intensity of the luminol-H2O2system. Thus, in this chapter, hollow Aushell@GOD nanoparticles were synthesized using glutaraldehyde cross-link with glucose oxidase. Then, the GOD/Aushell@GOD/chitosan/GCE was prepared to detect glucose through ECL technology. Results showed that, the obtained Aushell@GOD nanoparticles exhibited excellent catalytic effect towards the electro-chemiluminescence of luminol-H2O2system. The preparation of this glucose enzyme biosensor is simple, and the electro-chemiluminescence biosensor showed fast response, wide linear range, high sensitivity and good selectivity.