Solubilization Site Research Articles

Effects of 2-ethylbutyric acid, 2-ethyl-1-butanol, and 3-methylpentane on the micellization thermodynamics and physicochemical properties of HS 15 and TW 80 micelles based on differences in functional groups

Herein, we investigated the effects of 2-ethylbutyric acid, 2-ethyl-1-butanol, and 3-methylpentane, each possessing varying functional groups, on polyoxyl 15 hydroxystearate (HS 15) and polysorbate 80 (TW 80) micelles. Initially, the critical micelle concentration (CMC) for both systems was determined. Subsequent measurements included the particle size, zeta potential, cloud point, micropolarity, number of aggregates, and fluorophore release profile. Finally, the number of hydrogen bonds was confirmed through molecular docking technology. Results showed distinct effects of different functional groups on TW 80 and HS 15 micelles, exhibiting a decreasing trend of CMC, Amin, Gmin, particle size, and polydispersity index (PDI) with increased functional group polarity, alongside increased zeta potential, decreased cloud point, enlarged hydrophobic region, and rapid fluorophore quenching. In particular, acids with carboxyl groups exhibited enhanced stability with HS 15 and TW 80 micelles owing to differences in polarity, solubilization sites, and intermolecular forces. Using tanshinone extract as a model drug, the study explored HS 15 and TW 80 micelles as drug carriers, and results indicated that 2-ethylbutyric acid micelles exhibited better bacterial inhibition against Staphylococcus aureus. Considering that the surface of bacteria was negatively charged, the positively charged nanoparticles exhibited strong electrostatic interactions with the bacteria, which exerted a superior antibacterial effect. In summary, 2-ethylbutyric acid micelles displayed the smallest CMC, Amin, Gmin, particle size, and PDI, along with a positive charge, highlighting the potential application of 2-ethylbutyric acid.

Solubilization of polycyclic aromatic compounds into supralong-chain surfactants with double quaternary ammonium micelles

The dissolution of poorly water-soluble compounds in micelles via hydrophobic interactions is termed solubilization. The solubilization of polycyclic aromatic compounds, namely, naphthalene, anthracene, and pyrene, was studied using supralong-chain surfactants with two consecutive cationic hydrophilic groups [CnH2n+1N+(CH3)2-(CH2)2-N+(CH3)3 2Br-: Cn-2Am (n = 18, 20, and 22)] and typical cationic surfactants [CnH2n+1N+(CH3)3 Br-: Cn-Am (n = 12, 14, and 16)]. Long alkyl chains in hydrophobic surfactants are advantageous for forming a large micellar core. The maximum quantity of solubilized polycyclic aromatic compounds increased as the alkyl chain length of the surfactant increased. Therefore, the molar solubilization ratio (MSR), which represents the solubilization ability of the surfactant, was maximized when the alkyl chain length was C22-2Am. Similarly, the Gibbs free energy (ΔG0) associated with the solubilization of polycyclic aromatic compounds was also lowest for C22-2Am. Surfactants with long alkyl chains functioned as excellent solubilizers. The solubilization sites of the polycyclic aromatic compounds were determined using two-dimensional NMR and small-angle X-ray scattering (SAXS) measurements. As the molecular size of the polycyclic aromatic compounds increased, the solubilization positions in the micelles shifted from the palisade layer to the vicinity of the hydrophilic groups. Extension of the alkyl chain length of the surfactant resulted in an increase in the palisade region of the micelles, which was advantageous for solubilization.

Molecular insights into fragrance release from SDS and SLES micelles

Understanding the interaction between fragrance and surfactant micelles is essential for formulators to develop performing fragrant products. The equilibrium of fragrances in micellar solution of two commonly used surfactants in home and body care industries, namely sodium dodecyl sulphate (SDS) and sodium lauryl ether sulphate (SLES), has been investigated. The difference between SDS and SLES in the release of fragrant compounds is assessed by headspace measurements and explained at a molecular level by the different solubilization sites of the perfume within the micellar systems. Diffusion-Ordered Nuclear Magnetic Resonance Spectroscopy (DOSY NMR) shows that SLES micelles solubilize less fragrance than SDS. Subsequently, a shift from fragrance positioning through the water phase from SDS to SLES system is shown with COSMOmic calculations. This study brings knowledge on fragrance/surfactant interactions and shows the interest of using a computational method to screen and compare fragranced surfactants systems allowing formulators to anticipate the performance of their products.

