寡聚核苷酸/单链阳离子表面活性剂囊泡与沉淀共存(英文)

DNA(包括寡聚核苷酸)和阳离子表面活性剂可形成难溶复合物.本文通过浊度测试和透射电子显微镜观察,发现单链阳离子表面活性剂可以诱使寡聚核苷酸/单链阳离子表面活性剂沉淀转变成为寡聚核苷酸/单链阳离子表面活性剂囊泡,且寡聚核苷酸/单链阳离子表面活性剂囊泡可以与寡聚核苷酸/单链阳离子表面活性剂沉淀共存.在寡聚核苷酸/单链阳离子表面活性剂沉淀向囊泡的转变过程中,表面活性剂和沉淀之间的疏水作用力发挥了重要作用.此外,当体系温度达到寡聚核苷酸开始融解的温度后,寡聚核苷酸/单链阳离子表面活性剂体系更容易形成囊泡.因此,寡聚核苷酸的链越伸展,越易于寡聚核苷酸/单链阳离子表面活性剂囊泡的生成.据我们所知,有关寡聚核苷酸/阳离子表面活性剂囊泡的报道尚不多见.因此,考虑到DNA(包括寡聚核苷酸)/两亲分子体系在医学、生物学、药学和化学中的重要性,该研究应该有助于我们进一步了解该体系并对其进行更合理有效的应用.     

Aggregation phenomena on the ternary ionic-nonionic surfactant system: didodecyldimethylammonium bromide/octyl-beta-D-glucopyranoside/water. Mixed microaggregates, vesicles, and micelles

The formation of a variety of mixed colloidal aggregates has been investigated on a ternary ionic-nonionic system constituted by (i) a double-chain cationic surfactant with a 12-carbon atom hydrophobic tail, didodecyldimethylammonium bromide (di-C(12)DMAB), (ii) a nonionic single-chain surfactant, octyl-beta-D-glucopyranoside (OBG), and (iii) water. The study has been carried out by means of conductivity, zeta-potential, transmission electron microscopy (TEM), and cryogenic transmission electron microscopy (cryo-TEM) experiments on the highly diluted, very diluted, and moderately diluted regions. The formation of mixed microaggregates, prior to the appearance of mixed vesicles, has been undoubtly confirmed by conductivity, TEM, and zeta-potential results. The concentrations at which these mixed colloidal aggregates form, i.e., the mixed critical microaggregate concentration (CAC), the mixed critical vesicle concentration (CVC), and the mixed critical micelle concentration (CMC), have been determined from conductivity data, while the zeta-potential experiments allow for the characterization of the aggregate/solution interface. The shape and size of the microaggregates and vesicles have been evaluated from TEM and cryo-TEM micrographs, respectively. All of the experimental evidence has been also analyzed in terms of the theoretical packing parameter, P.     

Adsorption of mixtures of nonionic sugar-based surfactants with other surfactants at solid/liquid interfaces II. Adsorption of n-dodecyl-beta-D-maltoside with a cationic surfactant and a nonionic ethoxylated surfactant on solids

Synergy and antagonism between sugar-based surfactants, a group of environmentally benign surfactants, and cationic surfactants and nonionic ethoxylated surfactants have been investigated in this study with solids which adsorbs only one or other when presented alone. Sugar-based n-dodecyl-beta-D-maltoside (DM) does not adsorb on silica by itself. However, in mixtures with cationic dodecyltrimethylammonium bromide (DTAB) and nonionic nonylphenol ethoxylated decyl ether (NP-10), DM adsorbs on silica through hydrophobic interactions. In contrast, although DM does adsorb on alumina, the presence of NP-10 reduces the adsorption of DM as well as that of the total surfactant adsorption. Such synergistic/antagonistic effects of sugar-based n-dodecyl-beta-D-maltoside (DM) in mixtures with other surfactants at solid/liquid interfaces were systematically investigated and some general rules on synergy/antagonism in mixed surfactant systems are identified. These results have implications for designing surfactant combinations for controlled adsorption or prevention of adsorption.     

