Amino modified core–shell mesoporous silica based layered double hydroxide (MS-LDH) for drug delivery

Abstract

A layered double hydroxide-mesoporous silica core–shell nanostructure ([email protected]2) with perpendicularly-oriented mesochannels was synthesised using a surfactant-directing method and modified with amine functionality for drug delivery applications. Mg/Al-layered double hydroxide (Mg/Al-LDH) materials with a disc-like morphology were synthesised and then coated with mesoporous silica (Mg/[email protected]2) via the functionalisation of (3-aminopropyl)triethoxysilane using a post-synthesis route (NH2-Mg/[email protected]2). The materials were characterised using a range of techniques. The Mg/[email protected]2 and NH2-Mg/[email protected]2 materials possessed a spherical morphology and good porosity. Ibuprofen (IBU) and ciprofloxacin (CIPRO) were loaded into the pore channels of the NH2-Mg/[email protected]2 and the release properties were examined at pH 4.0 and 7.4. The delayed release property exhibited by NH2-Mg/[email protected]2 was attributed to the strong interactions of the drug molecules with the surface amino functionality and the charged LDH surface. The release profile from NH2-Mg/[email protected]2 was also compared with that of the Mg/[email protected]2 system under identical conditions. The porosity and functionalisation of the mesoporous silica shell and the surface charge density of the layered structure of Mg/Al-LDH are the major reasons for the controlled release of the cargo molecules. Moreover, the favourable delay in drug release from both materials at pH 4 was attributed to the higher level of ionisation and dissolution than at pH 7.4.