Effect of hydrophobic tail on the mixed micelles of diheptanoylphosphatidycholine with cationic and zwitterionic surfactants: a fluorescence study (original) (raw)
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International journal of pharmaceutics, 2010
The number of mixed micellar (MM) drug products being introduced into the commercial pharmaceutical market is very limited although there is need for alternative dosage forms for poorly soluble active drug substances. While known systems are composed of phosphatidylcholine and bile salts, it was the aim of this study to investigate if alternative surfactants are able to form isotropically clear solutions over a broad range of concentrations and at higher ratios of phosphatidylcholine (PC). It was a particular challenge of this work to find a MM system with a unimodal particle size distribution since it is known that surfactants often form vesicles with phospholipids instead of MM. The theoretical approach behind this work was the transfer of the packing parameter concept, which describes the molecular association of one amphiphilic species, to the organisation behaviour of two different amphiphilic species (water-insoluble phospholipid+surfactant leading to MM). Therefore the influe...
Journal of Colloid and Interface Science, 2005
Mixed micelles of the phospholipid 1,2-diheptanoyl-sn-glycero-3-phosphocholine (DHPC) with sodium dodecyl sulfate (SDS) or dodecyltrimethylammonium bromide (DTAB) in aqueous solutions and the effects of interactions between the components were studied by fluorescence and NMR measurements. The regular solution theory (RST) was applied to analyze the experimental critical micelle concentration values determined from the fluorescence spectra of pyrene in the mixed micelles. Negative values for the interaction parameter (β 12 ) were obtained for both DHPC + SDS and DHPC + DTAB mixtures, with the value being more negative in the former case. The negative β 12 values for the two systems imply that the interaction between the phospholipid and the two ionic surfactants is attractive in nature, being more intense in the case of DHPC + SDS. The interaction parameter, β 12 , varies with composition of the mixtures indicating changes in packing. The proton NMR shifts are quite different for the two systems and also vary with composition. An interpretation of these experimentally determined chemical shifts in terms of the degree of compactness attributed to electrostatic and steric interactions in the mixed micelle supports the conclusions derived from the fluorescence cmc experiments. 2004 Elsevier Inc. All rights reserved.
Micellization and Interaction of Anionic and Nonionic Mixed Surfactant Systems In Water
Colloids and Surfaces A: Physicochemical …, 2005
Interaction between binary surfactant mixtures containing anionic surfactants viz. sodium dodecyl sulphates (NaDS) and magnesium dodecyl sulphates (Mg(DS)2) and a nonionic surfactants viz. dodecyl dodecapolyethylene glycol ether (C12E12) and dodecyl pentadecapolyethylene glycol ether (C12E15) in water at different mole fractions (0–1) were studied by surface tension, viscometry and dynamic light scattering (DLS) methods. The composition of mixed micelles and the interaction parameter, β evaluated from the CMC data obtained by surface tension for different systems using Rubingh’s theory were discussed. Activity coefficient (f1 and f2) of metal dodecyl sulphates (MDS)/C12Em (m= 12, 15) mixed surfactant systems were evaluated, which shows extent of ideality of individual surfactant in mixed system. The estimated interaction parameter indicates an overall attractive interaction in the mixed micelles, which is predominant for NaDS as compared to Mg(DS)2. Counter ion valency has specific effect on the mixed micelles, as Mg(DS)2 has less interaction with nonionic surfactants in comparison to NaDS due to strong condensation of counter ion. The stability factors for mixed micelles were also discussed by Maeda’s approach, which was justified on the basis of steric factor due to difference in head group of nonionic surfactant. DLS measurements and viscosity data reveals the synergism in mixed micelles, showing typical viscosity trends and linearity in sizes were observed.
Química Nova, 2011
Mixed micellization and surface properties of cationic and nonionic surfactants dimethyl decyl-, tetradecyl-and hexadecyl phosphineoxide mixtures are studied using conductivity and surface tension measurements. The models of Rubingh, Rosen, and Clint, are used to obtain the interaction parameter, minimum area per molecule, mixed micelle composition, free energies of mixing and activity coefficients. The micellar mole fractions were always higher than ideal values indicating high contributions of cationics in mixed micelles. Activity coefficients were less than unity indicating synergism in micelles. The negative free energies of mixing showed the stability of the surfactants in the mixed micelles.
