Nonionic Surfactant Micelles Research Articles

What happens when pesticides are solubilised in binary ionic/zwitterionic-nonionic mixed micelles?

HypothesisSurfactants have been widely used as adjuvants in agri-sprays to enhance the solubility of pesticides in foliar spray deposits and their mobility through leaf cuticles. Previously, we have characterised pesticide solubilisation in nonionic surfactant micelles, but what happens when pesticides become solubilised in anionic, cationic and zwitterionic and their mixtures with nonionic surfactants remain poorly characterised. ExperimentsTo facilitate characterisations by SANS and NMR, we used nonionic surfactant hexaethylene glycol monododecyl ether (C12E6), anionic sodium dodecylsulphate (SDS), cationic dodecyltrimethylammonium bromide (DTAB) and zwitterionic dodecylphosphocholine (C12PC) as model adjuvant systems to solubilise 3 pesticides, Cyprodinil (CP), Azoxystrobin (AZ) and Difenoconazole (DF), representing different structural features. The investigation focused on the influence of solubilisates in driving changes to the micellar nanostructures in the absence or presence of electrolytes. NMR and NOESY were applied to investigate the solubility and location of each pesticide in the micelles. SANS was used to reveal subtle changes to the micellar structures due to pesticide solubilisation with and without electrolytes. FindingsUnlike nonionic surfactants, the ionic and zwitterionic surfactant micellar structures remain unchanged upon pesticide solubilisation. Electrolytes slightly elongate the ionic surfactant micelles but have no effect on nonionic and zwitterionic surfactants. Pesticide solubilisation could alter the structures of the binary mixtures of ionic/zwitterionic and ionic/nonionic micelles by causing elongation, shell shrinkage and dehydration, with the exact alteration being determined by the molar ratio in the mixture.

Analytical modeling of micelle growth. 3. Electrostatic free energy of ionic wormlike micelles – Effects of activity coefficients and spatially confined electric double layers

Hypotheses: To correctly predict the aggregation number and size of wormlike micelles from ionic surfactants, the molecular-thermodynamic theory has to calculate the free energy per molecule in the micelle with accuracy better than 0.01 kT, which is a serious challenge. The problem could be solved if the effects of mutual confinement of micelle counterion atmospheres, as well as the effects of counterion binding, surface curvature and ionic interactions in the electric double layer (EDL), are accurately described.Theory: The electric field is calculated using an appropriate cell model, which takes into account the aforementioned effects. Expressions for the activity coefficients have been used, which vary across the EDL and describe the electrostatic, hard sphere, and specific interactions between the ions. New approach for fast numerical calculation of the electrostatic free energy is developed.Findings: The numerical results demonstrate the variation of quantities characterizing the EDL of cylindrical and spherical micelles with the rise of electrolyte concentration. The effect of activity coefficients leads to higher values of the free energy per surfactant molecule in the micelle as compared with the case of neglected ionic interactions. The results are essential for the correct prediction of the size of wormlike micelles from ionic surfactants. This study can be extended to mixed micelles of ionic and nonionic surfactants for interpretation of the observed synergistic effects.

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.

Micellar Extraction Preconcentration and Colorimetric Determination of Some Phenols

We studied the extraction and preconcentration of phenol and its hydroxy derivatives using individual and mixed micelles of nonionic and cationic surfactants with the digital recording of the analytical signal. This approach is based on the color reaction of phenols with diazotized 4-nitroaniline and micellar extraction of the products of their interaction (azo compound). The micellar extraction parameters (pH, the concentration of reagents, NaOH, and ethanol) were optimized for the efficient extraction of azo compounds of the studied phenols. The proposed method enables the determination of phenol and resorcinol at the MPC level with an error not exceeding 10%. For a qualitative assessment of the presence of phenols, the geometric parameters (area S, perimeter P) of the corresponding radar plots were used along with colorimetric parameters (R, G, B). The calibration dependences are linear within 1 × 10–7–3 × 10–5 M for phenol and 1 × 10–7–2 × 10–5 M for resorcinol and phloroglucinol. The developed colorimetric method was tested in the determination of resorcinol in the Rezortsinol pharmaceutical preparation.