盐引发阴离子/非离子表面活性剂复配体系中囊泡自发形成

在无盐时, 阴离子表面活性剂十二烷基苯磺酸钠(SDBS)与非离子表面活性剂壬基酚聚氧乙烯(10)醚(TX-100)的复配体系中只有混合胶束存在, 而盐的加入即可以引发体系中囊泡的自发形成, 这使得囊泡的形成变得更加简单. 引发机理可以归因于盐对离子表面活性剂的极性头双电层的压缩作用, 减少了极性头的面积, 加上非离子表面活性剂的参与使得堆积参数P增加, 导致了半径更大的聚集体的形成. 制作了SDBS/TX-100/盐水拟三元相图, 通过目测和表面张力的变化确定了囊泡形成的带状区域, 并用负染色电镜(TEM)对囊泡进行了表征, 同时测定了盐度以及相同盐度下表面活性剂浓度对囊泡粒径的影响, 发现囊泡的粒径随着盐度的增加而增加, 而在同一盐度下, 囊泡的粒径基本不受表面活性剂浓度的影响.     

Investigation on the aggregation behaviors of DDAB/NaDEHP catanionic vesicles in the absence and presence of a negatively charged polyelectrolyte

The aggregation behaviors of the cationic and anionic (catanionic) surfactant vesicles formed by didodecyldimethylammonium bromide (DDAB)/sodium bis(2-ethylhexyl) phosphate (NaDEHP) in the absence and presence of a negatively charged polyelectrolyte are investigated. The amount of the charge on the vesicle can be tuned by controlling the DDAB/NaDEHP surfactant molar ratio. The charged vesicular dispersions made of DDAB/NaDEHP are mixed with a negatively charged polyelectrolyte, poly(4-styrenesulfonic acid-co-maleic acid) sodium (PSSAMA), to form complexes. Depending on the polyelectrolyte/vesicle charge ratio, complex flocculation or precipitation occurs. Characterization of the catanionic vesicles and the complexes are performed by transmission electron microscope (TEM), Cryo-TEM, dynamic light scattering (DLS), conductivity, turbidity, zeta potential, isothermal titration calorimetry (ITC) and small-angle X-ray scattering (SAXS) measurements.     

Electrochemical, microscopic, and spectroscopic characterization of prevesicle nanostructures and vesicles on mixed cationic surfactant systems

Several experimental techniques (conductivity, zeta potential, transmission electronic microscopy, and steady-state fluorescence spectroscopy) have been used to study the formation of mixed colloidal aggregates consisting of a cationic double-chain surfactant, di-dodecyldimethylammonium bromide (di-C12DMAB), and a single-chain alkyltrimethylammonium bromide with 10 and/or 14 carbon atoms (decyltrimethylammonium bromide, C10TAB, and/or tetradecyltrimethylammonium bromide, C14TAB). Special interest has been devoted to the prevesicle domain, within which the formation of aggregated nanostructures was first reported in our laboratory. For that purpose, studies have been carried out on the very dilute region by means of conductivity experiments, confirming the existence of two critical aggregation concentrations in that concentration domain: the so-called mixed critical aggregate concentration, CAC, and the mixed critical vesicle concentration, CVC. By carrying out TEM experiments on negatively stained samples, we were surprised to find a number of aggregates without a clear aggregation pattern and with a variety of sizes and shapes at concentrations below CAC, where only monomers were expected. However, the nanoaggregates found at concentrations between CAC and CVC, also by TEM microscopy, show a clear and ordered "fingerprint"-like aggregation pattern similar to the liquid-crystalline phases reported for DNA-liposome complexes and/or DNA packed with viral capsids. Finally, at total surfactant concentrations above CVC, the aggregates were confirmed, by means of cryo-TEM micrographs and zeta potential measurements, to be essentially unilamellar spherical vesicles with a medium polydispersity and a net-averaged surface density charge of around 12 x 10(-3) C m(-2). The fluorescence emission of two probes, TNS (anionic) and PRODAN (nonionic), allows for the analysis of the micropolarity and microviscosity of the different microenvironments present in aqueous surfactant solutions where the above-mentioned vesicle and prevesicle aggregates are present.     

Lipid bilayer elasticity measurements in giant liposomes in contact with a solubilizing surfactant

A new method to probe the modification of the elasticity of phospholipid bilayers is presented. The purpose here concerns the action of a solubilizing surfactant on a vesicle bilayer. This method is based on the measure of the under-field elongation of giant magnetic-fluid-loaded liposomes. The addition of the nonionic surfactant octyl-beta-d-glucopyranoside (OG) to vesicles at sublytic levels increases the elasticity of the membrane, as shown by the value of the bending modulus K(b), which decreases. K(b) measured around 20 kT for a pure 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) bilayer indeed reaches a few kT in the case of the mixed OG-DOPC bilayer. The purpose and interest of this study are to allow the determination of the membrane bending modulus before and after the addition of OG on the same magnetic liposome. Moreover, the experimental conditions used in this work allow the control of lipid and surfactant molar fractions in the mixed aggregates. Then, optical microscopy observation can be performed on samples in well-defined regions of the OG-phospholipid state diagram.     