Study of Mixed Micelles and Interaction Parameters for Polymeric Nonionic and Normal Surfactants
Journal of Nanoscience and Nanotechnology, 2006
Surface tension (ST) measurements were carried out on various binary mixtures of the "normal" surfactants, such as nonionic surfactant, hexaethylene glycol mono-n-dodecyl ether(C 12 EO 6 , and cationic surfactant, tetradecyltrimethylammonium bromide (TTAB), and polymeric copolymer, Pluronic F127, F127(PPO)-g-PVP, and F127(PEO)-g-PVP. In all cases mixed micellar aggregates were formed and critical micellar concentrations of binary mixtures containing different mole fractions of the surfactants were measured using surface tension measurement. In the region where mixed micelles are formed, the interaction of two "normal" surfactants and three "polymeric" nonionic surfactants showed synergistic behavior and the results were analyzed using a interaction parameter, , which characterize the interaction in the mixed micelle and introduced by a regular solution theory. The regular solution theory can be applied to describe the interaction between TTAB and C 12 EO 6 , and graft polymeric surfactants systems. The results discussed in this paper showed regular solution theory has broader extent of application.
Mixed micelles of cationic surfactants and sodium cholate in water
Indian journal of biochemistry & biophysics
Critical micelle concentrations (CMCs) of cationic surfactant (alkyltrimethylammonium bromides, CnTABr, where n = 10, 12, 14, 16 and 18), and a bile salt sodium cholate (NaC) were determined from surface tension, conductance and dye solubilization methods, while of their equimolar mixtures from surface tension and dye solubilization methods. The interaction parameter (beta) obtained from analysis of data, using Rubingh's theory showed strong interaction between NaC and cationic surfactant. Time-resolved fluorescence-quenching results revealed small-sized mixed spherical micelle with aggregation number much less than micelles of cationic surfactant.
Journal of Dispersion Science …, 2008
The micellization process of binary surfactant mixtures containing cationic surfactants viz.dodecyl pyridinium halide (C12PyX; X 5 Cl, Br, I), tetradecyl pyridium bromide (C14PyBr),and hexadecyl pyridium halide (C16PyX; X 5 Cl, Br) and a nonionic surfactants viz.dodecyl nonapolyethylene glycol ether (C12E9), dodecyl decapolyethylene glycol ether (C12E10), dodecyl dodecapolyethylene glycol ether (C12E12), and dodecyl pentadecapolyethylene glycol ether (C12E15) in water at different mole fractions (0–1) were studied by surface tension and viscosity methods. The composition of mixed micelles and the interaction parameter 'b' evaluated from the CMC data obtained by surface tension for different systems using Rubingh’s theory were discussed. Activity coefficient (f1 and f2) of cationic surfactant (CnPyBr)/C12Em (n 5 12, 14, 16 and m 5 10, 12, 15) mixed surfactant systems were evaluated, which shows extent of ideality of individual surfactant in mixed system. The stability factors for mixed micelles were also discussed by Maeda’s approach, which was justified on the basis of steric factor due to difference in head group of nonionic surfactant.
Colloid and Polymer Science, 2003
The effects of the addition of several propylene glycol oligomer additives on the micellar properties of the cationic mixed micelle system of cetyltrimethylammonium bromide (CTAB) and tetradecyltrimethylammonium bromide (TTAB) were investigated. Through conductivity studies, the critical micelle concentration (cmc) and counter-ion binding values were observed in the presence of the additives. A regular solution approach was employed to determine the effects of the additives on the interactions between the two surfactants to form the mixed micelles. The effects of the additives on the interaction parameter and the composition of the mixed micelles were evaluated. Excess Gibbs energy of mixing and the values of activity coefficients were also calculated and described in terms of non-ideality of the system.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2018
We report on combined experimental and theoretical investigations of the water/micelle interface of cationic, anionic, zwitterionic, and non-ionic surfactants using a new hydrophobic acid-base indicator 2,6dinitro-4-n-dodecylphenol. The indices of the so-called apparent ionization constant, app a pK , of the indicator fixed in the micellar pseudophase are determined by the spectrophotometric method. The data allows estimating the Stern layer's electrostatic potential of the ionic micelles . Molecular Dynamics modeling was used to locate the dye molecule and, in particular, its ionizing group OH Owithin the micelles of the studied surfactants. The comparison of the values estimated using 2,6-dinitro-4-ndodecylphenol with both our computer simulation and literature experimental results reveals obstacles in monitoring electrical interfacial potentials. In particular, the values of the surfactant micelles with alkylammonium groups determined via 2,6-dinitro-4-n-dodecylphenol are overestimated. The reason is specific interactions of the indicator anion with the surfactant head groups. For anionic surfactants, however, this indicator is quite suitable, which is confirmed by the location of HA and Aequilibrium forms in the pseudophase.