Polyelectrolyte-Surfactant Complexes As a Formulation Tool for Drug Delivery.

Aqueous polyelectrolyte-surfactant complexes (PESCs) are very rich with respect to their properties and the structures formed by them. By design they normally contain hydrophobic micellar surfactant aggregates complexed by long polyelectrolyte chains, thereby combining the formation of small hydrophobic domains given by the surfactant with large-scale structuring due to the presence of the polyelectrolyte chain. In addition, they contain highly polar regions of surfactant head groups in contact with polyelectrolyte, forming a shell around the micellar aggregates, which often also possesses a certain hydrophobic character. Accordingly, the ability for solubilization of water-insoluble compounds of different sorts is particularly versatile in PESCs. Their solubilization sites with very different polarities and hydrophobic characters make them very flexible in adapting to the requirements of a given drug molecule. This renders them attractive for potential applications in drug delivery. In addition, modification of the rheological properties via self-assembly and network formation can be very important in PESC applications. In the following, we discuss the structures of PESCs and their properties, with a focus on the solubilization properties. Subsequently, examples are described where PESCs have been employed in the context of drug solubilization and delivery. These comprise examples with individual aggregates, cross-linked hydrogels, and ones taking advantage of the high solubilization capacity of microemulsions.

Mechanism of the Micellar Solubilization of Curcumin by Mixed Surfactants of SDS and Brij35 via NMR Spectroscopy.

The micellar solubilization mechanism of curcumin by mixed surfactants of SDS and Brij35 was investigated at the molecular scale by NMR spectroscopy. Through the investigation of the micelle formation process, types and structures of mixed micelles and solubilization sites, the intrinsic factors influencing the solubilization capacity were revealed. For systems with αSDS = 0.5 and 0.2, the obtained molar solubilization ratios (MSRs) are consistent with the MSRideal values. However, for αSDS = 0.8, the solubilization capacity of curcumin is weakened compared to the MSRideal. Furthermore, only one single mixed SDS/Brij35 micelles are formed for αSDS = 0.5 and 0.2. However, for αSDS = 0.8, there are separate SDS-rich and Brij35-rich mixed micelles formed. In addition, NOESY spectra show that the interaction patterns of SDS and Brij35 in mixed micelles are similar for three systems, as are the solubilization sites of curcumin. Therefore, for αSDS = 0.5 and 0.2 with single mixed micelles formed, the solubility of curcumin depends only on the mixed micelle composition, which is almost equal to the surfactant molar ratio. Although curcumin is solubilized in both separate micelles at αSDS = 0.8, a less stable micelle structure may be responsible for the low solubility. This study provides new insights into the investigation and application of mixed micelle solubilization.

Effects of surfactant on the molecules of different polarity of solubilization: Based on the study of micellar microscopic morphology mechanism

Determining the macro-solubilization capacities and micro-mechanism of surfactant micelles with low concentration is significant for the optimization of the medium of displacement and the further enhanced oil recovery. In this study, the solubilization capacities and interaction of polar anisole, nonpolar white oil and kerosene (polar and nonpolar) in SDBS and industrial betaine were compared from microscopic to macroscopic point of view with cryogenic transmission electron microscopy, dynamic light scattering and UV–Vis's spectroscopy. The study finds that the solubilization capacities were positively correlated with the concentration of micelles and the polar of molecules. Considering the importance of morphology of micelles to the solubilization capacities, and the morphology of micelles gradually changed from spherical to vesicle with increasing concentration. And the size of micelles was determined, and size were roughly in common with the concentration below 1 wt% or else the size of betaine was bigger than that of SDBS, which indicated that betaine might be larger and more likely to form vesicles than SDBS at the same concentration. Moreover, anisole is localized in the surface of micelles and size of solubilizing anisole was the biggest, which indicates the solubilization maxima was positively correlated with the volume of swelling micelle. These results imply that the concentration, morphology and solubilization location of micelles appear to important factors affecting the solubilization performance of surfactant. • Solubilization of micelles: The solubilization capacity of betaine and SDBS is positively correlated with concentration of surfactance and that of SDBS was greatly higher than betaine at same concentration no matter what additions solubilized. • Morphology of micelles: Morphology of micelles gradually changed from spherical to vesicle with increasing concentration. • Size of micelles: The type of particle diameters indicates slightly that the ability of morphological transformation for SDBS is better than betaine solution with medium concentration. For high concentration of micelles, the conclusion is the opposite. • Solubilization site: The polar composition of anisole mainly solubilized in the surface of micelles and the nonpolar of white oil solubilized in the core.

