Vesicle Radius Research Articles

Comparative analyses of response surface methodology and artificial neural networks on incorporating tetracaine into liposomes

This study evaluated the incorporation of tetracaine into liposomes by RSM (Response Surface Methodology) and ANN (Artificial Neural Networks) based models. RCCD (rotational central composite design) and ANN were performed to optimize the sonication conditions of particles containing 100 % lipid. Laser light scattering was used to perform measure hydrodynamic radius and size distribution of vesicles. The liposomal formulations were analyzed by incorporating the drug into the hydrophilic phase or the lipophilic phase. RCCD and ANN were conducted, having the lipid/cholesterol ratio and concentration of tetracaine as variables investigated and, the encapsulation efficiency and mean diameter of the vesicles as response variables. The optimum sonication condition set at a power of 16 kHz and 3 minutes, resulting in sizes smaller than 800 nm. Maximum encapsulation efficiency (39.7 %) was obtained in the hydrophilic phase to a tetracaine concentration of 8.37 mg/mL and 79.5:20.5% lipid/cholesterol ratio. Liposomes were stable for about 30 days (at 4 °C), and the drug encapsulation efficiency was higher in the hydrophilic phase. The experimental results of RCCD-RSM and ANN techniques show ANN obtained more refined prediction errors that RCCD-RSM technique, therefore, ANN can be considered as an efficient mathematical method to characterize the incorporation of tetracaine into liposomes.

Lipid Unsaturation Properties Govern the Sensitivity of Membranes to Photoinduced Oxidative Stress

Unsaturated lipid oxidation is a fundamental process involved in different aspects of cellular bioenergetics; dysregulation of lipid oxidation is often associated with cell aging and death. To study how lipid oxidation affects membrane biophysics, we used a chlorin photosensitizer to oxidize vesicles of various lipid compositions and degrees of unsaturation in a controlled manner. We observed different shape transitions that can be interpreted as an increase in the area of the targeted membrane followed by a decrease. These area modifications induced by the chemical modification of the membrane upon oxidation were followed in situ by Raman tweezers microspectroscopy. We found that the membrane area increase corresponds to the lipids’ peroxidation and is initiated by the delocalization of the targeted double bonds in the tails of the lipids. The subsequent decrease of membrane area can be explained by the formation of cleaved secondary products. As a result of these area changes, we observe vesicle permeabilization after a time lag that is characterized in relation with the level of unsaturation. The evolution of photosensitized vesicle radius was measured and yields an estimation of the mechanical changes of the membrane over oxidation time. The membrane is both weakened and permeabilized by the oxidation. Interestingly, the effect of unsaturation level on the dynamics of vesicles undergoing photooxidation is not trivial and thus carefully discussed. Our findings shed light on the fundamental dynamic mechanisms underlying the oxidation of lipid membranes and highlight the role of unsaturations on their physical and chemical properties.

Analysis of the Vesicular Structure of Nanoparticles in the Phospholipid-Based Drug Delivery System Using SAXS Data

Small-angle X-ray scattering (SAXS) is used to characterize the vesicular structure of the phospholipid transport nanosystem (PTNS) at PTNS concentrations in water of 25, 31.25, and 37.5% (w/w). The average vesicle radius, size polydispersity, bilayer thickness, and internal structure are determined from the experiment using two models for the photon scattering density distribution. Two independent methods are used to calculate the SAXS spectra: the form factor of a heterogeneous spherical shell and the method of separated form factors. The two methods for calculating the spectra and two models for description of the internal structure of the lipid bilayer provide identical results, which demonstrate a decrease in the vesicle radius, thickness of the bilayer, and thickness of the hydrocarbon-chain region upon an increase in the maltose concentration in water. It is shown that a decrease in the lipid bilayer thickness upon an increase in the maltose concentration is caused by interdigitation of the hydrocarbon chains. The hydrophobic volume of one vesicle suitable for water-insoluble drugs is shown to have a maximum value of 14.55 × 106 A3 at a PTNS concentration in water of 25%. Increasing the PTNS concentration in water up to 37.5% leads to a decrease in the hydrophobic volume to 6.16 × 106 A3.

