Preparation Of Hydrotalcite-based Core-shell Materials For PH Resonsive Controlled Release

Stimuli responsive composite materials can provide a wide applicatio n in the drug release systems, and the research on the release materials has been remarkably attached to due to their promising potential. Stimuli-responsive composite materials can realize self-regulated controlled-release in response to the change of temperature, pH, magnetic field and special chemicals in external environment. In this thesis, focusing on the construction of p H-responsive drug-carriers, the pH stimuli-responsive hydrotalcite-based hollow mesoporous silica core-shell material was designed and prepared. At the same time, the controlled release properties of 5-fluorouracil（5-FU） were investigated, which including the following aspects.The MgAl-NO₃-LDH（LDH-NO₃） precursor was exfoliated in the formamide, and the exfoliated LDH nanosheets with irregular edges were verified by XRD and TEM methods. The 5-FU intercalated LDH（FU/LDH） was achieved through delamination/reassembling method with electrostatic interactions between exflolied LDH nanosheets and 5-FU. The in vitro release behavior of the FU/LDH was systematically studied. The release of 5-FU significantly depended on pH in environments, where the release rate increased with increasing the p H of the release medium. The 5-FU drug release kinetics was analyzed by fitting the release data, which was fitted with Bhaskar model indicating the intra-particle diffusion mechanism.The hollow mesoporous silica nanoparticles（HMS） were prepared by using CaCO₃ microspheres as hard templates, and then 5-FU molecular was immobilized in the HMS particles in order to gain the 5-FU-loaded particles（FU/HMS）. The pH-stimuli-responsive controlled release system was constructed by coating the exfoliated LDH nanosheets on the surface of the FU/HMS particles, where the LDH shell designed as a molecular switch. The morphology and structure of FU/HMS and FU/HMS@LDH were characterized by SEM、TEM、XRD、SAXD、BET/BJH、TG-DTG and UV-vis DRS analyses in order to manifest the surface functionalization of HMS particles. The controlled-release behavior of 5-FU molecules was investigated at different pH environments. The results showed that the FU/HMS@LDH material realized "zero premature release" at neutral condition and remarkable release at acidic conditions. The specific controlled release characteristics make the FU/HMS@LDH material to act as drug carriers in the organism realizing pH-responsive controlled release.