Single-chain Cationic Surfactants Research Articles

Oligomeric cationic Gemini surfactants: synthesis, surface activities and rheological properties as thickener

Abstract In this study, three oligomeric cationic Gemini surfactants (Ⅲ1, Ⅲ2, and Ⅲ3) were prepared from different major raw materials, including long-chain alkyl amine (dodecyl amine, tetradecyl amine or cetyl amine), formic acid, formaldehyde, diethyl amine hydrochloride and epichlorohydrin. The synthesis conditions for one of the three surfactants, bis-[2-hydroxy-3-(N,N-dimethyl-N-dodecyl)propyl]dipropylammonium chloride (Ⅲ1), were optimised by orthogonal experiments. The optimum synthesis conditions were: molar ratio of intermediate Ⅱ to intermediate Ⅰ1 = 1.0:2.2, reaction temperature = 85 °C and reaction time = 16 h. The structures of the three prepared compounds were characterised by FTIR and 1H NMR. Their thermal properties were evaluated by thermal gravimetric analysis (TGA). The Geminisurfactants prepared exhibited better surface active properties than conventional single chain cationic surfactants. With increasing carbon chain length from C12 to C16, both CMC and surface tension γ CMC decreased, while the viscosity of the thickening solution prepared with the synthesised oligomeric cationic Gemini surfactants as the main component increased. The optimum thickening formula was: 2.0 wt% Ⅲ3 + 0.8 wt% sodium salicylate (NaSal) + 0.6 wt% KCl. The viscosity of the optimum thickening formulation was 190.4 mPa s. Gemini oligomeric cationic surfactants could be used as thickeners in the production of fracturing fluids, flooding agents and drilling fluids for oil and gas production in oil fields.

Effect of Single/Mixed Surfactant Systems on Orientations of Liquid Crystals and Interaction of Proteins with Surfactants at Fluid Interfaces

A series of single surfactant systems, i.e, quaternary ammonium-based gemini surfactants with different spacers and alkyl chain lengths (m-n-m; m = 12, n = 2, 3, 4, 6; n = 3, m = 12, 14, 16), halogen-free surface-active ionic liquid (HF-SAILs) with different symmetries ([Cnmim][C12H25SO4]; n = 6, 8, 10, 12), and single-chain cationic surfactants including 1-dodecyl-3-methylimidazolium bromide ([C12mim]Br) and dodecyltrimethylammonium bromide (DTAB), along with certain combinations of different surfactants (12-3-12/[C12mim]Br and 12-3-12/DTAB) were applied to an aqueous/liquid crystal interface (ALI). All the surfactants could induce an orientational transition of liquid crystals (LCs) from a planar to homeotropic state, which caused a bright-to-dark optical shift. It was proved that double-chain surfactants and the mixed surfactants inclined to adsorb at the ALI triggering the orientational transition. Inspiringly, a quicker and more sensitive dark-to-bright optical response was observed for mixed surfactant system-decorated interfaces in contact with proteins (such as bovine serum albumin (BSA), lysozyme, and trypsin) as opposed to the single surfactant systems. The ALI decorated by the 12-3-12/[C12mim]Br system was particularly efficient and exhibited the most sensitive optical response for BSA (0.01 ng mL−1). The order parameters (SCD) of surfactants tails at the interface and the free energy of proteins with 12-3-12 and [C12mim]Br were calculated, respectively. The results explain that the 12-3-12/[C12mim]Br-laden ALI shows a quicker and more sensitive optical response for BSA. This work inspired us to study mixed surfactant systems-decorated LC interfaces and further provides new insights for different chemical and biological applications.