Pressure-driven flow of a vesicle through a square microchannel

The relative velocity and extra pressure drop of a single vesicle flowing through a square microchannel are quantified via boundary element simulations, lubrication theory and microfluidic experiments. The vesicle is modelled as a fluid sac enclosed by an inextensible, fluidic membrane with a negligible bending stiffness. All results are parametrized in terms of the vesicle sphericity (i.e. the reduced volume) and flow confinement (i.e. the ratio of the vesicle radius to the channel hydraulic radius). Direct comparison is made to previous studies of vesicle flow through circular tubes, revealing several distinct features of the square-channel geometry. Firstly, fluid in the suspending medium bypasses the vesicle through the corners of the channel, which in turn reduces the dissipation created by the vesicle. Secondly, the absence of rotational symmetry about the channel axis permits surface circulation in the membrane (tank treading), which in turn reduces the vesicle’s speed. At very high confinement, both theory and experiment indicate that the vesicle’s speed can be reduced below the mean speed of the suspending fluid through this mechanism. Finally, the contact area for lubrication is greatly reduced in the square-duct geometry, which in turn weakens the stress singularity predicted by lubrication theory. This fact directly leads to a breakdown of the lubrication approximation at low flow confinement, as verified by comparison to boundary element simulations. Since the only distinct property assumed of the membrane is its ability to preserve surface area locally, it is expected that the results of this study are applicable to other types of soft particles with immobilized surfaces (e.g. Pickering droplets, gel beads and biological cells).

The Small-Angle Neutron Scattering Data Analysis of the Phospholipid Transport Nanosystem Structure

The small-angle neutron scattering technique (SANS) is employed for investigation of structure of the phospholipid transport nanosystem (PTNS) elaborated in the V.N.Orekhovich Institute of Biomedical Chemistry (Moscow, Russia). The SANS spectra have been measured at the YuMO small-angle spectrometer of IBR-2 reactor (Joint Institute of Nuclear Research, Dubna, Russia). Basic characteristics of polydispersed population of PTNS unilamellar vesicles (average radius of vesicles, polydispersity, thickness of membrane, etc.) have been determined in three cases of the PTNS concentrations in D2O: 5%, 10%, and 25%. Numerical analysis is based on the separated form factors method (SFF). The results are discussed in comparison with the results of analysis of the small-angle X-ray scattering spectra collected at the Kurchatov Synchrotron Radiation Source of the National Research Center “Kurchatov Institute” (Moscow, Russia).

How To Characterize Individual Nanosize Liposomes with Simple Self-Calibrating Fluorescence Microscopy.

Nanosize lipid vesicles are used extensively at the interface between nanotechnology and biology, e.g., as containers for chemical reactions at minute concentrations and vehicles for targeted delivery of pharmaceuticals. Typically, vesicle samples are heterogeneous as regards vesicle size and structural properties. Consequently, vesicles must be characterized individually to ensure correct interpretation of experimental results. Here we do that using dual-color fluorescence labeling of vesicles-of their lipid bilayers and lumens, separately. A vesicle then images as two spots, one in each color channel. A simple image analysis determines the total intensity and width of each spot. These four data all depend on the vesicle radius in a simple manner for vesicles that are spherical, unilamellar, and optimal encapsulators of molecular cargo. This permits identification of such ideal vesicles. They in turn enable calibration of the dual-color fluorescence microscopy images they appear in. Since this calibration is not a separate experiment but an analysis of images of vesicles to be characterized, it eliminates the potential source of error that a separate calibration experiment would have been. Nonideal vesicles in the same images were characterized by how their four data violate the calibrated relationship established for ideal vesicles. In this way, our method yields size, shape, lamellarity, and encapsulation efficiency of each imaged vesicle. Applying this procedure to extruded samples of vesicles, we found that, contrary to common assumptions, only a fraction of vesicles are ideal.