Synthesis and Characterization of Silver Nanoparticles in Reverse Micelles of Nonionic Surfactants and in Their Mixed Micelles with AOT

Stable silver nanoparticles have been obtained in reverse micelles of known and available nonionic surfactants, sorbitan monooleate (Span 80) and tetraethoxylated dodecanol and p-nonylphenol (Brij 30 and Tergitol NP-4, respectively), in n-decane. The obtained nanoparticles have been characterized using a number of physicochemical methods. The stability, hydrodynamic diameter, and electrokinetic potential of the nanoparticles have been studied as depending on the amounts of added water; chloroform; and an anionic surfactant, sodium bis(2-ethylhexyl)sulfosuccinate (AOT). It has been shown that, for different surfactants, AOT should be introduced in different ways to provide the nanoparticles with the electrokinetic potential values sufficient for enhancing their stability and ensuring the possibility of concentrating them by nonaqueous electrophoresis. In the case of Brij 30, it is preferable to introduce AOT after the synthesis as a “charging additive,” while, in the case of Tergitol NP-4, it should be added as a cosurfactant at the stage of the synthesis. The nanoparticles synthesized in Span 80 micelles have a rather high electrokinetic potential even in the absence of the additives. In this case, the use of AOT as a cosurfactant decreases the electrokinetic potential of the nanoparticles, while, being added after the synthesis, it increases the potential.

Morphology, Size, and Properties of Micelles in Polyethylene Glycol Mono-p-(1,1,3,3-tetramethylbutyl)phenyl Ether (Triton X-100) Emulsions

The morphology of micelles of the Triton X-100 nonionic surfactant (NS) in aqueous emulsions was studied by optical microscopy and turbidimetry, and the micelle sizes were determined. In the Triton X-100/n-hexane/water system, micelles are elongated ellipsoids surrounded by a ring of water bonded with oxyethylene chains, which change their orientation relative to incident light depending on the NS concentration. The aqueous solutions and emulsions of Triton X-100 are conductive due to the rings of hydroxyl and hydroxonium ions formed on the surface, which ionize the micelles and the dispersion medium.

Co-solubilization of polycyclic aromatic hydrocarbon mixtures in aqueous micellar systems and its correlation with FRET for enhanced remediation processes.

Surfactant enhanced remediation (SER) is an effective approach for decontaminating the PAH polluted soils. Solubilization and Cosolubilization of Phenanthrene (Ph), Pyrene (Py) and Perylene (Pe) as single, binary and ternary mixtures have been studied employing cationic (CTAB), anionic (SDS), non-ionic surfactant (Brij 30) and block copolymer (P123) micelles. In the single solute solubilization studies, solubility of Pe follows the order Brij 30 > CTAB > SDS whereas Ph or Py followed the order of CTAB > Brij 30 > SDS. In the cosolubilization studies, an increase, decrease or no change in the mutual solubility of PAHs was observed. Synergism in solubilization was observed most in P123 in both binary and ternary PAH mixture where more PAHs could get solubilized in the dense micellar shell region, thereby enhancing the micellar core volume leading to enhanced solubilization of PAHs. The solubilizates as pairs (Ph-Pe and Py-Pe) were further tested for any possible energy transfer in presence of surfactant based restricted host environments using spectrofluorometry and spectrophotometry. Based on the solubilization and cosolubilization an efficient non-radiative energy transfer (FRET) was observed between Ph/Py (donor) and Pe (acceptor) in the non-ionic surfactant system as well as in CTAB-Brij 58 mixed system. The results of this work may improve the effective utilization of surfactants in their correct evaluation for the removal of PAHs from contaminated soils or aquifers treated with SER technology.

Incorporation of bioflavonoids from Bidens tripartite into micelles of non-ionic surfactants – experimental and theoretical studies

