Preparation And Characterization Of Novel Organic-inorganic Drug Loaded Microcapsules

In this paper, functional microcapsules loaded with drug was fabricated by the layer-by-layer self-assembly(LbL) or in-situ coacervation. The advantage of LbL assembly is that the structure, size, thickness and composition of the polyelectrolyte microcapsules are easy to be controlled. In this study, inorganic clay nanoparticles and magnetic particles were used in the LbL assembly to fabricate microcapsules with special functions. In another part of this study, in-situ coacervation was selected to prepare microcapsules in order to simplify the complicated preparation process of LbL assembly,.The organic-inorganic hybrid microcapsules were synthesized successfully by introduce inorganic particles during LbL assembly in order to improve the properties of the microcapsules. Two kinds of organic-inorganic hybrid microcapsules were made introducing laponite or Fe3O4 into microcapsules and using polystyrene(PS) microspheres as template. The laponite or Fe3O4 nanoparticles distributed uniformly in the wall of microcapsule. For the microcapsules doped with laponite, the amount of DOX loaded was 195.1μg/(mg microcapsules). The time of releasing 50% loaded DOX from microcapsules was extended compared to pure polyelectrolyte microcapsules, which means layered laponite particles could delay the drug release. For the microcapsules doped with Fe3O4, the amount of DOX loaded was 180.3μg/(mg microcapsules). The microcapsules showed significant magnetic orientation in the permanent magnetic field. The DOX loaded magnetic microcapsules showed magnetic response in the alternating magnetic field, in which the durg burst released probably because of magnetocaloric effect making the structure of polyelectrolyte membrane changed.For the purpose of improving the drug releasing property, core-shell drug carrier was prepared by using CaCO3 microspheres with rough surface and pore structure as templates. Ibuprofen(IBU) were loaded inside the pores of CaCO3, which were then coated with polyelectrolyte and laponite on the surface. The amount of IBU loaded in the CaCO3 was 28.487mg/g. The core-shell microspheres doped with laponite had better durg release effect compared to normal core-shell microspheres without inorganic particles.In-situ coacervation was used to simplify the preparation process of microcapsules, in which CaCO3 microspheres doped with PSS were using as templates. PDDA was then adsorbed on the templates, which followed by dissolving CaCO3 in EDTA. The microcapsules was obtained by coacervation of PDDA and PSS during the dissolvation of CaCO3. Zeta potential analysis showed that the outer layer of microcapsules is negatively charged. The more the PSS involved in the CaCO3, the thicker the membrane is. When the PDDA was added in the EDTA solution, the zeta potential of outer layer of microcapsules conversed to positive, which means the PDDA assembled on the outer layer of microcapsules. DOX loading amount of the positive microcapsules could be 300μg/(mg microcapsules) When the incubating temperature is 37℃and the initial concentration of drug is 100μg/ml. The drug release of the thicker microcapsules showed better sustained-release.