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Hao W, Chesnokov YM, Molchanov VS, Podlesnyi PR, Kuklin AI, Skoi VV, Philippova OE. Cryo-electron tomography study of the evolution of wormlike micelles to saturated networks and perforated vesicles. J Colloid Interface Sci 2024; 672:431-445. [PMID: 38850868 DOI: 10.1016/j.jcis.2024.06.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2024] [Revised: 06/02/2024] [Accepted: 06/02/2024] [Indexed: 06/10/2024]
Abstract
HYPOTHESIS The formation of micellar aggregates and the changes in their morphology are crucial for numerous practical applications of surfactants. However, a proper structural characterization of complicated micellar nanostructures remains a challenge. This paper demonstrates the advances of cryo-electron tomography (cryo-ET) in revealing the structural characteristics that accompany the evolution of surfactant aggregates. EXPERIMENTS By using cryo-ET in combination with cryo-transmission electron microscopy (cryo-TEM), small-angle neutron scattering (SANS), and rheometry, studies were carried out on a model system composed of zwitterionic and nonionic surfactants. In this system, the molecular packing parameter was increased gradually by increasing the molar fraction of nonionic surfactant. FINDINGS A series of structural transformations was observed: linear wormlike micelles (WLMs) → branched WLMs → saturated network of multiconnected WLMs → perforated vesicles (stomatosomes). The transformations occur through an increase in the number of branches at the expense of cylindrical subchains and semispherical endcaps. Exponential distribution of subchains length was confirmed experimentally for multiconnected saturated networks. The stomatosomes were formed when the length of subchains becomes much shorter than the persistence length, causing the three-dimensional (3D) structure to transform into a two-dimensional (2D) membrane. This work identifies the mechanism of the structural changes, which can be further used to design various surfactant self-assemblies.
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Affiliation(s)
- Wuyi Hao
- Physics Department, Moscow State University, 119991 Moscow, Russia
| | - Yuri M Chesnokov
- National Research Center "Kurchatov Institute", 123182, Moscow, Russia
| | | | - Pavel R Podlesnyi
- National Research Center "Kurchatov Institute", 123182, Moscow, Russia
| | | | - Vadim V Skoi
- Joint Institute for Nuclear Research, 141980 Dubna, Russia
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2
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Hisamatsu Y, Toriyama G, Yamamoto K, Takase H, Higuchi T, Umezawa N. Temperature Control of the Self-Assembly Process of 4-Aminoquinoline Amphiphile: Selective Construction of Perforated Vesicles and Nanofibers, and Structural Restoration Capability. Chemistry 2024; 30:e202400134. [PMID: 38361463 DOI: 10.1002/chem.202400134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2024] [Revised: 02/13/2024] [Accepted: 02/14/2024] [Indexed: 02/17/2024]
Abstract
The construction of diverse and distinctive self-assembled structures in water, based on the control of the self-assembly processes of artificial small molecules, has received considerable attention in supramolecular chemistry. Cage-like perforated vesicles are distinctive and interesting self-assembled structures. However, the development of self-assembling molecules that can easily form perforated vesicles remains challenging. This paper reports a lower critical solution temperature (LCST) behavior-triggered self-assembly property of a 4-aminoquinoline (4-AQ)-based amphiphile with a tetra(ethylene glycol) chain, in HEPES buffer (pH 7.4). This property allows to form perforated vesicles after heating at 80 °C (> LCST). The self-assembly process of the 4-AQ amphiphile can be controlled by heating at 80 °C (> LCST) or 60 °C (< LCST). After cooling to room temperature, the selective construction of the perforated vesicles and nanofibers was achieved from the same 4-AQ amphiphile. Furthermore, the perforated vesicles exhibited slow morphological transformation into intertwined-like nanofibers but were easily restored by brief heating above the LCST.
