Zwitterionic functionalised mesoporous silica nanoparticles for alendronate release

Novel zwitterionic surface modified mesoporous silica nanoparticles (MSNs) were prepared for alendronate release. Phospholipid moieties were generated by the ring-opening reaction of 2-chloro-2-oxo-1,3,2-dioxaphospholane (COP) subsequent to (3-bromopropyl) trimethoxysilane immobilisation. Studies confirmed the successful introduction of phosphorylcholine (PC) groups at the surface without sacrificing the original structure of MCM41. The adsorption of bovine serum albumin was reduced significantly by the introduction of PC groups onto MSN. Alendronate drug molecules were loaded effectively into MSN-PC samples under acidic conditions (pH 4). The drug-loaded MSN-PC showed the sustained release of alendronate molecules under physiological pH conditions (pH 7.4). A partial negative surface charge was generated on MSN-PC at this pH by the deprotonation of silanol groups, and the electrostatic interaction between the phosphoryl choline group and alendronate molecule was disturbed, which triggered the sustained release of the loaded molecules.