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New hexadecylpiperidinium surfactants, containing one or two butylcarbamate fragments, were synthesized. The antimicrobial activity, toxicity, aggregation behavior in aqueous solutions, and solubilization capacity of these surfactants towards the hydrophobic drug ibuprofen were characterized. These surfactants demonstrated a high antimicrobial activity against a wide range of pathogenic bacteria, including both Gram-positive and Gram-negative strains, as well as fungi. By forming mixed-micellar compositions of the cationic surfactant 1-CB(Bu)-P-16 and the nonionic surfactant Brij®35, highly functional and low-toxic formulations were obtained. Furthermore, the transition from mixed micelles to niosomes was accomplished, enhancing their potential as drug delivery systems. Niosomes were found to be less toxic compared to mixed micelles, while also increasing the solubility of ibuprofen in water. The modification of niosomes with cationic surfactants made it possible to increase the stability of the system and improve the solubility of the drug. The data obtained indicate that these new carbamate-containing hexadecylpiperidinium surfactants have significant potential in biomedical applications, particularly in the formulation of advanced drug delivery systems. [ABSTRACT FROM AUTHOR]

The aggregation behavior of mixed micellar solutions based on 2-hydroxyethylpiperidinium surfactants and nonionic surfactant Brij® 35 was investigated. The critical micelle concentrations determined by varying the component ratio suggest a negative deviation from the ideal mixing model (synergistic effect). It was demonstrated that the magnitude of the deviation from ideal mixing behavior depends on the alkyl chain length in the cationic surfactant and on the component ratio. The solubilization effect of the binary systems on hydrophobic substances was evaluated taking Orange OT dye and ibuprofen drug as examples. It was found that the piperidinium surfactants studied, both individually and in compositions containing up to 50% of the nonionic surfactant, exhibit high antimicrobial activity comparable to that of commercial antibiotics. [ABSTRACT FROM AUTHOR]

New hexadecylpiperidinium surfactants, containing one or two butylcarbamate fragments, were synthesized. The antimicrobial activity, toxicity, aggregation behavior in aqueous solutions, and solubilization capacity of these surfactants towards the hydrophobic drug ibuprofen were characterized. These surfactants demonstrated a high antimicrobial activity against a wide range of pathogenic bacteria, including both Gram-positive and Gram-negative strains, as well as fungi. By forming mixed-micellar compositions of the cationic surfactant 1-CB(Bu)-P-16 and the nonionic surfactant Brij®35, highly functional and low-toxic formulations were obtained. Furthermore, the transition from mixed micelles to niosomes was accomplished, enhancing their potential as drug delivery systems. Niosomes were found to be less toxic compared to mixed micelles, while also increasing the solubility of ibuprofen in water. The modification of niosomes with cationic surfactants made it possible to increase the stability of the system and improve the solubility of the drug. The data obtained indicate that these new carbamate-containing hexadecylpiperidinium surfactants have significant potential in biomedical applications, particularly in the formulation of advanced drug delivery systems.

Owing to their surface active properties, surfactants have numerous applications in different fields of life. In the present research work, the solubilization of reactive red 2 (RR2) has been studied in single and mixed micellar systems (MMS) using UV-visible spectroscopy and electrical conductivity measurements. The interaction of RR2 with ionic micelles of cetylpyridinium chloride (CPC) was investigated. In order to probe the interaction of RR2 in MMS, mixtures of CPC and TX-114 (Triton X-114, a nonionic surfactant) were used. UV-visible spectroscopy has been used to obtain the degree of solubilization of RR2 in terms of the partition coefficient (Kc) and Gibbs free energy of partitioning (ΔG°p). Electrical conductivity data have been employed to detect the critical micelle concentration (CMC) of the surfactant systems in the presence of RR2 and, accordingly, to calculate the thermodynamic parameters of the micellization. From the obtained data, it is concluded that the micellization is spontaneous at all studied temperatures. Moreover, the micellization was observed to be driven by both enthalpy and entropy. The results also indicated that MMS have better solubilizing power than single micellar solutions. [ABSTRACT FROM AUTHOR]

Self-organization in mixed compositions based on hexadecyltriphenylphosphonium bromide (TPPB-16) and nonionic surfactant Brij 35 was studied using a complex of physicochemical methods (tensiometry, fluorimetry, dynamic light scattering, spectrophotometry) by varying the molar fraction of cationic surfactant (α1 = 0, 0.3, 0.5, 0.7, and 1.0). The solubilization capacities of the obtained nanosized aggregates toward the model hydrophobic probe Orange OT and the drug indomethacin were calculated. The TPPB-16/Brij 35 systems demonstrate a synergistic effect, manifesting itself in a decrease of the critical micelle concentration. The obtained mixed compositions with molar fractions of 0.5 and 0.7 demonstrate solubilization capacities toward Orange OT and indomethacin comparable to those of cationic amphiphile. The formation of the mixed composition TPPB-16/Brij 35 reduces the toxicity of the system while maintaining high functional activity. [ABSTRACT FROM AUTHOR]

The catalytic performance of lipase, an interfacially active enzyme, depends on the reaction medium. Novel reaction media like mixed micelles affect lipase catalysis mostly by stabilizing the lipase structure and increasing the substrate solubilization. Nonionic surfactant addition in ionic micelles formed mixed micelles and increased lipase catalysis by lowering detrimental lipase‐ionic surfactant hydrophobic and electrostatic interactions. Nonionic/nonionic mixed micelles enhanced activity and enantiomeric selectivity of free lipase but reduced those for immobilized lipase. Nonconventional cationic/cationic, anionic/nonionic/ionic liquid, and substrate/nonionic mixed micelles also improved lipase catalysis. Lipase activity was high in bile salt/surfactant mixed micelles but was low in bile salt/phospholipid mixed micelle. Mixed micelles have advantages like improving lipase‐substrate interaction, increasing water nucleophilicity, sometimes greater emulsion stability, and reduced product inhibition. In mixed micelles, increasing the lipase concentration can overcome the problem regarding inaccessibility of insoluble substrates. [ABSTRACT FROM AUTHOR]