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Affiliation(s)
- Yosuke Hisamatsu
- Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya, 467-8603, Japan
| | - Go Toriyama
- Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya, 467-8603, Japan
| | - Katsuhiro Yamamoto
- Graduate School of Engineering, Nagoya Institute of Technology Gokiso-cho, Showa-ku, Nagoya, 466-8555, Japan
| | - Hiroshi Takase
- Graduate School of Medical Sciences, Nagoya City University, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya, 467-8601, Japan
| | - Tsunehiko Higuchi
- Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya, 467-8603, Japan
| | - Naoki Umezawa
- Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya, 467-8603, Japan
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Guitton-Spassky T, Junge F, Singh AK, Schade B, Achazi K, Maglione M, Sigrist S, Rashmi R, Haag R. Fluorinated dendritic amphiphiles, their stomatosome aggregates and application in enzyme encapsulation. NANOSCALE 2023; 15:7781-7791. [PMID: 37016756 DOI: 10.1039/d3nr00493g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Enzymes are more selective and efficient than synthetic catalysts but are limited by difficult recycling. This is overcome by immobilisation, namely through encapsulation, with the main drawback of this method being slow diffusion of products and reactants, resulting in effectively lowered enzyme activity. Fluorinated dendritic amphiphiles were reported to self-assemble into regularly perforated bilayer vesicles, so-called "stomatosomes". It was proposed that they could be promising novel reaction vessels due to their increased porosity while retaining larger biomolecules at the same time. Amphiphiles were synthesised and their aggregation was analysed by cryogenic transmission electron microscopy (cryo-TEM) and dynamic light scattering (DLS) in buffered conditions necessary for enzyme encapsulation. Urease and albumin were encapsulated using the thin-film hydration method and investigated by confocal and time-gated stimulated emission depletion microscopy (gSTED). Their release was then used to probe the selective retention of cargo by stomatosomes. Free and encapsulated enzyme activity were compared and their capacity to be reused was evaluated using the Berthelot method. Urease was successfully encapsulated, did not leak out at room temperature, and showed better activity in perforated vesicles than in closed vesicles without perforations. Encapsulated enzyme could be reused with retained activity over 8 cycles using centrifugation, while free enzyme had to be filtrated. These results show that stomatosomes may be used in enzyme immobilisation applications and present advantages over closed vesicles or free enzyme.
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Affiliation(s)
- Tiffany Guitton-Spassky
- Institut für Chemie und Biochemie, Organische Chemie, Freie Universität Berlin, Takustraße 3, Berlin, 14195 Germany.
| | - Florian Junge
- Institut für Chemie und Biochemie, Organische Chemie, Freie Universität Berlin, Takustraße 3, Berlin, 14195 Germany.
| | - Abhishek Kumar Singh
- Institut für Chemie und Biochemie, Organische Chemie, Freie Universität Berlin, Takustraße 3, Berlin, 14195 Germany.
| | - Boris Schade
- Forschungszentrum für Elektronenmikroskopie, Institut für Chemie und Biochemie, Freie Universität Berlin, Fabeckstraße 36a, Berlin, 14195 Germany
| | - Katharina Achazi
- Institut für Chemie und Biochemie, Organische Chemie, Freie Universität Berlin, Takustraße 3, Berlin, 14195 Germany.
| | - Marta Maglione
- Institut für Chemie und Biochemie, Organische Chemie, Freie Universität Berlin, Takustraße 3, Berlin, 14195 Germany.
- Institute for Biology, Freie Universität Berlin, Takustraße 6, Berlin, 14195 Germany
| | - Stephan Sigrist
- Institute for Biology, Freie Universität Berlin, Takustraße 6, Berlin, 14195 Germany
| | - Rashmi Rashmi
- Institut für Chemie und Biochemie, Organische Chemie, Freie Universität Berlin, Takustraße 3, Berlin, 14195 Germany.
| | - Rainer Haag
- Institut für Chemie und Biochemie, Organische Chemie, Freie Universität Berlin, Takustraße 3, Berlin, 14195 Germany.