Curcumin degradation kinetics in micellar solutions: Enhanced stability in the presence of cationic surfactants

In this work, the rate of curcumin degradation in the presence of various surfactants (anionic, cationic, and nonionic) and salts (i.e., NaCl, NaHCO3, Na2CO3, and NaOH) was investigated by photodiode-array UV–vis spectroscopy. The curcumin degradation at neutral pH or in the presence of NaCl during the first 16 h of the study was negligible (i.e., zero rate constant). Depending on the type and concentration of added alkaline salt, the color of the curcumin surfactant solution changed from yellow (λmax. = 420−430 nm) to orange (λmax. = 450−500 nm). The degradation rate constants and the final degradation percentage were obtained and reported for various conditions. The maximum curcumin degradation for the investigated surfactants was observed in the presence of 28.5 mM Na2CO3 at pH ∼10.8. The curcumin degradation rate was much lower in the presence of cationic surfactants (monomeric and gemini type). The gemini cationic surfactant (12-4-12) was even more efficient than the single chain cationic surfactant (DTAB) to suppress the curcumin degradation indicating the importance of cationic charge density of the surfactant head group on the electrostatic interaction with curcumin. Curcumin is deprotonated in alkaline conditions and carries negative charges; therefore, cationic surfactants can accommodate and protect it much better than anionic or nonionic surfactants against further degradation.

Interaction Mechanism of Different Surfactants with Casein: A Perspective on Bulk and Interfacial Phase Behavior.

Understanding the interaction mechanism between proteins and surfactants is conducive to the application of protein/surfactant mixtures in the food industry. The present study investigated the interaction mechanism of casein with cationic Gemini surfactant (BQAS), anionic Gemini surfactant (SGS), anionic single-chain surfactant (sodium dodecyl sulfate [SDS]), and two biosurfactants (rhamnolipid [RL] and lactone sophorolipid [SL]) at the interface and in bulk phase. BQAS/casein and SDS/casein mixtures exhibit a strong synergistic effect on the surface activity. For SGS, RL, and SL, the formation of surfactant/casein complexes caused no improvement in surface activity. Dilational elasticity results indicate the displacement of casein by SGS, RL, and SL at the surface. However, the BQAS/casein complexes manifested varying dilational properties from pure casein surface. The strong electrostatic interaction between BQAS and casein produced large-size precipitate particles. For other surfactants, no precipitate particles formed. Determination of ζ-potential, UV-vis absorption spectra, and fluorescence spectra demonstrated the stronger interaction of BQAS and SDS with casein than that of SGS, RL, and SL. Addition of BQAS initially increased and then decreased the α-helix structure of casein. For SGS, RL, and SL, no noticeable change occurred in the casein structure. However, the formation of SDS/casein complexes was conducive to the casein structure. In conclusion, the interaction between BQAS and casein is similar to that of cationic single-chain surfactant. Furthermore, SGS exhibits a significantly different interaction mechanism from the corresponding monomer (SDS), possibly resulting from its excellent interfacial activity, low critical micelle concentration values, and strong self-assembly capability. For RL and SL, the weak interaction is attributed to the relatively complicated structure and less charged degree of hydrophilic headgroups.

Silver nanoparticles stabilised with cationic single-chain surfactants. Structure-physical properties-biological activity relationship study

Increasing number of biological applications of silver nanoparticles requires a detailed determination of the relationship between nanoparticle structure and its physical and biological properties. In this paper, synthesis, measurements of nanoparticle size and zeta potential and some biological activities of silver nanoparticles stabilised with single-chain cationic surfactants are provided. The main goal of the study is the investigation of the relationship between molecular structure of stabilising agent, physicochemical properties and biological activity of cationic surfactant-stabilised silver nanoparticles. Two structural features, heterocyclic character of hydrophilic part of surfactant molecule and hydrophobicity change of its substituents, were correlated with synthesis, stability and biological activity of silver nanoparticles. Substituted ammonium, pyridinium and piperidinium surfactants were selected as stabilisers of silver nanoparticles. It was found that nanoparticle stabilising effect is improved by increasing the length of hydrophobic substituents on the ammonium polar head which results in the formation of nanoparticles small in size and with sufficiently positive zeta potential. Application of dibutyl-substituted ammonium surfactant molecules resulted in the formation of small silver nanoparticles in the size range 25–30 nm and a zeta potential of +60 mV. Aromatic pyridinium surfactant molecules provide slightly better stabilisation than saturated piperidinium surfactants. Surfactant-stabilised silver nanoparticles were antimicrobially efficient against Gram-positive pathogens and yeast. The highest cytotoxic activity was determined for silver nanoparticles stabilised with dibutyl-substituted ammonium surfactant and pyridinium surfactant which corresponds with small and charged nanoparticles formed by using these surfactants. Maximum cytotoxic activity was found in the surfactant concentration range 16–25 μM.

