Supramolecular Design of Polyrotaxanes as Advanced Nano-Biomaterials

Supramolecular architectures have been extensively studied in the last decade [1]. In particular, polyrotaxanes have been much interested as a novel class of molecular assemblies, in which cyclic compounds are threaded onto a linear polymeric chain capped with bulky end-groups. We have systematically studied a variety of biodegradable polyrotaxanes consisting of many cyclodextrins such as α-cyclodextrins (α-CDs) and a polyether such as poly(ethylene glycol) (PEG) and their hydrogels aiming at carriers for drug delivery or scaffolds for tissue regeneration. For instance, hydrolyzable polyrotaxane hydrogels have been designed as a scaffold for cartilage regeneration [2]. Here the hydrolysis of our designed polyrotaxane hydrogels is well controlled by inclusion complexation of ester groups located at the terminal of the PEG in the polyrotaxanes, and the time to complete hydrogel erosion varies from a few days to more than two year in spite of their highly swollen states in physiological conditions [3].