Darija Jurašin

Antioxidant properties of ganglioside micelles.

Antioxidant activity of gangliosides GM1 and GT1b in the Fenton type of reaction was investigated by EPR spectroscopy using DMPO as a spin trap. Hydroxyl radical spin adduct signal intensity was significantly reduced in the presence of gangliosides at their micellar concentrations. Mean micellar hydrodynamic diameter was not changed, whereas significant changes in negative Zeta potential values were observed as evidenced by Zetasizer Nano ZS. This study showed that the primary mode of ganglioside action was not due to direct scavenging of OH·, but rather to the inhibition of hydroxyl radical formation. This phenomenon is related to the ability of ganglioside micelles to bind oppositely charged ferrous ions, thus reducing their concentration and consequently inhibiting OH· formation.

Surface coating affects behavior of metallic nanoparticles in a biological environment.

Summary Silver (AgNPs) and maghemite, i.e., superparamagnetic iron oxide nanoparticles (SPIONs) are promising candidates for new medical applications, which implies the need for strict information regarding their physicochemical characteristics and behavior in a biological environment. The currently developed AgNPs and SPIONs encompass a myriad of sizes and surface coatings, which affect NPs properties and may improve their biocompatibility. This study is aimed to evaluate the effects of surface coating on colloidal stability and behavior of AgNPs and SPIONs in modelled biological environments using dynamic and electrophoretic light scattering techniques, as well as transmission electron microscopy to visualize the behavior of the NP. Three dispersion media were investigated: ultrapure water (UW), biological cell culture medium without addition of protein (BM), and BM supplemented with common serum protein (BMP). The obtained results showed that different coating agents on AgNPs and SPIONs produced different stabilities in the same biological media. The combination of negative charge and high adsorption strength of coating agents proved to be important for achieving good stability of metallic NPs in electrolyte-rich fluids. Most importantly, the presence of proteins provided colloidal stabilization to metallic NPs in biological fluids regardless of their chemical composition, surface structure and surface charge. In addition, an assessment of AgNP and SPION behavior in real biological fluids, rat whole blood (WhBl) and blood plasma (BlPl), revealed that the composition of a biological medium is crucial for the colloidal stability and type of metallic NP transformation. Our results highlight the importance of physicochemical characterization and stability evaluation of metallic NPs in a variety of biological systems including as many NP properties as possible.

Polymorphism and mesomorphism of oligomeric surfactants: effect of the degree of oligomerization.

A series of cationic oligomeric surfactants (quaternary dodecyldimethylammonium ions with two, three, or four chains connected by an ethylene spacer at the headgroup level, abbreviated as dimer, trimer, and tetramer) were synthesized and characterized. The influence of the degree of oligomerization on their polymorphic and mesomorphic properties was investigated by means of X-ray diffraction, polarizing optical microscopy, thermogravimetry, and differential scanning calorimetry. All compounds display layered arrangements with interdigitated dodecyl chains. The increase in the degree of oligomerization increases the interlayer distance and decreases the ordering in the solid phase; whereas the dimer sample is fully crystalline with well-developed 3D ordering and the trimer and tetramer crystallize as highly ordered crystal smectic phases. The number of thermal phase transitions and sequence of phases are markedly affected by the number of dodecyl chains. Anhydrous samples exhibit polymorphism and thermotropic mesomorphism of the smectic type, with the exception of the tetramer that displays only transitions at higher temperature associated with decomposition and melting. All hydrated compounds form lyotropic mesophases showing reversible phase transitions upon heating and cooling. The sequence of liquid-crystalline phases for the dimer, typical of concentrated ionic surfactant systems, comprises a hexagonal phase at lower temperatures and a smectic phase at higher temperatures. In contrast, the trimer and tetramer reveal textures of the hexagonal phase.

Interactions in aqueous mixtures of alkylammonium chlorides and sodium cholate

The interactions of alkylammonium chlorides (the number of carbon atom per chain was either 12, 14, or 16) with sodium cholate have been investigated by a combination of techniques including light and electron microscopy, surface tension, conductivity, light scattering, and microelectrophoretic measurements. The phase behavior has strongly depended on the molar ratio and actual concentration of oppositely charged surfactants. The change in the composition of the aggregates leads to a shape transformation from globular to elongated micelles to open and/or closed bilayers (vesicles) and precipitation. The length of micelles has been found to decrease dramatically with the concentration shift to the micellar regions of either surfactant. Upon a moderate excess of one surfactant, the mean hydrodynamic diameter of aggregates increases and wormlike micelles and/or open and closed bilayers are formed. Microscopic observations of alkylammonium cholates (novel catanionic surfactants precipitated in and/or close to equimolar region) have shown the presence of a variety of morphologies including twisted ribbons, tubules and bundles of tubules.

Does surface coating of metallic nanoparticles modulate their interference with in vitro assays

Screening programs for the evaluation of nanomaterial value and safety rely on in vitro tests. The exceptional physicochemical properties of metallic nanoparticles (NPs), such as large surface area and chemically active surface, may provoke their interference with in vitro methods and analytical techniques used for evaluation of biocompatibility or toxicity of NPs. This study aimed to determine if such interference could be predicted on the basis of the surface characteristics of metallic NPs by investigating the effect of different surface coatings of silver (AgNPs) and maghemite NPs (γ-Fe2O3NPs) on common in vitro assays scoring two of the main cytotoxic endpoints: cell viability and oxidative stress response. We examined optical, adsorptive and chemically reactive types of NP interference with cell viability assays (MTT, MTS, and WST-8) and assays employing fluorescent dyes as markers for production of reactive oxygen species (DCFH-DA and DHE) or glutathione level (MBCl). Each type of tested NPs affected all of the six investigated assays leading to false interpretation of obtained results. The extent and type of interference were dependent on the type and surface coating of NPs as well as on their stability in biological media. The results have shown that interference was concentration-, particle type- and assay type-dependent. This study demonstrated that common in vitro assays, without appropriate cause-and-effect analysis and adaptation or modification, are ineffective in the evaluation of biological effects of metallic NPs due to their interaction with optical readouts and assay components. A comprehensive and feasible experimental setup has been proposed to gain a reproducible and reliable in vitro evaluation as the first step in the health assessment of metallic NPs.