Size selection and stability of thick-walled vesicles

ABSTRACTIn recent experiments, small, thick-walled vesicles with a preferred size were formed from copolymers where the degree of polymerisation of the hydrophobic block, , was significantly greater than that of the hydrophilic block, . We show that a simple mean-field theory can reproduce several aspects of the behaviour of these vesicles. First, we find a minimum in the free energy of the system of vesicles as a function of their radius, corresponding to a preferred size for the vesicles, when is several times larger than . Furthermore, the vesicle radius diverges as is increased towards a critical value, consistent with the instability of the vesicles with respect to further aggregation seen in the experimental work. Finally, we find that this instability can also be triggered in our model by changing the interaction strength of the copolymers with the solvent.

(Invited) Vesicular Exocytosis in Neuronal and Neuroendocrine Cells: Quantifying Fusion Pore Size from Amperometric Data

It is well-known that amperometric measurements of vesicular exocytosis in artificial synapse configuration [1] provide two important advantages: unsurpassed temporal resolution of single exocytotic events and possibility to obtain massive data. These two advantages allow statistical analysis of exocytosis and its trends in different cell types and/or under various physico-chemical conditions (osmotic shocks, effect of drugs etc.). However, generally statistical analysis is restricted to the examination of some shape features of the individual spikes (half-time, charge released etc.) even though all relevant physico-chemical parameters are intricately convoluted in the monitored current. Extraction of these thought parameters is extremely difficult due to the fact that each exocytotic event is unique in terms of vesicle size, its internal composition, neurotransmitter load etc. During several last years we developed a theoretical framework providing means to extract statistically sound fusion pore sizes as well as pore dynamics from individual exocytotic spikes [2-4], that is information hardly accessible or not accessible by other approaches. This permits us to analyze and quantify vesicle pore sizes from amperometric data obtained at chromaffin cells [4] and rat neuro-muscular junctions [5]. Recently we dramatically simplified the fusion pore size extraction procedure (without sacrificing its accuracy) so that it can be easily implemented by the experimentalists, e.g. in spreadsheet programs. This advance allow us to address a larger data set of spikes obtained at chromaffin cells and reveal changes in fusion pores topology under modified conditions (osmotic stress, membrane lipid modification) with respect to control conditions. Of high interest was the finding that in all considered cases the fusion pore radii was never larger 30 nm, that is much smaller to the average radius of the chromaffin cell vesicle 156 nm. Taking into account significant size of the data set (more than 1000 spikes) this questions the ‘inevitable full fusion’ paradigm and statistically support a mode of exocytosis where the pore size is significantly smaller the vesicle size [6].

Adsorption and encapsulation of flexible polyelectrolytes in charged spherical vesicles.

We present a theory of adsorption of flexible polyelectrolytes on the interior and exterior surfaces of a charged vesicle in an electrolyte solution. The criteria for adsorption and the density profiles of the adsorbed polymer chain are derived in terms of various characteristics of the polymer, vesicle, and medium, such as the charge density and length of the polymer, charge density and size of the vesicle, electrolyte concentration and dielectric constant of the medium. For adsorption inside the vesicle, the competition between the loss of conformational entropy and gain in adsorption energy results in two kinds of encapsulated states, depending on the strength of the polymer-vesicle interaction. By considering also the adsorption from outside the vesicle, we derive the entropic and energy contributions to the free energy change to transfer an adsorbed chain in the interior to an adsorbed chain on the exterior. In this paper, we have used the Wentzel-Kramers-Brillouin (WKB) method to solve the equation for the probability distribution function of the chain. The present WKB results are compared with the previous results based on variational methods. The WKB and variational results are in good agreement for both the interior and exterior states of adsorption, except in the zero-salt limit for adsorption in the exterior region. The adsorption criteria and density profiles for both the interior and exterior states are presented in terms of various experimentally controllable variables. Calculation of the dependencies of free energy change to transfer an adsorbed chain from the interior to the exterior surface on salt concentration and vesicle radius shows that the free energy penalty to expel a chain from a vesicle is only of the order of thermal energy.

