Hollow spheres with α-cyclodextrin nanotube assembled shells

Monodisperse hollow spheres with radially oriented α-cyclodextrin nanotube assembled shells were synthesized using PEG-grafted silica as templates. (3-Aminopropyl)triethoxysilane-modified silica core was synthesized by the Stöber method and subsequently grafted with mPEG-succinimidyl carbonate through amide linkage. Maleic anhydride modified α-cyclodextrins were threaded onto the grafted-PEG chains, forming tubular polypseudorotaxanes. Adjacent polypseudorotaxanes were immobilized by crosslinking. After the extraction of the inner silica template by etching and the included PEG template by heating, hollow spheres of uniform size with α-CD nanotube assembled shells were prepared. The products were composed of intact and dispersed hollow spheres with diameter of about 50 nm, possessed uniform shell thickness of 12 nm as confirmed by transmission electron microscopy (TEM) measurement. α-CD nanotubes have a function of molecular recognization with PEG, which may endow the hollow nanospheres as promising target drug delivery vehicles by forming inclusion complexes with end-functionalized PEG.