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.
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- "The work reported here extends our recent studies on new drug delivery nanocarriers, their fabrication and imaging , drug encapsulation, release profiles and biological impact     and has been mainly focused on determination and comparing of three different preparation techniques, i.e., solventdiffusion (SD), hot homogenization-ultrasonification (HHU) and microemulsification (ME) of biocompatible phosphatidylcholine (PC)-SLNs, containing Polawax NF in the internal lipid phase. All these experiments were attempted to describe the physical state and stability, as well as enhanced availability in aqueous SLN dispersions of newly prepared 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 (for structures and abbreviations see Scheme 1). "
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; DOI:10.1016/j.colsurfa.2014.02.034 · 2.35 Impact Factor
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ABSTRACT: An ideal drug-delivery system should combine both the stimuli-responsiveness and biocompatibility to enhance the drug bioactivity as well as to reduce side effects. In the present work we focused on the influence of pH upon in vitro sustained dye-release from multilayer oil-core nanocapsules. Three types of polyelectrolytes (PEs), two strong synthetic, poly(diallyldimethylammonium chloride) (PDADMAC) and poly(sodium 4-styrenesulfonate) (PSS) and one weak biocompatible: poly(l-lysine) hydrobromide, were used for the formation of sustained release, oil-core nanocapsules via layer-by-layer (LbL) self assembly approach. All nanocarriers coated with PSS/PLL or PSS/PDADMAC bilayers were created on the oleic acid nanoemulsion templates stabilized by dicephalic-type surfactant and loaded with hydrophobic, cyanine-type photosensitizer, IR-786. Nanocapsules with different thicknesses of the PE shell and average size around 100 nm, demonstrated good capacity for cyanine IR-786 encapsulation. We determined the sustained release of cyanine dye in different pH-conditions – physiological, acidic and alkaline. The in vitro release profiles were obtained spectrophotometrically and interpreted in terms of diffusion-controlled processes. They proved that pH condition had some influence on the release rate of the dye. It indicates on the necessity of appropriate selection of anionic and cationic polyelectrolytes in the fabrication process of pH-responsive and long sustained release nanocapsules.Colloids and Surfaces A Physicochemical and Engineering Aspects 11/2012; 413:266–272. DOI:10.1016/j.colsurfa.2011.12.006 · 2.35 Impact Factor
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ABSTRACT: The physicochemical behavior of new dicephalic surfactants, derivatives of tertiary amines, N,N-bis[3,3′-(dimethylamine)propyl]alkylamide dichlorides Cn(DAPACl)2, was analyzed in terms of the advanced model of multicharge cationic surfactant adsorption, taking into account counterion specificity and the formation of surfactant ion-counterion associates. Interactions of the studied compounds in mixtures with model anionic polyelectrolyte, sodium poly(styrene sulfonate) (PSS) were also examined. Surface tension data indicate binding of surfactant to polyions occurring above a concentration threshold lying much below the critical micelle concentration (cmc) of the pure surfactant in an aqueous solution. Above this threshold very surface active surfactant/polyion complexes are formed and that leads to an abrupt drop of surface tension. The obtained results are compared with those previously reported for N,N-bis[3,3′-(trimethylammonio)propyl]alkylamide dibromides C12(TAPABr)2 and N,N-bis[3,3′-(trimethylammonio)propyl]alkylamide dimethylsulfates C12(TAPAMS)2.Colloids and Surfaces A Physicochemical and Engineering Aspects 11/2012; 413:108–114. DOI:10.1016/j.colsurfa.2012.02.026 · 2.35 Impact Factor