Self-assambly And Properties Of Magnetic/Fluorescent Multifunctional Nanocapsules

Cancer has become one of the severe diseases that threaten the physical health of humans.Due to the unique chemical and physical properties,the emerging functional nanaomaterials are promsing for the effective cancer treatments since they can overcome several nonnegligible drawbacks of traditional cancer therapies,like side effects and long treatment cycle.As for cancer diagnosis,transition metal doped quantum dots with narrow emission spectra,high quantum yield and good chemical resistance can be excellent fluorescent agents in fluorescent imaging of cancer.Generally,these functional nanoparticles are synthesized from oil phase,which contributes to the hydrophobicity and the excellent fluorescent properties,magnetic properties or photothermal properties of functional nanoparticles.However,the poor biocompability of these hydrophobic nanoparticles becomes a barrier for their biomedical applications.In order to improve the biocompatility,various methods have been proposed for the surface modification of these functional naonparticles,making them become soluble in water.Micelle-templated method,which is based on the formation of silica nanocapsules,is an effective way to encapsulate hydrophobic nanoparticles into the core of nanocapsules and consequently ensures the improvement of biocompability and minimal impact on the properties for the functional nanoparticles.Besides,the synthesis condition of this method is relatively mild and the synthesized silica nanocapsules exhibit good stability in water phase.In this paper,micelle-templated method was adopted to encapsulate hydrophobic quantum dots,iron oxide nanoparticles and anti-cancer drug paclitaxel into the silica nanocapsules.Targeted molecules（folic acid）were then conjugated to the surface of the hybrid nanocapsules.Thus,a kind of multifunctional naocapsules which can act as a theranostic agent with targeting property were obtained.The main content and results of this paper are summarized as follows:（1）The core-shell fluorescent quantum dots ZnSe:Mn/ZnS was synthesized by a modified high boiling organic solvent method,which were then encapsulated into the silica nanocapsules by F127 micelle-templated method to obtain QDs/PTX hybrid nanocapsules.Besides,the morphology of the hybrid nanocapsules was adjusted by changing the reaction parameters.It shows that the QDs concentration has remarkable influences on the encapsulation behavior,size and fluorescent properties of the hybrid nanocapsules.The silica precursor（TMOS）concentration has an effect on the silica thickness,while shows minimal decreasing effect on the fluorescent properties.Besides,the hybrid nanocapsules exhibits good temperature stability in the temperature range from 19℃to 49℃.The water solubility of PTX was dramatically improved by the nanocapsules.And PTX can be sustainedly released from the nanocapsules.（2）The folic acid-conjugated nanocapsules were synthesized through the reaction between the amino groups and NHS-folate.It reveals that the conjugation efficiency increases with the increase of NHS-folate concentration.The conjugation efficiency reaches 45%when the mole ratio between amino groups and NHS-folate is 0.5.The in vitro cytotoxicity of the nanocapsules for MCF-8 cells was conducted by CCK-8 assay.It was found that the blank nanocapsules and QDs nanocapsules show low cytotoxicity even under high nanocapsules concentration,while the PTX-loaded nanocapsules present cell-killing ability towards MCF-7cells.And the viability of MCF-7 cells decreases with the concentration increase of the PTX nanocapsules.For the folic acid-conjugated PTX nanocapsules,the cancer cell killing ability is stronger due to the targeting effect.The in vitro targeting fluorescent property of the folic acid-conjugated nanocapsules was studied by the fluorescent microscope.There was a significant increase in the intensity of red fluorescence observed in the confocal images of MCF-7 cells treated with folic acid-conjugated QDs nanocapsules as compared to those QDs nanocapsules without folate conjugation.（3）Hydrophobic Fe₃O₄ nanoparticles were synthesized by the high temperature decomposition method,following by the synthesis of Fe₃O₄ nanocapsules.The encapsulation remarkably improved the water solubility of Fe₃O₄ nanoparticles.It shows that Fe₃O₄nanoparticles was superparamagnetic.By changing the concentration of Fe₃O₄ nanoparticles and TMOS,the morphology and encapsulation behavior of magnetic nanocapsules can be tuned.