Surface Activity and Efficiency of Cat-Anionic Surfactant Mixtures.

The surface activity of surfactant mixtures is critically analyzed. Cat-anionic systems, in which two ionic species are mixed in non-stoichiometric ratios, are considered. With respect to the solution behavior, where a substantial decrease of is met compared to the pure components, a moderate effect on surface tension, γ, occurs.

Natural Products from Madagascar, Socio-Cultural Usage, and Potential Applications in Advanced Biomedicine: A Concise Review.

Natural products endowed of biological activity represent a primary source of commodities ranging from nutrition to therapeutic agents, as well as cosmetic tools and recreational principles. These natural means have been used by mankind for centuries, if not millennia. They are commonly used all over the world in socio-economical contexts, but are particularly attractive in disadvantaged areas or economically emerging situations all over the world.

Hybrid nano-composites made of ss-DNA/wrapped carbon nanotubes and titania.

Multi-walled carbon nanotubes, MWCNTs, are stabilized thanks to the surface wrapping of single-strand DNA, ss-DNA; the resulting adducts are kinetically and thermodynamically stable Such entities build up nano-hybrids with titania, TiO, nano-particles, in presence of surfactant as an adjuvant. The conditions leading to TiO adsorption onto ss-DNA/CNTs were investigated, by optimizing the concentration of adducts, nano-particles (NPs), and of the cationic surfactant (CTAB). Controlling the working conditions makes possible to get homogeneously organized hybrids.

Interactions and effects of BSA-functionalized single-walled carbon nanotubes on different cell lines.

Functionalized carbon nanotubes (CNTs) have shown great promise in several biomedical contexts, spanning from drug delivery to tissue regeneration. Thanks to their unique size-related properties, single-walled CNTs (SWCNTs) are particularly interesting in these fields. However, their use in nanomedicine requires a clear demonstration of their safety in terms of tissue damage, toxicity and pro-inflammatory response.

Titration of DNA/Carbon Nanotube Complexes with Double-Chained Oppositely Charged Surfactants.

1/1 dispersions of ss-DNA/CNT complexes in mass ratios were investigated in a mixture with didodecyldimethylammonium bromide, DDAB. Depending on the amounts of the surface-active agent and of the complexes, solutions, precipitates, or re-dissolution occur. DDAB titrates the phosphate groups on the outer surface of the complex and controls the phase sequence in these systems.

Characterization and stability of catanionic vesicles formed by pseudo-tetraalkyl surfactant mixtures.

The phase behavior of an ad hoc synthesized surfactant, sodium 8-hexadecylsulfate (8-SHS), and its mixtures with didecyldimethylammonium bromide (DiDAB) in water is reported. We dealt with dilute concentration regimes, at a total surfactant content of <30 mmol kg(-1) where vesicular aggregates may be formed. The high synergistic behavior of such catanionic mixtures is concomitant with strongly negative interaction parameters, β (≈-18 kBT), significant gain in the free energy of association, ΔGagg, and much lower association concentration compared to the pure surfactants.

Effects of single-walled carbon nanotubes on lysozyme gelation.

The possibility to disperse carbon nanotubes in biocompatible matrices has got substantial interest from the scientific community. Along this research line, the inclusion of single walled carbon nanotubes in lysozyme-based hydrogels was investigated. Experiments were performed at different nanotube/lysozyme weight ratios.

Formation and properties of gels based on lipo-plexes.

Aqueous systems containing sodium taurodeoxycholate and, eventually, soybean lecithin were investigated. Depending on the relative amounts of two such species, molecular, micellar, vesicular, liquid crystalline, and solid phases were formed. In the presence of bovine serum albumin, micellar and vesicular systems form lipo-plexes.

Ion distribution around synthetic vesicles of the cat-anionic type.

Aqueous alkyltrimethylammonium bromides, or dialkyldimethylammonium ones, were mixed with sodium alkyl sulfates and dialkanesulfonates. Depending on the overall surfactant concentration, charge and/or mole ratios, cat-anionic vesicles were formed by mixing nonstoichiometric amounts of oppositely charged species. The resulting vesicles are thermodynamically and kinetically stable.

Alkyl glucopyranoside-based niosomes containing methotrexate for pharmaceutical applications: evaluation of physico-chemical and biological properties.

We designed novel niosomes based on alkyl glucopyranoside surfactants and containing methotrexate as anticancer drug, to be used in the pharmaceutical field. The effects of surfactants with chains of different length on niosome size and their distribution, drug entrapment efficiencies and in vitro drug release were determined. Systems made of alkyl glucopyranosides and cholesterol form vesicles whose average size scales with the alkyl chains length of such surfactants.

Delivery of RNA and its intracellular translation into protein mediated by SDS-CTAB vesicles: potential use in nanobiotechnology.

Catanionic vesicles are supramolecular aggregates spontaneously forming in water by electrostatic attraction between two surfactants mixed in nonstoichiometric ratios. The outer surface charges allow adsorption to the biomembrane by electrostatic interactions. The lipoplex thus obtained penetrates the cell by endocytosis or membrane fusion.

Lysozyme binds onto functionalized carbon nanotubes.

Single walled carbon nanotubes have singular physicochemical properties making them attractive in a wide range of applications. Studies on carbon nanotubes and biological macromolecules exist in literature. However, ad hoc investigations are helpful to better understand the interaction mechanisms.

Size and charge modulation of surfactant-based vesicles.

Nonstoichimetric mixtures of two oppositely charged surfactants, such as sodium dodecylsulfate and hexadecyltrimethylammonium bromide or tetradecyltrimethylammonium bromide and tetraethylammonium perfluorooctanesulfonate, a fluorinated species, form vesicles in dilute concentration regimes of the corresponding phase diagrams. Vesicles size and charge density are tuned by changing the mole ratio between oppositely charged species, at fixed overall surfactant content. They are also modulated by adding neutral electrolytes, or raising T.

