Construction and reversible assembly of a redox-responsive supramolecular cyclodextrin amphiphile

Reduction-Responsive Cationic Vesicles from Bolaamphiphiles with Ionizable Amino Acid or Dipeptide Polar Heads

This paper presents a study of the aggregation of cationic bolaamphiphilic molecules into vesicles. These molecules are based on a cystamine core with protonated terminal dipeptide groups. The study found that vesicles can be formed at pH 4 for all of the dipeptide-terminated bolaamphiphiles containing different combinations of l-valine, l-phenylalanine, and l-tryptophan. The concentration for aggregation onset was determined by using pyrene as a fluorescent probe or light dispersion for compounds with tryptophan. Dynamic light scattering (DLS) studies and transmission electron microscopy (TEM) reveal that the vesicles have diameters ranging from 140 to 500 nm and show the capability of loading hydrophobic cargos, such as Nile red, and their liberation in reductive environments. Furthermore, the bolaamphiphiles are only fully protonated and prone to vesicle formation at acidic pH, making them a promising alternative for gastrointestinal delivery.

Supramolecular nanomedicines based on host-guest interactions of cyclodextrins

In the biomedical and pharmaceutical fields, cyclodextrin (CD) is undoubtedly one of the most frequently used macrocyclic compounds as the host molecule because it has good biocompatibility and can increase the solubility, bioavailability, and stability of hydrophobic drug guests. In this review, we generalized the unique properties of CDs, CD-related supramolecular nanocarriers, supramolecular controlled release systems, and targeting systems based on CDs, and introduced the paradigms of these nanomedicines. In addition, we also discussed the prospects and challenges of CD-based supramolecular nanomedicines to facilitate the development and clinical translation of these nanomedicines.

Fabrication of a β-cyclodextrin-based self-assembly containing a redox-responsive ferrocene

The current research involves fabrication of a redox-responsive self-assembly system based on a ferrocene (Fc)-containing β-cyclodextrin (β-CD) derivative (βCD-EG-Fc). βCD-EG-Fc was synthesized, and its redox-sensitive self-assembly behavior was investigated using various techniques. On the basis of the intermolecular host-guest recognition between the β-CD group and the Fc moiety, βCD-EG-Fc primarily formed network-like structures and then vesicles following aging for a specified time. The formation of these structures was primarily driven by hydrogen bonding. Conversely, the oxidized molecules (βCD-EG-Fc⁺) self-assembled into cationic vesicles with the absence of host-guest complexation. Upon controlling the oxidation and reduction of Fc/Fc⁺, reversible aggregate transformation was achieved. The current study resulted in a deeper understanding of β-CD/Fc redox-responsive self-assemblies and contributed to the development of a single-component host-guest inclusion model.

Physical stimuli-responsive liposomes and polymersomes as drug delivery vehicles based on phase transitions in the membrane

This paper reviews liposomes with crystalline phase and polymersomes exhibiting crystalline and thermotropic liquid crystalline phases in the membrane. Intriguing morphologies of vesicles are described, including spherical, ellipsoidal and faceted vesicles, produced by a large variety of amphiphilic molecules and polymers with nematic phase, smectic phase or crystalline phase. It is highlighted how the phase transitions and the phase grain boundaries could be used ingeniously to destabilize the vesicular structure and to achieve cargo-release under the action of external stimulation. These liposomes and polymersomes are responsive to physical stimuli, such as temperature variation, shear stress, light illumination, and magnetic and electric fields. These stimuli-responsive properties make them promising candidates as new smart drug delivery systems.

Redox-responsive self-assembly of β-cyclodextrin and ferrocene double-headed amphiphilic molecules

We present a redox-responsive self-assembly based on a unimolecular platform. Three double-headed amphiphilic molecules composed of β-cyclodextrin (β-CD) and ferrocene (Fc) each with an alkyl chain as a linker (βCD-C_m-Fc, m = 2, 6, and 10) were synthesized, and their self-assembly behaviors were investigated. The molecules self-assembled into polydisperse micelles that transformed into vesicles upon oxidization of the Fc moieties to Fc⁺. 2D ¹H NMR results suggest that although the three molecules formed aggregates with similar morphologies, their molecular configurations were different because of the different lengths of the alkyl chains. When the linker was a C₂ chain, no host-guest complexes were formed, whereas host-guest recognition was detected for linker lengths of C₆ and C₁₀. For the oxidized state samples, there were no host-guest interactions for linker lengths of C₂ and C₆, whereas the alkyl chain was locked in the cavity of β-CD by host-guest inclusion for the molecule with a C₁₀ linker. Moreover, reversible redox-responsive self-assemblies based on the three β-CD derivatives with a terminal Fc were successfully achieved. Our results enrich the field of β-CD/Fc reversible self-assembly systems, and provide a possible unimolecular host-guest complexation model in host-guest chemistry.