Preparation & Application Of Magnetic Nano-Particles

As a new functional material, magnetic particles have been developed quickly in recent years. It's applications in immunoassay lead to a new idea for bioseparation and detection. The development of magnetic particles with functional unites was described in this paper.Fe₃O₄ nanoparticles were synthesized from an aqueous Fe (OH)2 suspension by oxidizing it with H₂O₂, the size of which can be controlled by adjusting the temperature, the concentration of the oxidation and pH of the solution. The reaction took place under the neutrality condition, and can produce particles with good magnetic properties and dispersity, which is profitable for the application of the magnetic particles on biomedical use. We produced Fe₃O₄/Au core-shell composite particles by means of reducing HAuCl4 with NaBH4 with good dispersity in water after magetic separation. The UV spectra showed the maximum absorption at the peak of 549nm, the character peak of nanogold, and the average diameter of the nano particle was about 30nm according to TEM image. The characteristic peak of Au was found in the XRD spectra of nano-composites, which demonstrated Fe₃O₄ nanoparticles were coated with layers of Au. The Fe₃O₄@Au nano-composites were equipped with the properties of gold nanoparticles and magnetic nanoparticles, which broadened the applications in the bio-medical field.We provided a new method of synthesizing Fe₃O₄/SiO₂ nanoparticles. The Fe₃O₄ nanoparticles first modified by KH560 to enhance the monodispersity in C2H5OH, and then treated with TEOS to prepare the Fe₃O₄/SiO₂ composites which were well dispersed and with uniform size around 25nm, of which the thickness of the shell is about 3nm. According to the TEM image, we successfully got the shell/core nano-particle structure and the saturation intensity is about 44.03emu/g. Because of the good dispersity in the water, the nano magnetic composites can be better used in bio-medical field.Last but not the least, an immunochromatographic strip for the simple and rapid detection ofα-fetoprotein(AFP) is developed with the technique of the anti-AFP monoclonal antibodies labeled with nano-magnetic particles. The factors influencing the label-process as well as the sensitivity and the key process of the strip making are studied. The prepared strips can show the detection of the cut-off value for positive result was 20μg/L AFP within ten minutes. Compared with the gold immunochromatography, the new technique can reduce the cost notably and optimize the whole process.