MWNTs or PEG as Stability Enhancers for DNA-Cationic Surfactant Gel Particles.

Cationic surfactants interact with DNA (Deoxyribonucleic acid), forming surfactant-DNA complexes that offer particularly efficient control for encapsulation and release of DNA from DNA gel particles. In the present work, DNA-based particles were prepared using CTAB (Cetyltrimethylammonium bromide) as the cationic surfactant and modified using two different additives: (Multi-Walled Carbon Nanotubes) MWNT or PEG (Poly Ethylene Glycol). The use of both additives to form composites increased the stability of the gel particles.

Release of DNA and surfactant from gel particles: the receptor solution effect and the dehydration-hydration aspects.

DNA and cetyltrimethylammonium bromide (CTAB) have been used to prepare gel particles for controlled release studies. This article reports on the release of DNA and CTAB in four different solutions: in sodium bromide, in strong acid, pH 2 and pH 9 solutions for salmon testes DNA-CTAB gel particles. Also, compares results at extreme acid media and 10 mM NaBr solution with higher molecular weight DNA gel particles.

Effects of ionic strength on the surface tension and nonequilibrium interfacial characteristics of poly(sodium styrenesulfonate)/dodecyltrimethylammonium bromide mixtures.

We rationalize the surface tension behavior and nonequilibrium interfacial characteristics of high molecular weight poly(sodium styrenesulfonate)/dodecyltrimethylammonium bromide (NaPSS/DTAB) mixtures with respect to the ionic strength. Excellent agreement is achieved between experimental data and our recent empirical model [Langmuir 2013, 29, 11554], which is based on the lack of colloidal stability of bulk aggregates in the phase separation region and has no free fitting parameters. We show that the size of a surface tension peak positioned at the edge of the phase separation region can be suppressed by the addition of inert electrolyte, which lowers the critical micelle concentration in relation to the phase separation region.

The nanostructure of surfactant-DNA complexes with different arrangements.

The nanostructure of DNA with different cationic surfactant has been studied in order to elucidate the detailed arrangement concerning the position of DNA and surfactant domains in the complexes. Also, the orientation of the DNA cylinders in the thin films of the complexes was investigated. Attention was directed on the preparation methods of the complexes and to how the different surfactant structure affects the compaction of the DNA.

Self assembly of pH-sensitive cationic lysine based surfactants.

Three cationic surfactants of the type N(ε)-acyl lysine methyl ester hydrochloride have been studied with respect to solution behavior and adsorption on the air/water interface, as well as the thermolyotropic behavior. The self-assembly of these surfactants, which have the cationic charge on amine protonated groups, was assessed by different physicochemical methods. Depending on the pH value, these surfactants can dissociate in aqueous solutions, losing the cationic charge.

The impact of electrolyte on the aggregation of the complexes of hyperbranched poly(ethyleneimine) and sodium dodecyl sulfate.

The aggregation of the negatively charged complexes of hyperbranched poly(ethylenimine) (PEI) and sodium dodecyl sulfate (SDS) has been investigated at different sodium chloride (NaCl) concentrations using coagulation kinetics, electrophoretic mobility and dynamic light scattering measurements. The observed variation of the initial rate of coagulation with NaCl concentration indicates the formation of kinetically stable colloid dispersions in the investigated composition and pH range. These dispersions are electrostatically stabilized due to the adsorption of excess dodecyl sulfate ions on the surface of the polyelectrolyte/surfactant particles.

Nonequilibrium features of the association between poly(vinylamine) and sodium dodecyl sulfate: the validity of the colloid dispersion concept.

The effect of different mixing protocols on the bulk and surface properties of the aqueous mixtures of linear poly(vinylamine) (PVAm) and sodium dodecyl sulfate (SDS) has been investigated using pH, electrophoretic mobility, dynamic light scattering, coagulation kinetics, and surface tension measurements. For the preparation of the solutions, two kinds of mixing protocols were applied. The so-called "stop flow mixing" enables a very rapid mixing whereas in the case of "gentle mixing" the mixing of the components is less efficient.

Novel nanocomplexes of hyperbranched poly(ethyleneimine), and dodecyl maltoside.

The aqueous complexes of poly(ethyleneimine) (PEI), sodium dodecyl sulfate (SDS) and dodecyl maltoside (C12G2) have been studied under dilute conditions using dynamic light scattering, electrophoretic mobility, surface tension and pH measurements. According to the surface tension data the complexation between PEI and C12G2 can be neglected while a strong interaction was detected between PEI and SDS. The charged nature and size of the PEI-SDS-C12G2 complexes vary in a similar manner with SDS concentration as for the PEI-SDS systems.

Effect of mixing on the formation of complexes of hyperbranched cationic polyelectrolytes and anionic surfactants.

The effect of different mixing protocols on the charged nature and size distribution of the aqueous complexes of hyperbranched poly(ethylene imine) (PEI) and sodium dodecyl sulfate (SDS) was investigated by electrophoretic mobility and dynamic light scattering measurements at different pH values, polyelectrolyte concentrations, and ionic strengths. It was found that at large excess of the surfactant a colloidal dispersion of individual PEI/SDS nanoparticles forms via an extremely rapid mixing of the components by means of a stop-flow apparatus. However, the application of a less efficient mixing method under the same experimental conditions might result in large clusters of the individual PEI/SDS particles as well as in a more extended precipitation regime compared with the results of stop-flow mixing protocol.

Novel method for the estimation of the binding isotherms of ionic surfactants on oppositely charged polyelectrolytes.

One of the most important characteristics of the polyelectrolyte/surfactant interaction is the binding isotherm of the surfactant because it provides basic thermodynamic information about the binding mechanism. However, the amount of the surfactant bound to the polymer may crucially affect the surface properties of these systems via changing the thermodynamic activity of the components. Therefore, a knowledge of the binding isotherms can also be useful in tuning the efficiency of commercial products.