Effect of acetylation of biodegradable polyrotaxanes on its supramoleculardissociation via terminal ester hydrolysis

Acetylation of biodegradable polyrotaxanes was examined to estimate the eff ect on its supramolecular dissociation via terminal ester hydrolysis. The b iodegradable polyrotaxanes, in which many alpha-cyclodextrins (alpha-CD) ar e threaded onto a poly(ethylene glycol) chain capped with L-phenylalanine v ia ester linkages, were acetylated using acetic anhydride; alpha-CD release behavior was then characterized by in vitro hydrolysis. The degree of acet ylation was changed by the concentration of acetic anhydride and the reacti on time. The results of the in vitro hydrolysis indicate that the critical degree of acetylation to prolong supramolecular dissociation lies at around 30%. The terminal hydrolysis proceeded completely even with 100% of acetyl ation. These findings suggest that the hydrophobization of alpha-CDs in the polyrotaxane makes it possible to delay the time to complete the supramole cular dissociation. The hydrophobization of the polyrotaxane is of great im portance for designing implantable materials that maintain their supramolec ular structure until tissue regeneration with complete terminal hydrolysis.