E. A. Vasilieva

Structural, biocomplexation and gene delivery properties of hydroxyethylated gemini surfactants with varied spacer length.

Gemini surfactants with hexadecyl tails and hydroxyethylated head groups bridged with tetramethylene (G4), hexamethylene (G6) and dodecamethylene (G12) spacers were shown to self-assemble at the lower critical micelle concentration compared to their conventional m-s-m analogs. The lipoplex formation and the plasmid DNA transfer into different kinds of host cells were studied. In the case of eukaryotic cells, high transfection efficacy has been demonstrated for DNA-gemini complexes, which increased as follows: G6<G4<G12. Different activity series, i.e., G6>G4>G12 has been obtained in the case of transformation of bacterial cells with plasmid DNA-gemini complexes, mediated by electroporation technique. Solely G6 shows transformation efficacy exceeding the control result (uncomplexed DNA), while the inhibitory effect occurs for G4 and G12. Analysis of physico-chemical features of single surfactants and lipoplexes shows that compaction and condensation effects change as follows: G6<G4 ≤ G12, i.e., agree with the order of transfection efficacy, which is supported by membrane tropic properties of G12. On the other hand, gel retardation assay and docking study testify low electrostatic affinity in G12/DNA pair, thereby indicating that hydrophobic effect probably plays important role in the lipoplex formation. Two factors are assumed to be responsible for the inhibition effect of gemini in the case of transformation of bacterial cells. They are (i) an unfavorable influence of cationic surfactants on the electroporation procedure due to depressing the electrophoretic effect; and (ii) antibacterial activity of cationic surfactants that may cause the disruption of integrity of cell membranes.

Polyelectrolyte micro- and nanocapsules with varied shell permeability controlling the rate of esters hydrolysis

Two variants of layer-by-layer deposition of polyelectrolytes (polyacrylic acid and polyethyleneimine) for the encapsulation of low-molecular-weight hydrophobic substrates (carboxylic acid esters) were proposed. The spectrophotometric method was used to study the kinetics of alkaline hydrolysis of the esters by monitoring the permeability of microcapsule shells. The first procedure provides a preliminary microencapsulation of substrates into the carbonate matrix to form stable capsules 7–10 μm in size with a low wall permeability. According to the second procedure, the polyelectrolytes were adsorbed directly on the dispersed substrate. In this case, nanosized capsules are formed, whose permeability is controlled by the ultrasonic treatment and the number of deposited layers.

Supramolecular system 4-aza-1-hexadecyl-1-azoniabicyclo[2.2.2]octane bromide—sodium salicylate. Aggregation and rheological properties

The system based on the cationic surfactant 4-aza-1-hexadecyl-1-azoniabicyclo[2.2.2]-octane bromide (DABCO-16) and the organic electrolyte sodium salicylate was studied by tensiometry, conductometry, pH-metry, dynamic and electrophoretic light scattering, and viscosimetry. The critical concentration of micelle formation of DABCO-16 and the electrokinetic potential decrease sharply and the hydrodynamic diameter of the aggregates increases as the concentration of sodium salicylate increases. The rheological properties of the studied solutions are well described by the Maxwell model for a viscoelastic liquid with one relaxation time. Aqueous solutions DABCO-16—sodium salicylate exhibit the properties of an elastic gel and can be used for the formation of compositions with the improved rheological properties.

Supramolecular strategy of the encapsulation of low-molecular-weight food ingredients

Abstract A large number of additives (stabilizers, preservatives, vitamins, and nutraceuticals) are scarcely soluble in polar media, and therefore poorly mix with aqueous food dispersion. Besides, they are unstable against light, temperature, pH changing, and oxygen. Therefore, design of effective nanocontainers with controlled binding/release functions toward active components remains a challenge in the food industry. The chapter is oriented on the elucidation of recent trends in the field of engineering of delivery and storage systems for food ingredients. According to modern nanotechnological criteria and the green chemistry approach, food formulations tend to be polycomponent and polyfunctional, with natural and low toxic synthetic materials receiving special attention. Several lines of investigations have been reviewed, including the amphiphile- and polymer-based nanocontainers, supramolecular guest–host strategies involving macrocycle platforms, as well as binding/release behavior of loads.