[Display omitted] • Solubilization of H Acid has been compared in simple and mixed micellar systems. • Spontaneous mixed micelles formation improves solubilization capability. • Surfactant interaction was also investigated by DFT and absorption/emission spectra, MESP, FMO, DOS and band gap were successfully computed. • Micellization becomes less convenient with the increase in the CMC due to increase in temperature. • Thermodynamic parameters reveal the feasible and entropy driven nature of micellization process. The present research work investigates the solubility of an anionic dye 8-amino-1-naphthol-3,6-disulfonic acid (H Acid) within the micellar media of two cationic surfactants cetylpyridinium chloride (CPC) and cetyltrimethylammonium bromide (CTAB) as well as in the mixed micellar media of each cationic surfactant with Triton X-100 (TX-100). The data from differential absorption spectroscopy across a concentration range spanning from pre-micellar to post-micellar regions was used to determine the degree of solubilization by calculating the partition coefficient (K x), binding constant (K b) and Gibbs free energy associated with the relevant processes. Electrical conductivity of each cationic surfactant in the presence of H Acid was recorded in aqueous media and used to determine the CMC and subsequent thermodynamic parameters including entropy (ΔS m), enthalpy (ΔH m) and Gibbs free energy change (ΔG m) associated with the process of micellization. The computational analysis was carried out with GAUSSIAN 09 using a 6-311G + basis set with a DFT/ B3LYP hybrid approach and each set of energy minimization was executed to perform frequency calculations for Frontier molecular orbital analysis and to evaluate absorption spectra. Moreover, the molecular electrostatic potential surfaces (MESP) were also computed to find their suitable hydrophobic and hydrophilic interactions. [ABSTRACT FROM AUTHOR]

Critical micelle concentration (CMC) is a fundamental physical parameter of surfactant aggregation in solution. The CMC is determined by different methods, tensiometry, conductometry, microcalorimetry, fluorimetry, and so on. However, it is known that though CMC is reported as a single value, in reality, micelle formation occurs over a narrow range of concentration for different experimental procedures produce different results. We shall discuss about a unique procedure of measuring correct CMC applicable to all potential methods used in practice. This is essential for the evaluation of thermodynamic properties of the micelle forming process in pure and mixed states in terms of solution theories. As we in this short documentary want to deal with various aspects of Milton Rosen's research—wherein we have also worked—a few other facets of surfactant chemistry research, besides the micelle formation, are also briefly discussed. In mixed surfactant systems, synergistic effects in various surfactant properties like detergency, foaming, solubilization, and so on are found whereas in some others non‐synergistic effects are observed. Dehydration of micelles with an increase in temperature or by the addition of hydrophilic substances may cause clouding to the system. Soluble amphiphilic systems produce Gibbs monolayer at the air/water interface; insoluble amphiphiles form Langmuir monolayers. A documentary of the above aspects will be herein presented and discussed. We mention that this article is neither an original research article nor a review article. This is a mixture of the two: a documentary of both original research and some review of our works presented in memory of Prof. Milton Rosen. [ABSTRACT FROM AUTHOR]

The aggregation behavior of mixed micellar solutions of cationic hexadecylpiperidinium surfactants and nonionic surfactant Tween 80 is studied. The critical micelle concentration is determined by varying the component ratios, and a negative deviation from the ideal mixing model can be observed (synergistic effect). The adsorption parameters and surface potential of mixed micelles are estimated. The solubilizing effect individual and mixed compositions have on such hydrophobic biologically active compounds as bioflavonoid quercetin and systemic fungicide carboxin is characterized quantitatively via spectrophotometry. [ABSTRACT FROM AUTHOR]

[Display omitted] • Solubilization of BCA in Pluronics and their MMs was studied. • UV studies confirmed enhanced drug loading in 1:2 MMs than pure Pluronics. • DPV and Fluorescence studies validate the solubilization of BCA in micelles. • The in vitro release profile showed sustained release of BCA in 1:2 MMs. The present work was carried out to appraise the solubilization of Biochanin (BCA), a natural hydrophobic drug in pure Pluronics (P84, P123 and F127) as well as binary mixed micelles (P84-P123 and F127-P123) followed by an interactional study using various state of art techniques. The critical micelle concentration (CMC) of binary mixtures P84-P123 and F127-P123 was found to be significantly lower than pure Pluronics justifying the candidature of mixed micelles (MMs) as a better solubilizer for BCA. UV–visible studies revealed the enhanced solubility of BCA in P84-P123 (1:2) MMs (3.51 ± 0.087 mg/mL) and F127-P123 (1:2) MMs (2.94 ± 0.046 mg/mL) as compared to micelles of pure Pluronics (10% w/v), P84 (2.25 ± 0.039 mg/mL) and F127 (1.12 ± 0.036 mg/mL). Differential pulse voltammetry (DPV) results demonstrated significantly superior binding of BCA with P84-P123 (1:2) MM (K a = 2.60 × 105 M−1) as compared to pure P84 (K a = 1.415 × 105 M−1). Mixed micellization (P84-P123 (1:2)) leads to increase in micellar hydrodynamic diameter (D h = 16.09 nm) as compared to pure Pluronic P84 micelles (D h = 15.71 nm) which was further amplified (D h = 17.69 nm) after BCA loading. Different formulations of pure and MMs were subjected to in vitro drug release and MMs were found to slow down BCA release as compared to pure Pluronics (P84, P123). The results obtained in this study proved that P84-P123 (1:2) MMs are superior and more effective for the solubilization of BCA than pure and other MMs. Thus, the examined MMs hold the potential for advancing the development of solubilization techniques for other hydrophobic drugs with significant pharmacological value. [ABSTRACT FROM AUTHOR]