Surface tension and aggregation properties of novel cationic gemini surfactants with diethylammonium headgroups and a diamido spacer

A series of novel cationic gemini surfactants with diethylammonium headgroups and a diamido spacer were synthesized, and their surface and bulk properties were investigated by surface tension, electrical conductivity, fluorescence, viscosity, dynamic light scattering (DLS), and transmission electron microscopy (TEM) measurements. An interesting phenomenon, that is, the obvious decline in surface tension upon increasing concentration above the critical micelle concentration (cmc), was found in these gemini surfactant solutions, and two explanations were proposed. This surface tension behavior could be explained by the rapid increase in the counterion activity in the bulk phase or the continued filling of the interface with increasing surfactant concentration above the cmc. More interestingly, not only vesicles but also the surfactant-concentration-induced vesicle to larger aggregate (spongelike aggregate) transition and the salt-induced vesicle and spongelike aggregate to micelle transition were found in the aqueous solutions of these gemini surfactants. The spongelike aggregate that is first reported in the cationic gemini surfactant-water binary system is probably caused by the adhesion and fusion of vesicles at high surfactant concentration.     

Facilitation effect of oligonucleotide on vesicle formation from single‐chained cationic surfactant—Dependences of oligonucleotide sequence and size and surfactant structure

The interaction between DNA and surfactant has both biological and technological significances. Recently, we reported for the first time that oligo d(C)₂₅ can induce single‐chained cationic surfactant molecules to aggregate into vesicles. In this article, we studied systematically the formation of vesicles from traditional single‐chained cationic surfactant molecules in the presence of a series of oligonucleotides and found that the facilitation efficiency of oligonucleotide on vesicle formation depends on its size and base composition. Oligo d(T)_n cannot induce vesicle formation, whereas the other oligonucleotides can. Moreover, the oligonucleotide with a bigger size or with a hairpin structure favors vesicle formation more, and the increases in the size of the head group and/or the length of the alkyl group of surfactant decrease the facilitation efficiency of oligonucleotide. Since so far, there is very limited report about the vesicle formation in DNA/single‐chained cationic surfactant solution, this study could be expected to increase the efficiency and applicability for DNA/amphiphile system. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 434–449, 2009     

Control of phase behavior and properties of vesicle gels by admixing ionic surfactants to the nonionic surfactant Brij 30

The effect of the addition of two cationic surfactants of different chain length (decyl and dodecyl trimethylammonium bromide, DeTMABr and DTMABr, respectively) and one anionic surfactant of identical chain length (sodium dodecyl sulfate, SDS) on phase behavior, structure, and macroscopic properties of a bilayer forming nonionic surfactant (Brij 30) has been investigated by means of phase studies, rheology, turbidity measurements, dynamic light scattering, and freeze-fracture transmission electron microscopy. We concentrated on DTMABr because of the generically similar behavior for the other ionic surfactants. It is found that already very small amounts of added ionic surfactant have a very pronounced effect on the phase behavior of these systems. The pure nonionic surfactant forms bilayers and has a tendency for the formation of vesicles which becomes enhanced by charging the bilayer through the incorporation of the ionic surfactant. The presence of the ionic surfactant leads to much more viscous systems, which already at a total surfactant concentration of 150 mM become gel-like. For a given surfactant concentration, the elastic properties of the gels increase largely upon the addition of ionic surfactant. This effect is strongly synergistic, requiring only very small amounts of added ionic surfactant, and the elastic properties pass through a maximum for a content of ionic surfactant of about 3-5 mol %. This behavior can be explained in a self-consistent way by a simple rheological model and by combining it with light scattering data. For the addition of larger amounts, the elastic properties decrease again and the formed vesicles become structurally less defined as one is leaving the range of conditions for forming well-defined vesicles, which are required for forming elastic vesicle gels.     

