Supramolecular Engineering of Alkylated, Fluorinated, and Mixed Amphiphiles

Piperidinium surfactants functionalized with carbamate fragment: Aggregation, antimicrobial activity and cytotoxicity

The biomimetic nature of supramolecular systems, the structural similarity of synthetic surfactants to biomolecules (lipids, proteins), provide them with high membranotropy, the ability to overcome biological barriers, and affinity towards biosubstances. Despite rather high toxicity cationic surfactants are of importance as antimicrobial agents, gene nanocarriers and mitochondria targeted ligands. To minimize this limitation, cationic amphiphilic matrix undergoes modification with various functional groups. In this work, new piperidinium cationic surfactants containing one or two carbamate fragments were prepared; their aggregation behavior was systematically studied by tensiometery, spectrophotometry and fluorimetry. The presence of a carbamate fragment leads to a 2-3-fold decrease in critical micelle concentration and to a significant increase in solubilization capacity compared to unsubstituted analogue. Evaluation of the antimicrobial effect showed that all compounds exhibit high bactericidal and fungicidal activity against a wide range of pathogenic microorganisms, including their resistant forms. Importantly, the introducing carbamate moiety allows of decreasing hemolytic activity of cationic surfactants. The data obtained make it possible to recommend carbamate piperidinium surfactants as effective biocompatible and biodegradable nanocontainers for hydrophobic probes with high antimicrobial effect and moderate hemolytic activity.

PolySMart: a general coarse-grained molecular dynamics polymerization scheme

The development of simulation methods to study the structure and dynamics of a macroscopically sized piece of polymer material is important as such methods can elucidate structure-property relationships. Several methods have been reported to construct initial structures for homo- and co-polymers; however, most of them are only useful for short linear polymers since one needs to pack and equilibrate the far-from-equilibrium initial structures, which is a tedious task for long or hyperbranched polymers and unfeasible for polymer networks. In this method article, we present PolySMart, i.e., an open-source python package, which can effectively produce fully equilibrated homo- and hetero-polymer melts and solutions with no limitation on the polymer topology and size, at a coarse-grained resolution and through a bottom-up approach. This python package is also capable of exploring the polymerization kinetics through its reactive scheme in realistic conditions so that it can model the multiple co-occurring polymerization reactions (with different reaction rates) as well as consecutive polymerizations under stoichiometric and non-stoichiometric conditions. Thus, the equilibrated polymer models are generated through correct polymerization kinetics. A benchmark and verification of the performance of the program for several realistic cases, i.e., for homo-polymers, co-polymers, and crosslinked networks, is given. We further discuss the capability of the program to contribute to the discovery and design of new polymer materials.

Fluorinated dendritic amphiphiles, their stomatosome aggregates and application in enzyme encapsulation

Enzymes are more selective and efficient than synthetic catalysts but are limited by difficult recycling. This is overcome by immobilisation, namely through encapsulation, with the main drawback of this method being slow diffusion of products and reactants, resulting in effectively lowered enzyme activity. Fluorinated dendritic amphiphiles were reported to self-assemble into regularly perforated bilayer vesicles, so-called "stomatosomes". It was proposed that they could be promising novel reaction vessels due to their increased porosity while retaining larger biomolecules at the same time. Amphiphiles were synthesised and their aggregation was analysed by cryogenic transmission electron microscopy (cryo-TEM) and dynamic light scattering (DLS) in buffered conditions necessary for enzyme encapsulation. Urease and albumin were encapsulated using the thin-film hydration method and investigated by confocal and time-gated stimulated emission depletion microscopy (gSTED). Their release was then used to probe the selective retention of cargo by stomatosomes. Free and encapsulated enzyme activity were compared and their capacity to be reused was evaluated using the Berthelot method. Urease was successfully encapsulated, did not leak out at room temperature, and showed better activity in perforated vesicles than in closed vesicles without perforations. Encapsulated enzyme could be reused with retained activity over 8 cycles using centrifugation, while free enzyme had to be filtrated. These results show that stomatosomes may be used in enzyme immobilisation applications and present advantages over closed vesicles or free enzyme.

Interfaces with Fluorinated Amphiphiles: Superstructures and Microfluidics

This Minireview discusses recent developments in research on the interfacial phenomena of fluorinated amphiphiles, with a focus on applications that exploit the unique and manifold interfacial properties associated with these amphiphiles. Most notably, fluorinated amphiphiles form stable aggregates with often distinctly different morphologies compared to their nonfluorinated counterparts. Consequently, fluorinated surfactants have found wide use in high-performance applications such as microfluidic-assisted screening. Additionally, their fluorine-specific behaviour at solid/liquid interfaces, such as the formation of superhydrophobic coatings after deposition on surfaces, will be discussed. As fluorinated surfactants and perfluorinated materials in general pose potential environmental threats, recent developments in their remediation based on their adsorption onto fluorinated surfaces will be evaluated.

Synthesis and Linker-Controlled Self-Assembly of Dendritic Amphiphiles with Branched Fluorinated Tails

Amphiphiles containing fluorinated segments tend to aggregate in the aqueous solution into structure of lower curvature than their hydrocarbon analogs due to their larger diameter. A benefit of supramolecular structures incorporating fluorine moieties is their high electron density, which can be viewed in cryo-TEM with better contrast than their hydrogenated forms. A modular approach has been developed for the synthesis of a new family of nonionic branched amphiphiles consisting of oligoglycerol units (G2) as the hydrophilic part and a branched fluorinated (F27) hydrophobic part. The design of this hydrophobic moiety allows to achieve a higher fluorine density than the previously used straight-chain perfluoroalkanes. Two different chemical approaches, amide, and triazole, are used to link the hydrophilic and hydrophobic segments. In addition, the aggregation behavior is investigated by dynamic light scattering (DLS) and cryo-TEM. The measurements prove the formation of multivesicular (MVVs) and multilamellar (MLVs) vesicles as well as smaller unilamellar vesicles. Further, the cell viability test proves the low cell toxicity of these nanoarchitectures for potential biomedical applications.