Study On Multiresponsive Microcapsules And Their Targeted Drug Release Properties

In this study, a novel targeted carrier of drug release was fabricated by the layer-by-layer self-assembly. Natural polyelectrolytes chitosan and sodium alginate, magnetic nanoscale Fe₃O₄ particles, and lipid with negative charge or amphipathicity were adsorbed onto monodispersed colloids and drug microcrystal via self-assembly. A type of pH-, thermo- or magnetic-sensitive microcapsule was obtained.Chitosan and sodium alginate have been alternately adsorbed onto polystyrene(PS) microparticles by the layer-by-layer self-assembly. Hollow microcapsules with a diameter of 2-3μm were obtained, after the removal of the templates. We investigate the drug loading performance of the microcapsule, in the model of water-soluble drug doxorubicin hydrochloride (DOX). The drug loading amount can vary through changing drug feeding concentrations, salt concentrations, pH, temperature and layer number. The drug loading amount could reach to 224μg per 1mg microcapsules. The drug release rate is faster in low pH value, which demonstrates pH-sensitivity of the microcapsules.CaCO₃ microparticles were used as template in self-assembly, to obtain better biocompatible microcapsule. The micron-sized CaCO₃ particles were synthesized in the existence of carboxylmethyl cellulose (CMC) .The diameter of the particles differed from 2μm to 8μm with the different addition. The same components were adsorbed onto CaCO₃ particles, following with core removal. The drug loading amount can vary through changing salt concentrations, pH, temperature and layer number. The drug loading amount could reach to 312μg per 1mg microcapsules, which larger than that of the microcapsules made by PS. In the drug release system, the drug released fraction reached to 60% after 14 hours, which larger than that of the microcapsules made by PS.Ibuprofen (IBU) microparticles were encapsulated by chitosan and sodium alginate through layer-by-layer self-assembly and the core-shell particles were obtained. Because of the different dissolvability in pH1.0 HCl solution and pH7.4 PBS solution, the former dissolving rate of core-shell particles is faster. The encapsulation of IBU do not effect so much in delaying the burst release of IBU.The 45% DOX releasing fraction from microcapsules changed from 7h (without lipid layers) to 9h, 12h, 11h, after self-assembly with liposome of different lipid components (DPPC, DPPA, 90%DPPC-10%DPPA, respectively). Lipid layers enhanced the targeting of microcapsules as drag carriers.Magnetic microcapsules were fabricated by adsorbing Fe₃O₄ nanoparticles, which gathered to the permanent magnet. Precise targeting could implement by the magnetic microcapsules via magnetic field.