Synthesis, interfacial properties, and antimicrobial activity of a new cationic gemini surfactant

Tetramethylene-1,4-bis(N,N-dodecylammonium bromide), cationic gemini surfactant, (12-4-12) was first synthesized with an one-step and shortened procedure and its interfacial and antimicrobial properties were compared with a conventional single-chain cationic surfactant, cetyltrimethylammonium bromide (CTAB). The interfacial and thermodynamic properties of both surfactants reveal that critical micelle concentration (CMC) of this novel synthetic cationic dimeric surfactant is lower than that of cationic monomeric surfactant at almost 15 times of its magnitude, which is due to the increase in hydrophobicity of the surfactant molecules by having dual hydrocarbon chains. In comparison with CTAB, the produced compound 12-4-12 yields much better interfacial and thermodynamic properties. The antimicrobial activities of the synthesized gemini surfactant were tested against eight strains of bacteria, as well as two strains of fungi. The results showed that both 12-4-12 compound and CTAB exhibited higher inhibitory effects on the growth of Gram-positive bacteria and fungi than that of Gram-negative bacteria. The minimum inhibitory concentrations in molar of 12-4-12 against all tested Gram-negative bacteria were lower than those of CTAB, which is hypothetically due to the lower HLB together with smaller CMC values of our gemini surfactant.

Study of the Gemini Surfactants' Self-Assembly on Graphene Nanosheets: Insights from Molecular Dynamic Simulation.

Understanding the mechanism of adsorption and self-assembly of surfactants on graphene is highly important to perform better optimization of the graphene dispersion process. Because of Gemini surfactants' special structure, they have a high charge capacity, high hydrophobicity, and unique self-assembly properties compared to single-chain surfactants. Therefore, Gemini surfactants with their small concentrations are expected to disperse and stabilize graphene nanosheets in aqueous solutions more effectively. We conducted molecular dynamics simulations to study adsorption and self-assembly of single-chain cationic surfactant dodecyltrimethylammonium bromide (C12TAB) and its same family Gemini surfactant dimethylene-α,β-bis(dodecyldimethylammonium bromide) ([12-2-12]Br2) on graphene nanosheets. The results showed that assemblies morphology formed on graphene is affected by surfactant structure. We observed that increasing surface coverage, especially for [12-2-12]Br2, leads to a transmission in adsorption mechanism and most [12-2-12]Br2 head groups tend toward the aqueous phase and prevent water molecules from accessing graphene surface. It can be concluded from morphological assessments that [12-2-12]Br2 is more effective than C12TAB in stabilizing graphene aqueous suspensions. Moreover, we investigated the effect of graphene sheet size and Gemini surfactant spacer length on the structure of surfactant assemblies on graphene. The present study results can expand our comprehension of dispersion mechanism of graphene nanosheets by Gemini surfactants.

Importance of hydrophobic interactions in the single-chained cationic surfactant-DNA complexation

The goal of this work was to understand the key factors determining the DNA compacting capacity of single-chained cationic surfactants. Fluorescence, zeta potential, circular dichroism, gel electrophoresis and AFM measurements were carried out in order to study the condensation of the nucleic acid resulting from the formation of the surfactant-DNA complexes. The apparent equilibrium binding constant of the surfactants to the nucleic acid, Kapp, estimated from the experimental results obtained in the ethidium bromide competitive binding experiments, can be considered directly related to the ability of a given surfactant as a DNA compacting agent. The plot of ln(Kapp) vs. ln(cmc), cmc being the critical micelle concentration, for all the bromide and chloride surfactants studied, was found to be a reasonably good linear correlation. This result shows that hydrophobic interactions mainly control the surfactant DNA compaction efficiency.