Abstract Mixed micelles (MMs) of Pluronic F127 (F127), Pluronic P123 (P123), and Vitamin E TPGS (TPGS) copolymers were prepared by the thin-film sonication method to encapsulate two phenolics with different polarities: magniferin (MGF) and quercetin (QCT). Mixture design was applied for the multi-response optimization of formulations of MGF-loaded MMs (MGF-MMs) and QCT-loaded MMs (QCT-MMs) with high encapsulation efficiency (EE) and drug loading (DL), but low critical micelle concentration (CMC). The optimal mass fractions of F127/P123/TPGS were 0.120/0.328/0.552 for MFG-MMs and 0.131/0.869/0.000 for QCT-MMs, providing EE (>95% (w/w)) and DL (>4.5% (w/w)) higher than those obtained by their individual copolymer components. The CMCs of MFG/QCT-MMs, detected by dynamic light scattering (DLS), were 0.009 ± 0.001 and 0.011 ± 0.001% (w/v), respectively, slightly lower than those obtained by profile analysis tensiometry (PAT). The results revealed that the PAT-CMC represented complete MM formation, while the DLS-CMC detected mono-molecular micelles. The MGF/QCT-MMs showed spherical morphology with diameters of 14.26 ± 0.52 and 21.50 ± 0.37 nm, and their zeta-potentials were −2.89 ± 1.70 and −3.22 ± 1.92 mV, respectively. Nuclear overhauser effect spectroscopy showed that MGF located in both hydrophilic and hydrophobic parts of MMs by orienting its xanthone backbone towards the core, but its glucoside close to the corona. QCT was preferentially located in the PPO core. Both MGF/QCT-MMs had excellent dissolution ability and sustained release in the simulated gastrointestinal environment. This study demonstrated that mixture design was successfully applied for multi-response optimization MM formulations of MGF and QCT, and the developed MMs had potential application as nanoparticle-based drug delivery systems. Graphical abstract Unlabelled Image Highlights • Mixed micelles (MMs) containing mangiferin (MGF) or quercetin (QCT) were developed. • Mixture design provides high multi-responses desirability of MGF/QCT-loaded. • The CMC values of MMs detected by PAT were more accurate than DLS. • QCT tightly located in MMs core, while MGF was close to both core and corona of MMs. • Both MMs sustain the release of loaded phenolics during gastrointestinal digestion. [ABSTRACT FROM AUTHOR]

Mixed micelles are formed in the binary compositions based on the cationic surfactant functionalized by the butyl carbamate fragment and nonionic surfactant Tween 80 in aqueous solutions. The aggregation parameters of the formed micelles (critical micelle concentration, size, and surface potential) depend on the component ratio in the system. The solubilization effect of individual and mixed micelles on the drugs of the heterocyclic series, indomethacin and 1-[5-(4-chlorophenyl)-3-phenylpyrrol-2-yl)]benzimidazol-2(3H)-one, was quantitatively characterized. [ABSTRACT FROM AUTHOR]

The present manuscript reports a systematic investigation on the solubilization of hydrophobic drug Quercetin (QCT) in pluronic F108 and its mixed micelles with surface active ionic liquids (SAILs) having same alkyl chain length but different hydrophobic head groups viz. 1-dodecyl-3-methylimidazolium bromide [Mim]; N-dodecyl-Nmethylpiperidinium bromide, [Pip]; N-dodecyl-Nmethylpyrrolidinium bromide, [Pyr]. Employing UV–visible spectroscopy, we have determined the solubility, loading efficiency and partition coefficient of QCT in the pluronic F108 and F108-SAILs mixed micelles. The F108-SAIL mixed micellar system possessed higher solubilization capacity for QCT. Further, the effect of varying composition of mixed micelles on the solubilization of QCT has also been evaluated and discussed in detail. A significant difference between the hydrodynamic diameter ( D h ) of loaded and unloaded F108 as well as F108-SAILs mixed micelles confirmed that QCT has been solubilized in these micelles. Differential pulse voltammetry (DPV) measurements have been successfully employed to determine the possible location of the QCT in the both pluronic F108 and pluronic F108-SAILs mixed micelles. These measurements indicated that most of QCT is solubilized in the core of the F108 and F108-SAILs mixed micelles. In vitro drug release study of three different F108-SAILs mixed micellar formulations show sustained release behavior according to their interaction with the QCT. Higher anticancer effects were observed in the case of micellar QCT than the free QCT confirm the efficiency of the prepared formulations. The results demonstrated that the composition of mixed micelles had a profound effect on solubilization capacity and the drug release behavior from the F108-SAILs mixed micelles can be easily tuned by changing the head group of SAILs. [ABSTRACT FROM AUTHOR]

Study of mixed micellization by (SDS + DTAB) in aqueous ionic liquid ([C 2 C 1 im][EtSO 4 ]) media. [Display omitted] • Aggregation behaviour of oppositely charged surfactants is presented in aqueous ionic liquid (IL) media. • Miscibility of surfactant mixtures gets drastically enhanced even with addition of small amount of IL. • IL induces charge screening around surfactant headgroups, thus influencing micellar composition and interaction parameters. • System exhibited near ideal behaviour at X W = 0.80 in terms of CMCs as well as micellar composition. • System has shown a transition from synergism (1.00 ≥ X W ≥ 0.90) to antagonism (0.70 ≥ X W ≥ 0.30). Surfactant self-aggregation within ionic liquid (IL) - based media has been investigated to compare and contrast the role of such media with that of water. Behavior of a surfactant mixture constituting of two surfactants with oppositely charged head groups, namely anionic sodium dodecylsulfate (SDS) and cationic n -dodecyltrimethylammonium bromide (DTAB), is assessed in aqueous IL media. Contrary to what is observed in water, it is shown earlier that effective charge screening of the surfactant headgroups by IL ions in a typical IL 1-ethyl-3-methylimidazolium ethylsulfate ([C 2 C 1 im][EtSO 4 ]) results in formation of (SDS + DTAB) mixed micelles with critical micelle concentrations (CMCs) ranging between those of SDS and DTAB, respectively. The miscibility of (SDS + DTAB) mixture in aqueous [C 2 C 1 im][EtSO 4 ] reveals that as the content of IL [C 2 C 1 im][EtSO 4 ] is increased, the miscibility of the surfactant mixture improves indicating increased charge screening involving ions of the IL and the surfactant headgroups. For water mole fraction (X W) ≤ 0.90, (SDS + DTAB) surfactant mixture is miscible in aqueous [C 2 C 1 im][EtSO 4 ] system in all proportions. For 1.00 ≥ X W ≥ 0.90, while synergism persists due to the presence of attractive electrostatic attraction between SDS and DTAB headgroups leading to mixture CMCs below the CMCs of SDS and DTAB, respectively, the extent of synergism diminishes with increase in IL [C 2 C 1 im][EtSO 4 ] in the solution. For X W = 0.80, the (SDS + DTAB) mixture exhibits CMC values that are closest to the values estimated assuming ideal behavior. For 0.70 ≥ X W ≥ 0.30, the (SDS + DTAB) exhibits antagonistic trend with CMC values higher than those estimated for ideal solution; the antagonistic trend gradually decreases with increase in [C 2 C 1 im][EtSO 4 ] and again attains close to ideal behavior in neat IL [C 2 C 1 im][EtSO 4 ]. This trend is subsequently manifested in the composition of the mixed micelles as well as in the net interaction parameter, β. Addition of small proportion of IL to water helps in solubilization of surfactant mixture of oppositely charged surfactants due to effective charge screening of the surfactant headgroups and results in formation of mixed micelles in aqueous IL media over complete composition range. [ABSTRACT FROM AUTHOR]

