Surfactants can be used to increase the solubility of poorly soluble drugs in water and to increase drug bioavailability. In this article, solubilization of macrolide antibiotic erythromycin is investigated by employing spectrophotometry and tensiometry in micellar solutions of nonionic (Brij56, Brij58, Brij35, Brij30), cationic (cetyltrimethylamonium bromide, CTAB; tetradecyltrimethylammonium bromide, TTAB; dodecyltrimethylammonium bromide, DTAB), and anionic (sodium dodecylbenzenesulfonate, SDBS; sodium dodecylsulfate, SDS) surfactants and then compared. The results showed that irrespective of the surfactant type, the solubility of erythromycin increases linearly with increasing surfactant concentration, as a consequence of association between the drug and micelles. Solubilization capacity has been quantified in terms of molar solubilization ratio (Rm,S), micelle−water partition coefficient (KM), binding constant (K1) between solubilizate monomer and vacant micelle, and the free energy of solubilization...

Solubilization Capabilities of Some Cationic, Anionic, and Nonionic Surfactants toward the Poorly Water-Soluble Antibiotic Drug Erythromycin

Supramolecular solvents (SUPRAS) have progressively become a suitable alternative to organic solvents for sample preparation in chromatographic analysis. The inherent properties of these nanostructured solvents (e.g. different polarity microenvironments, multiple binding sites, possibility of tailoring their properties, etc.) offer multiple opportunities for the development of innovative sample treatment platforms not approachable by conventional solvents. In this review, major achievements attained in the combination SUPRAS–chromatography in the last 20 years as well as the challenges that should be addressed in the near future are critically discussed. Among achievements, particular attention is paid to the theoretical and practical knowledge gained that has helped make substantial progress in the area. In this respect, advances in the understanding of the mechanisms involved in SUPRAS formation and SUPRAS–solute interactions driving extractions are discussed, with a view to the setting up of knowledge-based extraction procedures. Likewise, the strategies followed to improve the compatibility of SUPRAS extracts with liquid and gas chromatography and adapt SUPRAS-based extractions to different formats are presented. Ongoing efforts to apply SUPRAS in multicomponent extractions and synthesize tailored SUPRAS for the development of innovative sample treatments are highlighted. Among challenges identified, discussion is focused on the automation of SUPRAS-based sample treatment and the elucidation of SUPRAS nanostructures, which are considered essential for their acceptance in routine labs and the design of tailored SUPRAS with programmed functions.

Twenty years of supramolecular solvents in sample preparation for chromatography: achievements and challenges ahead.

Hypothesis The current mechanism of surfactant enhanced oil recovery (EOR) mainly relies on forming middle-phase microemulsions to get ultra-low oil-water interfacial tension. However, residual oil can also be recovered using low concentration surfactant solutions without microemulsion formation, and the interaction between the surfactant solution and crude oil at very early contact has not been studied yet. We hypothesize micelle solubilization of oil as an alternative EOR mechanism. Experiments Sodium dodecylbenzenesulfonate (SDBS), anisole and 1-hexene were used as a model surfactant and model polar and nonpolar compounds in crude oil, respectively. The interaction between SDBS micelles and these two additives was investigated with dynamic light scattering, UV–Vis spectroscopy, 1H NMR spectroscopy, cryogenic transmission electron microscopy, confocal microscope and small angle neutron scattering. Findings SDBS micelles become larger upon increasing additive concentration to transfer into swollen micelles. 1-Hexene is localized in the micelle core, and retains the spherical micelle shape, while anisole resides in the palisade layer and weakens the electrostatic repulsions among surfactant headgroups, inducing a sphere–rod transition. No emulsion droplets were observed for 0.2 wt% SDBS solution until 1.5 wt% anisole or 1-hexene was introduced. These findings help understanding the role surfactant micelles in EOR and propose a new mechanism for surfactant EOR processes.

Oil solubilization in sodium dodecylbenzenesulfonate micelles: New insights into surfactant enhanced oil recovery.

Measurements of the cloud point (CP) of non-ionic surfactant polyoxyethylene (20) sorbitan monooleate (Tween 80) were performed in aqueous solution and in the presence of ceftriaxone sodium trihydrate (CFT) drug, with specific attention to CFT drug + different salts mixtures studied and discussed in detail. The CP values of Tween 80 in aqueous medium tend to reduce with enhanced concentration of surfactant. The CP values of Tween 80 solutions were also found to be decreased with increasing concentrations of drug used. The CP values of Tween 80 + drug mixtures were found to be lower in magnitude in the presence of salts in comparison to their absence, and the outcomes of sodium salts (between 0.001 and 0.2 mol·kg–1) in reducing CP values were found to be in the following order: NaCl < Na2SO4 < Na2CO3. In the case of potassium salt the order of reducing the CP values of Tween 80 + drug is similar, but in the case of ammonium salt the order is NH4Cl < Na2CO3 < (NH4)2SO4. The influence of cationic co-ions suc...

