Role Of Micelles Research Articles

Diffusiophoretic Transport of Charged Colloids in Ionic Surfactant Gradients Entirely below versus Entirely above the Critical Micelle Concentration.

When placed in an ionic surfactant gradient, charged colloids will undergo diffusiophoresis at a velocity, uDP = MDP∇ ln S, where MDP is the diffusiophoretic mobility and S is the surfactant concentration. The diffusiophoretic mobility depends in part on the charges and diffusivities of the surfactants and their counterions. Since micellization decreases surfactant diffusivity and alters charge distributions in a surfactant solution, MDP of charged colloids in ionic surfactant gradients may differ significantly when surfactant concentrations are above or below the critical micelle concentration (CMC). The role of micelles in driving diffusiophoresis is unclear, and a previously published model that accounts for micellization suggests the possibility of a change in the sign of MDP above the CMC [Warren, P. B.; . Soft Matter 2019, 15, 278-288]. In the current study, microfluidic channels were used to measure the transport of negatively charged polystyrene colloids in sodium dodecyl sulfate (SDS) surfactant gradients established at SDS concentrations that are either fully above or fully below the CMC. Interpretation of diffusiophoresis was aided by measurements of the colloid electrophoretic mobility as a function of SDS concentration. A numerical transport model incorporating the prior diffusiophoretic mobility model for ionic surfactant gradients was implemented to elucidate signatures of positive and negative diffusiophoretic mobilities and compare with experiments. The theoretically predicted sign of the diffusiophoretic mobility below the CMC was determined to be particularly sensitive to uncertainty in colloid and surfactant properties, while above the CMC, the mobility was consistently predicted to be positive in the SDS concentration range considered in the experiments conducted here. In contrast, experiments only showed signatures of a negative diffusiophoretic mobility for these negatively charged colloids with no change of sign. Colloid diffusiophoretic transport measured in micellar solutions was more extensive than that below the CMC with the same ∇ ln S.

Surfactin as a Green Agent Controlling the Growth of Porous Calcite Microstructures.

This study presents a new, simple way to obtain mesoporous calcite structures via a green method using an eco-friendly surface-active compound, surfactin, as a controlling agent. The effects of synthesis time and surfactin concentration were investigated. The obtained structures were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) coupled with gas mass spectrometry (QMS) analysis. The experimental data showed that surfactin molecules significantly changed the morphology of the calcite crystals, roughening and deforming the surface and creating a greater specific surface area, even at low biosurfactant concentrations (10 ppm). The size of the crystals was reduced, and the zeta potential value of calcium carbonate was more negative when more biosurfactant was added. The XRD data revealed that the biomolecules were incorporated into the crystals and slowed the transformation of vaterite into calcite. It has been shown that as long as vaterite is present in the medium, the calcite surface will be less deformed. The strong influence of surfactin molecules on the crystal growth of calcium carbonate was due to the interaction of surfactin molecules with free calcium ions in the solution as well as the biomolecules adsorption at the formed crystal surface. The role of micelles in crystal growth was examined, and the mechanism of mesoporous calcium carbonate formation was presented.

Fabrication of polypyrrole (PPy) nanotube electrode for supercapacitors with enhanced electrochemical performance

PPy nanotubes were successfully fabricated by a simple situ polymerization method, using FeCl3 as oxidant, methyl orange (MO) formed by the role of micelles as a guide and soft template. By varying the ratio of oxidant to pyrrole (Py) monomer, the best nanotube structure is obtained when the ratio of Py is 0.5 (mark this specimen as A3). Moreover, the electrochemical properties of PPy nanotube electrode are investigated by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS). A3 exhibits excellent cycle performance and electrochemical performance. Meanwhile, the specific capacitance of sample A3 is 281.2 F g−1 at a current density of 1 A g−1 and can still retain about 78% after 1000 cycles.