[Display omitted] • The interaction of BDMC with CTAB + Tween 20/Tween 60 mixed micelles was studied. • The encapsulation of BDMC by CTAB + Tween 60 mixed micelles was stronger. • The hydrophobic interaction was the main driving force for the encapsulation of BDMC. • BDMC was encapsulated in the hydrophobic alkyl chains of the mixed micelles. • The encapsulation of the mixed micelles enhanced the solubility and stability of BDMC. Bisdemethoxycurcumin (BDMC), one of the main curcuminoids, has numerous biological activities. However, the low solubility and stability of BDMC limit its application. In this work, in order to improve the solubility and stability of BDMC, we encapsulated BDMC using cetyltrimethylammonium bromide (CTAB) + Tween 20/Tween 60 mixed surfactants. The molar ratio of CTAB to Tween 20/Tween 60 was optimized by response surface analysis. The thermodynamic parameters (binding constant, enthalpy change, entropy change and Gibbs free energy change) for the interaction of BDMC with CTAB + Tween 20/Tween 60 mixed micelles were obtained by fluorescence spectroscopy and UV–visible absorption spectroscopy. Positive enthalpy change and entropy change indicated that hydrophobic interaction was the main driving force. Moreover, due to the longer alkyl chains of Tween 60, the encapsulation of BDMC by CTAB + Tween 60 mixed micelles was stronger. The encapsulation of BDMC in the hydrophobic alkyl chains by the mixed micelles was determined by fluorescence polarization technology, time-resolved fluorescence assay, and 1H nuclear magnetic resonance spectroscopy. Solubilization and stability experiments showed that the solubility of BDMC was improved and the alkaline hydrolysis of BDMC was inhibited due to the encapsulation of the mixed micelles. The improvement of the solubility and stability of BDMC was more obvious in CTAB + Tween 60 mixed micelles because of the stronger interaction between them. The above results indicated that CTAB + Tween 20/Tween 60 mixed micelles could be used to encapsulate BDMC to improve its solubility and stability. [ABSTRACT FROM AUTHOR]

In this study, the solubilization of anthracene and pyrene was investigated in micellar solutions of ethane-1,2-diyl bis( N , N -dimethyl- N -dodecylammoniumacetoxy) dichloride (C 12 H 25 (CH 3 ) 2 N + (CH 2 COOCH 2 ) 2 N + (CH 3 ) 2 C 12 H 25 ·2Cl − , 12-E2-12) and its equimolar binary mixtures of conventional cationic, anionic and nonionic surfactants in water. Critical micelle concentration ( cmc ) and other physicochemical parameters were determined by the surface tension and conductivity measurements at 30 °C. Much lower cmc value was obtained for 12-E2-12 than the corresponding monomeric surfactant dodecyltrimethylammonium chloride (DTAC). Lower experimental cmc than the ideal cmc and the negative interaction parameters imply synergistic interaction between the surfactants in the binary solutions. Order of solubilization capacity of the pure/mixed surfactant micelles, for anthracene and pyrene, are not the same. Among the pure surfactants, Brij 58 has highest and SDBS has least efficiency for dissolution of the solutes. The mixed systems 12-E2-12 + SDS and 12-E2-12 + Brij 58 have highest dissolution power for anthracene and pyrene, respectively. Solubility enhancement was observed for both the solutes in the equivalent binary mixtures of the dicationic gemini 12-E2-12 with the anionic conventional surfactants SDS and SDBS. To determine the toxicity of 12-E2-12 and to quantify its interaction with erythrocytes, we have performed the hemolytic assessment. As regards the hemolytic activity and biodegradability test, 12-E2-12 is less toxic and readily biodegradable. [ABSTRACT FROM AUTHOR]

Pluronic/bile salt/phospholipid mixed micelles (Pluronic/BS/PS-MM) drug carrier system for solubilization hydrophobic drugs was developed. A typical hydrophobic compound, pyrene, was selected as a representative hydrophobic compound to model the hydrophobic drugs. Five Pluronics, F68, F88, F98, F108, and F127 with different PPO chain length were studied. CMC data and solubilization capacities were obtained from a pyrene solubilization method. A closed association model was used to obtain the thermodynamic parameters: Gibbs free energy (ΔG°), enthalpy, (ΔH°) and entropy (ΔS°) of micellization. The results obtained from these experiments suggest that the mixed micelles was more stable and solubilize more pyrene than single one; and the solubilization of pyrene was strong effected by the PPO block size, thus accentuating synergistic interaction mechanism in Pluronic/BS/PS-MM. The study generated an important dataset so as to compare the effect of different Pluronics on solubility capacity of Pluronic/BS/PS-MM. [ABSTRACT FROM AUTHOR]

Although detergents are routine tools in biomembrane research, their use remains empirical. We propose that solubilization is the result of a balance between two parameters: (i) the energy associated with bending of phospholipid monolayers into a curved micellar surface, and (ii) the energy associated with filling the void in the center of the resultant mixed micelle. In this review, we show that reliable data on the phase boundaries, and their dependence on various conditions, are consistent with this hypothesis, even if the data might have been interpreted differently. Although most of the experimental data discussed here were obtained with the non-ionic detergent Triton X-100, the conclusions should be applicable to a wide variety of detergents. [ABSTRACT FROM AUTHOR]

Abstract: Pluronic block copolymers offer affluent phase behavioral characteristics and are extensively investigated for drug delivery applications. Hydrophobic Pluronics produce larger aggregates whereas hydrophilic Pluronics often generate small-sized micelles in aqueous milieu. To overcome the limitations and combine the advantages of different kinds of Pluronics the mixing of such two types of Pluronics is studied here, especially for hydrophobic Pluronic L81 and relatively hydrophilic Pluronic P123. Critical micelle concentration (CMC) of the developed binary mixtures was 0.032mg/ml as evidenced from pyrene fluorescence spectroscopy and is located in between that of the individual Pluronics. Dynamic light scattering (DLS) showed very small particle sizes (∼20nm) and low polydispersity indices for most of the mixed micelles. Transmission electron microscopy (TEM) demonstrated spherical shape of micelles. Based upon the ratio of hydrophobic and hydrophilic Pluronics, dispersions of varied stability were obtained. With 0.1/1.0wt.% and 0.5/3.0wt.% of Pluronic L81/P123, stable dispersions were obtained. Stability was assessed from turbidity measurement, size analysis and clarity of dispersion on standing. Micelles were also found to be stable in bovine serum albumin (BSA) solution. Mixed micelles showed fairly high entrapment efficiency, loading capacity and sustained release profile for aceclofenac (Acl), a model hydrophobe. Presence of salt lowered Acl solubilization in micelles. Thermodynamic parameters for Acl solubilization in mixed micelles revealed high partition coefficient values and spontaneity of drug solubilization. Thus, the developed novel mixed micelles hold promise in controlled and targeted drug delivery owing to their very small size, high entrapment efficiency and stability. [Copyright &y& Elsevier]

