Synthesis And Characterization Of Mesoporous Silica-based Multifunctional Nanocomposites

Owe to its unique pore structure, large surface area and excellent biocompatibility, mesoporous silica materials have been wildly used in the field of adsorption and durg delivery. However, the function of pure mesoporous silica materials is singler and could not meet the some special demands, such as controlled drug release, selective adsorption and so on, limiting its application in our life. So, developing mesoporous silica-based multifunctional nanocomposites has attacted much attention in the field of biological and environmental application. In this thesis, we fabricated some mesoporous silica-based multifunctional nanocomposites combining with inorganic nanoparticles, organic moleculars and functional polymer. These multifunctional nanocomposites not only could be used for controlled drug release to enhance the bioavailability, but also could be used for diagnosis and tracking the behavior of nanocomposites in vivo due to the fluorescence and magnetism. Moreover, the selective adsorption-desorption properties make the nanocomposites a potential material in the environmental remediation.（1） Novel multifunctional nanocomposites were successfully prepared for controlled release of anti-cancer drug and magnetic resonance imaging（MRI） via a simple self-assembly process. In this strategy, superparamagnetic iron oxide nanoparticles（SPIONPs） were “ fixed” between the hydrophobic segment of the pH-sensitive amphiphilic polymer（HAMAFA-b-DBAM） and surface of hollow mesoporous silica nanoparticles（HMS） which modified by long-chain hydrocarbon octadecyltrimehtoxysilane（C18）. Since the amphiphilic polymer was conjugated with a folic acid（FA） group, the nanocomposites could target the folic acid receptor（FR） over-expressed tumor cells efficiently. Moreover, high drug loading content was obtained simultaneously due to the hollow core of HMS. The loaded drug could release from HMS core triggered by the mildly acidic pH environment in the cancer cells due to the hydrolysis of the pH-sensitive polymer shell. The targeting process of the nanocomposites could be easily tracked by MRI due to the magnetism of the SPIONPs. Therefore, a nanocarrier with high drug-loading capacity and controlled drug release property for tumor diagnosis and therapy was obtained via the self-assembly of HMS core, magnetic Fe3O4 nanoparticles and targetable pH-sensitive polymer shell.（2） The core-shell nanocomposites based on photo-degradable polymer coated hollow mesoporous silica nanoparticles（HMS） was successfully prepared for targeted drug delivery and visible-light triggered release as well as fluorescence cell imaging. HMS nanoparticles were first modified by long-chain hydrocarbon octadecyltrimehtoxysilane（C18） and fluorescent agent Rhodamine B Isothiocyanate（RITC）, and then encapsulated by photodegradable amphiphilic copolymer via a self-assembly process. The obtained nanocarrier showed a high drug loading content due to the hollow core and mesopores of HMS and could target the folic acid receptor over-expressed tumor cells efficiently for conjugating folic acid（FA） in the amphiphilic polymer. And then the drug release could be triggered by irradiation of green light（500-540 nm） due to the photo-degradation of amphiphilic copolymer coated on HMS. Furthermore, the targeting drug delivery and controlled release processes could be tracked by fluorescence imaging for the doping of RITC on HMS. In vitro results suggested that a smart visible-light responsive drug delivery system was successfully prepared for potential application of cancer diagnosis and therapy.（3） The light-triggered controlled release of anticancer drugs accompanied with NIR-responsive photodynamic therapy was prepared via self-assembly. Firstly, Mn2+-doped upconversion nanoparticles（UCNPs） were coated with mesoporous silica shell and modified with photosensitizer（Chlorin e6） and long alky chains. And then the NIR light-responsive amphiphilic copolymer containing 9,10-dialkoxyanthracene groups was synthesized and then coated as the outermost layer. Upon the irradiation of 980 nm laser, the CCUCNPs@PM would absorb and then convert the NIR light to higher-energy visible red light（660 nm） by the UCNPs-based core, which could excite Chlorin e6（Ce-6） to produce singlet oxygen（1O2）. Then the 1O2-sensitive dialkoxyanthracene group in the amphiphilic copolymer would be degraded and detached from the surface of the CCUCNPs@PM, following with the controlled release of the pre-loaded drugs and the photodynamic therapy for cancer cells caused by the excess 1O2. Therefore, the NIR light-controlled chemotherapy and photodynamic therapy could be realized simultaneously by CCUCNPs@PM.Mesoporous silica-based nanocomposites were wildly used not only in the drug deliverry system, but also in the filed of enviromental application due to its large surface area and pore volume.（4） Hydrophilic molecularly imprinted microspheres（MIP@SiO₂） for adsorption of Water-soluble molecules in real aqueous samples were successfully synthesized. In this strategy, molecular imprinted polymer（MIP） was encapsulated in the hollow core of hollow mesoporous silica（HMS） particles via a ‘ship in a bottle’ process. Due to the HMS shell containing plenty of Si-OH groups, the as-prepared microspheres proved to be hydrophilic and could be well dispersed in water. On the other hand, the MIP encapsulated in HMS could specifically recognize the small molecule with good binding efficiency through mesoporous silica shell. MIP@SiO₂ provided excellent specific molecule-recognition ability via binding experiments in real aqueous solutions. Suggesting MIP@SiO₂ are highly promising alternatives to biological receptors with great potential in many analytical applications, such as environment, food, and clinical analyses and other areas.（5） Mycobacterium-based treatments have been widely exploited to remove soluble organic molecules from wastewater, but the process is slow when compared to adsorption and chemical treatment. To address this challenge, here we engineered bacteria cells with thermally responsive nanocomposites for the highly efficient removal and biodegradation of small molecules from water. The absorption-desorption properties of the thermally responsive nanocomposite under heating and cooling treatment enabled the capture and controlled release of soluble small molecules in water, leading to relatively high local concentration of molecules around the bacterial cell and consequently an accelerated biodegradation process.Functionalize the MSNs with inorganic nanoparticles, muleculars and polymer to prepare smart nanocomposites. The nanocomposites not only could be used as targeting drug delivery and controlled relesed, but also used as imaging agents for cancer diagnosis and tracing the drug carrier. Moreover, nanocomposites could be used to adsorb the contaminants selectively, and performed well in the application of enviormental remediation.