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One of the most widely used approaches for improving drug permeation across the stratum corneum barrier of the skin is the use of chemical penetration enhancers, such as surfactants. In this study, two anionic surfactants, named C12-OPK and C18-OPK, were synthesized via condensation of itaconic acid and fatty amines, with C12 and C18 alkyl chains, respectively. Assessment of impacts on HaCaT keratinocyte cell viability was used as indicator of their potential to cause skin irritation 24 h post exposure (Alamar Blue assay). The LC50 values of C12-OPK and C18-OPK (144 and 85 mg/L, respectively) were lower than LC50 values of the most used commercial surfactants (e.g. SDS). The effect of different surfactant concentrations (up to ten times the critical micellar concentration, CMC) on hydrocortisone (HC) solubility and permeation through porcine skin was also evaluated. Results showed that drug solubility increased linearly with increasing concentrations of both surfactants, as a consequence of the association between drug and micelles. In vitro permeation results showed that the permeability coefficient increased at surfactant concentrations lower than the CMC. In particular, a higher enhancement effect on drug permeation was obtained with C18-OPK, due to its hydrophobic properties that ensured a more effective HC permeation in comparison to C12-OPK.

The purpose of this work is to provide a mechanistic understanding of the dissolution behavior of cocrystals under the influence of ionization and micellar solubilization. Mass transport models were developed by applying Fick’s law of diffusion to dissolution with simultaneous chemical reactions in the hydrodynamic boundary layer adjacent to the dissolving cocrystal surface to predict the pH at the dissolving solid–liquid interface (i.e., interfacial pH) and the flux of cocrystals. To evaluate the predictive power of these models, dissolution studies of carbamazepine–saccharin (CBZ-SAC) and carbamazepine–salicylic acid (CBZ-SLC) cocrystals were performed at varied pH and surfactant concentrations above the critical stabilization concentration (CSC), where the cocrystals were thermodynamically stable. The findings in this work demonstrate that the pH dependent dissolution behavior of cocrystals with ionizable components is dependent on interfacial pH. This mass transport analysis demonstrates the importance of pH, cocrystal solubility, diffusivity, and micellar solubilization on the dissolution rates of cocrystals.

The disposal of phenol-bearing wastewaters impacts the environment and, consequently, the health of living bodies. This work evaluates the viability of using micellar solubilization followed by ionic flocculation in the removal of phenol from aqueous solutions. Initially, an anionic surfactant, based on vegetable oil and animal fat, was used to promote the solubilization of phenol in the micelles. Then, calcium was added to the solution to promote the formation of flocs with the ability to capture the phenol-rich micelles. At the end of the experiment, the authors investigated the influence of phenol removal considering surfactant, phenol, and electrolytes concentrations; calcium/surfactant ratio; temperature; pH; equilibrium time; and stirring speed. Phenol desorption from the floc surface was evaluated considering process efficiency and kinetics. The removal efficiency reached values close to 60% using: [Phenol] = 100 ppm, [surfactant] = 1300 ppm, 0.5 calcium/surfactant ratio, T = 35 °C, pH = 9.7. A 90% desorption was observed, indicating that desorption of phenol from the floc surface occurs spontaneously. Phenol desorption kinetics was fitted using the Lagergren's pseudo-first order model (R2 = 0.98).

The treatment of effluent is a fundamental part of processing of textile materials due to large volumes produced and the presence of toxic dyes in it. Micellar solubilization followed by ionic flocculation of carboxylate anionic surfactants occurs in two stages. Firstly, solubilization of organic matter occurs inside the micelle, secondly, a solution of calcium is added to the system containing the micelles, causing precipitation of the surfactant in the form of flocs, which drag the organic compound on its surface, bringing the organic compound retained on the surface of the floc, then to be removed from the aqueous medium by a physical separation process. This process was used to remove Reactive Blue 14 (RB14) dye from synthetic effluent. Surfactant carboxylate used was produced from animal/vegetable fat. The effect of surfactant concentration, temperature, stirring speed, contact time, pH and electrolyte concentration were evaluated by observing dye removal efficiency. Enthalpy and entropy show that the process is exothermic and with decreasing randomness. The dye removal efficiency reached 86% at the temperature of 30 °C. Thus, it can be affirmed that application of ionic flocculation using anionic surfactant is an efficient technique in the treatment of textile effluent.