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Emelyanova KA, Sorina PO, Victorov AI. Transmembrane potential in vesicles formed by catanionic surfactant mixtures in an aqueous salt solution. Phys Chem Chem Phys 2020; 22:26438-26451. [PMID: 33180892 DOI: 10.1039/d0cp05248e] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The transmembrane potential plays a key role in a multitude of natural and synthetic systems because it is the driving force for the flow of mobile charged species across the membranes. We develop a molecular thermodynamic theory to study the transmembrane potential of metastable and equilibrium vesicles as a function of the vesicle structural parameters, and salinity and acidity of the surrounding aqueous solution. We show that addition of salt to the external solution may reverse the sign of the transmembrane potential, indicating the reversal of sign of the net charges accumulated in the vesicle interior and exterior. We discuss maxima/minima of the transmembrane potential as a function of added salt and propose a simple formula to estimate the location of these extrema. We demonstrate that a vesicle brought to equilibrium with an acidic environment may take up and hold alkaline solution in its interior. We also show that bending of a symmetrically charged planar membrane leads to a buildup of the transmembrane potential. The catanionic vesicles considered in this work are composed of a series of classical surfactants and model surfactants differing in their molecular structure. These vesicles may serve as a simple prototype for capsules formed by the amphiphilic membranes of a more complex structure, e.g., in nanoreactors or drug-delivery systems.
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Affiliation(s)
- Ksenia A Emelyanova
- St. Petersburg State University, 7/9 Universitetskaya Nab., 199034 St. Petersburg, Russia.
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5
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Emelyanova KA, Victorov AI. Molecular thermodynamic modeling of a bilayer perforation in mixed catanionic surfactant systems. Phys Chem Chem Phys 2018; 20:27924-27929. [DOI: 10.1039/c8cp04593c] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
An interplay between electrostatics and deformation of surfactant tails is responsible for the spontaneous formation of pores in self-assembled bilayers.
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Emelyanova KA, Victorov AI. Driving Force for Spontaneous Perforation of Bilayers Formed by Ionic Amphiphiles in Aqueous Salt. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:13438-13443. [PMID: 29064715 DOI: 10.1021/acs.langmuir.7b02885] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Spontaneous perforation of amphiphilic membranes is important in both living matter and technology because of an impact on functions of biological membranes and shape transitions of self-assembling structures. Nevertheless, no definite molecular mechanism has been established so far even for simple ionic surfactant systems. We show that spontaneous perforation of a bilayer formed by an ionic amphiphile is driven by electrostatics. Creation of large pores with a concave-convex geometry of the rim is promoted by lower electrostatic free energy than that for a flat nonperforated bilayer. The opposite effect comes from the elasticity of the hydrocarbon tails of the amphiphile that prefer flat geometry of a nonperforated bilayer. The balance between electrostatics and tail deformation controls the appearance of pores; this balance is modulated by added salt that screens the electrostatic interactions. We illustrate the proposed mechanism with the aid of classical aggregation model that has been extended by including an analytical description of the electrostatic contribution for the toroidal rim of a pore. Numerical solution of the linearized Poisson-Boltzmann equation confirms the role of electrostatic forces in formation of pores. For the ionic surfactants of CnTAB family, we predict shape transitions including bilayer perforations and formation of branched micellar networks induced by changing salinity or temperature and demonstrate the effect of surfactant's molecular parameters on these transitions.
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Affiliation(s)
- Ksenia A Emelyanova
- St. Petersburg State University , 7/9 Universitetskaya nab., 199034 St. Petersburg, Russia
| | - Alexey I Victorov
- St. Petersburg State University , 7/9 Universitetskaya nab., 199034 St. Petersburg, Russia
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7
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Dhawan VV, Nagarsenker MS. Catanionic systems in nanotherapeutics – Biophysical aspects and novel trends in drug delivery applications. J Control Release 2017; 266:331-345. [DOI: 10.1016/j.jconrel.2017.09.040] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2017] [Accepted: 09/28/2017] [Indexed: 01/10/2023]
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Zhang J, Wang Y, Xu G, Lin M, Fan T, Yang Z, Dong Z. Formation and rheological behavior of wormlike micelles in a catanionic system of fluoroacetic acid and tetradecyldimethylaminoxide. SOFT MATTER 2017; 13:670-676. [PMID: 28009918 DOI: 10.1039/c6sm02653b] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
From catanionic fluoro-/hydro-carbon mixtures of fluoroacetic acid (CF3COOH) and tetradecyldimethylaminoxide (C14DMAO) in water, viscoelastic wormlike micelles are successfully constructed which are determined by cryo-TEM measurements. It is found that the formation and rheological behavior of the wormlike micelles are greatly affected by the total concentration and mixing ratio of CF3COOH and C14DMAO as well as temperature. The driving force for the formation of wormlike micelles here is considered to be the electrostatic attractive interaction between the two molecules which is confirmed by 1H NMR measurements. As far as we know, such wormlike micelles formed from the catanionic mixtures of fluorofatty acids and hydrocarbon surfactants have been rarely reported. Our work provides a simple method through mixing a perfluorofatty acid with a hydrocarbon surfactant to construct and understand the formation mechanism of catanionic fluoro-/hydro-carbon wormlike micelles, which should be a great advance in the fundamental research of wormlike micelles.
