Controlled Release of Guest Molecules from Mesoporous Silica Particles Based on a pH-Responsive Polypseudorotaxane Motif

摘要

Cyclodextrins (CDs) have been a target of intensive research owing to unique structural, physical, and chemical properties.[1] In particular, their capability to form inclusion complexes with guest molecules would be the most interesting characteristics. Furthermore, inclusion complexes with various types of guest molecules could be reversibly dissociated by external stimuli.[1] These interesting features have provided a unique route to construct nanomachines by using CDs.[1] Several groups have reported on functional rotaxane systems based on cyclodextrin as a host. Recently, pH-responsive polypseudorotaxanes consisting of polyethyleneimine (PEI) and CDs were reported.[2]-[4] Furthermore, Lee et al. reported on the pH-dependent polypseudorotaxane formation of -CD with the triblock copolymer (PEI-b-PEG-b-PEI; PEG=poly(ethylene glycol)) where CDs undergo unique reversible complexation and decomplexation selectively with the PEI block through pH variation.[4] Therefore, we reasoned that the incorporation of this type of reversible pseudorotaxane onto the surface of mesoporous materials can create pH-responsive nanocarrier systems in which CDs play the role of a pH-responsive valve for pores of mesoporous materials.