Fabrication, Modification and Drug Delivery Application of Hollow Magnetic Particles
|Keywords||Fe3O4 hollow structure MFe2O4 （M=Mn, Zn, Co） structure-directing reagent solvothermal route modification Fe3O4@PMMA magnetic composites drug delivery|
Nanotechnology has witnessed a rapid development era; as we all know, many kinds of nanoparticles could applied in biomedical areas after surface functionalization. Among those nanoparticles applied in drug delivery, the magnetic hollow nanoparticles have attracted widespread interest not only owing to their fascinating magnetic properties but also owing to their enlarged interiors space. Considering the above facts, our research focused on the preparation of thermosensitive & magnetic nanocomposites and application in drug delivery, and the thesis findings consist of the following results:1. First of all, hollow monodisperse magnetite particles were prepared with tunable size and structure by employing ferric chloride as the only ion resource and ethylene glycol as solvent in the co-presence of NH4HCO3 and NH4Ac as the synergistic structure-directing reagent. And then, a series of ferrite spinel MFe2O4 （M=Mn, Co, Zn） particles were further prepared though similar solvothermal route. The preparation factors were investigated in the synthesis process. Among which, the MnFe2O4 and CoFe2O4 particles were prepared by individually employing NH4HCO3 as single structure-directing reagent and PVP as assistant reagent. All the factors that affect the morphology and property were investigated. The particles were characterized and proved some results in detail as follows:（1） In our system, NH4HCO3 and NH4Ac concentration are crucial factors to the formation and transformation of the interior structure, size and morphology of final products because of their dual gas-bubbled generating effect. And the molar ratio of NH4HCO3 and NH4Ac, the reaction time are beneficial to obtain pore-hollow structure of final products with enlarged interior space. The molar ratio of NH4HCO3 and NH4Ac strongly influenced the morphology and size of magnetite particles, even deciding the kind of architecture of solid, hollow or porous to form. Particularly, ammonium ion molar concentration plays a significant role in controlling size and magnetic property for magnetite particles.（2） The MFe2O4 （M=Mn, Co, Zn） particles were further prepared by adding structure-directing reagents via solvothermal route. And both the hollow and solid structure particles appeared in the finally products if NH4HCO3 and NH4Ac was employed as structure-directing reagents. The molar ratio of NH4HCO3 and NH4Ac, the reaction time played key roles in controlling the size, morphology, structure, and constituents. As a result, highly monodisperse and uniform MFe2O4 particles were obtained by using NH4Ac only. The particles size was smaller than that of the Fe3O4 particles prepared under the parallel conditions. However, the Ms of the former was stronger than that of the latter.（3） Whether by using PVP or not, both the MFe2O4 series products were composed with a number of small and large particles as NH4HCO3 was applied as structure-directing reagents. In the growth process, the NH4HCO3 concentration plays a dominating role in controlling size, shape, composition and magnetic property. So did the calcination and calcinations temperature. As-prepared CoFe2O4 products by using NH4HCO3 in our solvothermal route presented a saturation magnetization （Ms=63.2 emu g-1） and a high coercive force （Hc=675.64 Oe） that may be excellently compatible in MRI application.2. After modification withγ-methyl-acryloyl trimethoxysilane （KH570）, the surface of hollow magnetite particles were grafted with temperature-sensitive polymer Methyl methacrylate （MMA）. The process of modification and grafting process conditions were investigated. And major results were detailed as follows:（1） First, the pH needs to be adjusted in the KH570 hydrolysis process. The hydrolysis effect at pH=3 is better than at pH=4, and the effect of hydrolysis for 4h at pH=3 is better than that for 3h.（2） The effect of pre-grafted particles for 6h is maximized in the process of pre-grafting. Comparablely, the Fourier Transform Infrared spectroscopy （FT-IR） peaks intensity of grafted for 6h is maximized, 7h is the second place, and 8h is the last. And the magnetic property of the grafted magnetic particles is weaker than that of un-grafted.3. The grafted-magnetic composites were investigated and tested in preliminary drug delivery, and then the responsiveness to the temperature and the drug loading was evaluated. The mainly results as follows:（1） The solution（after removal of the drug-loaded particles） UV-Vis absorption at 32℃maximized, 34℃took the second place, and 38 ℃minimized. However, the greater the absorbance is, the less the drug loading amount. Hence, the drug loading amount at 38℃is maximum.（2） Drug loading experiments were performed to evaluate the effect of grafted-magnetic composites with different grafting time. The results showed that the drug loading on magnetic composites grafting for 6h is minimum, for 8h maximum and for 7h the second place.