Fabrication of metalosomes (metal containing cationic liposomes) using single chain surfactants as a precursor via formation of inorganic organic hybrids.

Among the self-assembled forms of surfactants, vesicles/liposomes are a highly promising and interesting feature of surfactants, which are usually formed from water insoluble surfactants. Herein, we demonstrate the formation of liposomes from single-chain cationic surfactants with the help of metals as a part of the counter ion, and these metal embedded liposomes are termed as metalosomes. It is a noteworthy advancement in the area of self-assembled molecular structures since we report the preparation of metal embedded liposomes (metalosomes) from a water soluble single chain cationic surfactant, which is otherwise a property or an arrangement made by double tailed surfactants, or more precisely lipids that are poorly water soluble. We can use this method for various cationic surfactants and metal combinations and the studies are still in process. However, this preliminary report on manganese-based surfactants depicts the successful formation of cationic metalosomes (with/without cholesterol), and the formation, structure and size has been verified using TEM, FE-SEM, DLS XRD and SAXS. The comparison of metalosomes with reverse vesicles in different solvents further gave an insight of microstructure and solvent environment effects on the self-assembly of metallosurfactants. In addition, we have also evaluated the encapsulation ability of metalosomes for fluorescein dye. High encapsulation efficiency of Mn-somes makes them promising candidates for several applications, particularly because of its water solubility.

Effects of Sterol-Like Additives on Phase Transition Behavior of Ion-Pair Amphiphile Bilayers.

The incorporation of additive in lipid bilayers is one of the ordinary approaches for modulating their properties. Additive effect on phase transition of ion-pair amphiphile (IPA) bilayers, however, is not known. In this work, four double-chained IPAs with different hydrocarbon chain lengths and symmetry were designed and synthesized from single-chained cationic and anionic surfactants by the precipitation method. By using differential scanning calorimetry (DSC), the thermotropic transition behavior from gel phase (Lβ) through rippled phase (Pβ') if any to liquid-crystalline phase (Lα) was studied for bilayers of these lipid-like IPAs in excess water. The effects of three sterol-like additives (cholesterol, α-tocopherol, and α-tocopheryl acetate) in IPA bilayers on thermal phase behavior were then systematically investigated. The experimental results revealed that with increasing concentration of additive, the phase transition temperatures were unaffected on the one hand and the enthalpies of phase transition were decreased on the other hand. When the addition of additive exceeded a specific amount, the phase transition disappeared. More hasty disappearance of phase transition was found for IPAs with lower total number of carbon atoms in the hydrocarbon chains. For IPAs with the same total number of carbon atoms in the hydrocarbon chains, the disappearance of phase transition is more hasty for the asymmetric one than for the symmetric one. Similar effects on thermal phase behavior of four IPA bilayers were exhibited by the three additives with similar chemical structures. Possible mechanism of additive effects on phase transition of IPA bilayers was then proposed in line with that of lipid bilayers.

Interaction of bovine serum albumin with cationic monomeric and dimeric surfactants: A comparative study

The interaction of bovine serum albumin (BSA) with a single chain cationic surfactant, dodecyl trimethylammonium bromide (DTAB) and three dimeric surfactants viz., butanediyl-1,4 bis(dimethyldodecylammonium bromide (12–4-12,2Br−), 2- butanol-1,4-bis(dimethyldodecylammonium bromide) (12–4(OH)-12,2Br−), 2,4-dibutanol-1,4 bis(dimethyldodecylammonium bromide) (12-4(OH)2-12,2Br−) have been investigated by means of surface tension, conductance, viscosity, fluorescence and UV–Visible spectroscopic measurements. The results obtained depict that the hydroxyl group substitution in linker of gemini surfactants affects the BSA-surfactant interactions. As compared to single chain cationic surfactants, gemini surfactants show more interactions with BSA. The negetive values of thermodynamic parameters viz., Gibbs free energy of micellization (ΔG°m), Gibbs free energy of adsorption (ΔG°ads) and Gibbs free energy of quenching process (ΔG°q) showed spontaneity of micellization process.