Vesicles of a new salt-free cat-anionic fluoro/hydrocarbon surfactant system

Weakly basic tetradecyldimethylaminoxide (C14DMAO) molecules can be protonated to form a cationic surfactant, C14DMAOH+, by an acidic fluorocarbon surfactant, an 8-2-fluorotelomer unsaturated acid (C7F15CF==CHCOOH), to form a salt-free cationic and anionic (cat-anionic) fluoro/hydrocarbon surfactant system in aqueous solution. The high Krafft point of C7F15CF==CHCOOH was largely reduced as a result of being mixed with a C14DMAO micelle solution. A study of the phase behavior of the new salt-free cat-anionic fluoro/hydrocarbon surfactant system clearly indicates the existence of a birefringent Lalpha-phase region at (25.0+/-0.1) degrees C. The birefringent Lalpha phase consists of vesicles, which include uni- and multilamellar vesicles with one to dozens of shells, and oligovesicular vesicles, as demonstrated by freeze-fracture and cryo-transmission electron microscopy (FF- and cryo-TEM) images. The size distribution and structural transitions in the salt-free cat-anionic fluoro/hydrocarbon surfactant system were studied by dynamic light scattering (DLS) and 1H and 19F NMR spectroscopy. The formation of a salt-free cat-anionic vesicle phase could be induced by the strong electrostatic interaction between the cationic hydrocarbon C14DMAOH+ and the anionic fluorocarbon C7F15CF==CHCOO-, which provided evidence that the electrostatic interaction between the cationic and anionic surfactants is larger than the nonsynergistic interaction between the stiff fluorocarbon and the soft hydrocarbon chains of the surfactants.     

Characterization and Aggregation Behaviors of Mixed DDAB/SDS Solution With and Without Poly(4-styrenesulfonic Acid-Co-Maleic Acid) Sodium

Synthetic vesicles are formed by cationic and anionic surfactants, didodecyldimethylammonium bromide (DDAB), and sodium dodecylsulfate (SDS). The morphology, size, and aqueous properties of cationic/anionic mixtures are investigated at various molar ratios between cationic and anionic surfactants. The charged vesicular dispersions made of DDAB/SDS are contacted or mixed with negatively charged polyelectrolyte, poly(4-styrenesulfonic acid-co-maleic acid) sodium (PSSAMA), to form complexes. Depending on DDAB/SDS molar ratio or PSSAMA/vesicle charge ratio, complexes flocculation or precipitation occur. Characterization of the cationic/anionic vesicles or complexes formed by the catanionic vesicles and polyelectrolytes is performed by transmission electron microscope (TEM), dynamic light scattering (DLS), conductivity, turbidity, and zeta potential measurements. The size, stability, and the surface charge on the mixed cationic/anionic vesicles or complexes are determined.     

One-dimensional assemblies of platinum nanoparticles on a graphite surface using nonionic/ionized mixed hemicylindrical micelle templates

One-dimensional (1-D) self-assemblies of Pt nanoparticles on a graphite surface have been synthesized via a template-directed sintering process of individual nanoparticles, using nonionic/cationic mixed hemicylindrical micelle templates of dodecyldimethylamine oxide surfactant at graphite/solution interfaces. The dimension and morphology of Pt nanoparticles can be widely controlled by the concentration of Pt ions equivalent to the mixing ratio of nonionic and cationic species in the surfactant micelle. This approach could be extended to fabricate a wide range of self-assembling metallic nanostructures on surfaces using various nonionic/cationic mixed micelle-like self-assemblies carrying metal ions at interfaces, while providing a fundamental insight into a 1-D self-assembly from individual nanoparticles.     

Vesicle-micelle transition in aqueous mixtures of the cationic dioctadecyldimethylammonium and octadecyltrimethylammonium bromide surfactants

The vesicle-micelle transition in aqueous mixtures of dioctadecyldimethylammonium and octadecyltrimethylammonium bromide (DODAB and C(18)TAB) cationic surfactants, having respectively double and single chain, was investigated by differential scanning calorimetry (DSC), steady-state fluorescence, dynamic light scattering (DLS) and surface tension. The experiments performed at constant total surfactant concentration, up to 1.0 mM, reveal that these homologous surfactants mix together to form mixed vesicles and/or micelles, depending on the relative amount of the surfactants. The melting temperature T(m) of the mixed DODAB-C(18)TAB vesicles is larger than that for the neat DODAB in water owing to the incorporation of C(18)TAB in the vesicle bilayer. The surface tension decreases sigmoidally with C(18)TAB concentration and the inflection point lies around x(DODAB) approximately 0.4, indicating the onset of micelle formation owing to saturation of DODAB vesicles by C(18)TAB molecules. When x(DODAB)>0.5 C(18)TAB molecules are mainly solubilised by the vesicles, but when x(DODAB)<0.25 micelles are dominant. Fluorescence data of the Nile Red probe incorporated in the system at different surfactant molar fractions indicate the formation of micelle and vesicle structures. These structures have apparent hydrodynamic radius R(H) of about 180 and 500-800 nm, respectively, as obtained by DLS measurements.     

