Preparation Of Functional Magnetic Microspheres

After being modified by functional groups, magnetic microspheres could be chemically coupled with cells, antigen and antibodies, which would be applied in disease diagnosis and treatment. In this paper, we used BSA as a model protein, and then explored the ability of chemical bonding BSA of various functional magnetic microspheres in order to lay the foundation for its further application in the biomedical field.Firstly, we prepared supermagnetic nanoparticles Fe₃O₄ by co-precipitation method, simple preparation in oil phase, and high-temperature solution phase reaction, respectively, which were characterized by TEM, XRD, VSM, and so on. The average size of Fe₃O₄ nanoparticles by co-precipitation method was 10-20nm in obvious aggregation, and its saturation magnetization was 52.17 emu/g; the average size of Fe₃O₄ nanoparticles by simple preparation in oil phase was 10-15nm, and its saturation magnetization was 56.19 emu/g; through high-temperature solution phase reaction, we could get monodisperse nanoparticles with controlled size from 4nm-18nm, and its saturation magnetization could reach 91.27 emu/g. Due to obvious advantages of Fe₃O₄ prepared by high-temperature solution phase reaction, we studied its properties and application in the next section.We used two different methods to modify Fe₃O₄. The first one was reverse phase evaporation, which coated Fe₃O₄ with CTS-Lys. The characterizations such as TEM,VSM,IR indicated that the average size of CTS-Lys magnetic microspheres was 90-100nm with better disperse, and its saturation magnetization was 43.09 emu/g with supermagnetic property. Adsorption of bovine serum albumin (BSA) on magnetic microspheres was carried out in the presence of carbodiimide EDC, as a coupling agent. From UV spectrometer, we could get that 0.9175mg BSA was coupled on 1 mg magnetic microspheres, and its coupling degree was 91.75%.We used SiO2 to coat Fe₃O₄ nanoparticles through reverse microemulsion, which were modified by silane coupling agent in order to provide–NH₂ and–SH functional groups. The characterizations such as TEM,VSM,IR indicated that the average size of SiO₂ magnetic microspheres was 20-50nm with monodierperse, and its saturation magnetization was 29.87 and 28.45 emu/g, respectively. From UV spectrometer, we could get that 0.409mg BSA was coupled on 1 mg magnetic microspheres–NH2 group, as well as 0.364mg BSA was coupled on 1 mg magnetic microspheres–SH group. And their coupling degrees were 40.90% and 36.41%.To sum up, the average size of CTS-Lys magnetic microspheres was larger and they could couple more BSA; and SiO2 magnetic microspheres were monodisperse and controlled size, but they coupled fewer BSA. They had their own advantages, which provided important base for their applications in the biomedical field.