Synthesis, Characterization, and Micellization Behavior of Cationic Surfactants: n‐Alkyl‐3‐Methylpyridinium Bromides and Their Drug Interaction Study by UV–Visible Spectroscopy and Conductometry

AbstractThe synthesis of new cationic surfactants i.e., n‐hexyl‐3‐methylpyridium bromide (a) and n‐octyl‐3‐methylpyridium bromide (b), and their characterization using multinuclear nuclear magnetic resonance spectroscopy (NMR) (1H, 13C) and Fourier‐transform infrared spectroscopy (FT‐IR) spectroscopic techniques were reported. The micellization behavior of the synthesized surfactants was studied using conductometry and ultraviolet–Visible spectroscopy. The critical micelle concentration (CMC) of compounds a and b was found to be 0.41 and 0.35 m mol L−1, respectively. The effect of temperature on the CMC of these compounds was examined in the range of 298–318 K and thermodynamic parameters (ΔG, ΔH, and ΔS) of the micellization process were calculated. The antibacterial study of the synthesized surfactants revealed their strong activity against different bacterial strains. Moreover, the interaction of drugs i.e., flurbiprofen and ketoprofen, with the synthesized surfactants was investigated for gaining insights into the role of micelles as drug‐delivery devices. Drug–surfactant interactions were also confirmed via a conductometric method.

Role of (single/double chain surfactant) micelles on the protein aggregation

To investigate the interaction between the bovine serum albumin (BSA) and cationic surfactants (monomeric, cetyltrimethylammonium bromide, CTAB) and dimeric/gemini, 1, 6 bis (N, N-hexadecyl dimethyl ammonium bromide, 16-6-16) and to find out the role of micelles in the aggregation of the protein using spectroscopic (UV–visible, fluorescence, fluorescence lifetime measurements, circular dichroism (CD), etc.) and microscopic (atomic force microscope (AFM)) techniques. The different surfactant has an effect on the polarity of the microenvironment of the protein shows in all the spectroscopic technique at below and above the critical micelle concentration (CMC). The far-UV CD spectra show that BSA is more disrupted by the dimeric surfactant compared to the monomeric CTAB above the CMC. The binding of the surfactant induce changes in the microenvironment around the aromatic amino acids residues and disulfide bond of the BSA at different pHs. The binding constant values were found to be 20.278×103M and 8.443M for the BSA-CTAB complex and BSA-16-6-16 complex, respectively. Atomic force microscope indicates the aggregation is more in case of dimeric (16-6-16) surfactant compared to the monomeric (CTAB) surfactant at the higher concentration (above their CMCs). Below and above the CMC, all changes are noticeable.

Micelle-enhanced flow injection analysis

AbstractSurface-active agents are organic compounds of amphiphilic nature. When the concentration of surfactants is higher than a certain value, the monomers adhere to form well-defined aggregates known as micelles. These micelles have been employed in flow injection analysis (FIA) for various purposes. In chemiluminescence-based FIA, micelles can improve sensitivity by changing the chemical structures of the reagents, facilitating intramicellar energy transfer, accelerating the reaction kinetics, or stabilizing the excited singlet states. Micelles can improve sensitivity in FIA/ultraviolet-visible by electrostatic or solubilization effects. In FIA/fluorescence, emission intensity is considerably enhanced in micellar media due to the protective environment that restricts nonemissive energy transfer processes. If FIA is coupled with flame atomic absorption, the signals are enhanced with surfactants due to the decreased surface tension that results in the generation of smaller droplets during the aspiration and nebulization processes. In addition, surfactants promote the enrichment of the analyte in the double layer at the air-water interface. The FIA/cloud point extraction technique is based on using surfactants as alternatives to organic solvents. This review discusses the different roles of micelles in FIA methods.

Recent advances in amphiphilic polymers for simultaneous delivery of hydrophobic and hydrophilic drugs.

Nanomedicine has evolved with the use of biological compounds such as proteins, peptides and DNA. These hydrophilic and often highly charged compounds require a delivery system to allow effective transport and release at the site of action. These new biological therapeutics have not replaced the more traditional smaller molecule, but instead are working synergistically to the benefit of the end user. To that end, drug delivery systems are now required to encapsulate both larger hydrophilic compounds as well as the smaller and generally more hydrophobic compound. This review highlights the emerging role in drug delivery of amphiphilic polymers that by their very nature can associate with compounds of differing physicochemical properties, in particular the role of micelles, polymersomes and nanocapsules.

