A novel synthetic strategy for covalently bonding dendrimers to ordered mesoporous silica: potential drug delivery applications

The surface of mesoporous silica SBA-15 has been functionalized by the post-synthesis method with new amine dendritic precursors. The synthesis and structural characterization of the new precursors based on poly(propyleneimine) dendrimers have been carried out. Some of the peripheral amine groups of the starting dendrimers can be used to introduce a spacer unit with a terminal T-silyl function. Therefore, these precursors can later be bonded to the SBA-15 by means of covalent linkages with the silanol groups on the surface of the mesoporous silica. The novel organic-inorganic hybrid materials have been characterized by means of powder XRD, N-2 adsorption, solid state MAS NMR, thermogravimetric and zeta potential measurements, proving the ordered mesoporous structures and the successful covalent anchoring of the dendritic macromolecules to the SBA-15. This synthetic route represents an alternative to the preparation of amine functionalized SBA-15 with a highly dense population of amine groups, avoiding several reaction steps of the iterative procedure usually followed for dendritic growth inside the channels of mesoporous materials. The effects of dendrimer generation and degree of surface functionalization on the confinement and release of ibuprofen, chosen as a model drug, evidence the capability of these hybrid materials to act as controlled delivery systems.