Multi- to unilamellar transitions in catanionic vesicles.

Sodium dodecylsulfate (SDS) and cetyltrimethylammonium bromide (CTAB) dispersed in aqueous solution form catanionic vesicles. Depending on composition, such vesicles show different net charge, stability, and interaction capability, indicative of the strong impact that catanionic systems may have in gene therapy and drug delivery technologies. To reveal the interplay among composition, net charge, sensitivity to temperature changes, vesicle size, and inner structure, a series of experiments on catanionic vesicles prepared at different SDS/CTAB mole ratios was performed.

Interaction of bovine serum albumin with gemini surfactants.

The interactions between bovine serum albumin and cationic gemini surfactants were investigated as a function of concentration, under different pH conditions. The investigation deals with dielectric relaxation, dynamic light scattering, zeta-potential, circular dichroism, and UV spectroscopy. The interactive behavior of the anionic form is quite different from the cationic species.

Biological activity of SDS-CTAB cat-anionic vesicles in cultured cells and assessment of their cytotoxicity ending in apoptosis.

SDS-CTAB cat-anionic vesicles are supramolecular aggregates forming complexes with biopolymers and enter the cells via membrane fusion or endocytosis. Different applicative areas exist: gene therapy, drug delivery and nanotechnology. We previously examined the absorption/release of biopolymers from vesicles in solution.

Catanionic vesicles formed with arginine-based surfactants and 1,2-dipalmitoyl-sn-glycero-3-phosphate monosodium salt.

We report on mixing an anionic diacyl phospholipid (1,2-dipalmitoyl-sn-glycero-3-phosphate monosodium salt, DPPA) with either monoacyl and diacyl arginine-based surfactants. These mixtures are part of the rich family of pseudo-triple-chain and pseudo-tetra-chain catanionic mixtures, respectively. Vesicle size and zeta-potential were measured at several mixing ratios.

Assembly kinetics in binary mixtures of strongly attractive colloids.

The early stages of aggregation kinetics in a binary mixture of asymmetric colloids, aggregating irreversibly via biotin-streptavidin bonds, are experimentally and numerically studied. Experiments are performed by DLS methods, and data are analyzed in terms of a Smoluchowski-like coagulation equation. Focus is on the case of small (S) biotin-covered particles interacting with large (L) streptavidin-covered ones.

Niosomes from alpha,omega-trioxyethylene-bis(sodium 2-dodecyloxy-propylenesulfonate): preparation and characterization.

The synthesis and characterisation of new surfactants with peculiar physical-chemical properties are amongst the most promising and expanding issues in pharmacological colloid science. The most used vesicular carriers are liposomes prepared from a wide variety of natural and synthetic phospholipids, but several ionic and non-ionic amphiphiles have been used to form multilamellar and/or unilamellar vesicles. In the present study the synthesis of alpha,omega-trioxyethylene-bis(sodium 2-dodecyloxy-propylenesulfonate), an anionic Gemini surfactant, and its ability to form niosomes are elucidated.

Electrostatic interactions between a protein and oppositely charged micelles.

Micellar solutions made of a fully fluorinated surfactant, LiPFN, form water-soluble complexes with lysozyme in a wide concentration range. Such complexes are stabilized by electrostatic and, very presumably, double-layer interactions. The mixtures were investigated by combining electrophoretic mobility, DLS, and dielectric relaxation methods.

Dynamics of DNA adsorption on and release from SDS-DDAB cat-anionic vesicles: a multitechnique study.

DNA adsorption and release from cat-anionic vesicles made of sodium dodecylsulfate-dodecyldimethylammonium bromide (SDS-DDAB) in nonstoichiometric amounts was investigated by different electrochemical, spectroscopic, and biomolecular strategies. The characterization of the vesicular system was performed by dynamic light scattering, which allowed estimating both its size and distribution function(s). The interaction dynamics was followed by dielectric spectroscopy and zeta-potential, as well as by agarose gel electrophoresis, AGE.

Supra-molecular association and polymorphic behaviour in systems containing bile acid salts.

A wide number of supra-molecular association modes are observed in mixtures containing water and bile salts, BS, (with, eventually, other components). Molecular or micellar solutions transform into hydrated solids, fibres, lyotropic liquid crystals and/or gels by raising the concentration, the temperature, adding electrolytes, surfactants, lipids and proteins. Amorphous or ordered phases may be formed accordingly.

A biophysical investigation on the binding and controlled DNA release in a cetyltrimethylammonium bromide-sodium octyl sulfate cat-anionic vesicle system.

The interactions between cat-anionic (an acronym indicating surfactant aggregates (micelles and vesicles) formed upon mixing cationic and anionic surfactants in nonstoichiometric amounts) vesicles and DNA have been the subject of intensive studies because of their potential applications in biomedicine. Here we report on the interactions between DNA and cetyltrimethylammonium bromide (CTAB)-sodium octyl sulfate (SOS) cat-anionic vesicles. The study was performed by combining dielectric relaxation spectroscopy, circular dichroism, dynamic light scattering, ion conductivity, and molecular biology techniques.

Interactions between gemini surfactants and polymers: thermodynamic studies.

Aqueous mixtures containing a homopolymer, poly(vinylpyrrolidone) (PVP), or a hydrophobically modified graft copolymer, HM-pullulan, (PULAU9, where 9 stands for the nominal substitution degree), and different Gemini surfactants have been investigated at 25.0 degrees C. A wide variety of experimental conditions were addressed by changing the amount of polymer and of surfactant.