Factors influencing the immunogenicity of therapeutic proteins

Several diseases and disorders are treatable with therapeutic proteins, but some of these products may induce an immune response, especially when administered as multiple doses over prolonged periods. Antibodies are created by classical immune reactions or by the breakdown of immune tolerance; the latter is characteristic of human homologue products. Many factors influence the immunogenicity of proteins, including structural features (sequence variation and glycosylation), storage conditions (denaturation, or aggregation caused by oxidation), contaminants or impurities in the preparation, dose and length of treatment, as well as the route of administration, appropriate formulation and the genetic characteristics of patients. The clinical manifestations of antibodies directed against a given protein may include loss of efficacy, neutralization of the natural counterpart and general immune system effects (including allergy, anaphylaxis or serum sickness). An upsurge in the incidence of antibody-mediated pure red cell aplasia (PRCA) among patients taking one particular formulation of recombinant human erythropoietin (epoetin-alpha, marketed as Eprex(R)/Erypo(R); Johnson & Johnson) in Europe caused widespread concern. The PRCA upsurge coincided with removal of human serum albumin from epoetin-alpha in 1998 and its replacement with glycine and polysorbate 80. Although the immunogenic potential of this particular product may have been enhanced by the way the product was stored, handled and administered, it should be noted that the subcutaneous route of administration does not confer immunogenicity per se. The possible role of micelle (polysorbate 80 plus epoetin-alpha) formation in the PRCA upsurge with Eprex is currently being investigated.

Solubility of nonylphenol and nonylphenol ethoxylates. On the possible role of micelles

The water solubility of nonylphenol (NP) has been estimated to be 4.9±0.4 mg/l corresponding to (2.22±0.18)×10 −5 mol/l at 25°C using shake flask and surface tension techniques. The low solubility in combination with an observed rather slow dissolution process will limit the leachability of NP in the terrestrial environment. Based on indirect evidence, it is suggested that NP, in contrast to nonylphenol ethoxylate (NPEO) with, e.g., 12 ethoxylate moieties, is not subject to micelle formation, and as such does not constitute a potential vehicle for the transport of hydrophobic pollutants in the environment. For NPEOs with a very high number of ethoxy moieties, e.g., 100, the compounds appear water soluble without micelle formation.

Surface Reconstruction of the Unstable {110} Surface in Gold Nanorods

Gold nanorods prepared electrochemically and capped in micelles are examined using high-resolution transmission electron microscopy (TEM). It is found that they have an axial growth direction of [001] and have surfaces made of {100} and the unstable {110} facets. A detailed examination of the defect sites of both of these facets shows that while the defective regions of the stable {100} facets show atom-height steps with no reconstruction, the less stable higher energy {110} surfaces show missing-row reconstruction. The role of micelles in stabilizing the {110} facet in the gold nanorod is briefly discussed.

Influence of alcoholic modifiers on the selectivity of the separation of a group of polycyclic aromatic hydrocarbons by micellar liquid chromatography

The role of micelles and alcohols as the modifiers of the aqueous mobile phase in reversed-phase liquid chromatography in controlling retention and selectivity of polyaromatic hydrocarbons (PAHs) is studied. Elution strength increases with an increase in the alcohol or micelle concentration, and enhancement of separation selectivity with elution strength was observed. Increasing micelle concentration has an opposite effect, when compared to increasing alcohol modifier concentration, on the separation selectivity, showing that for this group of PAHs the separation selectivity is better with mobile phases of medium concentration of micelles and moderately high alcohol percentages. The selectivity enhancement can be explained in terms of the competing equilibria in micellar liquid chromatography.