Synthesis of phosphor-free luminescent, monodisperse, mesoporous silica nanoparticles in the co-presence of double- and single-chain cationic surfactants

Phosphor-free luminescent, mesoporous silica nanoparticles (MSNs) were synthesized with a sol–gel method in the presence of cetyltrimethylammonium bromide (CTAB) and/or didodecyldimethylammonium bromide (DDAB). The surfactants were employed to play double roles as a template to form mesopores and as an organic compound to introduce luminescent centers in calcination step. The incorporation of DDAB produced MSN that was better in luminescent properties than the CTAB-incorporated nanoparticles. A low molar ratio of CTAB to DDAB in their coexistence system could produce highly monodisperse MSN that showed emission intensity higher than that of a conventional phosphor-free luminescent silica nanoparticle having no mesopores.

Microfluidic processing of concentrated surfactant mixtures: online SAXS, microscopy and rheology.

We investigate the effect of microfluidic flow on the microstructure and dynamics of a model surfactant mixture, combining synchrotron Small Angle X-ray Scattering (SAXS), microscopy and rheology. A system comprising a single-chain cationic surfactant, hexadecyl trimethyl ammonium chloride (C16TAC), a short-chain alcohol (1-pentanol) and water was selected for the study due to its flow responsiveness and industrial relevance. Model flow fields, including sequential contraction-expansion (extensional) and rotational flows, were investigated and the fluid response in terms of the lamellar d-spacing, orientation and birefringence was monitored in situ, as well as the recovery processes after cessation of flow. Extensional flows are found to result in considerable d-spacing increase (from approx 59 Å to 65 Å). However, under continuous flow, swelling decreases with increasing flow velocity, eventually approaching the equilibrium values at velocities ≃2 cm s(-1). Through individual constrictions we observe the alignment of lamellae along the flow velocity, accompanied by increasing birefringence, followed by an orientation flip whereby lamellae exit perpendicularly to the flow direction. The resulting microstructures are mapped quantitatively onto the flow field in 2D with 200 μm spatial resolution. Rotational flows alone do not result in appreciable changes in lamellar spacing and flow type and magnitude evidently impact the fluid microstructure under flow, as well as upon relaxation. The findings are correlated with rheological properties measured ex situ to provide a mechanistic understanding of the effect of flow imposed by tubular processing units in the phase behavior and performance of a model surfactant system with ubiquitous applications in personal care and coating industries.

Vesicle aggregation based on hydrophobic interactions

Vesicles were formed in aqueous mixtures of gemini anionic surfactant, O,O′-bis(sodium 2-alkylcarboxylate)-p-dibenzenediol (referred to as Cmϕ2Cm, m = 10, 12), and single-chain cationic surfactant, alkyltrimethylammonium bromides CnNBr (n = 8, 10, 12). This was confirmed by measurements of solution turbidity, dynamic light scattering (DLS) and freeze-fractured TEM. The improvement of the Cmϕ2Cm molecular geometry by CnNBr was considered to have been due to vesicle formation. As the temperature was raised, these vesicles were found to associate together and DLS measurements showed a rapid increase of the aggregate size at the critical temperature Tc. The mechanism of vesicle aggregation was assumed to be due to the temperature-induced configuration transition of a few Cmϕ2Cm molecules in the vesicles from cis- into trans-form. Thus, a few tails of Cmϕ2Cm stretched toward the solution. When the vesicles approached, these projecting tails interacted hydrophobically, thereby non-covalently attaching one vesicle to another. This should benefit from the special molecular structure of Cmϕ2Cm with a long, rigid spacer.

