Synthesis And Surface Modification Of The Superparamagnetic Magnetite Nanoparticles And The Studies On Its Interaction With DNA

Part one: The preparation methods of nanosized magnetite particles such as precipitation and hydrothermal method are summarized, and its widely uses in the fields such as biotechnology was reported, for example, in bio-separation, immunoassays, and DNA immobilization. In this part, surface modification is also introduced as a new nano-technology. the modification methods, modification kinetics and the recent research in surface modifications of nanoparticles was reported. Part two: The amino-silane modified magnetite nanoparticles were synthesized by the coprecipitation and surface modification with 3-aminopropyl-triethoxysilane (APTTS). Characterized by TEM and UV-vis, the ultrafine APTTS/Fe3O4 nanospheres had well dispersion and stabilization in aqueous fluids, The superparamagnetic APTTS/Fe3O4 nanospheres with an average diameter of 10 nm were characterized significantly with functional group, as well as a maximized saturation magnetization of 63.54 emu/g, and the optimal surface modification molar ratio of APTTS to Fe3O4 was found to 4:1. Displaying functional group of –NH2, high saturation magnetization, the superparamagnetic APTTS-modified Fe₃O₄ NPs are of significance for magnetic applications in biomedicine. Part three: Adsorption of DNA on magnetic nanoparticles was carried out, the interaction between magnetite and DNA and kinetics of the adsorption process were studied. Fe3O4 nanoparticles were prepared by the chemical precipitation method and modified with 3-Aminopropyltriethoxysilane on the surface of magnetite NPs. Characterization of magnetic particles were carried out using transmission electron microscopy and a vibrating sample magnetometer. Fourier-transform infrared spectroscopy was used to confirm the attachment of DNA on magnetic particles. Effect of pH and salt concentrations were investigated on the adsorption process. The experiment results show the adsorption of DNA on magnetic particles was effected greatly by the pH and ionic strength. Adsorption kinetics were analyzed by a linear driving force mass-transfer model.