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Affiliation(s)
- Juan Zhang
- Institute of Enhanced Oil Recovery, China University of Petroleum, Beijing 102249, China.
| | - Yingxia Wang
- Institute of Enhanced Oil Recovery, China University of Petroleum, Beijing 102249, China.
| | - Guiying Xu
- Key Laboratory of Colloid and Interface Chemistry, Shandong University, Ministry of Education, Jinan 250100, P. R. China
| | - Meinqin Lin
- Institute of Enhanced Oil Recovery, China University of Petroleum, Beijing 102249, China.
| | - Tianyu Fan
- Institute of Enhanced Oil Recovery, China University of Petroleum, Beijing 102249, China.
| | - Zihao Yang
- Institute of Enhanced Oil Recovery, China University of Petroleum, Beijing 102249, China.
| | - Zhaoxia Dong
- Institute of Enhanced Oil Recovery, China University of Petroleum, Beijing 102249, China.
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9
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Danino D, Abezgauz L, Portnaya I, Dan N. From Discs to Ribbons Networks: The Second Critical Micelle Concentration in Nonionic Sterol Solutions. J Phys Chem Lett 2016; 7:1434-1439. [PMID: 27031669 DOI: 10.1021/acs.jpclett.6b00266] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
At the critical micelle concentration (CMC), amphiphiles self-assemble into spherical micelles, typically followed by a transition at the second CMC to cylindrical micelles that are uniform in width but are polydispersed in length and have swollen ends. In this Letter, we report on a new structural path of self-assembly that is based on discoidal (coin-like), rather than spherical, geometry; the nonionic sterol ChEO10 is shown to form monodisperse equilibrium disc assemblies at the first CMC, transitioning at the second CMC into flat ribbons that (like the cylindrical micelles) have uniform width, polydispersed length, and swollen ends. Increase in ChEO10 concentration or the temperature leads to ribbon elongation, branching, and network formation. This self-assembly path reveals that (1) surfactants can form equilibrium nonspherical assemblies at the CMC and (2) aggregate progression around the second CMC is similar for the disc and sphere geometries.
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Affiliation(s)
- Dganit Danino
- Department of Biotechnology and Food Engineering, Technion-Israel Institute of Technology , Haifa 3200003, Israel
| | - Ludmila Abezgauz
- Department of Biotechnology and Food Engineering, Technion-Israel Institute of Technology , Haifa 3200003, Israel
| | - Irina Portnaya
- Department of Biotechnology and Food Engineering, Technion-Israel Institute of Technology , Haifa 3200003, Israel
| | - Nily Dan
- Department of Chemical and Biological Engineering, Drexel University , Philadelphia, Pennsylvania 19104, United States
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10
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Bergström LM, Skoglund S, Edwards K, Eriksson J, Grillo I. Spontaneous transformations between surfactant bilayers of different topologies observed in mixtures of sodium octyl sulfate and hexadecyltrimethylammonium bromide. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:3928-3938. [PMID: 24697326 DOI: 10.1021/la4042259] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The influence of adding salt on the self-assembly in sodium octyl sulfate (SOS)-rich mixtures of the anionic surfactant SOS and the cationic surfactant hexadecyltrimethylammonium bromide (CTAB) have been investigated with the two complementary techniques, small-angle neutron scattering (SANS) and cryo-transmission electron microscopy. We are able to conclude that addition of a substantial amount of inert salt, NaBr, mainly has three effects on the structural behaviors: (i) the micelles become much larger at the transition from micelles to bilayers, (ii) the fraction of bilayer disks increases at the expense of vesicles, and (iii) bilayer aggregates perforated with holes are formed in the most diluted samples. A novel form factor valid for perforated bilayer vesicles and disks is introduced for the first time and, as a result, we are able to directly observe the presence of perforated bilayers by means of fitting SANS data with an appropriate model. Moreover, we are able to conclude that the morphology of bilayer aggregates changes according to the following sequence of different bilayer topologies, vesicles → disks → perforated bilayers, as the electrolyte concentration is increased and surfactant mole fraction in the bilayer aggregates approaches equimolarity. We are able to rationalize this sequence of transitions as a result of a monotonous increase of the bilayer saddle-splay constant (k(c)(bi)) with decreasing influence from electrostatics, in agreement with theoretical predictions as deduced from the Poisson-Boltzmann theory.