Classical extraction methods used for an isolation of active substances from the plant material are expensive, complicated and often environmentally unfriendly. The ultrasonic assistance micelle-mediated extraction method (UAMME) seems to be an interesting alternative. The aim of this work was to compare an efficiency of water solutions of three non-ionic surfactants: C9-11 Pareth-5, PPG-6 Steareth-7 and PPG-4 Laureth-5 in UAMME of Bidens tripartita. Subsequently, the obtained extracts were separated into two immiscible phases, a polyphenols rich surfactants phase and an aqueous phase by its heating above surfactants cloud points (CPC) or by salting out with NaCl. Along with decreasing the Hydrophilic/Lipophilic Balance (HLB) factor value of surfactants, i.e. increase of the hydrophobicity, a significant decreasing of the flavonoid content was observed. While polyphenols content and antioxidant activity increased. The good surface properties of all surfactants correspond to the high content of phenolic compounds in extracts and both concentration methods resulted in even a 50-fold increase of polyphenols content. Dynamic light scattering measurements (DLS) provided that solubilization of polyphenols, i.e. their incorporation into surfactants’ micelles, occurred with significant enlarging of particle size. Based on the molecular dynamic simulations, the mechanism of polyphenols incorporation into micelles was discussed.

Structure and Dynamics of Spherical and Rodlike Alkyl Ethoxylate Surfactant Micelles Investigated Using NMR Relaxation and Atomistic Molecular Dynamics Simulations.

Predicting and controlling the properties of amphiphile aggregate mixtures require understanding the arrangements and dynamics of the constituent molecules. To explore these topics, we study molecular arrangements and dynamics in alkyl ethoxylate nonionic surfactant micelles by combining NMR relaxation measurements with large-scale atomistic molecular dynamics simulations. We calculate parameters that determine relaxation rates directly from simulated trajectories, without introducing specific functional forms to describe the dynamics. NMR relaxation rates, which depend on relative motions of interacting atom pairs, are influenced by wide distributions of dynamic time scales. We find that relative motions of neighboring atom pairs are rapid and liquidlike but are subject to structural constraints imposed by micelle morphology. Relative motions of distant atom pairs are slower than nearby atom pairs because changes in distances and angles are smaller when the moving atoms are further apart. Large numbers of atom pairs undergoing these slow relative motions contribute to predominantly negative cross-relaxation rates. For spherical micelles, but not for cylindrical micelles, cross-relaxation rates are positive only for surfactant tail atoms connected to the hydrophilic headgroup. This effect is related to the lower packing density of these atoms at the hydrophilic-hydrophobic boundary in spherical vs cylindrical arrangements, with correspondingly rapid and less constrained motion of atoms at the boundary.

Preparation of Mesoporous Silica by Nonionic Surfactant Micelle\u2013Templated Gelation of Na2SiO3 and H2SiF6 and Application as a Catalyst Carrier for the Partial Oxidation of CH4

Mesoporous silica (MSPN12) was prepared by nonionic surfactant micelle–templated gelation of sodium silicate (Na2SiO3) and fluorosilicic acid (H2SiF6) in aqueous solution, characterized by a range of instrumental techniques, and tested as a support for Ni and Rh catalysts in the partial oxidation of methane (POM). Calcined and sintered MSPN12 exhibited well-defined d00l-spacings (3.5–4.39 nm), narrow pore distributions (2.4–3.1 nm), and large specific surface areas (552–1,246 m2 g−1), and was found to be highly thermally stable. Microscopic imaging revealed that MSPN12 comprised spherical particles with a uniform diameter of ~0.7 µm, with each particle featuring firm and regular honeycomb-type pores. MSPN12-loaded Ni and Rh maintained stable POM activity at 700 °C during almost 100 h on stream, which were comparable to those for the commercial Rh(5)/Al2O3 catalyst in terms of methane conversion and H2 formation selectivity. Thus, the combination of structural stability and favorable physicochemical properties resulted in good POM performance.

How does solubilisation of plant waxes into nonionic surfactant micelles affect pesticide release?

HypothesisNonionic surfactants are used as adjuvants in agri-sprays to stabilise pesticides, but what happens when pesticide-loaded micelles are brought into direct contact with plant leaves? As pesticide solubilisation dehydrates the micellar shell and increases the effective hydrophobicity of the surfactant, we hypothesise that these micelles would uptake plant waxes and alter the amount of pesticide solubilized as a result of the re-equilibrating process. ExperimentsThe solubility of the pesticide cyprodinil (CP) and its effect on the shape of hexaethylene glycol monododecyl ether (C12E6) micelles were studied using changes in cloud point, nuclear magnetic resonance (NMR), cryogenic transmission electron microscopy (Cryo-TEM) and small-angle neutron scattering (SANS). Similarly, the solubility of wheat leaf waxes was examined, as was the effect of adding leaf waxes to pre-dissolved cyprodinil in micellar C12E6. FindingsWax solubilisation caused pesticide release and shell hydration, and shortened the length of the cylindrical micelles of the CP loaded C12E6. Temperature increase led to a significant rise in the amount of the dissolved waxes, increased pesticide release, increased micellar length, and caused shrinkage and dehydration of the shell. This study indicates that agrochemical sprays are capable of dissolving leaf waxes, and may trigger pesticide release from surfactant micelles upon contact with plant surfaces.