Phase Behavior in Mixtures of Cationic Dimeric and Anionic Monomeric Surfactants

The formation of mixed aggregates has been investigated in the mixture of oppositely charged surfactants vastly differing in molecular geometry and size. The systems considered is mixture of the cationic gemini surfactant, ethanediyl-1,2-bis(dodecyldimethylammonium bromide), and anionic surfactant, sodium dodecyl sulfate. Various mixed nano- and microaggregates (micelles, vesicles, thin lamellar sheets, and tubules) were formed depending on bulk composition and total surfactant concentration. Two types of aggregates were found in precipitate, the tubules as prevailing aggregates on the gemini-rich side, and vesicles as prevailing aggregates on the SDS-rich side. The tubules formation was ascribed to mutual influence of specific structure of cationic dimeric surfactant and electrostatic interactions at the bilayer/solution interface. The proposed mechanism involved the formation of lamellar sheets, which rolled-up into tubules.

Lamellar to hexagonal columnar liquid crystalline phase transition in a catanionic surfactant mixture: dodecylammonium chloride–sodium bis(2-ethylhexyl) sulfosuccinate

Phase transitions from a dispersed lamellar to hexagonal liquid crystalline phase have been investigated in a catanionic surfactant mixture formed by mixing a single tailed cationic surfactant, dodecylammonium chloride, with a double tailed anionic surfactant, sodium bis(2-ethylhexyl) sulfosuccinate. Depending on the bulk composition and total surfactant concentration, mixed micelles, vesicles, lamellar and hexagonal columnar liquid crystalline phases have been identified. Differences in the geometry of the two hydrophobic chains stabilize vesicles of different shapes (spherical, tubular and pearled) relative to the liquid crystalline phase even in stoichiometric mixtures. At higher surfactant concentrations the phase transition from a dispersed lamellar to hexagonal columnar liquid crystalline phase proceeds continuously, with both phases coexisting over a range of concentrations. The transition proceeds through processes of vesicle aggregation, reorganization into multilayer sheets rolled-up into tubules, and formation of a hexagonal columnar liquid crystalline phase.

Impact of cationic surfactant on the self-assembly of sodium caseinate.

The impact of a cationic surfactant, dodecylammonium chloride (DDACl), on the self-assembly of sodium caseinate (SC) has been investigated by light scattering, zeta potential, and rheological measurements as well as by microscopy (transmission electron and confocal laser scanning microscopy). In SC dilute solutions concentration-dependent self-assembly proceeds through the formation of spherical associates and their aggregation into elongated structures composed of connected spheres. DDACl interacts with SC via its hydrophilic and hydrophobic groups, inducing changes in SC self-assembled structures. These changes strongly depend on the surfactant aggregation states (monomeric or micellar) as well as concentration ratio of both components, leading to the formation of soluble and insoluble complexes of nano- to microdimensions. DDACl monomers interact with SC self-assembled entities in a different way compared to their micelles. Surfactant monomers form soluble complexes (similar to surfactant mixed micelles) at lower SC concentration but insoluble gelatinous complexes at higher SC concentration. At surfactant micellar concentration soluble complexes with casein chains wrapped around surfactant micelles are formed. This study suggests that the use of proper cationic surfactant concentration will allow modification and control of structural changes of SC self-assembled entities.

How protein coronas determine the fate of engineered nanoparticles in biological environment

Abstract Nanomedicine is a booming medical field that utilises nanoparticles (NPs) for the development of medicines, medical devices, and diagnostic tools. The behaviour of NPs in vivo may be quite complex due to their interactions with biological molecules. These interactions in biological fluids result in NPs being enveloped by dynamic protein coronas, which serve as an interface between NPs and their environment (blood, cell, tissue). How will the corona interact with this environment will depend on the biological, chemical, and physical properties of NPs, the properties of the proteins that make the corona, as well as the biological environment. This review summarises the main characteristics of protein corona and describes its dynamic nature. It also presents the most common analytical methods to study the corona, including examples of protein corona composition for the most common NPs used in biomedicine. This knowledge is necessary to design NPs that will create a corona with a desired efficiency and safety in clinical use.

Recent Advances in Catanionic Mixtures

Most surfactant mixtures display synergistic physicochemical properties, which have led to their extensive application in various technologies. Aqueous mixtures of two oppo‐ sitely charged surfactants, so‐called catanionic surfactant mixtures, exhibit the strongest synergistic effect, which is manifested as high surface activity, enhanced adsorption and a low critical aggregation concentration. In addition, catanionic systems display rich phase behavior and a range of nano and microstructures, including small spherical micelles, rod‐like micelles as well as open and closed bilayers (vesicles). The spontaneous forma‐ tion of catanionic vesicles is of special interest due to their various applications in nano‐ technology and pharmaceutical formulations. In this chapter, the properties of catanionic mixtures of amphiphilic molecules with advantageous properties are discussed. Since numerous papers dealing with catanionic mixtures of monomeric surfactants already exist, the aim of this chapter is to summarize recent progress in mixtures of structurally different surfactants. At the end of the chapter, special emphasis is placed on applications of catanionic mixtures.