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Affiliation(s)
- L Magnus Bergström
- School of Chemical Science and Engineering, Department of Chemistry, Surface and Corrosion Science, KTH Royal Institute of Technology , , SE-10044 Stockholm, Sweden
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11
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Teng HN, Hu LS, Chen Y, Yang CY, Du TT. Effects of Surfactant Carbon-Chain Length on the Phase Behaviors of ATPS. J DISPER SCI TECHNOL 2011. [DOI: 10.1080/01932691.2010.505881] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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12
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Cano-Sarabia M, Angelova A, Ventosa N, Lesieur S, Veciana J. Cholesterol induced CTAB micelle-to-vesicle phase transitions. J Colloid Interface Sci 2010; 350:10-5. [DOI: 10.1016/j.jcis.2010.04.069] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2009] [Revised: 04/26/2010] [Accepted: 04/27/2010] [Indexed: 10/19/2022]
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13
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Li X, Yang Y, Eastoe J, Dong J. Rich Self-Assembly Behavior from a Simple Amphiphile. Chemphyschem 2010; 11:3074-7. [DOI: 10.1002/cphc.201000500] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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14
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Zhong S, Pochan DJ. Cryogenic Transmission Electron Microscopy for Direct Observation of Polymer and Small-Molecule Materials and Structures in Solution. POLYM REV 2010. [DOI: 10.1080/15583724.2010.493254] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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15
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Salt effect on the rheological properties of the aqueous mixed cationic and anionic surfactant systems. Colloids Surf A Physicochem Eng Asp 2010. [DOI: 10.1016/j.colsurfa.2010.03.035] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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16
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Alakoskela JM, Parry MJ, Kinnunen PKJ. The intermediate state of DMPG is stabilized by enhanced positive spontaneous curvature. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:4892-4900. [PMID: 20205407 DOI: 10.1021/la100411p] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
1,2-Dimyristoyl-sn-glycero-3-phospho-rac-glycerol (DMPG) at low salt concentrations has a complex endotherm with at least four components and extending over the span of 20 degrees. During this ongoing melting, the solution becomes viscous and scatters light poorly. This multipeak endotherm was suggested to result from the effects of curvature on the relative free energies of gel and fluid DMPG bilayers, further relating to the formation of an intermediate sponge phase between the lamellar gel and fluid phases. Although later studies appear to exclude a connected bilayer network, the relation of the endotherm peaks to curvature remains an appealing hypothesis. This was tested by including in the system both water-soluble small molecules (dimethyl sulfoxide, ethanol, and urea) as well as amphiphiles (myristoyl-lyso-PG, cholesterol, cholesterol-3-sulfate, and dimyristoylglycerol) known to alter the spontaneous curvature of bilayers. All compounds increasing the monolayer positive spontaneous curvature (ethanol, urea, myristoyl-lyso-PG, cholesterol-3-sulfate) increased the temperature span of the intermediate state and elevated the temperature of its dissolution, while all compounds increasing the negative spontaneous curvature (dimethyl sulfoxide, cholesterol, dimyristoylglycerol) had the opposite effect, implying that the intermediate state contains a structure with positive curvature. The results support the view that the intermediate state consists of vesicles with a large number of holes. The viscosity increase could be related to vesicle expansion needed to accommodate the numerous holes.
