With the development of materials science and pharmaceutics, the application of mesoporous silica nanoparticles with a gated switch in the field of drug delivery has attracted much attention in the past decades. Cyclodextrins (CD) as promising gated materials have become a new area of interest in recent years due to their properties of self-assembly and function of host-guest interaction. CD is one kind of extensively studied host molecules and the host-guest interactions with different guest molecules can respond to different signals, and thus can be applied as intelligent gated switches for smart drug carriers. Switchable gatekeepers based on CD hosts with different guest molecules (such as benzimidazole, azobenzene, and ferrocene) respond to different stimuli modes (such as pH, light, and redox) that change the host-guest interactions and trigger drug release. The different structural features, mechanisms of action, and potent applications of these switchable gatekeepers are discussed. In addition, some personal perspectives and challenge on this field are presented.

Spurred on by recent progress in nanotechnology and precision medicine, smart drug carriers are entering an entirely new era. Smart drug carriers have been widely studied in recent years as a result of their ability to control drug release under different microenvironments (such as pH, redox, and enzyme) in vivo. Host-guest interactions based on cyclodextrins have proven to be an efficient tool for fabricating smart drug carriers. Because of the application of host-guest interactions, many kinds of biological molecules or supramolecular building blocks can combine into an organic whole at the molecular level. In this review, the features, mechanisms of action, and potent applications of biological stimuli-responsive drug carriers based on cyclodextrins are discussed. In addition, some personal perspectives on this field are presented.

A novel β-cyclodextrin pendant polymer (ε-PL-CD), composed of poly(ε-lysine) (ε-PL) main chain and glycine-β-cyclodextrin (Gly-CD) side chains, was prepared by a simple two-step procedure. The ε-PL-CD was investigated as a drug carrier of hydrophobic drug scutellarin (SCU). The characterization and complexation mode of the SCU:ε-PL-CD were researched in both solution and solid state by means of photoluminescence spectroscopy, 1 H and 2D NMR, X-Ray powder diffraction (XRPD), thermal gravimetric analysis, Particle size and Zeta potential. The solubility test indicated that the solubilizing ability of SCU:ε-PL-CD was significantly improved compared with SCU:β-CD and free SCU. Besides, in vitro cell experiment, it was found that SCU:ε-PL-CD has a strong inhibitory effect on the growth and invasion of tumor cells. The present study provides useful information for ε-PL-CD as a drug carrier material.