Glucose Biosensor Enhanced By Nanoparticles

Diabetes mellitus is a common and frequently-occurring disease, which seriously menaces the healthy of the human beings. Therefore, the diagnosis and treatment of diabetes mellitus is a heavy responsibility for the biomedical engineering field of the world. Glucose biosensor is the major technique for glucose analyses in clinical practice, for the advantages of glucose biosensors are obvious: high specificity, short time, simplicity and low cost of analysis, etc. One of the developments of glucose biosensor is the third generation amperometric enzyme electrode with direct electron transfer, which is commonly prepared by conducting organic salts and conducting polymers. Development of a third generation enzyme electrode is one of the long-term goals of biosensor program in the world. It is very necessary to search new methods to prepare the third generation biosensor. Another development of biosensor is miniaturization and integration. For the purpose, glucose biosensors have to overcome the problem topic: to enhance the current response. Therefore, it is very essensial to explore new materials and methods for preparation of new direct electron transfer biosensor with high response.In the present thesis, we make use of the unique effects of nanoparticle materials to enhance the current response of biosensor. Glucose oxidase is immobilized by silica, platinum, hydrophobic and hydrophilic gold, silver, and composite nanoparticles. These new glucose biosensors with approximate direct electron transfer are prepared by these materials. For example, hydrophobic silver nanoparticles can enhance the current response of glucose biosensor by 62.5 times for 11.1 mM glucose solution. It will open up a new road to miniaturize the biosensor. The enhancement mechanism is discussed from the surface effect, conductivity, macroscopic quantum tunneling, chemical activity, catalytic activity and matrix micro-electrode effect of nanoparticles. It can make a basis of research, preparation and use of the glucose biosensor enhanced by nanoparticles.The long-term stability and interference-free of the biosensor is one of the crucialfactors in clinical practice. The deactivation kinetics of the electrodes enhanced by nanoparticles was researched, and the first-order enzyme deactivation kinetics fit the data reasonably well. The main reason of the loss hi response of the enzyme electrodes is the leakage of glucose oxidase, which is obtained form the research of the enzyme dynamics. So an outer protective membrane and appreciate crosslinker glutaraldehyde can improve the stability of the electrode.The electroactive interferants such as ascorbic acid can seriously influence the proper operation of glucose biosensor. The permselective membranes, which separate glucose from the interferences, can improve the anti-interferential property of the biosensor. The research found that the 8% polyvinyl chloride inner permselective membranes effectively prevent the interference from ascorbic acid. The results illuminated that the introduction of 2% cellulose acetate diffusion limited membranes extend the linear range of glucose biosensor to 27.8mM. Nanoparticlse can not only enhance the current response, but also increase the ratio of signal to noise of the glucose biosensor, which can also effectively decrease the interference of ascorbic acid, etc.