Contrast Variation Small-Angle Neutron Scattering Study of Solubilization of Perfumes in Cationic Surfactant Micelles.

Perfume solubilization is an important process in the production of commercial products such as beverages, foods, and cosmetics. In the present study, small-angle neutron scattering (SANS) experiments were performed to investigate the solubilization behavior of perfumes in cetyltrimethylammonium bromide (CTAB) micelles. The solubilization of linalool (LL) and l-menthol (MT), which are relatively hydrophilic perfumes, did not change the size of the CTAB micelles although the perfumes were incorporated in the micelles, as indicated by a decrease in scattering length density. On the other hand, the solubilization of d-limonene (LN), a hydrophobic perfume, led to the swelling of CTAB micelles. An internal contrast variation SANS study was performed by the deuteration of CTAB molecules to directly observe the perfumes in the micelles. The radius of d-CTAB micelles solubilizing LL or MT corresponds to that of h-CTAB, which indicates that these perfumes are accommodated in the palisade layers of the micelles and are homogeneously distributed in the micelles. On the other hand, LN formed small droplets, as indicated by the SANS profile, which implies the solubilization of LN molecules in the core of the CTAB micelles. We found that the relatively hydrophilic perfumes (LL and MT) show less impact on the sizes of the cationic micelles in comparison to nonionic micelles. Thus, the internal contrast variation method of SANS allowed the direct observation of the solubilization sites of perfumes with different hydrophilicity-hydrophobicity balances. This method is a powerful tool to determine the solubilization states that affect the solubilization capacity, volatilization, or release speed of perfumes.

INTERACTION OF 3-HYDROXY PYRIDINE AND SURFACTANT MICELLES: A FLUORESCENCE STUDIES

Objective: Micellar solubilization is a powerful alternative for dissolving hydrophobic compound in aqueous environment. 3-hydroxy pyridine (3- HP) derivatives are the potential endogenous photosensitizers. 3-HP derivatives show protective effect in clinical extreme condition such as hypoxia, hyperthermia, hypokinesia. Micellization of 3-HP followed by solubilization would catalyze its pharmaceutical activities which may serve better results in medicinal and analytical fields. Methods: Fluorescence and absorption spectroscopy techniques are used to monitor the micellar solubilization studies of 3-HP. Solubilization studies of 3-HP with various anionic, cationic and nonionic surfactants have been performed in aqueous medium around 23–25°C temperature. The solubilization action of the surfactant has also been determined by theoretical calculated spectral parameters such as empirical fluorescence coefficient, quantum yield, stokes, shift and molar absorption coefficient. Results: 3-HP shows fluorescence excitation peak at 315 nm and emission peak at 390 nm respectively while the absorbance of 3-HP has been found to be maximum at 305 nm. The fluorescence as well as the theoretically calculated spectral data has been used to characterize the hetero environment of the micelles in terms of their polarity, probe solubilization site and critical micelle concentration. Conclusion: This article briefly discusses the importance of surfactants in biological system model as well as the use of micelles in pharmacy as an important tool that finds numerous applications.

The Total Solubility of the Co-Solubilized PAHs with Similar Structures Indicated by NMR Chemical Shift.

