Study On The Preparation Of Novel Nanozymes And Their Applications

Over the past few decades, researchers have established artificial enzymes as highly stable and low-cost alternatives to natural enzymes in a wide range of applications. Recently, some nanozymes including metal oxides, metal nanoparticles, graphene derivatives and nanocomposites have been found to exhibit unexpected enzyme-like activities. And the research in this field has become one of the most active areas in analytical chemistry due to the unique characteristics of nanomaterials. Although, there are numerous challenges to be addressed in the field. For example, compared with natural enzymes and organic catalysts, the efficiency of most nanozymes is still lower. However, many nanomaterials have been found with enzyme-like activities, but their enzyme-like activities are not widely used in real life. Therefore, the development of high performance nanozymes and expansion of practical application will find its unique significance in nanomedicine, biotechnology and related areas. Based on the previous works, the following major innovative researches were carried out in order to develop high performance nanozymes and expand practical application.(1) Fe3O4 MNPs were prepared via a coprecipitation method at room temperature. Novel colorimetric methods have been developed for the determination of reduced glutathione (GSH) in A549 cells and catechol from Yellow River based on Fe3O4 MNPs as peroxidase mimetics.(2) rGO-ZnFe2O4 and rGO-CoFe2O4 hybrids were prepared by a one-pot solvothermal method. The enzyme-like activities, kinetic analysis, catalytic mechanism and practical application of rGO-ZnFe2O4 and rGO-CoFe2O4 nanozyme were thoroughly discussed.This thesis consists of six partes.Part 1:The development of nanozymes in recent years is summarized. The enzyme-like activities, kinetic analysis, catalytic mechanism and practical application of nanozymes were reviewed.Part 2:Fe3O4 MNPs were prepared via a coprecipitation method at room temperature. A novel and simple colorimetric method for the determination of GSH based on Fe3O4 MNPs as peroxidase mimetics was developed. The Fe3O4 MNPs were used as a catalyst in the color development reaction of a peroxidase substrate ABTS and H2O2. The existence of GSH can consume H2O2 and cause a color change of the reaction system which can be detected by the naked eye. Accordingly, the GSH can be detected by measuring the wastage of H2O2. The results indicated that a good linear relationship was obtained from 3.0 to 30.0 mM of GSH. This method offers several distinct advantages, including simplicity, high sensitivity, and good reproducibility. Finally, this colorimetric method was successfully applied to detect GSH in A549 cells.Part 3:Fe3O4 MNPs were prepared by a coprecipitation method. Based on the Fe3O4 MNPs catalytic activity for the color development reaction of ABTS and H2O2, a novel and simple visual method for the determination of catechol was developed. Under the optimum conditions, a good linear relationship was obtained from 1.30 μM to 11.70 μM for catechol, and the limit was 0.4 μM. The visual method was simple and low cost. Furthermore, the visual method has been used to detect catechol in the water sample from Yellow River.Part 4:rGO-ZnFe2O4 hybrids were prepared by a one-pot solvothermal synthesis method. The peroxidase activity of rGO-ZnFe2O4 was discovered for the first time. We investigated various factors influencing on the catalytic activity of rGO-ZnFe2O4, discussed its catalytic reaction kinetics and its mechanism. The rGO-ZnFe2O4 nanozyme was efficient, stable and repeatable over other peroxidase nano-mimetics and HRP. Finally, a colorimetric method for the detection of glucose was developed, in which rGO-ZnFe2O4 hybrids were as peroxidase mimetics. This method has succeeded in detecting glucose in urine.Part 5:rGO-CoFe2O4 hybrids were prepared by a one-pot solvothermal synthesis method. For the first time, we systematically studied the intrinsic peroxidase, catalase and oxidase mimetics of rGO-CoFe2O4 hybrids. Various factors influencing on the catalytic activity of rGO-CoFe2O4 were investigated, and its catalytic reaction kinetics and its mechanism were discussed. The research results illustrated that the catalytic behavior of rGO-CoFe2O4 nanozyme was in line with Michaelis-Menten equation. And the catalytic mechanism of rGO-CoFe2O4 nanozyme followed a ping-pong mechanism. Furthermore, a colorimetric method for the detection of glucose was developed based on rGO-CoFe2O4 hybrids as peroxidase mimetics.Part 6:Conclusion...