Experimental and theoretical approach to nonequivalent adsorption of novel dicephalic ammonium surfactants at the air/solution interface.
ABSTRACT The interfacial behavior of novel dicephalic cationic surfactants, N,N-bis[3,3'-(trimethylammonio)propyl]alkylamide dibromides and N,N-bis[3,3'-(trimethylammonio)propyl]alkylamide dimethylsulfates, was analyzed both experimentally and theoretically in comparison to their linear standards, 3-[(trimethylammonio)propyl]dodecanamide bromide and 3-[(trimethylammonio)propyl]dodecanamide methylsulfate. Adsorption of the studied double head-single tail surfactants depends strongly upon their structure, making them less surface active in comparison to the single head-single tail structures having the same alkyl chain length. Surface tension isotherms of aqueous solutions of the studied dicephalic derivatives were measured using the pendant drop shape analysis method and interpreted with the so-called surface quasi-two-dimensional electrolyte (STDE) model of ionic surfactant adsorption. The model is based on the assumption that the surfactant ions and counterions (bromide and methylsulfate ions in the studied case) undergo nonequivalent adsorption within the Stern layer, and it allows for accounting for the formation of surfactant ion-counterion associates in the case of multivalent surfactant headgroup ions. As a result, good agreement between theory and experiment was obtained. Additionally, the presence of surfactant-counterion complexes was successfully confirmed by both measurements of the concentration of free bromide ions in solution and molecular modeling simulations. The results of the present study may prove useful in the potential application of the investigated dicephalic cationic surfactants.
- Colloids and Surfaces A Physicochemical and Engineering Aspects 10/2014; 460:312-320. · 2.35 Impact Factor
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ABSTRACT: A series of soft cationic surfactants, containing a saccharide-derived moiety in their hydrophilic grouping – 2-(alkyldimethylammonio) ethylgluconamide bromides, denoted as CnGAB, n = 10, 12, 14 and 16 – were analyzed with respect to their influence on the thermotropic phase behavior of phosphatidylcholine (DPPC)/cholesterol bilayers. The compounds were found to be uniformly distributed in the studied lipid bilayer. As usual, the longer the chain of CnGAB, the stronger was the effect on Tm and ΔHm, except C16GAB. Having the longest chain, C16GAB reduces Tm to the smallest extent and does not affect ΔHm until the molar ratio of surfactant/DPPC is 0.15. The interactions with model cells in vitro were determined by cytotoxicity evaluation with respect to two cell lines – mouse fibroblast cell line L929 and human lung cancer cell line A549. The toxicity of CnGABs is much lower than a classical DTAB.Thermochimica Acta 08/2014; 590:219–225. · 2.11 Impact Factor
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ABSTRACT: The present study has been focused on determination and evaluation of three different preparation techniques i.e., solvent-diffusion, hot homogenization-ultrasonification and microemulsification, applied in fabrication of biocompatible phosphatidylcholine solid lipid nanoparticles ((PC)-SLNs), containing Polawax National Formulary (NF) in the internal lipid phase. The fabricated lipid nanoparticles were loaded with the newly synthesized flavonoid cocrystals i.e., baicalein-nicotinamide (1:1) (BaiNam), myricetin-piracetam (1:1) (MyrPac) and myricetin-caffeine (1:1) (MyrCaf) cocrystals in relation to the starting flavonoids, differing in solubility and physical state. The assessment of all studied drugs entrapment and availability in aqueous SLN dispersions has been carried out; the size along with size distribution of lipid nanoparticles loaded with the studied flavonoids cocrystals and flavonoids was determined by the DLS technique, while the structural changes–by FT-IR spectroscopy and X-Ray powder diffraction (XRPD) of the lipid nanomatrices. XRPD and FT-IR analyses confirmed that parent flavonoids as well as their cocrystals are present in the nanoparticles fabricated with solvent-diffusion method as physical mixtures with the lipid and their crystalline structures at least partially conserved. Summarizing, we designed and fabricated the biocompatible SLN-type nanocarriers of enhanced physical stability and availability for the flavonoids delivery - a vast group of naturally occurring polyphenolic compounds, considered as active pharmaceutical ingredients.Colloids and Surfaces A Physicochemical and Engineering Aspects 10/2014; · 2.35 Impact Factor