The synergism/inhibition level, solubilization sites and the total solubility (St) of co-solubilization systems of phenanthrene, anthracene and pyrene in Tween 80 and sodium dodecyl sulfate (SDS) are studied by 1H-NMR, 2D nuclear overhauser effect spectroscopy (NOESY) and rotating frame overhauser effect spectroscopy (ROESY). In Tween 80, inhibition for phenanthrene, anthracene and pyrene is observed in most binary and ternary systems. However, in SDS, synergism is predominant. After analysis, we find that the different synergism or inhibition situation between Tween 80 and SDS is related to the different types of surfactants used and the resulting different co-solubilization mechanisms. In addition, we also find that three polycyclic aromatic hydrocarbons (PAHs) have similar solubilization sites in both Tween 80 and SDS, which are almost unchanged in co-solubilization systems. Due to the similar solubilization sites, the chemical shift changes of surfactant and PAH protons follow the same pattern in all solubilization systems, and the order of chemical shift changes is consistent with the order of changes in the St of PAHs. In this case, it is feasible to evaluate St of PAHs by chemical shift. In both Tween 80 and SDS solutions, the ternary solubilization system has relatively high St rankings. Therefore, in practical applications, a good overall solubilization effect can be expected.

Solubilization of fullerene in polyoxyethylene tetradecyl ether type nonionic surfactants

Fullerene is insoluble in water owing to its bulky spherical structure composed of 60 carbons. Herein, polyoxyethylene tetradecyl ether-type nonionic surfactants with a varying number of oxyethylene groups, i.e., C14En (n = 5, 6, and 7), were used to solubilize fullerene. In addition, a solubilization experiment was conducted using the aromatic compound naphthalene as a reference substance. Fullerene tended to solubilize in aqueous solutions of surfactants bearing long EO chains. Particularly, the maximum solubilization quantities of fullerene increased with an increasing number of EO chains in 100 mmol L−1 C14En solutions ranging from 43.2 (n = 5) to 76.9 (n = 6) and 115.6 μmol L−1 (n = 7). In contrast, naphthalene was well solubilized in surfactants bearing relatively shorter EO chains and showing an opposite tendency to that of fullerene. The Gibbs free energy change (ΔG0) per EO chain for the solubilization of fullerene and naphthalene was –1.51 and +0.27 kJ mol−1, respectively. These results indicated that the extension of EO chain of nonionic surfactants is thermodynamically advantageous for achieving the solubilization of fullerene. In addition, the solubilization site of fullerene in the micelles was studied by analyzing its absorption spectrum in four types of solvents with different polarities. The peak wavelength of fullerene suggested that the surrounding environment possessed an intermediate polarity between water and organic solvents. According to the 1H NMR measurements, the waveform of the EO groups in the NMR spectra significantly split upon solubilization of fullerene. From these results, it was concluded that fullerene located in the vicinity of the EO chains (shell area) in the micelles.

Apparent molal volumes and hydration numbers from viscosity studies for microemulsions with a nonionic surfactant derived from castor oil and a series of polar oils

The cloud point of a nonionic surfactant is related to the hydration of its polar shell. Viscosity data can be used to determine the total amount of water associated with micelles. The aim of this study was to apply this model to a more complex system comprising a series of oil-in-water microemulsions. These consisted of the nonionic surfactant, Kolliphor® RH 40, with and without polar oils. The oils used were isopropyl myristate (IPM), neopentyl glycol diethylhexanoate (NGDO), diisopropyl sebacate (DIS) and diisopropyl adipate (DIA) while the alcoholic solvents ethanol, 2-propanol and diethylene glycol monoethyl ether (DEG) were the co-surfactants. The apparent molal volumes were determined from the densities using a pycnometric method while the viscosities were measured using capillary viscometry. The partial excess volumes with IPM ranked as DEG>2-propanol>ethanol while the excess volumes varied as IPM>NGDO>DIS>DIA. These results were most likely related to the effect of the co-surfactant on the size and curvature of the micellar pseudophase and to the site of oil solubilization, respectively. The presence of oil induced increases in the intrinsic viscosities, the Huggins constants and the hydration numbers. The magnitudes of the latter two parameters were in excellent agreement with the values reported for micelles of nonionic surfactants. With DIS, the changes in the hydration numbers showed a good relationship with the excess volumes. Therefore, meaningful hydration values for microemulsions may be obtained with polar oils which are solubilized in the palisade layer rather than in the core as occurs with hydrophobic oils.