Complexation of mono- and dicationic surfactants with decanucleotide. Influence of the head group nature

Complexation of decanucleotide (GCGTTAACGC) with mono- and dicationic surfactants (hydrodynamic diameter of lipoplexes ≤200 nm) is accompanied by the compensatory change of electrokinetic potential from −54 to +50 mV. The complexation efficiency considerably increases with introduction of a hydroxyethyl fragment into the surfactant head group.

Supramolecular systems based on cationic surfactants: an influence of hydrotropic salts and oppositely charged polyelectrolytes

For cationic surfactant 4-aza-1-dodecyl-1-azoniabicyclo[2.2.2]octane bromide (DABCO-16), a significant decrease in the critical micelle concentration (CMC) is shown in the presence of hydrotropic salts, which is due to the efficient binding of organic counterions with the surface of micelles and charge compensation of the head groups. The effect of salts increases in the series sodium benzoate < sodium tosylate < sodium salicylate. In the presence of hydrotropes, the electrokinetic potential decreases and the size of the aggregates increases. For micellar solutions DABCO-16 in the presence of sodium tosylate and sodium salicylate, the viscosity of the solution increases significantly, which is not observed in the case of sodium benzoate. In the presence of strong polyelectrolyte sodium polystyrenesulfonate, an increase in the critical aggregation concentration is observed compared to the CMC of an individual DABCO-16 solution, whereas weak polyelectrolyte polyacrylic acid induces a significant decrease in the aggregation threshold of the surfactant. Both polyelectrolytes exert no substantial effect on the rheological properties of micellar systems.

Encapsulation of quantum dots in supramolecular systems based on amphiphilic compounds and polyelectrolytes

Supramolecular nanocontainers based on monocationic and gemini surfactants and oppositely charged polyelectrolytes (polyacrylic acid, polyethyleneimine) for the stabilization and enhancement of solubility of hydrophobic quantum dots CdSe/ZnS were formed. The size (from 2 to 70 nm depending on the type of nanocontainers) and shape of aggregates containing quantum dots were determined by transmission electron microscopy. It was shown that the nature of the stabilizing agent influences the morphology of aggregates. The increase in photostability of quantum dots in micellar solutions of gemini surfactants and the possibility of their preservation in the polyelectrolyte capsules are identified.

The synthesis and properties of homologous series of surfactants containing the pyrrolidinium head group with hydroxyethyl moiety

The surface activity, micelle formation, and solubilization ability towards hydrophobic compounds were estimated for the series of new cationic surfactants belonging to the type of 1-alkyl-1-(2-hydroxyethyl)pyrrolidinium bromides. The presence of 2-hydroxyethyl group in these surfactants leads to the twofold increase in their micelle-forming ability as compared to unsubstituted analogs. The critical micelle concentration for the investigated series of pyrrolidinium surfactants is lower at the same hydrophobicity than that for the analogs belonging to the alkylpyridinium, alkylimidazolium, and alkylmorpholinium types. The data acquired for the studied surfactants on their solubilization ability, antimicrobial activity, and hemolytic efficiency indicate their prospective applications to encapsulate hydrophobic biologically active molecules and as the promising bactericidal agents.

Properties of the surfactant—calix[4]resorcinol binary system studied using spectral and fluorescent probes

The solubilization capacities of binary systems based on cationic surfactants (cetyltrimethylammonium bromide and dodecanediyl-1,12-bis(hydroxyethylmethylhexadecylammonium bromide)) and new amphiphilic calix[4]resorcinol with amino acid residues at the upper rim and alkyl substituents at the lower rim with respect to the spectral probe Sudan I and the fluorescent labels (pyrene and prodan) were studied by spectrophotometry and fluorimetry. Critical aggregation concentrations were determined and aggregation numbers were calculated. The sizes of surfactant—calix[4]resorcinol complexes were determined by dynamic light scattering.