Determination of micelle aggregation numbers of alkyltrimethylammonium bromide and sodium dodecyl sulfate surfactants using time-resolved fluorescence quenching

Abstract The time-resolved fluorescence quenching method was applied to determine the micelle aggregation number of cationic single-chain surfactants dodecyltrimethylammonium bromide (DTAB), cetyltrimethylammonium bromide (CTAB) and anionic surfactant sodium dodecyl sulfate (SDS). The concentration dependence of micelle aggregation number was found to be linear for all investigated surfactants in the concentration range 2‒15 × the value of critical micelle concentration of the respective surfactant. The values of micelle aggregation number were found in the range 30‒77. Different trends in the linear concentration dependence of micelle aggregation number were observed for cationic surfactants and for the anionic surfactant SDS. A small slope value was found for cationic surfactants, while the SDS micelle aggregation number concentration dependence showed significantly a larger slope value. The aggregation number increase with the increasing SDS concentration results in the micellar growth. Results from a simple analysis based on computer models of cationic and anionic surfactant molecules with dodecyl chains supports, the formation of intramicellar hydrogen bonding between surfactant molecules in SDS micelle shell.

Effect of [C n mim][Br] Based Ionic Liquids on the Aggregation Behavior of Tetradecyltrimethylammonium Bromide in Aqueous Medium

In order to gain insight into the role of environmentally benign imidazolium based ionic liquids (ILs) to alter the physicochemical properties of single chain cationic surfactants, we have investigated the effect of 1-hexyl-3-methylimidazolium bromide ([C6mim][Br]) and 1-octyl-3-methylimidazolium bromide ([C8mim][Br]) on the aggregation behavior of aqueous tetradecyltrimethylammonium bromide (TTAB). The critical micelle concentration (CMC) of TTAB at different concentrations of ILs was determined through conductance, surface tension, spectral change of a dye by UV–Vis measurement, and the pyrene fluorescence probe measurement techniques at 298.15 K. Decreasing of the CMC of aqueous TTAB with increasing ILs concentration proves the micellization is favorable. The effect of ILs on the properties of TTAB was verified by using NaBr. Surface tension measurements complimented by dynamic light scattering (DLS) data revealed the packing density of TTAB aggregates at different concentrations of ILs. The effective area of TTAB molecules at the air/water interface was calculated by the Gibbs adsorption isotherm and found to decrease up to 0.6 wt% of ILs followed by an increase at higher concentration. DLS data revealed an increase in micellar size of TTAB at higher concentration of IL with decrease in the aggregation number (N agg), determined by the fluorescence quenching method.

Role of surfactant structure in aqueous dispersions of carbon nanotubes

Gemini surfactants typically consist of two single-chain surfactant schemically connected by a spacer chain. Recently, it has been shown experimentally that they are able to effectively disperse and stabilize carbon nanotubes (CNTs) in aqueous solutions at very low surfactant concentration. To aid elucidate the role of surfactant structure in the CNT dispersion process, we report herein the results of fully atomistic molecular dynamics (MD) simulations of the adsorption and surface self-assembly of a cationic single-chain surfactant, dodecyltrimethyl-ammonium bromide (C12TAB), and its related Gemini surfactant dimethylene-α,β-bis (dodecyldimethylammonium bromide) [12-2-12]Br2, on (5,7), and (10,14) single-walled carbon nanotubes (SWNTs) in aqueous solution at ambient conditions. We find that the morphology of surfactant aggregates on the SWNT is influenced by the surfactant structure. The same number of [12-2-12]Br2 Gemini surfactants adsorbed are able to cover a larger surface area of SWNT and their head-groups are protruded more extensively toward the aqueous phase, preventing water molecules from accessing the nanotube surface. These morphological results propose that [12-2-12]Br2 should be more effective than C12TAB at stabilizing aqueous dispersions of carbon nanotubes. Furthermore, the influence of SWNT diameter and length of the Gemini surfactant spacer on the structure of aggregates formed onto nanotubes are investigated. These simulation results advance our understanding of the mechanism of CNT solubilization via Gemini surfactants.