Self-assembly of amphiphilic meso-aryl-substituted porphyrin derivatives in the presence of surfactants

Surfactant-assisted self-assembly of porphyrin molecules in aqueous solutions sometimes leads to the formation of hybrid supramolecular structures with unusual photophysical properties resulting from the dipole–dipole interactions between the neighboring aromatic systems. The macrocycle orientation and interchromophore distance in such assemblies are determined by the dye–surfactant interactions, and hence, strongly depend on the molecular structure of both surfactant and porphyrin molecules. In this paper we studied the influence of the number and position of the peripheral alkyl chains of amphiphilic meso-aryl-substituted porphyrins on their aggregation behavior and intermolecular interactions with different surfactants in aqueous solutions. The studies revealed a crucial role of the local acidity on the micellar surface in the protolytic equilibrium of the porphyrin derivatives, as well as the influence of the macrocycle hydrophilic–lipophilic balance on its solubilization site within a micellar system. These findings enable prediction of the photophysical properties of amphiphilic porphyrin derivatives in the presence of different solubilizing agents and membrane-mimetic systems, and hence, selection the most suitable drug delivery systems for the novel amphiphilic porphyrin-based photosensitizers.

Three different types of solubilization of thymol in Tween 80: Micelles, solutions, and emulsions- a mechanism study of micellar solubilization

The micellar solubilization process and mechanism with thymol and Tween 80 as the model drug and surfactant were studied by the tensiometric study, 1H NMR spectroscopy, 2D diffusion ordered spectroscopy (DOSY) and NOESY. First of all, changes in chemical shifts and line shapes of thymol and Tween 80 in mixed solutions compared with those in pure solutions, the co-diffusion of thymol and Tween 80 molecules, and cross peaks between them prove that thymol molecules are solubilized in Tween 80 micelles. The thymol-incorporated Tween 80 micelles form, and its critical micellar concentration (CMC) was obtained. Almost synchronously, the independent diffusion of thymol molecules was observed. These indicate that when the CMC of thymol-incorporated Tween 80 micelles is reached, a portion of thymol molecules are solubilized in Tween 80 micellar solutions. Finally, with the continuous increase of thymol concentration, there is another resonance group of Tween 80 shown up, accompanied by turbid solutions. The independent diffusion of the new Tween 80 resonance group, and its cross peaks with thymol indicate the formation of another aggregate-emulsions, meanwhile, which are coexisted with thymol molecules solubilized in micelles and those dissolved in solutions. The solubilization of thymol in Tween 80 aqueous solutions follows the order of micelles> solutions> emulsions. Besides, different cross peak patterns suggest that solubilization sites of thymol in micelles and emulsions are different. In micelles, thymol molecules are likely to be wrapped in the folded alkane chains of Tween 80. However, in emulsions, they are possibly solubilized in the core of emulsions made of stretched hydrophobic chains. The surface tension results are consistent with the conclusions obtained from NMR studies.

Novel eco-friendly ionic liquids to solubilize seven hydrophobic pesticides

In line with the requirements of green chemistry, the preparation of eco-friendly pesticide formulations has become an inevitable development trend. In this work, we explored the feasibility of four new ionic liquids (ILs, [Octyl trimethyl ammonium] anions, anions = proline, valine, leucine, tartaric acid) as environmentally-friendly solvents for pesticide emulsifiable concentrates, and also as alternatives to traditional imidazole-based ILs since they do not contain the imidazole ring and the anions are natural substances. The results showed that the solubility of pesticides (clethodim, metolachlor, acetochlor, prochloraz, thiamethoxam, glyphosate, acetamiprid) in water with 25%w/v ILs was significantly improved, especially for acetamiprid, where the solubility was increased 19-fold, while it only increased about 4 to 5-fold after adding imidazole-based ILs in our previous work. In addition, the solubilization mechanism was explored by many methods and found that the solubilization effect does not completely depend on the critical micelle concentration (CMC) value but has a great relationship with the hydrophilicity of the ILs which may affect the size of micelles and release behavior to pesticides. Finally, 1H NMR was used to investigate the solubilization sites of ILs for glyphosate, and the interaction between pesticides and anions was explored by the quantum chemical method.