Structural changes in non-ionic surfactant micelles induced by ionic liquids and application thereof for improved solubilization of quercetin

We report the effect of concentration of 1-butyl-3-methylimidazolium ([C4mim]+) based ionic liquids (ILs) with different anions (Cl, BF4, CF3SO3, PF6, NTf2 and OS) on micelles of d-α-tocopheryl polyethylene glycol succinate (TPGS). A distinct series of ILs possessing identical anion (Cl−) but cation [Cnmim+) with increasing alkyl chain length (butyl, hexyl, octyl and decyl) was also tested. TPGS-IL mixed micelles were characterized through small angle neutron scattering (SANS).Depending upon IL-TPGS interaction, two distinct observations were recorded on clouding and aggregation of TPGS; (a) insignificant changes for ILs with short alkyl chain (C4mim), independent of concentration and type counter anions (Cl−, BF4−, CF3SO3−, PF6− and NTf2−), and (b) steep increase in cloud point, and reduction in size and aggregation number of micelles upon increasing the alkyl chain (C8 and C10) with concentration (10 to 200 mM). Our observations suggest that C4 (except C4mimOS) and C6mim ILs acted as solvent whereas C8mimCl, C10mimCl and C4mimOS served as secondary surfactants, thus promoting mixed micelle formation. For surface active ILs (C8 and C10), SANS parameters showed a progressive reduction in micelle size and increase in number density. Importantly, TPGS-C10mimCl association helped in improving the solubilization of quercetin (QCT) up to 700-fold. We speculate that high QCT solubilization resulted from the formation of small sized mixed micelles (hydrodynamic diameter ≈ 10 nm) at a high number density. Solubilization potential of TPGS-IL mixed system is practically exploitable for the development of injectable drug concentrates.

Analytical modeling of micelle growth. 1. Chain-conformation free energy of binary mixed spherical, wormlike and lamellar micelles

HypothesesA quantitative molecular-thermodynamic theory of the growth of giant wormlike micelles of nonionic surfactants can be developed on the basis of a generalized model, which includes the classical “phase separation” and “mass action” models as special cases. The generalized model describes spherocylindrical micelles, which are simultaneously multicomponent and polydisperse in size. TheoryBy analytical minimization of the free-energy functional we derived explicit expressions for the chain-extension and chain-end distribution functions in the hydrocarbon core of mixed micelles from two surfactants of different chainlengths. FindingsThe hydrocarbon core of a two-component micelle is divided in two regions, outer and inner, where the ends of the shorter and longer chains are located. The derived analytical expression for the chain-conformation free energy implies that the mixing of surfactants with different chainlengths is always nonideal and synergistic, i.e. it leads to decrease of the micellar free energy and to enhancement of micellization and micelle growth. The derived expressions are applicable to surfactants with different headgroups (nonionic, ionic, zwitterionic) and to micelles of different shapes (spherical, wormlike, lamellar). The results can be incorporated in a quantitative theory of the growth of giant mixed micelles in formulations with practical applications in detergency.

Self-assembled micellar clusters based on Triton-X-family surfactants for enhanced solubilization, encapsulation, proteins permeability control, and anticancer drug delivery