Cationic vesicles of a carnitine-derived single-tailed surfactant: Physicochemical characterization and evaluation of in vitro gene transfection efficiency

Spontaneous vesicle formation in water by single-chain surfactants is rare. Here we show that in aqueous solution, a single-chain cationic surfactant 3-(dodecylcarbamoyl-2-hydroxypropyl)-trimethylammonium chloride (C12-CAR) derived from d,l-carnitine spontaneously forms vesicles with hydrodynamic diameters in the range of 30–70nm. A detailed self-assembly study of the C12-CAR surfactant was performed for the first time by use of a combination of techniques, including surface tension, conductivity, fluorescence probe, dynamic light scattering and transmission electron microscopy. The cationic surfactant was found to have a reasonably low critical aggregation concentration (3.4±0.2mM) in water at 298K. The vesicles were observed to be stable at the physiological temperature (310K) over a long period of time. Although the vesicles formed were found to be unstable and exhibit vesicle-to-tubule transition in the presence of salt, in the presence of 10mol% cholesterol the stability of vesicles is enhanced. When compared with lipofectamine-2000, the C12-CAR was found to act as an effective gene transfection agent in COS-1 cell line. The surfactant-DNA complex was also found to be nontoxic toward CHO cells.

Vesicle formation between single-chained cationic surfactant and plasmid DNA and its application in cell transfection

In the present study, we found that plasmid DNA could induce single-chained cationic surfactants cetyltrimethylammonium bromide (CTAB), dodecyltrimethylammonium bromide (DTAB), and dodecyltriethyl ammonium bromide (DEAB) to form vesicles once its concentration reached a critical value. Moreover, the gene for follicle-stimulating hormone was delivered into cells with these single-chained cationic surfactant/DNA vesicles and the transfection efficiency was comparable to that with lipofectamine™ 2000, a famous and widely used commercial transfection reagent, and also to that using electroporation method, although it was generally thought conventional single-chained cationic surfactant was not suitable for gene transfer. The conventional single-chained cationic surfactant is very cheap and stable and the vesicles are very easy to be prepared. Thereby, this study may suggest that the vesicles formed between plasmid DNA and surfactant should be prospective to transfer DNA.

Preparations of Ethosome-like Catanionic Vesicles from Ion-Pair Amphiphiles( IPAs ) for Dermal Drug Delivery

ABSTRACTEthosomes which are phospholipid vesicular systems embodying ethanol in relatively high concentrations have ever been discovered for enhanced skin delivery of drugs. The development of competent ethosome-like catanionic vesicles for dermal drug delivery is demonstrated in this work. Double-chained ion-pair-amphiphiles (IPAs or catanionic surfactants) were prepared from single-chained cationic and anionic surfactants by the precipitation method. These lipid-like surfactants were thereafter used as the material to prepare the catanionic vesicles with the aid of ethanol as the cosolvent in aqueous buffer solution by a simple semispontaneous process. Formability and physical stability of the as-prepared ethosome-like catanionic vesicles were discussed based on the viewpoint of mixed solvent dielectric constant. The potential application of the ethosome-like catanionic vesicles as nano-carriers in dermal drug delivery was illustrated by the encapsulation of hydrophobic and hydrophilic drugs. Furthermore, effects of ethanol and cholesterol addition on physical stability, bilayer membrane rigidity, encapsulation efficiency, and release rate of the ethosome-like catanionic vesicles were systematically studied. The performance of ethosome-like catanionic vesicles as drug delivery nano-carriers, eventually, can be tailored by the concentrations of ethanol and. cholesterol. The results of gelation of drugs loaded ethosome-like catanionic vesicles by water soluble polymers with and without hydrophobical modifications, as revealed by the phase maps and the rheological properties, then provide useful information for practical use of the ethosome-like catanionic vesicles in dermal delivery of drugs.