Abstract: The effects of sodium dodecyl sulfate (SDS) and dodecyl trimethylammonium bromide (DTAB) and polyoxyethylene (10) isooctyl phenyl ether (TX-100) as additives on the association characteristics of an amphiphilic tri-block copolymer P105 (E37P56E37) were monitored by surface tension, dynamic light scattering and viscosity measurements at 303.15 and 313.15K in water as well as in 200mM sodium chloride aqueous solutions. The successive addition of surfactants resulted not only in the increase of critical micelle concentration (CMC) of the copolymer and also in CMC/C 20 values indicating that the adsorption tendency of the copolymer–surfactant complexes at water/air interface is more than the association in the bulk. The experimental CMC data of binary mixtures were analyzed using regular solution theory to calculate the interaction parameter. The mixtures exhibited synergistic interaction behavior. The apparent hydrodynamic radius of copolymer micelles decreased drastically by the addition of surfactants and this destabilization effect has been attributed to the shift of copolymer micelle↔unimer equilibrium in favor of latter. Dexamethasone, a drug poorly soluble in aqueous media was solubilized into individual copolymer or copolymer–surfactants solutions followed by their loading onto agar agar hydrogels for its immobilization and dispersion. The drug release profiles were established and drug diffusion coefficients were calculated. [Copyright &y& Elsevier]

Abstract: The structure of Gemini surfactants makes them potentially useful candidates in terms of their performance, particularly in mixed micelles for different surfactant applications. We have studied mixed micellization and surface properties of binary mixtures of cationic Gemini pentanediyl-1,5-bis(dimethylcetylammonium bromide) (G5, 16-5-16) with conventional cationic cetylpyridinium chloride (CPC), anionic sodium bis(2ethylhexylsulfosuccinate) (AOT), and nonionic polyoxyethylene 10 cetyl ether (Brij 56) in detail by conductometric and tensiometric methods. The interfacial and bulk behaviors were investigated using theoretical models of Clint, Rubingh, Rosen, and Maeda to explain and compare the results of binary mixtures of G5 with the conventional surfactants. The synergism was observed in all the binary systems in the micelle as well as at the interface with expansion of molecular area per molecule. Greater synergistic interaction in the micelles has been found to reduce the solubilizing capacity towards polyaromatic hydrocarbons (PAHs). [Copyright &y& Elsevier]

Abstract: The solubilisation of the functionalized silicone oil aminoethyl aminopropyl methylpolysiloxane WR 1300 has been investigated in aqueous solutions of the surfactant pentaethoxy-iso-tridecanol (iC13E5). The silicone oil consists of a linear backbone with an average of 200 dimethylsiloxane units and 2–3 functionalized side groups. In various applications the compound is considered a silicone oil. The surfactant iC13E5 forms a Lα-phase in water, and with decane a microemulsion can be obtained. The solubilisation experiments started with lamellar iC13E5 phases. With proper amounts of WR 1300 transparent, optically isotropic but highly viscous single phases are formed. These phases cannot be considered true microemulsions with an oil core and a surrounding surfactant layer. Cryo-TEM micrographs show micelles with irregular shapes and about 25nm diameter. Their size is independent of the oil/surfactant ratio. It can be explained on the basis of a model where the amino groups of the oil are all found at the surface of the micelles, limiting the radius of the aggregates to the largest length of the polydimethylsiloxane backbone between two such groups or between one end of the oil and one functionalized group. The micellar structures contain only a few siloxane molecules exposing their hydrophilic groups to the water. The functionalized silicone oil molecules can thus be considered as surfactant molecules with a few polar groups and a large hydrophobic chain from dimethyl siloxane. [ABSTRACT FROM AUTHOR]

Abstract: A remarkable part of newly developed active pharmaceutical ingredients is rejected in early phase development and will never find a way to a patient because of poor water solubility which is often paired with poor bioavailability. Considering such arising solubility problems the development of application vehicles like mixed micelles (MM) is a challenging research topic in pharmaceutical technology. While known classical MM systems are composed of phosphatidylcholine and bile salts, it was the aim of this study to investigate if alternatively developed MM systems were superior in solubilization of different hydrophobic drugs. The novel MM were also comprised of phosphatidylcholine and (contrarily to bile salts) different other suitable surfactants forming binary MM. As model water-insoluble drug substances two benzodiazepines, diazepam and tetrazepam, and the steroid estradiol were chosen. In this study the solubilization capacities of newly developed MM were compared to those of classical lecithin/bile salt MM systems and different other surfactant containing systems. The MM system with sucrose laurate and hydrogenated PC (hPC) at a weight fraction of 0.5 was found to be superior in drug solubilization of all investigated drugs compared to the classical lecithin/bile salt mixed micelles. Further, a polysorbate 80 solution, also at 5%, was inferior with regard to solubilize the investigated hydrophobic drugs. The MM sizes of the favorite developed MM system, before and after drug incorporation, were analysed by dynamic light scattering (DLS) to evaluate the influence of the drug incorporation. Here, the particle sizes, before and after drug incorporation, remained constant, indicating a stable formation of the solubilizate. Further the critical micelle concentration (CMC) of MM before and after drug incorporation was analysed by three different determination techniques. Constant CMC-values could be obtained regardless if diazepam was encapsulated within the MM or unloaded MM were analysed. [Copyright &y& Elsevier]

Numerical characteristics of the aggregation behavior of geminal alkylammonium surfactants in aqueous solutions (the size of micelles, the packing of surfactant molecules, the surface potential, the extent of counterion binding) were determined. The formation of mixed micelles geminal surfactant/decylamine resulted in substantial decrease in amine pK; this is the crucial factor determining the strong catalytic effect of the system in ester bond cleavage processes. [ABSTRACT FROM AUTHOR]