Protein binding onto surfactant-based synthetic vesicles

Synthetic vesicles were prepared by mixing anionic and cationic surfactants, aqueous sodium dodecylsulfate with didodecyltrimethylammonium or cetyltrimethylammonium bromide. The overall surfactant content and the (anionic/cationic) mole ratios allow one to obtain negatively charged vesicles. In the phase diagram, the vesicular region is located between a solution phase, a lamellar liquid crystalline dispersion, and a precipitate area. Characterization of the vesicles was performed by electrophoretic mobility, NMR, TEM, and DLS and we determined their uni-lamellar character, size, stability, and charge density. Negatively charged vesicular dispersions, made of sodium dodecylsulfate/didodecyltrimethylammonium bromide or sodium dodecylsulfate/cetyltrimethylammonium bromide, were mixed with lysozyme, to form lipoplexes. Depending on the protein/vesicle charge ratio, binding, surface saturation, and lipoplexes flocculation, or precipitation, occurs. The free protein in excess remains in solution, after binding saturation. The systems were investigated by thermodynamic (surface tension and solution calorimetry), DLS, CD, TEM, 1H NMR, transport properties, electrophoretic mobility, and dielectric relaxation. The latter two methods give information on the vesicle charge neutralization by adsorbed protein. Binding is concomitant to modifications in the double layer thickness of vesicles and in the surface charge density of the resulting lipoplexes. This is also confirmed by developing the electrophoretic mobility results in terms of a Langmuir-like adsorption isotherm. Charges in excess with respect to the amount required to neutralize the vesicle surface promote lipoplexes clustering and/or flocculation. Protein-vesicle interactions were observed by DLS, indicating changes in particle size (and in their distribution functions) upon addition of LYSO. According to CD, the bound protein retains its native conformation, at least in the SDS/CTAB vesicular system. In fact, changes in the alpha-helix and beta-sheet conformations are moderate, if any. Calorimetric methods indicate that the maximum heat effect for LYSO binding occurs at charge neutralization. They also indicate that enthalpic are by far the dominant contributions to the system stability. Accordingly, energy effects associated with charge neutralization and double-layer contributions are much higher than counterion exchange and dehydration terms.     

Spontaneous Formation of Biocompatible Vesicles in Aqueous Mixtures of Amino Acid‐Based Cationic Surfactants and SDS/SDBS

The spontaneous formation of vesicles by six amino acid‐based cationic surfactants and two anionic surfactants (sodium dodecylbenzene sulfonate (SDBS) and sodium dodecyl sulfate (SDS)) is reported. The head‐group structure of the cationic surfactants is minutely altered to understand their effect on vesicle formation. To establish the regulatory role of the aromatic group in self‐aggregation, both aliphatic and aromatic side‐chain‐substituted amino acid‐based cationic surfactants are used. The presence of aromaticity in any one of the constituents favors the formation of vesicles by cationic/anionic surfactant mixtures. The formation of vesicles is primarily dependent on the balance between the hydrophobicity and hydrophilicity of both cationic and anionic surfactants. Vesicle formation is characterized by surface tension, fluorescence anisotropy, transmission electron microscopy, dynamic light scattering, and phase diagrams. These vesicles are thermally stable up to 65 °C, determined by temperature‐dependent fluorescence anisotropy. According to the MTT assay, these catanionic vesicles are nontoxic to NIH3T3 cells, thus indicating their wider applicability as delivery vehicles to cells. Among the six cationic surfactants examined, tryptophan‐ and tyrosine‐based surfactants have the ability to reduce HAuCl₄ to gold nanoparticles (GNPs), which is utilized to obtain in‐situ‐synthesized GNPs entrapped in vesicles without the need for any external reducing agent.     

