The Synthesis And Characterization Of Functional Magnetic Nanoparticles Used In Biomedical Applications

The research of magnetic nanoparticles is one of the foucs in the field of biomedical nanomaterials. Magnetic nanoparticles coated by different polymers or molecules could be used in different biomedical applications such as cell separation, magnetic resonance imaging contrast enhancement, tissue repair, immunoassay, hyperthermia and drug delivery, etc. In order to synthesize the functional magnetic nanoparticles that could arrived the requairs applied in biomedical fields, we respectively modified the surface of nanoparticles by polymers, PVA and PEG, which were nontoxicity, biodegradablity, and had good water-solubility and biocompatibility. Fe₃O₄/PVA and Fe₃O₄/PEG magnetic polymer microsphere prepared were characterized by FTIR,TEM,TG,DLS,ICP-MS and VSM. The specific content in this paper are as follows:Fe₃O₄ magnetic nanoparticles firstly were coated by PVA via hydrogen bond. After representation, We concluded that the contents of PVA coating on the surface of magnetic nanoparticles in Fe₃O₄/PVA complex was 7.4%; the water-solubility of coated nanoparticles had improved; the dispersivity had increased because that the electrostatic repulsive force between particles increased after modifyed. Because the size of the Fe₃O₄ magnetic nanoparticles used as the magnetic core was bigger and poor distributed, the magnetic polymer microsphere gained also had larger size and the dispersibity of it didn't arrived the prospective state. To synthesize good magnetic polymer microsphere, there must be magnetic core which has favorable properties. So we decided to make the experiment for preparing Fe₃O₄ magnetic nanoparticles that has small size, narrow distribution, good water-solubility and high magnetic responsive.We prepared Fe₃O₄ magnetic nanoparticles by coprecipitation method and the optimal concition was obtained through the orthogonal experiment. The results of characterization shew that the surface of synthetical magnetic nanoparticles adsorbed plenty of–OH functional groups which offered the nanoparticles good hydrophilcity and many surface electric charges; the particle size was uniform and the average diameter was only 11±3 nm; the hydrodynamic diameters was 168 nm and the distribution of size was narrow; Fe₃O₄ magnetic nanoparticles had high saturation magnetization and nearly superparamagnetic feature. In addition, the purity of nanoparticles was 99.9313% obtained by ICP-MS. Afer comparing the properties of synthetical magnetic nanoparticles with purchased, we conclued that it was successfully prepared that magnetic nanoparticles had small size, narrow distribution, good water-solubility and excellent magnetism.PEG was used as dressing agent for modified the surface of Fe₃O₄ magnetic nanoparticles by the method of incubation in water bath and ultrasonication in turns. The better condition was obtained through discussing the factor influenced the size of nanoparticles by DLS. It was found that PEG was combined on the surface of nanoparticles via Fe-O-Si covalent bond; coated nanoparticles had less surface electric charges but favorable dispersivity, the reason for that was discussed and analyzed by the theory about colloidal dispersion stability; the Fe content of complex was 63.467±2.82% and the purity of sample was 99.955%; VSM results shew the high saturation magnetization and better paramagnetic feature of Fe₃O₄/PEG nanoparticles.In short, we successfully prepared the Fe₃O₄ magnetic nanoparticles that had better performances. The modification of PEG improved the biocompatibility, dispersivity and water-solubility of nanoparticles. The magnetic nanoparticles protected by PEG polymer could escape the uptake of macrophage so as to prolong the time of blood circulation. It is clear that Fe₃O₄/PEG magnetic complex has attained the requairs for the biomedical application and can potentially used in biology separation, drug delivery and immunoassay.