Cosolubilization of phenanthrene and pyrene in surfactant micelles: Experimental and atomistic simulations studies

Solubilization of mixed phenanthrene (PHE) and pyrene (PYR) in Triton X-100 (TX), sodium dodecyl sulfate (SDS) and mixed TX-SDS surfactant solutions were done to observe their cosolubilization effect. Moreover, molecular dynamics (MD) simulations were performed to reveal how polycyclic aromatic hydrocarbons (PAHs) coexist in the micelle. Cosolubilization of PHE and PYR exhibited synergism along with decreasing synergistic extent with increasing SDS in mixed micelle. MD simulations verified the distribution of PHE and PYR in the shell and core regions of pure SDS and mixed SDS-TX micelles (with molar ratio of 1: 1), which were chosen as the representative systems for simulation study. The movement of PHE and PYR inside the micelle along with their different probability to contact with SDS non‑hydrogen atoms in pure SDS and mixed SDS-TX solubilization systems suggests the different solubilization sites of the two PAHs inside the micelle leading to their coexistence in the micelle. This study implies the significance of considering cosolubilization effects between PAH mixtures in determining surfactant concentration for environmental remediation.

Role of the spacer of Gemini surfactants in solubilization into their micelles

We report the role of a spacer chain in gemini surfactants for solubilization of poor soluble compounds to the aqueous medium. Solubilization of n-alkylbenzenes into micellar solutions of alkanediyl-1,s-bis(dimethyltetradecylammonium bromide) (14-s-14,2Br−, s=2, 6, and 12) has been studied in the temperature range from 288.2 to 308.2K. The equilibrium concentrations of all the solubilizates are determined spectrophotometrically. The solubility of the solubilizates remains constant below the critical micelle concentration (cmc) and increases linearly with an increase in the surfactant concentration above the cmc. The hydrodynamic diameter of the micellar aggregates with or without the solubilizates is measured by means of dynamic light scattering (DLS). The enthalpy, entropy, and Gibbs energy changes for the solubilization of n-alkylbenzenes have been calculated to evaluate a driving force of a transfer of the solubilizates into the micelle. These results indicate that the driving force and solubilization site in the aggregates are changed depending on the spacer chain length of surfactants. Furthermore, the inner core of the solubilized aggregates has been investigated by Fourier transform infrared (FTIR) spectra and two-dimensional nuclear Overhauser effect spectroscopy (2-D NOESY).

Fate of edible solid lipid nanoparticles (SLN) in surfactant stabilized o/w emulsions. Part 2: Release and partitioning behavior of lipophilic probes from SLN into different phases of o/w emulsions

The release and partitioning of encapsulated compounds from solid lipid nanoparticles (SLN) to other matrix constituents was investigated in o/w emulsions stabilized by different surfactants (CTAB, SDS, Tween 20) by confocal laser scanning microscopy (CLSM) and electron paramagnetic resonance spectroscopy (EPR) spectroscopy. CLSM images revealed that the encapsulated probe Coumarin 6 (C6) was located in the oil droplets after SLN were mixed with the different emulsions. The EPR spin probe TEMPOL‐benzoate (TB) showed different dynamics as a function of its specific solubilization sites in SLN. Four different populations of the spin probe could be separated giving the smallest population in the aqueous environment and the major population at the SLN interface. Two further populations were associated with differently crystalized lipid environments. This implies that both loosely structured regions with α- and β’-polymorphs and environments of β-polymorphs are present in SLN. In separated model emulsion systems, a prolonged release of TB from SLN was evident which predominately originated from the SLN interface. The released TB partitioned into the oil phase (25%) and into the o/w interface (30–45%), regardless of the presence or absence of additional surfactant micelles. Hence, these edible SLN may be used as delivery system for bioactive compounds in food emulsions with low impact of the surfactant used to stabilize the emulsion. The partial redistribution of the encapsulated compounds should be taken into account, but can also offer benefits when a prolonged release of lipophilic additives is desired.