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Affiliation(s)
- Juha-Matti Alakoskela
- Helsinki Biophysics and Biomembrane Group, Institute of Biomedicine, Division of Biochemistry, P.O. Box 63, 00014 University of Helsinki, Finland.
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17
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Silva BFB, Marques EF, Olsson U, Pons R. Headgroup effects on the unusual lamellar-lamellar coexistence and vesicle-to-micelle transition of salt-free catanionic amphiphiles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:3058-3066. [PMID: 19780558 DOI: 10.1021/la902963k] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Salt-free ion-paired catanionic amphiphiles of the C(m)(+)C(n)(-) type, with a high solubility mismatch (n >> m or m >> n) display a remarkable phase behavior in water. A temperature-driven vesicle-to-micelle transition in the dilute side together with a coexistence of two lamellar phases on the concentrated side is one of the peculiar effects that have been reported for the hexadecyltrimethylammonium octylsulfonate surfactant, C(16)C(8) or TA(16)So(8) (extensive to C(14)C(8) and C(12)C(8)). In this work, with TA(16)So(8) as a reference, the cationic trimethylammonium (TA(+)) and pyridinium (P(+)) headgroups are combined with the anionic sulfate (S(-)) and sulfonate (So(-)) headgroups to yield other C(16)C(8) compounds: hexadecyltrimethylammonium octylsulfate (TA(16)S(8)), 1-hexadecylpyridinium octylsulfonate (P(16)So(8)), and 1-hexadecylpyridinium octylsulfate (P(16)S(8)). We show that, if the asymmetry of the chain lengths is kept constant at C(16)C(8) and the headgroup chemistry is changed, most of the unusual self-assembly properties are still observed, indicating that they are not system-specific but extensive to other combinations of headgroups and mainly dictated by the ion-pair solubility mismatch. Thus, all the compounds in water quite remarkably show a lamellar-lamellar phase coexistence and spontaneously form vesicles upon solubilization. Moreover, P(16)So(8) undergoes a temperature-driven vesicle-to-micelle transition that involves an intermediate planar lamellar state, similar to TA(16)So(8). Some interesting effects on the global phase behavior, however, do arise when the headgroups are changed. Geometric packing effects are shown to be important, but the differences in phase behavior seem to be mainly dictated by (i) the charge density of the headgroups, which tunes the solubility mismatch of the ion-pair, and (ii) specific interactions between headgroups, which affect the short-range repulsive force that controls the swelling of the concentrated lamellar phase.
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Affiliation(s)
- Bruno F B Silva
- Centro de Investigação em Química, Department of Chemistry, Faculty of Science, University of Porto, Rua do Campo Alegre, no 687, P 4169-007 Porto, Portugal
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SANS investigation of the microstructures in catanionic mixtures of SDS/DTAC and the effect of various added salts. J Colloid Interface Sci 2009; 337:472-84. [PMID: 19540508 DOI: 10.1016/j.jcis.2009.05.039] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2009] [Revised: 05/16/2009] [Accepted: 05/18/2009] [Indexed: 11/24/2022]
Abstract
The aggregation behavior of two common ionic surfactants with opposite charges, sodium dodecylsulfate (SDS) and dodecyltrimethylammonium chloride (DTAC), was studied for their mixtures and for different added salts. The aggregates formed were characterized by means of small-angle neutron scattering (SANS), at two temperatures: 25 and 50 degrees C (below and above the "Krafft point" of the catanionic salt) and at two overall concentrations (50 and 200 mM). Results have been compared to the well-known SDS+DTAB system. Similar results are found, showing that with no excess of salt the nature of the counter-ion, bromide or chloride, has no dominant effect on this mixture of oppositely charged surfactants. Further SANS experiments were carried out to check the effect of ions on the pure surfactants, the ions being chosen to mimic the head group of the paired surfactant in the catanionic mixture. Tetramethylammonium chloride (TMACl) was added to SDS and sodium methylsulfate (SMS) to DTAC. Their effects were compared to NaCl, which was included in this study as a reference, and explained in terms of competition between the behavior of simple ions (screening) and that of a "binding ion" (attachment to the micellar surface). Apparently the effect of salt addition to these two surfactants is clearly strongly ion-specific.
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