Facile fabrication of Sudan red particle microcapsules by a polymerizable gemini surfactant and molecular assembly mechanisms

Phase Behavior and Polymerization of the Ternary Polymerizable Cationic Gemini Surfactant/Fatty Alcohol/Water System

We studied the phase behavior of a ternary polymerizable gemini surfactant (PC11-6-11)/1-undecanol/water system and stabilized these liquid crystalline structures through the polymerization of surfactants. The addition of 1-undecanol to a PC11-6-11/water system formed bicontinuous cubic (V₁) and reversed hexagonal (H₂) liquid crystal phases in addition to hexagonal (H₁) and lamellar (L_α) phases, which were also formed using the binary system of PC11-6-11/water. These new phases were formed because the fatty alcohol penetrated the palisade layer of the PC11-6-11 micelles. The polymerization of PC11-6-11 with a thermal initiator successfully preserved the L_α and H₂ phases. Layered or honeycomb structures of these liquid crystals were clearly observed by transmission electron microscopy. The nanomaterials have potential applications as membranes for nano- or microfiltration and catalyst support materials.

A multifunctional supramolecular hydrogel: preparation, properties and molecular assembly

A novel supramolecular hydrogel was designed and constructed by molecular self-assembly of a cationic gemini surfactant, 1,3-bis(N,N-dimethyl-N-cetylammonium)-2-propylacrylate dibromide (AGC₁₆), and an anionic aromatic compound, trisodium 1,3,6-naphthalenetrisulfonate (NTS). Owing to its unique structure, the hydrogel (abbreviated as AGC₁₆/NTS) has the potential to be used as a multifunctional drug delivery system. The structure and properties of AGC₁₆/NTS were characterized by rheological measurements, differential scanning calorimetry, variable-temperature ¹H nuclear magnetic resonance, ultraviolet-visible spectroscopy, variable-temperature fluorescence emission spectroscopy, cryogenic scanning electron microscopy, transmission electron microscopy and X-ray diffraction methods. The rheological and DSC analysis results revealed that the gel AGC₁₆/NTS was formed below 57 °C. It was found from UV-vis, fluorescence and ¹H NMR spectroscopy characterization that aromatic π-π stacking and hydrophobic forces were indispensable to the formation of AGC₁₆/NTS. The Cryo-SEM and TEM observation results indicated that gelators AGC₁₆ and NTS self-assembled into one-dimensional fibers which further tightly intertwined to form a three-dimensional network structure. Based on the spectroscopic data and X-ray diffraction measurement results, a self-assembly model was proposed, helping to further understand the molecular self-assembly mechanism of AGC₁₆/NTS. It was also found that the electrostatic force, hydrophobic force and π-π interaction were the three main driving forces for the gelation. The multiple non-covalent interactions between AGC₁₆ and NTS endowed the hydrogel with excellent performance when the hydrogel was used as a carrier for drug delivery, due to multiple micro-domains within the same gel system. We further investigated the encapsulation and releasing properties of the hydrogel, using the hydrophobic model drug curcumin (Cur) and the model drug naproxen sodium (Npx) with aromatic ring structure. The fluorescence spectroscopy analysis confirmed that Npx was carried through aromatic π-π stacking and the ¹H NMR measurement result revealed that Cur was encapsulated within the hydrophobic cavities of AGC₁₆/NTS through hydrophobic interaction. Moreover, the drug release study results showed a sustained release of drugs from the hydrogel, indicating good application prospects in exploring new multifunctional drug delivery systems.

Self-assembled pH-responsive supramolecular hydrogel for hydrophobic drug delivery

In this study, a novel supramolecular hydrogel system, abbreviated as AGC₁₆/NTS, prepared by molecular self-assembly of cationic gemini surfactant 1,3-bis(N,N-dimethyl-N-cetylammonium)-2-propylacrylatedibromide (AGC₁₆) and anionic aromatic compound trisodium 1,3,6-naphthalenetrisulfonate (NTS), was used to encapsulate hydrophobic model drug curcumin (Cur), constructing a pH-responsive drug delivery system. Cur was effectively encapsulated into the hydrophobic domains of AGC₁₆/NTS through hydrophobic interaction, which was confirmed by ¹H NMR measurement. The effects of Cur on the mechanical strength, phase transition behaviour and morphology of AGC₁₆/NTS were characterized by rheology and cryogenic scanning electron microscopy (cryo-SEM) methods. The pH-responsive release of Cur from AGC₁₆/NTS was obtained and the release amount of Cur ascended with pH value decreasing from 7.4 to 3.0. The hydrodynamic sizes of the released Cur-aggregates determined by dynamic light scattering (DLS) were used to analyse the release process of Cur at different pH. The cell viability assay and cell imaging experiment demonstrated that Cur-loaded hydrogel has much higher cytotoxicity and better cell uptake compared to free Cur. Overall, the AGC₁₆/NTS hydrogel is a prospective material for use in encapsulation and controlled-release of hydrophobic drug molecules.

Supramolecular hydrogel, AGC₁₆/NTS, was used to encapsulate hydrophobic drug curcumin (Cur), constructing a pH-responsive drug delivery system; the uptake of released Cur by cancer cells also occurred.