Effect of Surfactants on the Formation,Morphology, and Surface Property of Synthesized SiO2 Nanoparticles

Abstract

This study investigated the effect of cationic, anionic (saturated and unsaturated), and nonionic surfactants on the formation, morphology, and surface properties of silica nanoparticles synthesized by the ammonium‐catalyzed hydrolysis of tetraethoxysilane in alcoholic media. Results indicate that at a relatively low surfactant concentration (1 × 10^?3–1 × 10^?6 M), cationic surfactants significantly affected the growth of silica particles as measured by dynamic light scattering and transmission electron microscopic analyses. In contrast, the anionic and nonionic surfactants showed relatively minor effects in the low concentration range. The magnitude of negative zeta potential was reduced for silica colloids that were synthesized in the presence of cationic surfactant because of charge neutralization. The presence of anionic surfactants only slightly increased the negative zeta potential while the nonionic surfactant showed no obvious effects. At high surfactant concentrations (>1 × 10^?3 M), cationic and anionic surfactants both induced colloid aggregation, while the nonionic surfactant showed no effect on particle size. Raman spectroscopic analysis suggests that molecules of cationic surfactants adsorb on silica surfaces via head groups, aided by favorable electrostatic attraction, while molecules of anionic and nonionic surfactants adsorb via their hydrophobic tails.     

Salinity Controlled Vesicle Formation and Growth in Aqueous Mixture of Aerosol OT/Triton X‐100

Mixed vesicles can be formed spontaneously from aqueous mixture of the double‐tailed anionic surfactant sodium bis(2‐ethylhexyl) sulfosuccinate (AOT) and the nonionic surfactant octylphenoxypolyethoxyethanol (Triton X‐100) under the inducement of salt, the formation mechanism of which should be attributed to the compression of salt on the electric bilayers of the head groups. The stability and the polydispersity of the vesicles are superior to single‐component AOT vesicles, which can be proved by the TEM image and visual observation. The vesicle region was presented in a pseudo‐ternary diagram of AOT/TX‐100/brine. The size of the vesicle was measured using dynamic light scattering. It is found that the vesicle size increases with the salinity but decreases with the content of TX‐100 in the mixture at the same salinity. Especially, the vesicle size is independent of the surfactant concentration at fixed salinity.     

Micellar Interactions in Nonionic/Ionic Mixed Surfactant Systems

To study the influence of the chemical nature of headgroups and the type of counterion on the process of micellization in mixed surfactant systems, the cmc's of several binary mixtures of surfactants with the same length of hydrocarbon tail but with different headgroups have been determined as a function of the monomer composition using surface tension measurements. Based on these results, the interaction parameter between the surfactant species in mixed micelles has been determined using the pseudophase separation model. Experiments were carried out with (a) the nonionic/anionic C(12)E(6)/SDS ((hexa(ethyleneglycol) mono-n-dodecyl ether)/(sodium dodecyl sulfate)), (b) amphoteric/anionic DDAO/SDS ((dodecyldimethylamine oxide)/(sodium dodecyl sulfate)), and (c) amphoteric/nonionic C(12)E(6)/DDAO mixed surfactant systems. In the case of the mixed surfactant systems containing DDAO, experiments were carried out at pH 2 and pH 8 where the surfactant was in the cationic and nonionic form, respectively. It was shown that the mixtures of the nonionic surfactants with different kinds of headgroups exhibit almost ideal behavior, whereas for the nonionic/ionic surfactant mixtures, significant deviations from ideal behavior (attractive interactions) have been found, suggesting binding between the head groups. Molecular orbital calculations confirmed the existence of the strong specific interaction between (1) SDS and nonionic and cationic forms of DDAO and between (2) C(12)E(6) and the cationic form of DDAO. In the case for the C(12)E(6)/SDS system, an alternative mechanism for the stabilization of mixed micelles was suggested, which involved the lowering in the free energy of the hydration layer. Copyright 2000 Academic Press.     

Effects of salt and temperature on single‐chained cationic surfactant/oligodeoxynucleotide vesicle formation

Recently, we found oligodeoxynucleotide could induce single‐chained cationic surfactant to organize into vesicles. In this article, we will report the effects of NaCl and temperature on the surfactant/oligodeoxynucleotide vesicle formation. A moderate content of NaCl can facilitate vesicle formation and high content of NaCl makes vesicle degraded. The enhanced hydrophobic interaction between surfactant and oligodeoxynucleotide with NaCl plays a key role for facilitating vesicle formation. Moreover, surfactant/oligodeoxynucleotide vesicles tend to aggregate at high temperature and the change is irreversible. However, the presence of NaCl makes this change reversible. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012