https://pubs.acs.org/doi/pdf/10.1021/acs.jced.0c00542

Investigation of the Effect of Various Additives on the Clouding Behavior and Thermodynamics of Polyoxyethylene (20) Sorbitan Monooleate in Absence and Presence of Ceftriaxone Sodium Trihydrate Drug

Dynamic light scattering (DLS) measurements have been performed at 30 °C to see the effects of additives on the microstructure of gemini alkanediyl-α,ω-bis(dimethylcetylammonium bromide) surfactants, (Br-, n-C16H33N+Me2−(CH2)s−Me2− N+n-C16H33, Br-, 16−s−16, where s = 4, 5, 6). In pure aqueous solutions, the hydrodynamic diameter, Dh, was found to increase rapidly with geminis in comparison to their monomeric counterpart cetyltrimethylammonium bromide (n-C16H33N+Me3, Br-, CTAB) on increasing surfactant concentration. The additives considered in the present study are n-alcohols (C4-C6OH) and n-hexylamine (C6NH2) on the micellar growth of 0.03 M 16−4−16 in the presence and absence of 0.001 M KBr. The presence of 0.001 M KBr or organic additives at lower concentrations singly or jointly has little effect on the micellar size. As the chain length of the additive increases, the size increases with the increase of additive concentration, the magnitude being substantial in the presence of 0.001 M KBr. However, fo...

Dynamic light scattering studies of additive effects on the microstructure of aqueous gemini micelles

Clouding phenomenon and SANS studies on tetra-n-butylammonium dodecylsulfate micellar solutions in the absence and presence of salts

Hydrophobic interactions control the morphologies of both surfactant aggregates and proteins. Globular proteins "denature" upon addition of excess amounts of denaturants such as urea. Understanding the microscopic basis of the urea effect on proteins or supramolecular aggregates such as micelles has always been a debated issue. Inspired by this need, the effect of urea (U), thiourea (TU), monomethylurea (MMU), dimethylurea(DMU), tetramethylurea (TMU), dimethylthiourea (DMTU), and tetramethylthiourea (TMTU) on the structural transition (spherical micelles to rod-shaped micelles, s --> r) in the sodium dodecylbenzenesulfonate (SDBS)-1-pentanol system has been investigated through dynamic light scattering(DLS) and viscosity measurements at 25 degrees C. 1-Pentanol, at 0.14 M, is found to promote s --> r in this system (0.2 M SDBS). The presence of the additives causes, in almost all cases, a decrease and increase in this 1-pentanol concentration depending upon the concentration and nature of the additive. These effects are explained in terms of an increased dielectric constant of the solvent medium due to the presence of additives and increased micellar hydration due to the repulsion of charged monomers caused by adsorption of the additives. Taken together, the data signal the exposure of biological assemblies to water at higher [additive], which causes a decrease in hydrophobic interactions responsible for compact structure formation (i.e., native protein).

Structural modifications of aqueous ionic micelles in the presence of denaturants as studied by DLS and viscometry.

A phase study was completed on aqueous sodium dodecylbenzenesulfonate (SDBS) and tetra-n-butyl-ammonium bromide (Bu4NBr) systems, and consolute boundaries were drawn through cloud points. Samples were selected from both miscibility regions [under the lower consolute boundary (LCB) and above the upper consolute boundary (UCB)] for small-angle neutron scattering (SANS) studies. In the first set of experiments, the effect of varying Bu4NBr concentration on micellular parameters of 100 mM SDBS was studied at 30°C. The pure SDBS micelle has an aggregation number (n
 s
 ) of 51, and the effective charge on the monomer (α) is 0.17. With the addition of Bu4NBr, the n
 s
 of SDBS micelles increases while α decreases. The system with [Bu4NBr]=39.5 mM (an above-UCB sample) showed clouding near room temperature (≈29°C) and had a high n
 s
 value (300) and a low α (=0.09). The data indicated that the micelles lose ionic character in the presence of Bu4NBr. The temperature effect on this sample shows that α remains almost constant, while n
 s
 decreases on heating. A similar effect was observed with samples of lower Bu4NBr concentration (32 or 25 mM) in the presence of 100 mM SDBS. The same type of temperature effect was seen on a sample of under-LCB region (50 mM SDBS+32 mM Bu4NBr); the n
 s
 values increased significantly as the LCB was approached. The overall SANS observations suggest that the micelles have low ionic character together with high n
 s
 values (a case of micellar growth) near LCB/UCB.

Small-angle neutron scattering studies on sodium dodecylbenzenesulfonate-tetra- n -butylammonium bromide systems

Effect of ureas and alkylureas on the sphere-to-rod transition in aqueous ionic micellar solutions

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Clouding phenomenon and SANS studies on tetra-n-butylammonium dodecylsulfate micellar solutions in the absence and presence of salts

Structural modifications of aqueous ionic micelles in the presence of denaturants as studied by DLS and viscometry.

Small-angle neutron scattering studies on sodium dodecylbenzenesulfonate-tetra- n -butylammonium bromide systems

Effect of ureas and alkylureas on the sphere-to-rod transition in aqueous ionic micellar solutions