Abstract: A mixed micelle that comprised of MPEG–PLA (MPP) and Pluronic® copolymers was developed for enhanced bioavailability and to overcome multidrug resistance of docetaxel in cancer therapy. The mixed micelles that sufficiently solubilized docetaxel were evaluated for the effect of Pluronic® copolymers weight ratio on the mixed micelles with respect to drug loading and drug release. In vitro, cell viability and cytotoxicity studies in KB and KBv cells revealed that the mixed micellar formulations were more potent than the commercial docetaxel formulation (Taxotere®). In vivo pharmacokinetics study in rats showed that the mixed micelles significantly enhanced the bioavailability of docetaxel (3.6 fold) than Taxotere®. Moreover, antitumor activity assessed in KBv cancer xenograft BALB/C nude mice models showed that the mixed micelles significantly reduced the tumor size than the control (Taxotere®). Clear differences in the intracellular uptake of docetaxel between MPP and mixed micelles were observed using confocal laser scanning microscopy. This study presents not only a new micelle structure for a diblock–triblock copolymer system, but also a method for enhanced bioavailability of docetaxel and to overcome some of the limitations on its multidrug resistance in cancer therapy. [Copyright &y& Elsevier]

The effect of combining butyl benzene sulfonate as hydrotrope with a surfactant in aqueous solutions is investigated for isolation of piperine, an alkaloid, from black pepper. The standard free energy change associated with piperine solubilization in the aqueous solutions of surfactant and hydrotrope individually and in their mixtures is determined from the solubility of piperine in these solutions. A combination of sodium dodecyl sulfate (SDS) and the hydrotrope gives increased percentage extraction of piperine as compared to the hydrotrope alone. The piperine purity recovered from aqueous solutions was higher as compared to the purity of piperine recovered using organic solvents. The piperine crystallized from aqueous solutions of surfactants and hydrotrope also showed cleaner surfaces and uniform structures with sharp edges, unlike the particles crystallized from organic solvents. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the solubilization capacity of sodium cholate/lecithin-mixed micelles and to evaluate the potential of mixed micelles as a carrier of cyclosporine A for intravenous infusion. The mixed micelles were prepared by coprecipitation technique. The formulation components and preparation procedures, which may affect the solubilization of cyclosporine A, were studied. The dilution stability of cyclosporine A-containing mixed micelles was investigated. Pharmacokinetic behaviors of mixed micelles in rabbits after intravenous infusion were compared with Sandimmun®. Results showed the strategies to increase the solubility of cyclosporine A include lowering the molar ratio of sodium cholate to lecithin, increasing the concentration of lecithin, and reducing the ionic strength of the dispersion medium and temperature. The largest solubility was found to be 5.42±0.16 mg/ml. The leakage of mixed micelles in 5%glucose (5.84%) was much less than that in saline solution (36.7%). The relative bioavailability of mixed micelles versus Sandimmun®was 112±20%, and statistical analysis demonstrated both preparations were bioequivalent. Sodium cholate/lecithin-mixed micelles are promising carriers in the intravenous delivery of cyclosporine A, considering their capability of large-scale production and low-toxic property. [ABSTRACT FROM AUTHOR]

Most of the studies on the solubilization of model membranes conducted thus far involved model membranes made of liquid-crystalline phospholipids. Relatively little is known on the influence of temperature and of the phase of the lipid bilayers on their solubilization by detergents. The aim of the present study was to gain knowledge about the temperature and phase dependence of the solubilization of phospholipid bilayers by the non-ionic detergent Triton X-100 (TR). Detailed investigation of the kinetics of the solubilization of dipalmitoylphosphatidylcholine (DPPC), as well as of palmitoyloleoylphosphatidylcholine (POPC) by TR at different temperatures reveals that: (i) solubilization of DPPC is a relatively slow process, especially below Tm. This means that in order to prevent misleading conclusions it is important to monitor the solubilization after a steady state is established. (ii) Both the steady state structure and size of DPPC/TR aggregates and the kinetics of solubilization depend on temperature. (iii) The TR concentration required for solubilization of POPC bilayers is an increasing function of temperature, although no phase change of bilayers occurs in the studied temperature range. (iv) Detailed studies of the temperature-induced changes of the aggregates present in DPPC/TR or POPC/TR mixtures suggest that the state of aggregation at any temperature above 23 °C represents equilibrium. By contrast, for DPPC/TR mixtures at 4 °C all the processes are very slow, which complicates the interpretation of results obtained through the common practice of studying “rafts” by investigating detergent-resistant membranes. [Copyright &y& Elsevier]

Tensiometric studies on several binary surfactant mixtures containing anionic surfactants, viz., metal (lithium, sodium, potassium, copper, cobalt, and magnesium) dodecyl sulfates and a nonionic surfactant (Triton X-100) in water at different mole fractions (0–1) provide critical micelle concentration (CMC) values. The composition of mixed micelles and the interaction parameter, β, evaluated from the CMC data for different systems using Rubingh's theory, are discussed. Marked interaction is observed with monovalent dodecyl sulfates. The influence of counter-ion valence on the formation of mixed micelles was investigated for anionic-nonionic systems, and results indicated that mixed systems with bivalent counter-ions in metal dodecyl sulfate resembled nonionic-nonionic systems where weak/negligible interaction has been reported. Salt addition revealed the weakening of interaction in the mixed systems, which is attributed to the head group charge neutralization and the dehydration of the ethylene oxide units of the nonionic surfactants. A few cloud point and viscosity data are also reported. [ABSTRACT FROM AUTHOR]

Organic dyes are extensively used in various industries i.e. textile. Their hydrophobicity is the main bottleneck in their applications, where the dispersion medium is water. The poor solubility of such colorants is addressed by the addition of different surfactants, but none of the single surfactants proved fully satisfactory so far. Herein, different formulations of anionic and cationic surfactants (SDS, SDBS, CTAB, and TTAB) have been employed to enhance the solubility and stability of a cationic dye, ethyl violet (EV). Spectrophotometric data helped to calculate the values of the partition coefficient (K x), binding constant (K b), and Gibbs energies of respective processes. The said parameters are indicators of the degree of solubilization which were calculated at 298.15 K. The data of specific conductance was utilized to estimate critical micelle concentration (CMC) and to calculate thermodynamic parameters; Gibbs energy (ΔG m), entropy (ΔS m), and enthalpy (ΔH m) of micellization for surfactants in the presence of dye at different temperatures (303.15–318.15 K). The obtained results from both techniques revealed the spontaneous nature of micellization and solubilization. Furthermore, the binding and partitioning ability of mixed micellar media came out to be significantly different than that of the solo surfactant system due to the synergistic effect of cationics on micellar media of anionics. It shows how dye is lying inside the SDS and SDBS micelle. [Display omitted] • Locus of incorporated dye is near water-micelle interface. • Charge density of a micelle governs its solubilizing efficacy. • Mixing of different surfactants has a synergistic effect on solubilizing power. [ABSTRACT FROM AUTHOR]