International audience; Complex interactions of phenol (PhOH), heptanol (HeOH) and heptanoic acid (HeOIC) with micellar aggregates of hexadecyltrimethylammonium bromide (HTAB) in aqueous solutions at surfactant concentrations close to the CMC, HeOH or HeOIC content of 0.5 mmol kg_1, and phenol molality of 1, 5, or 10 mmol kg_1 have been investigated at 303 K by means of 1H NMR spectroscopy, titration calorimetry and solution conductimetry. The analysis of the composition-dependence of the 1Hchemical shifts assigned to selected protons in the surfactant and additive units revealed the location of PhOH both within the hydrophobic micelle core and in the vicinity of the quaternary ammonium groups, the phenol penetration being somewhat deeper in the presence of HeOIC. The phenomenon was globally more exothermic with increasing extent of PhOH solubilization and it was accompanied by a gradual decrease in the positive entropy of micellization. The solubilization was competitive for high phenol contents in the aqueous phase, with some HeOH and HeOIC units being displaced progressively towards the aqueous phase.

The interaction of Procaine hydrochloride (PC) with cationic, anionic and non-ionic surfactants; cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS) and triton X-100, were investigated. The effect of ionic and non-ionic micelles on solubilization of Procaine in aqueous micellar solution of SDS, CTAB and triton X-100 were studied at pH 6.8 and 29°C using absorption spectrophotometry. By using pseudo-phase model, the partition coefficient between the bulk water and micelles, Kx, was calculated. The results showed that the micelles of CTAB enhanced the solubility of Procaine higher than SDS micelles (Kx = 96 and 166 for SDS and CTAB micelles, respectively) but triton X-100 did not enhanced the solubility of drug because of weak interaction with Procaine. From the resulting binding constant for Procaine-ionic surfactants interactions (Kb = 175 and 128 for SDS and CTAB surfactants, respectively), it was concluded that both electrostatic and hydrophobic interactions affect the interaction of surfactants with cationic procaine. Electrostatic interactions have a great role in the binding and consequently distribution of Procaine in micelle/water phases. These interactions for anionic surfactant (SDS) are higher than for cationic surfactant (CTAB). Gibbs free energy of binding and distribution of procaine between the bulk water and studied surfactant micelles were calculated.

Interactions of phenol (PhOH) with micellar aggregates of hexadecyltrimethylammonium bromide (HTAB) in aqueous solutions at surfactant concentrations close to the CMC and phenol contents of 1, 5, or 10 mmol kg −1 have been investigated at 303 K by means of titration calorimetry, solution conductimetry, and 1 H NMR spectroscopy. Estimates of the main thermodynamic parameters related to HTAB micellization were made for PhOH/HTAB/H 2 O systems based on the specific conductivity measurements and calorimetric determination of the cumulative enthalpy of dilution as functions of the surfactant concentration at a fixed additive content. The combined analysis of the results obtained in H 2 O solutions pointed to the preferential location of PhOH in the outer micelle parts by an enthalpy-driven mechanism. Additional PhOH molecules were located increasingly deeper within the micelle core. The 1 H NMR study of PhOH solubilization by 1.5 mmol kg −1 HTAB solutions in D 2 O indicated that the two categories of the solubilization site became saturated with the solubilizate already at the lowest additive content. Dissimilar amounts of the solubilized material in H 2 O and D 2 O solutions were ascribed to the difference in the initial micelle structures formed in the two solvents, as inferred from calorimetry and 1 H NMR studies of the HTAB micellization in D 2 O and H 2 O.

