Magnetic Fe₃O₄/Gold Nanoclusters/Mesoporous Silica Drug Delivery System

Multi-functional drug controlled delivery system takes advantages of a few of functions such as targeting drug release,fluorescent imaging drug controlled release and so on,which is intensive focused by the researchers.In this article,we fabricated a magnetic targeting/fluorescent multiple functional controlled release system that the mesoporous silica was used as drug loading support,combining with the magnetic targeting of Fe₃O₄ nanoparticles and the fluorescent imaging of Au nanoclusters?AuNCs?.This system can be induced to the lesion site under external magnetic field,and images the lesion site at the same time.This research was carried out as follows:1.Two kinds of different Fe₃O₄ nanoparticles with different sizes were synthesized by co-precipitation and solvothermal method respectively,and their properties were compared.The results showed that the Fe₃O₄ prepared by co-precipitation method and solvothermal method were both superparamagnetic,and their saturation magnetisms were 65 emu/g and 71 emu/g respectively.The average particle size of Fe₃O₄ nanoparticles prepared by co-precipitation method was 14 nm,which were aggregated significantly.The average particle size of Fe₃O₄ prepared by the method of solvent thermal method was 200 nm,which were well dispersed.The structure of Fe₃O₄ nanoparticles prepared by solvent thermal method was of interspaces inside,with a secondary structure which was composed of small Fe₃O₄ particles with size at 20-30 nm.2.Mesoporous silica was in situ coated on the surface of Fe₃O₄ nanoparticles prepared by co-precipitation and solvothermal method respectively to form Fe₃O₄@mSiO₂ nanoparticles.The results showed that the Fe₃O₄@mSi O2 nanoparticles based on co-precipitated magnetic nanoparticles formed disperse-set structure that the Fe₃O₄ nanoperticles were dispersed in the mesoporous silica framework The disperse-set Fe₃O₄@mSiO₂ particles were irregular ellipsoid and the size distribution was uneven from 50-300 nm The Fe₃O₄@mSiO₂ nanoparticles based on magnetic nanoparticles prepared solvothermal method formed core-shell structure that Fe₃O₄ nanoparticles were the cores coated with mesoporous silica shells.The size distribution of core-shell Fe₃O₄@mSiO₂ particles was concentrated at about 285 nm.The saturation magnetism of core-shell Fe₃O₄@mSi O2 nanoparticles was 38 emu/g,and that of the disperse-set Fe₃O₄@mSiO₂ nanoparticles was 11.5emu/g,which was much weaker than that of the former.The surfaces of the core-shell Fe₃O₄@mSiO₂ nanoparticles were modified by amino.According to the results,we choosed the core-shell Fe₃O₄@mSi O2 nanoparticles as drug loading supports in the next experiments.3.AuNCs were prepared by the green and mild method and the Fe₃O₄@mSiO₂-AuNCs composite nanoparticles were prepared by AuNCs linked to the surface of Fe₃O₄@Si O2 nanoparticles covalently.The results showed that the AuNCs were of strong red fluorescence under ultraviolet light and the maximum fluorescence emission peak was 650 nm.The Fe₃O₄@mSiO₂-AuNCs composite nanoparticles were of dark red fluorescence and the fluorescence emission peak was at 620 nm.The saturation magnetism of the Fe₃O₄@mSiO₂-AuNCs particles was 24 emu/g,and the particle size was about 300 nm.The pore diameter of the Fe₃O₄@mSiO₂-AuNCs particles was 3 nm?5 nm and 8 nm,with the specific surface area of 27.822 m²/g.4.The drug loading and releasing properties of Fe₃O₄@mSiO₂-AuNCs multifunctional nanoparticles were investigated using Ibuprofen as drug model.The effects of different times,different temperatures and different pH values on the drug adsorption of Fe₃O₄@mSiO₂-AuNCs were discussed.The results showed that the drug loading capacity increased accompanying the increase of loading time,and then decreased while the loading time reached 70 min,with a most.For loading temperature,the drug loading capacity increased at first and then decreased with the increase of loading temperature,and the optimized temperature was 40 °C.The drug loading capacity decreased with the increase of pH,and that reached maximal when the pH was 7.4.Under the optimized conditions,the maximal drug loading capacity could reach 54.83 mg/g.This paper also discussed the release properties of Fe₃O₄@mSiO₂-AuNCs under different pH values.The results showed that the optimized p H value of drug release was 7.4 and the cumulative drug releasing percentage reached 90% within 24 hours.