Janus particles self-assembled from a small organic atypical asymmetric gemini surfactant

Rethinking the Esterquats: Synthesis, Stability, Ecotoxicity and Applications of Esterquats Incorporating Analogs of Betaine or Choline as the Cation in Their Structure

Esterquats constitute a unique group of quaternary ammonium salts (QASs) that contain an ester bond in the structure of the cation. Despite the numerous advantages of this class of compounds, only two mini-reviews discuss the subject of esterquats: the first one (2007) briefly summarizes their types, synthesis, and structural elements required for a beneficial environmental profile and only briefly covers their applications whereas the second one only reviews the stability of selected betaine-type esterquats in aqueous solutions. The rationale for writing this review is to critically reevaluate the relevant literature and provide others with a "state-of-the-art" snapshot of choline-type esterquats and betaine-type esterquats. Hence, the first part of this survey thoroughly summarizes the most important scientific reports demonstrating effective synthesis routes leading to the formation of both types of esterquats. In the second section, the susceptibility of esterquats to hydrolysis is explained, and the influence of various factors, such as the pH, the degree of salinity, or the temperature of the solution, was subjected to thorough analysis that includes quantitative components. The next two sections refer to various aspects associated with the ecotoxicity of esterquats. Consequently, their biodegradation and toxic effects on microorganisms are extensively analyzed as crucial factors that can affect their commercialization. Then, the reported applications of esterquats are briefly discussed, including the functionalization of macromolecules, such as cotton fabric as well as their successful utilization on a commercial scale. The last section demonstrates the most essential conclusions and reported drawbacks that allow us to elucidate future recommendations regarding the development of these promising chemicals.

Long-term sciatic nerve block led by a supramolecular arrangement of self-delivery local anesthetic nano systems

Classical local anesthetics are unsuitable to treat regional pain lasting several days due to their limited duration and systemic toxicity. Self-delivery nano systems without excipients were designed for long-term sensory blocks. 1a self-assembled into different vehicles with different fractions of intermolecular π-π stacking, transported itself into nerve cells, and released single molecules slowly to achieve long-term duration for rats' sciatic nerve block for 11.6 h in water, 12.1 h in water with CO₂ and 3.4 h in NS (normal saline). After the counter ions were changed to SO₄^2-, 1e can self-assemble into vesicles and prolong the duration to 43.2 h, which was much longer than the 3.8 h led by (s)-bupivacaine hydrocloride (0.75%). This was mainly caused by the enhancement of self-release and counter ion exchange inside nerve cells, which were affected by the gemini surfactant structure, pK_a of the counter ions and π-π stacking interactions.

Behaviors of self-delivery lidocaine nano systems affected by intermolecular interaction

Lidocaine salts self-assembled into different nano systems in water at a clinical dosage (2%, 0.2 mL) without excipient addition, and led to different sensory block durations and acute systemic toxicities, which were affected by the self-delivery and self-release behaviors of the salts in vivo. These differences were mainly caused by intermolecular π-π stacking under different conditions, which was proved by the unique supramolecular arrangement of gourd-shaped Janus particles. π-π stacking in lidocaine nano systems can be enhanced by carbon dioxide addition or the exchange of counter ions from Br^- to Cl^-. Without π-π stacking, nano systems self-assembled by lidocaine hydrobromide achieved 7.8 h sensory block by intradermal administration on rats, which is much longer than the efficacy of classical local anesthetics and more suitable for postoperative treatment.

Switchable Nanostructures Triggered by Noyori-Type Organometallics

Janus particles (JPs) self-assembled by a typical small organic gemini surfactant in water were reported by us. After the addition of a small amount Noyori-type organometallics to an organic solvent, these gourd-shaped JPs became new nanostructures, such as nanotubes (NTs), nanoribbons (NRs), and new types of JPs. Significant changes in specific rotation occurred on the solution-like samples, triggered by chiral organometallics in 20 μL of ethyl acetate. Almost all of these organometallics-triggered nanostructures can be conveniently detached and reversed within 5 min due to the easy-phase separation of ethyl acetate from the emulsion and the chemical-selective unstable binding between the organometallics and carbonate group on the surfactant.

Microfluidic and hydrothermal preparation of vesicles using sorbitan monolaurate/polyoxyethylene (20) sorbitan monolaurate (Span 20/Tween 20)

Here, we present a method for preparing vesicles by combining hydrothermal emulsification with solvent diffusion (SD). The sorbitan monolaurate/polyoxyethylene (20) sorbitan monolaurate (Span 20/Tween 20) system was used as the target lipid because these lipids are cheap and advantageous for the production scale. The water-in-oil (W/O) emulsion stabilized with lipids was formed under hydrothermal conditions (240 °C under 10 MPa), followed by mixing with water that included lipids to obtain a W/O-in-water (W/O/W) emulsion. The SD for the W/O/W emulsion as a subsequent process yielded vesicles. The optimal preparation conditions were 50:50 wt% Span 20/Tween 20 as a mixing ratio (final lipid concentration 12 mM), octanoic acid as an organic solvent, 240 °C for 4 min during the hydrothermal treatment, and 4 °C for 24 h in the SD process. The diameter of the vesicles obtained was at most 100 nm, which was comparable to that of the W/O/W emulsion before SD. This suggested that the W/O/W emulsion acted as a template for vesicle formation. The number density, diameter, and membrane properties of vesicles depend on the mixing ratio of the water/oil/lipid system. Specifically, the number density of vesicles was low relative to that of vesicles prepared by the conventional method.