Distribution Equilibria of Thiazolylazophenols between Aqueous Micellar Pseudo Phases in Nonionic Surfactant Solutions and the Role of Micelles in High-Performance Liquid Chromatography

he solubilization equilibria of 2-(2-thiazolylazo)-4-methylphenol (TAC) and 2-(2-thiazolylazo)-5-dimethylaminophenol (TAM) in aqueous micellar solutions of nonionic surfactants were investigated according to a distribution model between the micellar and aqueous phases. The distribution constants of TAC and TAM, thus obtained, decreased with an increase in the oxyethylene chain length of nonionic surfactants, indicating the possibility of controlling the distribution of TAC and TAM into micelles. Based on this finding, we tested the micellar reversed-phase high-performance liquid chromatography (micellar RP-HPLC) of vanadium(V)-TAM chelate, which was hardly separated from free TAM in conventional RP-HPLC. Micellar RP-HPLC was effective in preferentially eluting the vanadium(V) chelate in advance of free TAM when a nonionic surfactant with a longer oxyethylene chain was employed.

Simultaneous enhancement of separation selectivity and solvent strength in reversed-phase liquid chromatography using micelles in hydro-organic solvents

The role of micelles and organic solvents as the modifiers of the aqueous mobile phase in reversed-phase liquid chromatography (RPLC) in controlling retention and selectivity is discussed. Elution strength increases in RPLC with an increase in organic solvent or micelle concentration. Simultaneous enhancement of separation selectivity with elution strength in the hybrid eluents of water-organic solvent-micelles was observed. This selectivity enhancement occurs systematically, i.e. peak separation increases monotonically with volume fraction of organic solvent added to micellar eluent, and is observed for a large number of ionic and nonionic compounds with different functional groups and for two surfactants (anionic and cationic). For two test mixtures, 13 amino acids/peptides and 15 phenols, it is shown that a better separation and shorter analysis time are observed at stronger hybrid eluents. This selectivity enhancement can be attributed to the competing partitioning equilibria in micellar LC systems and/or to the unique characteristics of micelles to compartmentalize solutes and organic solvents.

Are theoretical surface chemistry measurements really practical?

AbstractThe principles and concepts of surface chemistry can be of enormous aid in the application of surfactant chemicals to practical cleaning and foaming problems. The use of surfactants for foam stability was seen to be dependent on rheological properties of the foam (bulk and surface viscosity) and to the energetics of the adsorbed surfactant monolayer (area/surfactant molecule, monolayer clasticity modulus, rate of monolayer spreading and rate of surfactant adsorption into the interface). From these principles, an equation predicting foam volume in the presence or absence of soil was derived and found to be in good agreement with experiment. In detergency, the performance was dictated by the thermodynamic work of adhesion between the soil and substrate. The adhesion was a function of surface properties (soil/water interfacial tension and soil/water/substrate). The role of agitation in detergency was shown to be that energy which was needed to overcome the adhesive bond between soil and substrate. The implicit form of the agitation term was discussed (dependent on substrate configuration, agitator system geometry and mechanics) but not explicitly deduced. The role of interfacial tension was discussed in relation to foam stability and detergency. In both applications, low interfacial tension is beneficial to performance. However, because other surface chemical effects play a role in performance in detergency and foam stability, it was noted that interfacial tension is not the sole correlating parameter with performance. The situations in which low interfacial tension is not sufficient to give improved detergency and foam stability performance were delineated. A possible new method of aiding in optimizing oil/surfactant performance also was discussed. Finally, the role of micelles in detergency was examined in light of very recent experimental work which suggests that micelles may be detrimental to detergency and foam stability performance. This study suggests that surfactants which form mesomorphic phases with soil give better performance. Micelles, instead of solubilizing soil in their hydrophobic cores, are said to be competing with the mesomorphic phase formation process, thereby hindering detergency performance. It is suggested by the sheer weight of new theoretical and innovative approaches to surface chemistry applied to detergency and foam stability performance that “theoretical surface chemistry measurements really (are) practical!”

Stereochemical course of deamination of acyclic secondary carbinamines in water. The role of micelles

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStereochemical course of deamination of acyclic secondary carbinamines in water. The role of micellesRobert A. Moss and David W. RegerCite this: J. Am. Chem. Soc. 1969, 91, 26, 7539–7541Publication Date (Print):December 1, 1969Publication History Published online1 May 2002Published inissue 1 December 1969https://doi.org/10.1021/ja01054a071RIGHTS & PERMISSIONSArticle Views51Altmetric-Citations23LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (436 KB) Get e-Alerts Get e-Alerts