Novel Nanomaterials As Peroxidase Mimetics For The Visual Determination Of Glucose

Natural enzymes, as the catalyst, can catalyze the biochemistry reaction and encourage the metabolism due to their high catalytic efficiency and strong substrate specificity in the condition of mild reaction. And natural enzymes are applied widely in the medicine,chemical industry, food processing and agriculture. However, they bear the serious disadvantage of instability to the high temperature, strong acid and base. At the same time, the natural enzymes are denatured due to the digestion by proteases. In addition, the content of natural enzymes is low in living body and the preparation, purification and storage of natural enzymes are usually time-consuming and expensive. These factors limit their widespread applications. Thus, the development of natural enzymes mimetic is becoming a significant field. Owing to their surface effect, little size effect, volume effect and macroscopic quantum tunneling effect, quantum size effect, they have many special optical, magnetic, electrical, thermal, chemical and mechanical properties. Recently, it was reported firstly that Fe3O4magnetic nanoparticles (MNPs) possessed intrinsic peroxidase-like activity. And some metal oxide nanomaterials, carbon nanometerials, metal sulfide nanomaterials, noble metal nanomaterials and nanocomposites displayed intrinsic enzyme mimetic activity. Based on the above reasons, this paper is focused on the development of novel peroxidase-like nanomaterials, the study of catalytic mechanism and the application of visual colorimetric detection of glucose.The thesis consists of four chapters:Chapter1:The development of nanomaterials as intrinsic peroxidase-like mimic enzyme in recent years is summarized.Chapter2:CO3O4nanoparticles were preparated and their intrinsic peroxidase-like activity was investigated. The results showed that like horseradish peroxidase (HRP), Co3O4nanoparticles were able to catalyze H2O2to oxidize peroxidase substrate TMB, ABTS and OPD. And the catalytic activity of Co304nanoparticles is dependent on pH, temperature, and H2O2concentration.Using the colorimetric reaction of H2O2-TMB as the model, we investigate the intrinsic peroxidase-like activity of the different particle size of Co3O4nanoparticles. The results showed that the apparent Km and Fmax of the different particle size of Co3O4nanoparticles is in the order of18nm>5nm>52nm and5nm>18nm>52nm, respectively. At last, this peroxidase-like activity of Co3O4NPs leads to a simple and sensitive detection of urine glucose by naked eyes.Chapter3:In this paper, we preparated ZnFe2O4magnetic nanoparticles (MNPs) and discovered they possess intrinsic peroxidase-like activity. The results showed that ZnFe2O4MNPs exhibit several advantages such as high catalytic efficiency, good stability, monodispersion, and rapid separation over other peroxidase nano-mimetics and HRP. At last, ZnFe2O4MNPs were used as colorimetric biosensor for the detection of H2O2and glucose. Under the optimum reaction conditions, the linear range of detection of H2O2and glucose were4.5x10-7to4.5×10’6M and1.25×10-6to1.875×10-5M, respectively. This method is simple, inexpensive, high sensitive and selective for urine glucose detection. The approach depicted here seems to be important, particularly in third world countries where high tech diagnostics aids are inaccessible to the bulk of the population.Chapter4:MFe2O4(M=Mg, Ni, Cu) magnetic nanoparticles (MNPs) were preparated and found to have catalytic activity similar to those of biological enzymes such as catalase and peroxidase. Thus, these materials not only can catalyze the decomposition reaction of H2O2into water and oxygen, but they can also catalyze the oxidation of substrate2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)(ABTS) by H2O2. Kinetic analysis indicated that the peroxidase-like catalytic behavior of MFe2O4(M=Mg, Ni) MNPs was in accord with typical Michaelis-Menten kinetics and followed a ping-pong mechanism. Furthermore, NiFe2O4MNPs were used as a colorimetric biosensor for the detection of9.4x10-7to2.5×10-5M glucose with a limit of detection (LOD) of4.5×10-7M. Significantly, the existence of glucose in urine can be visually evaluated easily without the aid of any instrumentation. The detection platform showed great potential applications in varieties of physiological importance substances when merged with appropriate H2O2-producing oxidases.