As we enter the new millennium, manufacturers of laundry detergents would like to provide new products for the twenty-first century. With the goal of achieving new and better performance characteristics, design strategies for research and development should be defined. This paper highlights the importance of micellar relaxation kinetics in processes involved in detergency. Earlier Shah and coworkers showed that the stability of sodium dodecyl sulfate (SDS) micelles plays an important role in various technological processes. The slow relaxation time (τ2) of SDS micelles, as measured by the pressure-jump technique, was in the range of 10−4 to 101 s, depending on the surfactant concentration. A maximal relaxation time and thus a maximal micellar stability was found at 200 mM SDS (5 s), corresponding to the least-foaming, largest bubble size, longest wetting time of textile, largest emulsion droplet size, and the most rapid solubilization of oil. These results are explained in terms of the flux of surfactant monomers from the bulk to the interface, which determines the dynamic surface tension. More stable micelles lead to less monomer flux and hence to a higher dynamic surface tension. The relaxation time for nonionic surfactants (as measured by the stopped-flow technique) was much longer than for ionic surfactants because of the absence of ionic repulsion between the head groups. The τ2 was related to dynamic surface-tension experiments. Stability of SDS micelles can be greatly enhanced by the addition of long-chain alcohols or cationic surfactants. In summary, relaxation time data of surfactant solutions enable us to predict the performance of a given surfactant solution. Moreover, results suggest that one can design appropriate micelles with specific stability, or τ2, by controlling surfactant structure, concentration, and physicochemical conditions, as well as by mixing anionic/cationic or ionic/nonionic surfactants for a desired technological application, e.g., detergency. [ABSTRACT FROM AUTHOR]

The solubilization of cholesterol by anionic surfactant mixtures was studied as a function of their HLB values. The relationship between the logarithm of the critical micelle concentration and the HLB value of the mixtures was not linear, which was attributed to a lack of strict additivity of the HLB values. The solubilized cholesterol/surfactant ratio was determined and it was found to be higher than that in bile salts in all the studied surfactant mixtures. Below HLB=24, emulsions were obtained, and the remaining cholesterol was solid. Above that value, limpid solutions were obtained, giving a solubility maximum at HLB≈35. The non-solubilized cholesterol was mainly in the form of lamellar mesophase. [ABSTRACT FROM AUTHOR]

Solubilization of decafluorobiphenyl (FBIP) by surfactants in aqueous solution was examined to investigate the properties of micelles composed of surfactants having a per-fluorocarbon chain. Fluorocarbon surfactants solubilize FBIP better than hydrocarbon surfactants. Significant solubilization by fluorocarbon surfactants was observed upon addition of salt. Highly synergistic solubilization of FBIP using surfactant mixtures was also observed for fluorocarbon and hydrocarbon surfactants in the presence of salt. The high solubilization ability of surfactants can be attributed to micelle growth. A simple geometrical consideration of molecular packing in micelles revealed that the characteristic micelle is composed of bulky fluorocarbon chains. The solubilization behavior accompanied by micelle growth would be closely associated with a change in interfacial contact area between the micelle core and bulk water. The behavior of fluorescence intensity of micelle-solubilized FBIP also indicated a change in micropolarity of fluorocarbon micelles accompanied by micelle growth. [ABSTRACT FROM AUTHOR]

The aqueous solubility of teniposide in detergent and phospholipid mixed micelles was investigated as functions of the detergents and lipids composing the mixed micelles, the molar ratio of detergent to phospholipid, and the total lipid concentration of the system. The polarity, the charge of the phospholipid, and its saturation affected the solubilization potential of the micelles. Physical chemical factors such as the pH, ionic strength, and temperature of the dispersion medium also altered the solubilization capacity of the system. The results are explained by the changes occurring in the critical micelle concentration and packing arrangements of the aggregates. The desired solubility of teniposide can be achieved by adjusting the studied parameters to the optimum values. Teniposide-containing mixed micelles were spontaneously converted to drug-containing vesicles upon aqueous dilution; therefore, the precipitation of the drug was totally eliminated. In conclusion, mixed micelles as proliposomes can be a suitable drug carrier system for insoluble compounds such as teniposide. [ABSTRACT FROM AUTHOR]

Solubilization of octafluoronaphthalene (OFN) by fluorocarbon and hydrocarbon surfactants in aqueous solutions has been examined to investigate the effects of mixing surfactants and added salt. Diethylammonium perfluoronanoate (DEAPFN) micelles have the most solubilization power toward OFN. The difference in micellar solubilization power will be caused by the hydrophobicity of ionic groups and micellar size. Large positive synergistic effects on solubilization behavior were observed in the DEAPFN-diethylammonium tetradecyl sulfate mixed micellar systems. Solubilization of OFN depended on the concentrations of added salt and the aggregation number, that is, the micellar size. [ABSTRACT FROM AUTHOR]

Most of organic compounds being hydrophobic in nature are insoluble or sparingly soluble in water. The improvement in solubility is one of the major challenges in their industrial applications. Said issue can be addressed using micellar solutions of surfactants. Surfactants, owing to their inherent amphiphilic nature, have invited the interest of many researchers. It has, however, been observed that the stability and solubilizing capability of a single surfactant-based colloidal system is not up to the mark. To overcome this problem, we have formulated and applied composite micelles of CTAB/TX-100 and CPC/TX-100 as carriers of direct red 28 molecules to aid dispersion, solubility and stability of the dye in aqueous medium. Herein, thermodynamics of micellization and degree of the dye partitioning have been quantified conductometrically and spectroscopically. Results suggest that blend of different surfactants act synergistically to augment the dye partitioning. Furthermore, it has also been noted that micellization of surfactants, counterion binding and the dye partitioning are spontaneous processes. It is representing how do micellization and solubilization of the DR-28 take place in aqueous micellar media. Unlabelled Image • Solubility of DR-28 improved significantly by surfactant media. • Mixed micelles of surfactants are more stable and more hydrophobic. • Mixed system of CPC/TX-100 is better choice for solubilization of DR-28. • Mixed micellar enhanced solubilization is more spontaneous. • The locus of solubilized dye is near water-micelle interface. [ABSTRACT FROM AUTHOR]

