| dc.description.abstract | Functionalization of drug carriers using engineered inorganic nanoparticles (NPs) is currently an important topic. Polyelectrolyte microcapsules, as one of potential drug delivery systems, can be facilely functionalized with various modifiers including inorganic NPs. In recent years, gold NPs, Fe3O4 and ZnO were incorporated into polyelectrolyte multilayers, forming polyelectrolyte/inorganic NPs composite capsules. Despite the fact that the physiochemical properties of these composite capsules were investigation by several scientific groups in the world, application of this special inorganic/organic composite capsules in drug delivery provides enormous amount of work to be done, such as encapsulation of small molecules. Except loading of cargos with different molecule weight, microcapsules used for drug delivery should also meet other constraints, which contains the controlled release of them via external triggering or irradiation that are harmless to living body. The main aim of this work is to design and synthesis of composite microcapsules with potential to seal small molecules and unique external triggering responsive properties. Different from incorporating pre-fabricated inorganic NPs into polyelectrolyte multilayers, NPs were synthesized and incorporated in one step in this study. Such method provides possibility to concrete soft polymer and rigid inorganic NPs into one integrity. Three different NPs, i.e. silica, TiO2 and fluorescent carbon dots (CDs) were chosen to functionalize polyelectrolyte layer-by-layer (LbL) microcapsules. The properties and applications of the formed composite capsules were studied in detail. The feasibility of incorporating in situ formed NPs into soft polyelectrolyte multilayers was demonstrated in this thesis. For silica coating, the formed polyelectrolyte/silica composite II shells showed a reduced permeability, strengthened mechanics and enhanced ultrasound sensitivity. They were able to seal small molecules inside the cavities and to prevent acid molecules going through the shells. As an example model, Rh-B molecules were in situ encapsulated inside and released by ultrasound treatment. The biocompatibility of silica coated capsules was proved by MTT assays. In addition, capsules composed of biodegradable polyelectrolytes and in situ coated silica NPs were investigated and the results demonstrated that they can be degraded in B50 cells. For TiO2 coating, the formed TiO2 NPs on the surface of the composite capsules showed a fiber-like morphology, and behaved as a UV absorber and an ultrasound enhancer, enabling the capsules to be dual-responsive to ultrasound and UV light. For CDs incorporation, they were introduced into polyelectrolyte multi-layered microcapsules by hydrothermal carbonization of dextran. The formed composite capsules were endowed with strong fluorescent signal and became detectable. The feasibilities to in situ encapsulate Rh-B inside the polyelectrolyte/CDs capsules and to break them via ultrasound treatment (20 kHz, 50 W) and NIR laser irradiation (840 nm) were demonstrated. | en_US |
