The Application Of Functionalized Magnetic Nanoparticles

Due to the high surface-to-volume ratio, relatively great saturation magnetization values and easily surface functionalization of the nagnetic nanoparticle, it has been widely used in the immobilization of proteins and enzymes, drug delivery and targeting, cell separation, bioimaging and so on.This dissertation mainly focused on the design of novel analytic methods, which combining the magnetic silica nanoparticles, mimetic enzyme (hemin) and the receptor molecules. And then, these novel methods can be used in real sample detection. This dissertation consists of five chapters.In chapter one, the progress and development of nano-biomaterials were introduced. And it briefly summaries how to synthesize and apply the silica nanoparticles and magnetic nanoparticles, especially describes the application of magnetic composite nanoparticles in the biological and catalytic fields. In addition, the bases, objectives and contents for designing this thesis were also presented.In chapter two, synthesis and application of magnetite-hemin/Silica nanoparticles in the analytical field were reported. In this chapter, a method for coating magnetite and mimetic enzyme with amorphous silica to form a novel magnetic composite catalyst has been developed by combining reverse microemulsion and Sober method. By using the magnetite-hemin/Silica nanoparticles as catalysis, which can catalyze the oxidation reaction of p-hydroxyphenyl acetic acid by hydrogen peroxide, a novel fluorimetric method was proposed for the detection of trace amount of hydrogen peroxide. This method is sensitive and reliable, with a detection limit of 7.3 nmol/L in the determination of hydrogen peroxide.In chapter three, a magnetic-mimetic enzyme fluorescence immunoassay method for antigen detection has been developed by taking advantage of a magnetic separation process and the amplification feature of hemin label. This method is based on twice amplified fluorescence signal: the signal is firstly amplified due to the ultrasmall size and the high surface-to-volume ratio of the silica-coated magnetite nanoparticles, which enable the nanoparticles to carry much more antibodies. Then mimetic enzyme (hemin) as a labeling reagent which catalyzes the reaction of p-hydroxyphenyl acetic acid and H₂O₂ can further amplify fluorescence signal. The detection limit was 9.8 ng/mL for the determination of human IgG, which is comparable to or better than other immuoassay formats. Besides this, a satisfactory result was acquired by using this proposed method for the analysis of real samples.Chapter four was about the preliminary investigation of the absorption and fluorescence spectral properties of the synthesized sensor (3-pyridyl-4-amino-5-mercapto-1,2,4-triazole) and its response to metal ions in NH₄OH-NH₄Cl buffer (pH 11). Moreover, it is fully anticipated that this sensor can be combined with magnetic nanoparticles to apply in the detection of silver ion in the wastewater.In chapter five, the final part of the dissertation, the prospect of this research was discussed.