The poor bioavailability of polycyclic aromatic hydrocarbons (PAHs) is the main limiting factor for their biodegradation in contaminated sites. The addition of biosurfactant is an effective method for enhancing the bioavailability of PAHs. Suitable low molecular weight (LMW) organic matters have been shown to increase the bioavailability of PAHs. Therefore, we investigated the effect of phenol, which often co-exists with PAHs, on the biodegradation of PAHs in biosurfactant solution. The results show that the critical micelle concentration (CMC) of the biosurfactant decreased after phenol was added. The formation of mixed micelles resulted in enhancement of PAHs dissolution. The weight solubilization ratio (WSR) values of biosurfactant for Phe, Pyr and BaP in phenol solution are approximately 1.34, 1.40 and 1.67 times that of the control group, respectively. Phenol, therefore, can assist biosurfactant to increase the availability of PAHs by microbes. The bioavailability of PAHs in sludge increased from 27.7% to 43.1% after the biosurfactant was added, and reached a maximum of 49.2%, following the simultaneous addition of phenol and biosurfactant. Phenol also improved the degradation of PAHs by Stenotrophomonas sp. N5 in biosurfactant solution. Image 1 • Phenol decreased the critical micelle concentration (CMC) of biosurfactants. • Phenol increased the dissolution of PAHs in biosurfactant solutions. • Phenol improved the biodegradation of PAHs in solutions containing biosurfactants. [ABSTRACT FROM AUTHOR]

This study is an approach to especially investigate (i) the micellization behaviour of a cationic gemini surfactant 16-E2-16 (ethane-1,2-diylbis(N,N-dimethyl-N-hexadecylammoniumacetoxy) dichloride) and its equimolar binary mixtures with conventional cationic (CTAC), anionic (SDS), non-ionic (Brij 58) surfactants, and (ii) the solubilization capacity of the pure/mixed surfactant systems towards polycyclic aromatic hydrocarbons (PAHs) by 1H NMR spectroscopy. Proton chemical shifts (δ , ppm) of the binary or ternary surfactant/solute systems have been compared with the pure surfactant solutions. The results (δ values) indicate favoured micellization for all the surfactant solutions and the extent of solubilization depends on the nature of surfactants as well as solutes. Location of the PAHs in different parts, such as palisade layer, inner palisade layer and core of micelles alter the δ values. More pronounced changes in δ value of various protons of CTAC and Brij 58 indicate higher solubilization of pyrene. Among all the three surfactant combinations, 16-E2-16 + SDS is the most compact system as compared to the 16-E2-16 + CTAC and 16-E2-16 + Brij 58 systems. Image 1 • Study of equimolar gemini-conventional surfactant mixtures by 1H NMR spectroscopy. • Chemical shift (δ) data imply attractive interaction among surfactant components. • Pure Brij 58 and CTAC micelles show maximum dissolution capacity towards pyrene. • PAH−solubility in anionic surfactant micelles is lower than the cationic micelles. • Change in δ values suggest distinct location sites of solutes in micellar solutions. [ABSTRACT FROM AUTHOR]

The present study reports the enhanced solubilizing power of mixed micellar media in comparison to single micellar media. The solubilization of anionic direct dye, Direct Brown 2 (DB-2) has been investigated in micellar media of cationic surfactants; cetyltrimethyl ammonium bromide (CTAB), cetylpyridinium chloride (CPC) and in mixed micellar media of each with nonionic surfactant Triton X-100 (TX-100) using UV–visible spectroscopy and conductometry. The UV–visible spectroscopy has been used to evaluate the degree of solubilization in terms of binding constant, K b , Gibbs energy of binding, ΔG b , partition coefficient, K x , and Gibbs energy of partition, ΔG p. Furthermore, electrical conductivity data, taken at different temperatures, has been employed to find out critical micelle concentration (CMC) and different thermodynamic parameters like enthalpy, ΔH m , entropy, ΔS m and Gibbs energy of micellization, ΔG m of reported surfactants in presence of dye. Results reveal spontaneous nature solubilization and binding of dye in both micellar and mixed micellar solutions of surfactants. The micellar system of CTAB as well as mixed micellar solutions of CTAB/TX-100 are recommended to be used to achieve higher degree of solubilization. DB-2 is anionic in nature so it favorably tends to reside close to positively charged surface of micelle in all micellar and mixed micellar media. Unlabelled Image • The composite micelles of both surfactants are more hydrophobic and stable. • Mixed micellar medium of CTAB/TX-100 is better than CPC/TX-100 for DB-2. • DB-2 is solubilized near water-micelle interface in all surfactant systems. • Mixed micellar enhanced solubilization is more spontaneous. [ABSTRACT FROM AUTHOR]

The effect of solubilized cholesterol and 1-monoolein on the size of micellar aggregates of sodium taurocholate (3α,7α,12α-trihydroxy-5β-cholanoyl taurine) has been determined in vitro.Measurements of the self-diffusion coefficient of sodium taurocholate (0.15 m in Na+) at 37°C and pH 7.4 led to the conclusion that at concentrations above the critical micelle concentration (6.7 mm) the solutions contain, besides monomeric ions, a single micellar species containing five taurocholate ions. In the presence of cholesterol, much larger micelles are formed, apparently containing one molecule of cholesterol and 25 of taurocholate. These mixed micelles coexist with small micelles of pure taurocholate as well as the taurocholate monomers. The addition of 1-monoolein increases the solubility of cholesterol in the taurocholate solution, but not by reducing the size of the micelle into which the cholesterol will fit: three-component micelles (monoolein-taurocholate-cholesterol) are, if their diffusion coefficients are any guide, still larger than taurocholate-cholesterol micelles. The molar ratio of cholesterol to taurocholate is higher in these solutions than in the absence of monoolein.Comparison with work by other authors on taurodeoxycholate-cholesterol micelles suggests that more than 25 molecules of either dihydroxy or trihydroxy bile salts are needed to transport each molecule of cholesterol through an aqueous solution in the absence of other amphipathic molecules.