Non-ionic surfactants have raised a considerable interest for solubilization, encapsulation, permeabilization and controlled release of various compounds due to their unique physicochemical properties. Nevertheless, it is still challenging to create convenient self-assembled multifunctional materials with high solubilization and encapsulation capacities by preserving their advanced capabilities to protect loaded cargos without altering their characteristics. In this work, we present an extended concept of micellar clusters (MCs) formation based on partial entrapment and stabilization of chelate ligands by hydrophobic forces found on the non-ionic surfactant micelle interface of the Triton-X family (TX-100/TX-114), followed by subsequent complexation of the preformed structures either by metal ions or a supporting chelator. The formation aspects, inner structure and the role of external factors such as the addition of competitive ligands have been extensively studied. MCs loaded by hydrophobic fluorescent compounds with high encapsulation efficiency demonstrate an excellent optical response in aqueous media without crystallization as well as sufficient increase in solubility of toxic hydrophobic compounds such as bilirubin (>50 times compared to pure surfactants). Furthermore, Triton-X-based MCs provide a unique feature of selective permeability to hydrophilic ligand-switching proteins such as UnaG and BSA demonstrating bright “turn-on” fluorescence signal either inside the cluster or on its interface via complexation. The proposed strategies allowed us to successfully encapsulate and visualize a newly synthesized, highly hydrophobic anticancer PTR-58-CLB-CAMP peptide drug, while MCs loaded by the drug exhibit a considerable antitumor activity against HeLa cells.

What happens when pesticides are solubilized in nonionic surfactant micelles

Nonionic surfactants have been widely used in agri-sprays to enhance the solubility and mobility of pesticides, but what happens when pesticides become solubilized into surfactant micelles remains poorly characterized. To facilitate physical characterisations, we used the nonionic surfactant hexaethylene glycol monododecyl ether (C12E6) as a model system to solubilize 4 pesticides including Cyprodinil (CP), Diuron (DN), Azoxystrobin (AZ) and Difenoconazole (DF). The investigation focused on the influence of solubilizate and temperature in driving changes to the micellar nanostructures. Dynamic light scattering (DLS), cryogenic transmission electron microscopy (Cryo-TEM) and small-angle neutron scattering (SANS) measurements were used to reveal changes to the micellar structure before and after pesticide solubilisation. Nuclear magnetic resonance (NMR) was also applied to investigate the solubility and location of each pesticide in the micelles. Pesticides clearly altered the micellar structure, by increasing the aggregation number and micellar lengths, whilst shrinking and dehydrating the shells, leading to a consequent decrease in the dispersion cloud points. Increases in temperature affected micellar structures in a similar way. Thus, temperature increases and the solubilisation of pesticides can both make the surfactant effectively more hydrophobic, altering the micellar nanostructures and shifting the pesticide location within the micelles. These changes subsequently implicate how pesticides are delivered into plants through the natural wax films.

A generalized strategy for the synthesis of two-dimensional metal oxide nanosheets based on a thermoregulated phase transition.

Two-dimensional (2D) metal oxide (MO) nanomaterials, like graphene, possess unique electrical, mechanical, optical and catalytic performances, and have attracted substantial research interest recently. However, it remains a challenge to easily obtain 2D MO nanosheets by a generalized synthetic pathway. Here, we report a general and facile strategy for the synthesis of 2D MO nanosheets induced by nonionic surfactant micelles. Notably, the novel strategy primarily relies on the thermoregulated phase transition of the micelles. The resulting 2D MO nanosheets show high specific surface areas. As a demonstration, Sb2O3 nanosheets synthesized by our method as anodes for sodium-ion batteries (SIBs) have a high reversible capacity of 420 mA h g-1 and a high capacity retention of 99% after 150 cycles at 0.1 A g-1. Mn3O4 nanosheets for supercapacitors have a remarkable specific capacitance of 127 F g-1 at a current density of 0.5 A g-1. Even at a large current density of 5 A g-1 after 10 000 cycles, 96% of the specific capacitance is retained, demonstrating the remarkable performance of these nanosheets for energy storage applications.

Efficient production of red Monascus pigments with single non-natural amine residue by in situ chemical modification.

Filamentous fungi Monascus sp. has been utilized for fermentative production of food colorant (Red Yeast Rice) for more than 1000years in China. The main colorant components of Red Yeast Rice are mixture of red Monascus pigments (RMPs) with various primary amine residues. In the present work, the non-natural primary amine p-aminobenzamide, exhibiting as non-involved in nitrogen microbial metabolism, nontoxicity to microbial cells, and chemical reactivity with orange Monascus pigments (OMPs), was screened. Based on the screened result, RMPs with the single p-aminobenzamide residue were produced by cell suspension culture in a nonionic surfactant micelle aqueous solution via in situ chemical modification of OMPs. Furthermore, in situ chemical modification of OMPs also provided a strategy for maintaining a relatively low OMP concentration and then efficient accumulation of high concentration of RMPs (3.3g/l).

