Preparation, Characterization And Primary Application Of Fluorescent Magnetic Nano-microspheres

In the present paper, we systematically study the preparation, characterization and primary application of the fluorescent magnetic nano-microspheres, which involved the preparation and characterization of hydrophilic Fe3O4 magnetic fluid, the preparation and characterization of rare earth coordinated fluorescent magnetic nano-microspheres Fe3O4@PHEMA-RE(RE=Sm,Eu,Tb,Dy), the synthesis of Dy:Fe3O4@PHEMA-Tb doped with Dy core-shell structures and its primary application in protein labeling and as drug carriers. Concretely, we have achieved several innovative achievements as follows:Firstly, we improved the chemical co-precipitation method and mixed Fe3+ with Fe2+ in proportion as 1.5:1 (n(Fe3+)/n(Fe2+)). We used NH3·H2O as precipitator rather than NaOH and PEG-4000 with high hydrophility and compatibility as surfactant to form stable magnetic fluid to avoid Na+ being coated with Fe3O4. As the reaction temperature was controlled at 35-40℃and PH at 6-8, we got the best product. Depending on the single element preliminary experiment and three levels-four elements orthogonal experiment, we decided the main parameters that affected the performance of the magnetic fluid in preparation, discussed the influences that the mole ratio of Fe3+ and Fe2+(n(Fe3+)/n(Fe2+)), the kinds and concentrations of precipitant and surfactant, reaction temperature, stirring velocity, ultrasonic dispersing had on formation of the magnetic fluid respectively. Besides, we simplified the preparation process, optimized the preparation conditions and conducted the characterization work of the product. As a result, we got magnetic nano-microspheres with a magnetism content to be 22.3%, average size 22.3 nm, polydispersity index 0.26, specific saturation magnetization 60.2 emu/g and without coercive force and remanent magnetism. The product had superparamagnetism.Secondly, we synthesized the magnetic PHEME microspheres using the photochemical in situ polymerization method. In the experiment, we used HEMA as monomer, MBA as crosslinking agent and carried it out without any initiator and emulsifier in the hydrophilic Fe3O4 magnetic fluid. Meanwhile, we devised a three levels-four elements orthogonal experiment to decide the best process conditions for Fe3O4@PHEMA and discussed the influences of the mole ratio of magnetic fluid and monomer, the mole ratio of crosslinking agent and monomer, illumination time, reaction temperature and stirring velocity had on the magnetic microspheres respectively. Based on the luminescence-prone property of rare earth ion, after its coordination reaction with monomer we got the dual functional superparamagnetic fluorescent magnetic nano-microspheres with an average size between 20nm and 30nm and a high dispersivity. The possible mechanisms for the chain increase caused by the generation of free radicals and the coordination reaction between rare earth ions and monomers were deeply studied.To improve the magnetic responsibility of this fluorescent magnetic microspheres in application, we doped Dy3+ whose magnetic moment is higher than iron and then prepared the dysprosium-ferrite magnetic fluid successfully. The addition of Dy changed the distribution of the positive charged magnetic ion, enhanced the magnetism of the ferrite and thus guaranteed the acquisition of the superparamagnetic fluorescent magnetic nano-microspheres with smaller range of size, more even distribution, higher specific saturation magnetization and lower coercive force. Through the comparison and discussion about the fluorescent magnetic microspheres with and without Dy3+, we got satisfying results and thus expanded its application space in biological and medical areas.At the meantime, we discussed the primary application of the fluorescent magnetic microspheres in fluorescence labeling and as targeted drug carriers. As clinical diagnosis and treatment are two indispensable steps in medical field, labeling BSA with fluorescent magnetic microspheres offered a theoretical basis for clinical diagnosis and the ability to be targeted drugs carriers that the fluorescent magnetic microspheres had provided a reference in method for clinical treatment.Rare earth ions in the fluorescent magnetic microspheres have some characteristics like containing several fluorescent properties, a high luminescence efficiency, a long life span of fluorescence and a long Stock’s displacement. These characteristics were used to mix rare earth Tb3+ with a certain dose of magnetic microspheres Dy:Fe3O4@PHEMA and BSA to synthesize a kind of fluorescent magnetic protein microspheres. Depending on the Infrared Spectrum, we discussed the structure of macromolecular polymer on the surface of the microspheres. And the Fluorescence Spectrum indicated that compared with Dy:Fe3O4@PHEMA, the addition of BSA increased the magnetic microspheres’fluorescence significantly and the increase of fluorescence intensity was in linear relationship with the concentration of BSA in a certain range. Besides, we successfully conducted the fluorescent labeling to the magnetic microspheres under a certain PH. Therefore, it is a new way which has a high sensitivity and more alternative in labeling BSA that the fluorescent magnetic nano-microspheres Dy:Fe3O4@PHEMA-Tb is used as fluorescent probe. This simple and quick way with advantages of no toxicity and no radioactivity is sure to be a novel probe used in clinical BSA examination.Because the fluorescent magnetic microspheres doped with Dy3+ had magnetic ferrite core with high magnetic responsibility, we prepared fluorescent magnetic microspheres with drugs which had a high drug loading capacity and embedding ratio when Dy:Fe3O4@PHEMA, Tb3+, and anti-tumor broad-spectrum medicine MMC reacted under a certain condition. The result show that PH has a great effect on the preparation of the fluorescent magnetic microspheres with drugs, as in vitro, they would have a great difference in release ratio under different PH and has a very remarkable magnetic responsibility. To sum up, the way we used here is simple, having a satisfying drug loading capacity as well as relaxation ability and therefore can be used as drug carrier. It is a good way in gastroenteric tumor treatment.Every sample we prepared was overall characterized using photon correlation spectroscopy, infrared spectroscopy, ultraviolet spectroscopy, scanning electron microscope, fluorescence spectroscopy, vibration sample magnetometer, thermogravimetry analysis and so on. It is a must as well that understanding the fluorescent magnetic nano-microspheres’ structure, composition, morphology, magnetic properties and fluorescent properties. So it will lay a foundation in method for the fluorescent nano-microspheres functioning as protein labels and drug carriers.