Yuxia Gao

Organogels of triterpenoid–tripeptide conjugates: encapsulation of dye molecules and basicity increase associated with aggregation

Two triterpenoid–peptide conjugates containing oleanolic acid and glycyrrhetinic acid were synthesized and the properties of self-assembly into organogels were studied systematically. The results showed that the xerogels could selectively adsorb dyes from water and it could be utilized in water purification by removing toxic dyes. In addition, the formation of supramolecular gels was associated to basicity increase by employing pH-indicator dyes in water.

Self-assembly of sodium glycyrrhetinate into a hydrogel: characterisation and properties

Sodium glycyrrhetinate, a simple triterpenoid derivative, was found to form a hydrogel with dipole–dipole interaction of sodium carboxylates as the main driving force. The hydrogel showed properties in selective dye adsorption and sustainable release.

Solvent-Directed Assembly of a Pyridinium-Tailored Methyl Oleanolate Amphiphile: Stepwise Growth of Microrods and Nanofibers

Although a few architectures have been fabricated by the self-assembly of natural triterpenoids, the precise control of shape and size is rarely studied. Herein, a methyl oleanolate-bearing amphiphile, 1-[2-(methyl oleanolate)-2-oxoethyl]pyridinium bromide (MOP), has been designed and its assembly behavior was investigated. It was found that the morphologies of MOP assemblies ranged from nanoparticles to rigid microrods and flexible nanofibers in chloroform/p-xylene and methanol/water, respectively. During the assembly process, the systematical variational solvophobic/solvophilic effect resulted in the formation of spherical nanoparticles with opposite dipoles and converse bilayer structures. Moreover, such opposite molecular orientations lead to the inversion of supramolecular chirality and distinct mechanical properties. The driving forces and packing patterns of MOP in each solvent system were clearly demonstrated by the combination of NMR, UV-vis, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), theoretical computation, and contact angle experiments, which revealed the roles of triterpenoids and pyridinium cations in the assembly process. This work provides a facile strategy to control the supramolecular structures in triterpenoid-based assemblies by adjusting the solvent polarity and composition.

Water tuned nano/micro-structures in a redox-responsive supramolecular gel

A redox-responsive chiral supramolecular gel based on coumarin-tailed cholesterol linked with disulfide was reported. It was found that the gelation was primarily driven by the combination of hydrogen bonding, π–π stacking, and van der Waals forces. Moreover, its assembled morphology could be regulated from nanofibers to micro flowers and ribbons by water on account of its amphiphilic nature.

First preparation of a triterpenoid-based supramolecular hydrogel in physiological phosphate buffered saline

A glycyrrhetinic acid-based (GA, a natural pentacyclic triterpenoid) supramolecular hydrogel was attained in physiological phosphate buffered saline for the first time. Its assembly process and potential applications in drug release were preliminarily explored.

Photo-induced conversion from supramolecular to covalently linked polymers based on anthracene-appended amphiphiles

A photosensitive amphiphile 2 was synthesized, in which the anthracene moiety in each arm was connected to a dipyridinium center by an alkyl chain. Using host–guest interactions between γ-CD and the anthracene moiety in 2, a supramolecular polymer was achieved, and such a supramolecular polymer can be further converted into its corresponding covalent polymer upon irradiation at 365 nm via [4 + 4] photocyclodimerization of anthracenes within the cavity of γ-CD. This approach affords a strategy in the transformation from supramolecular to covalently linked polymers.

A charge-transfer induced self-healing supramolecular hydrogel

In this study, a dual-component charge-transfer (CT)-induced supramolecular hydrogel was fabricated using pyrene-tailored pyridinium (PYP) and 2,4,7-trinitrofluorenone (TNF) as the electron donor and acceptor, respectively. Its thermal stability and mechanical property have been modulated effectively by altering the concentration or molar ratio of PYP and TNF. Moreover, this CT hydrogel exhibited a distinct injectable self-healing property that could be utilized to create desired patterns on substrates. Such property holds potential for this CT hydrogel in fields like three-dimensional printing and surface coating.

Cooperative supramolecular helical assembly of a pyridinium-tailored methyl glycyrrhetate

Taking a natural triterpenoid as the building block, we have regulated a pyridinium-functionalized methyl glycyrrhetate (C4-MGP) into P-type helices in water primarily driven by hydrophobic forces. By analysing their temperature-dependent CD and UV-Vis spectra, these hierarchical chiral assemblies were found to be formed in a cooperative supramolecular polymerization manner.

A Natural Triterpene Saponin-Based Pickering Emulsion

The abuse of chemical surfactants in pesticide formulations is a potential threat to agricultural development and environmental safety. Thereby, developing an efficient eco-friendly pesticide formulation is of great significance. In this research, a biocompatible and ultrastable pesticide formulation has been developed in which merely 1 wt % natural glycyrrhizic acid (GA) was used to emulsify and stabilize 80 wt % agricultural oils. During the preparation process, amphiphilic GA molecules initially self-assembled into 1D nanofibers with a favorable surfactivity, and then afforded GA-based Pickering emulsions with fine droplets. Consequently, the Pickering emulsions transformed into gel-like Pickering emulsions as a result of the formation of a 3D network of nanofibers. On account of the unique chemical structure and admirable assembly behavior of GA, the gel-like Pickering emulsions exhibit ultrastability, thixotropy, and broad pH resistance. In addition, this formulation was investigated for its potential application to pesticides by using pure carbosulfan as the oil phase; up to 60 wt % carbosulfan could be coated, which is more than in the current commercial formulations. This work not only provides new insights into the application of natural biosurfactants to pesticides, but also proposes a biocompatible and eco-friendly pesticide formulation for use in ecological agriculture.

Natural Triterpenoid- and Oligo(Ethylene Glycol)-Pendant-Containing Block and Random Copolymers: Aggregation and pH-Controlled Release

In this research, a series of random and block amphiphilic copolymers of norbornene derivatives containing biocompatible natural triterpenoid and oligo(ethylene glycol) pendants were synthesized by ring-opening metathesis polymerization. These copolymers were heat and pH responsive, and could self-assemble into core-shell spherical micelles in aqueous solution. Their hydrodynamic diameters corresponded to pH values and monomer sequences. By evaluating the loading and release capacity of hydrophobic molecules, it was found that 1) the higher the content of the hydrophobic triterpenoid, the higher the loading capacity; 2) the release speed could be trigged by the pH because of the deprotonation of the carboxyl groups on the triterpenoid. Additionally, the copolymers exhibited low cytotoxicity toward L929 cells, which makes them potential nanocarrier candidates for controlled drug delivery.