Research Progress on the Inclusion Mechanism of Cyclodextrin-Based Supramolecular Self-Assemblies

Abstract

Cyclodextrin, which has a unique “outer hydrophilic and inner hydrophobic” structure, can be used as an excellent carrier to protect volatile bioactive compounds that are susceptible to oxidative degradation for improved solubility, stability, and bioavailability. In this paper, we summarize the structures and properties of cyclodextrins and elucidate their inclusion mechanism with respect to the interactions between the host cyclodextrins and guest molecules and the factors influencing them including the inclusion reaction between cyclodextrin monomers and guests, the self-assembly behavior of cyclodextrin monomers, and the inclusion mechanism between the supramolecular system formed by this self-assembly behavior and guest molecules. Then, the mechanism for the interface stability of cyclodextrins in the presence and absence of surfactants and the mechanism by which composite emulsifiers formed from the self-assembly of cyclodextrins with a surfactant stabilize guests. Finally, the release mechanism and the kinetic models of sustained release of guest molecules from inclusion complexes of cyclodextrins as well as the factors affecting them are elucidated, and future research prospects of cyclodextrins in the supramolecular field are discussed in order to provide a reference for follow-up research.

Keywords

• cyclodextrin; self-assembly; inclusion mechanism; interface stability mechanism; surfactant; release mechanism