Location of Solvated Probe Molecules Within Nonionic Surfactant Micelles Using Molecular Dynamics

An iconic textbook that pharmaceutical scientists encounter in undergraduate courses is “Martin’s Physical Pharmacy and Pharmaceutical Sciences.” Within the chapter on Colloids, a figure indicates the location of solubilization of molecules within spherical, nonionic surfactant micelles. The surfactant consists of polyethylene glycol (PEG) hydrophilic headgroups and alkane chains for the hydrophobic tail. The figure shows benzene and toluene within the alkane core, salicylic acid (2-hydroxybenzoic acid) at the interface between the core and PEG chains, and then para-hydroxybenzoic acid (4-hydroxybenzoic acid) located between the PEG chains. Molecular dynamics simulations of octaethylene glycol monododecyl ether micelles were performed with a series of probe molecules, including those within the Martin’s figure, to determine their solubilization location. Relative placement of molecules within the micelle was correct; however, some specifics were different. In particular, benzene and toluene are excluded from the core, and 4-hydroxybenzoic acid prefers to maintain contact with the core. A series of molecules containing 6 carbon atoms were also studied to determine the effects of cyclization (moves out of core), polar functionalization (anchored to interface), and aromatization (excluded from central core). Molecular dynamics was found to be a useful tool for gaining insight into interactions important in solubilization of molecules.

Combined UV–Vis-absorbance and reflectance spectroscopy study of dye transfer kinetics in aqueous mixtures of surfactants

We report an analytical approach to study the competitive processes of solubilisation in micelles and of adsorption onto hydrophobic surfaces of poorly soluble hydrophobic dyes. The method is demonstrated on model systems containing two sources of Disperse Red 60: a bulk powder and a donor red textile, with molecularly dissolved dye stabilised in an aqueous environment by mixed micelles of anionic and non-ionic surfactants. The process of dye transfer between a donor textile (red polyester), surfactant micelles and an acceptor textile (white polyamide) was quantified by a combination of colorimetric analyses. UV–Vis absorbance was used to follow the extraction of the dye and to evaluate the solubilisation capacity of the micellar solution. A calibration curve for textile reflectance versus the adsorbed dye was generated to quantify the mass of dye transferred onto the acceptor textile. A combination of both techniques allowed us to compare the amount of dye desorbed from the donor textile and adsorbed onto the acceptor textile as a function of time for systems undergoing exhaustion-solubilisation mechanisms and only solubilisation mechanism. Up to ≃10 min of the washing process, the released dye is predominantly solubilised in surfactant micelles. At later times, the adsorption of the dye on the hydrophobic surface is energetically favoured. The shift of the desorption equilibrium in the presence of the acceptor textile results in ≃30% increase in the release of the dye. The reported methodology provides direct comparative analysis between the solubilisation capacity of amphiphilic stabilisers and the tendency of the dye to adsorb on solid substrates, important for designing novel concepts of disperse dye solubilisation and dye transfer inhibition during textile washing.

Drug Partitioning in Micellar Media and Its Implications in Rational Drug Design: Insights with Streptomycin.

Oral bioavailability of a drug molecule requires its effective delivery to the target site. In general, majority of synthetically developed molecular entities have high hydrophobic nature as well as low bioavailability, therefore the need for suitable delivery vehicles arises. Self-assembled structures such as micelles, niosomes, and liposomes have been used as effective delivery vehicles and studied extensively. However, the information available in literature is mostly qualitative in nature. We have quantitatively investigated the partitioning of antibiotic drug streptomycin into cationic, nonionic, and a mixture of cationic and nonionic surfactant micelles and its interaction with the transport protein serum albumin upon subsequent delivery. A combination of calorimetry and spectroscopy has been used to obtain the thermodynamic signatures associated with partitioning and interaction with the protein and the resulting conformational changes in the latter. The results have been correlated with other class of drugs of different nature to understand the role of molecular features in the partitioning process. These studies are oriented toward understanding the physical chemistry of partitioning of a variety of drug molecules into suitable delivery vehicles and hence establishing structure-property-energetics relationships. Such studies provide general guidelines toward a broader goal of rational drug design.