Solubilization of active ingredients of different polarity in Pluronic® micellar solutions – Correlations between solubilizate polarity and solubilization site

The solubilization of two pharmaceutically active ingredients (AI) with significantly different water solubility, namely carbamazepine and fenofibrate (solubility of 150ppm and 10ppm, respectively), has been investigated using a series of Pluronics® (Poloxamers) containing different ethylene oxide and propylene oxide (EO/PO) units in the molecule. The results show largely enhanced solubilization of fenofibrate by Pluronic® micelles that increases with the PPO chain length provided the temperature is above the critical micelle temperature (cmt). In contrast the more water-soluble carbamazepine only shows a moderate increase in solubilization upon addition of Pluronics®. Small angle neutron scattering (SANS) and pulsed field gradient (PFG) NMR experiments show that the solubilization of fenofibrate occurs in the core of the micelles, whereas carbamazepine shows no direct association with the micelles. These clearly different solubilization mechanisms for the two AIs were confirmed by Nuclear Overhauser Enhancement Spectroscopy (NOESY) experiments, which show that fenofibrate interacts only with the PPO core of the micelle, whereas carbamazepine interacts with both PPO and PEO similarly. Accordingly, the large enhancement of the solubilization of fenofibrate is related to the fact that it is solubilized within the PPO core of the Pluronic® micelles, while the much more moderate increase of carbamazepine solubility is attributed to the change of solvent quality due to the presence of the amphiphilic copolymer and the interaction with the EO and PO units in solution.

Preservative solubilization induces microstructural change of Triton X-100 micelles

The interaction of preservatives which are extensively used in food, pharmaceutical and personal care products, such as p-hydroxy benzoic acid esters (parabens) and gallic acid ester for instance propyl gallate has been investigated with commonly used non-ionic surfactant p-tert-octylphenoxy polyethylene (9.5) ether, Triton X-100 (TX-100). Solubilization of these preservatives alters the micellar behaviour of TX-100 elucidated by cloud point (CP), viscometry, dynamic light scattering (DLS), small angle neutron scattering (SANS) and NOESY measurement techniques. The changes in size/shape of TX-100 micelles depend on the hydrophilic and hydrophobic interactions with preservatives. These types of interaction facilitate the site of solubilization of preservatives in TX-100 micelles. Micellar growth of TX-100 was more pronounced for parabens as their alkyl ester chain length increases. Moreover, the micellar growth was more prominent for propyl paraben (PP) as compared to more polar propyl gallate (PG). The salt induced changes in the interaction between preservatives and TX-100 micelles have also been determined.

Cosolubilization of Coumarin30 and Warfarin in Cationic, Anionic, and Nonionic Micelles: A Micelle-Water Interfacial Charge Dependent FRET.

Solubilization of structurally varied coumarins, viz., Warfarin (WF; a 4-hydroxy coumarin) and Coumarin30 (C30, a 7-amino coumarin) individually and in mixed states (cosolubilization) within the aqueous surfactant self-assemblies of varying architectures has been explored, exploiting steady-state, time-resolved fluorimetric, and spectrophotometric techniques. Cosolubilization studies within micelles, which have rarely been done in the literature, were specifically undertaken with the aim of understanding the effect of micelles on their photophysical phenomena when simultaneously present within these nanocarriers and assess their prospective use as an efficient FRET pair. WF solubilizes within CTAB micelles, whereas little or no solubilization is observed in Brij30 and SDS micelles. On the other hand, C30 solubilizes deep into the palisade layer of CTAB micelles, between negatively charged head groups in SDS micelles and between OE groups in Brij30 micelles. C30 and WF maintain their solubilization sites during cosolubilization. In SDS and Brij30 micelles, an increase in WF causes fluorescence quenching of C30 molecules, while in CTAB, an increase in WF causes an increase in fluorescence of C30 by excited WF molecules indicating FRET between the two molecules.