Solubility micellar solubilization

Other solubilization and partitioning phenomena are important, both within the context of microemulsions and in the absence of added immiscible solvent. In regular micellar solutions, micelles promote the solubility of many compounds otherwise insoluble in water. The amount of chemical component solubilized in a micellar solution will, typically, be much smaller than can be accommodated in microemulsion fonnation, such as when only a few molecules per micelle are solubilized. Such limited solubilization is nevertheless quite useful. The incoriDoration of minor quantities of pyrene and related optical probes into micelles are a key to the use of fluorescence depolarization in quantifying micellar aggregation numbers and micellar microviscosities [48]. Micellar solubilization makes it possible to measure acid-base or electrochemical properties of compounds otherwise insoluble in aqueous solution. Micellar solubilization facilitates micellar catalysis (see section C2.3.10) and emulsion polymerization (see section C2.3.12). On the other hand, there are untoward effects of micellar solubilization in practical applications of surfactants. Wlren one has a multiphase... 

Ismail, A. A., M. W Gouda, and M. M. Motawi. 1970. Micellar solubilization of barbiturates. I. Solubilities of certain barbiturates in polysorbates of varying hydrophobic chain ledcJRtiarm. Sci. 59 220-224. 

The solubility and release of naproxen from Pluronic PF-127 micelles were studied as a function of temperature and pH by Suh and Jun (1996). The solubility of the drug at pH 2 was signiLcantly increased as a linear function of PF-127 concentrations for three temperatures. Naproxen was highly entrapped by the micelles as indicated by large partition coefLcient. The micellar solubilization was a spontaneous (AG 0) and exothermic (AH< 0) process that resulted in a less ordered state (AS > 0). In the presence of PF-127, the release of naproxen was sustained at pH 2 and inversely proportional to the surfactant concentration. In contrast, at pH 7, PF-127 had little effect on the membrane transport of naproxen. The release of naproxen from the PF-127 gel into isopropanol myristate was also found to be dependent on the medium pH with the highest release observed at pH 6.3. 

The process by which the solubility of a solute is increased by the presence of another solute. Micellar solubilization refers to the incorporation of a solute (solubilizate) into or on micelles of another solute to thereby increase the solubility of the first solute. 

Identification of pharmaceutically acceptable vehicles that afford sufficient solubilization while maximizing physiological compatibility for preclinical pharmacokinetic evaluation is critical. The most frequently used solubilization techniques include pH manipulation for ionizable compounds use of cosolvents such as PEG 400, ethanol, DMSO, and propylene glycol micellar solubilization with surfactants such as Tween 80 or SLS complexation with cylodextrins [40]. By using the solubilization techniques, the enhancement in solubility of poor water-soluble compounds can be significant compared to aqueous solubility and can facilitate the absorption of drug molecules in the gastrointestinal tract when delivered in solution form. 

The micellar solubilization of drugs in the small intestine is increased not only due to the higher bile add secretion induced by a meal but also by lipid components of nutritional origin, such as fatty acids and monoglycerides. The solubility of six drugs... 

Bates, Gibaldi and Kanig have studied the relative solubilizing tendencies of four bile salts with respect to hexesterol, griseofulvin and glutethimide. The effect, which is ascribed entirely to micellar solubilization, was determined at several temperatures and at salt concentrations up to 0.6m. The most marked effect was noted with hexestrol and least for glutethimide. Connors and Mollica have compared the theoretical relationships of stability constants obtainable by solubility and other methods. 

Over 50 methods have been employed in the literature to determine CMC values of bile salt solutions (reviewed in [6]). These can be divided into two broad categories (a) methods requiring no physical or chemical additive in the bulk solution and (b) methods involving the use of an additive in the bulk solution. The former methods, also called non-invasive, include surface tension and the measurements of a variety of colligative bulk properties (conductivity, turbidimetry, osmometry, self-diffusion, refractive index, modal volumes, electrometric force) or electromagnetic bulk properties (NMR, sound velocity and adsorption, etc.), all as functions of bile salt concentration. The second set of methods, also called invasive, depends upon a change in some physical or chemical property of an additive which occurs with the formation of micelles. These include the spectral change of a water-soluble dye, micellar solubilization of a water-insoluble dye, interfacial tension at liquid-liquid interfaces, and partition coefficients between aqueous and immiscible non-polar phases. Whereas a detailed discussion of the merits and demerits of both approaches can be found elsewhere [6], non-invasive methods which are correctly utilized provide the most reliable CMC values. 

Organic molecules with limited water solubility were solubilized by those poly soaps for which viscosity studies indicated micellar behavior (6). The solubilization had varied effects on the viscosity of the polysoap solutions, depending on the nature of the solubilized compound and the concentration... 

Surfactants Surfactants are amphiphilic compounds with both hydrophilic and hydrophobic moieties. Because of their amphiphilic nature, surfactants accumulate at interfaces and thus minimize system-free energies. Surfactants increase PAH solubility by lowering interfacial tension as well as by accumulating the hydrophobic materials in micelles (the micellar solubilization) (Rosen, 1978 West and Harwell, 1992). 

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