An important property of micelles with particular significance in pharmacy is their ability to increase the solubility of poorly soluble drugs in water, thus increasing their bioavailability. In this work, the solubilization of ibuprofen (IBU) was studied in micellar solutions of three surfactants possessing the same hydrocarbon tail but different hydrophilic head groups, namely sodium dodecyl sulphate (SDS), dodecyltrimethylammonium bromide (DTAB), and n-dodecyl octa(ethylene oxide) (C12EO8). The results showed that, irrespective of the surfactant type, the solubility of IBU increased linearly with increasing surfactant concentration, as a consequence of the association between the drug and the micelles. The 80 mM DTAB and the 80 mM C12EO8 micellar solutions resulted in a 16-fold increase in solubility of IBU when compared to the buffer solution, whereas the 80 mM SDS micellar solution resulted in a 5.5-fold increase in IBU solubility. The highest value of molar solubilization capacity (chi) was obtained with DTAB, chi = 0.97, followed by C12EO8 ,chi = 0.72, and finally SDS, chi = 0.23. However, due to the stronger tendency of the nonionic surfactant in forming micelles in solution, at the same surfactant concentration, we obtained the same solubility of IBU in both DTAB and C12EO8. Uma propriedade importante das micelas, do ponto de vista farmacêutico, refere-se ao potencial destas em solubilizar fármacos pouco solúveis em água, aumentando sua biodisponibilidade. No presente trabalho, estudou-se a solubilização de ibuprofeno (IBU) em soluções micelares constituídas de três tensoativos apresentando a mesma cauda apolar, porém diferentes grupos hidrofílicos. Os tensoativos estudados foram dodecil sulfato de sódio (SDS), brometo de dodeciltrimetilamônio (DTAB) e óxido de n-dodecil octaetileno (C12EO8). De acordo com os resultados obtidos, a solubilidade do IBU aumentou linearmente com o aumento da concentração de todos os tensoativos estudados, devido às interações entre as micelas e o fármaco. O fármaco IBU apresentou um aumento de 16 vezes em sua solubilidade na presença de DTAB 80 mM e de C12EO8 80 mM. Por outro lado, na presença de SDS 80 mM a solubilidade do IBU aumentou apenas 5,5 vezes. O maior valor para o parâmetro capacidade molar de solubilização (chi) foi observado com o tensoativo DTAB, chi = 0,97, seguido pelo C12EO8, chi = 0,72 e, finalmente, o SDS, chi = 0,23. Entretanto, devido à grande tendência do C12EO8 em formar micelas, o perfil de solubilidade do IBU foi semelhante em DTAB e C12EO8.

The solubilities of methane, carbon dioxide, ethane, and propane have been determined experimentally at 1 atm partial pressure and 25deg;C in aqueous solutions of sodium dodecyl sulfate and cetyltrimethylammonium bromide. For this purpose a specially developed apparatus is used, which is relatively simple compared to those reported in the literature hitherto. Above the CMC, the solubility of each gas increases linearly with surfactant concentration indicating micellar solubilization. The degree of solubilization is greatest for propane and decreases in the order propaneethanecarbon dioxidemethane. Both the length of the alkyl chain and the properties of the head-group region (i.e., the micelle-water interfacial tension) are observed to determine the intramicellar solubility. A method for estimating the solubilities is also proposed based on the rationale that the micellar phase may be represented by a droplet of a "model solvent" into which the solubilizate molecule dissolves as it would in a bulk solvent. The mixture of the solute species and the model solvent is assumed to behave as a regular solution. Accordingly, a characteristic solubility parameter is estimated for the model solvent from the interaction potential between two adjacent surfactant molecules in a micelle. The solubility computed using the regular solution approximation is further corrected for the Laplace pressure that acts across the curved micelle-water interface and generally reduces the intramicellar solubility. It is concluded that for small nonpolar solutes, micellar solubilities may be reasonably well predicted by assuming that the model solvent has a solubilizing capacity (i.e., solubility parameter) close to that of a bulk equivalent alkane. Copyright 1997 Academic Press. Copyright 1997Academic Press