MP94-10 THE VISCOELASTIC, REVERSIBLY PLASTIC, BEHAVIOR OF DETRUSOR SMOOTH MUSCLE EXPLAINS BLADDER HIGH COMPLIANCE

You have accessJournal of UrologyBladder & Urethra: Anatomy, Physiology & Pharmacology II1 Apr 2017MP94-10 THE VISCOELASTIC, REVERSIBLY PLASTIC, BEHAVIOR OF DETRUSOR SMOOTH MUSCLE EXPLAINS BLADDER HIGH COMPLIANCE Randy Vince, John Speich, Adam Klausner, Christopher Neal, Amy Miner, and Paul Ratz Randy VinceRandy Vince More articles by this author , John SpeichJohn Speich More articles by this author , Adam KlausnerAdam Klausner More articles by this author , Christopher NealChristopher Neal More articles by this author , Amy MinerAmy Miner More articles by this author , and Paul RatzPaul Ratz More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2017.02.2913AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES : Biological soft tissues are viscoelastic materials because they display time-independent pseudo-elasticity and time-dependent viscosity. Upon an imposed ramp increase then decrease in strain, the resultant increase and decrease in stress, termed loading and unloading respectively, produce nonlinear stress-strain curves, and a reversible reduction in the stress-strain work area that identifies the viscous component. However, there is evidence that bladder tissue may also display plastic behavior, defined as an increase in strain that is unrecoverable unless work is done by the material. In the present study, an electronic lever was used to induce controlled changes in stress and strain to determine whether the material properties of rabbit detrusor smooth muscle (rDSM) represent a viscoelastic or viscoelastic-plastic material. METHODS Strips of DSM free from underlying mucosa were removed from rabbit bladders. Each tissue was placed in an organ bath connected to an electronic lever and length-adjuster and subjected to a length-tension protocol to identify the length (Lref) that produced the strongest active force induced by KCl. Each ring was subsequently set to 80% Lref and subjected to sequential ramp loading and unloading cycles, stress-strain and stiffness-stress analyses, and a step-loading, load-clamp, step-unloading (creep) protocol. RESULTS Ramp loading-unloading cycles revealed that rDSM displayed reversible viscoelasticity. The viscous component was responsible for establishing a high stiffness at low stresses that increased only modestly with increasing stress compared to the large increase produced when the viscosity was absent and only pseudo-elasticity governed tissue behavior. The creep protocol revealed that rDSM underwent extensive softening correlating with plastic deformation and creep that was reversible upon activation of muscle contraction. Softening reversal was prevented by inhibitors of actomyosin crossbridge cycling. CONCLUSIONS Together, the data support a model of DSM as exhibiting not only viscoelasticity, but also plasticity, the degree of which is controlled by the degree of motor protein activation. This model explains the mechanism of instrinsic bladder compliance as “slipping” crossbridges, predicts that wall tension is dependent not only on vesicle pressure and radius but also on actomyosin crossbridge activity, and identifies a novel molecular target for compliance regulation both physiologically and therapeutically. © 2017FiguresReferencesRelatedDetails Volume 197Issue 4SApril 2017Page: e1249 Advertisement Copyright & Permissions© 2017MetricsAuthor Information Randy Vince More articles by this author John Speich More articles by this author Adam Klausner More articles by this author Christopher Neal More articles by this author Amy Miner More articles by this author Paul Ratz More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Slowly cycling Rho kinase-dependent actomyosin cross-bridge "slippage" explains intrinsic high compliance of detrusor smooth muscle.

Biological soft tissues are viscoelastic because they display time-independent pseudoelasticity and time-dependent viscosity. However, there is evidence that the bladder may also display plasticity, defined as an increase in strain that is unrecoverable unless work is done by the muscle. In the present study, an electronic lever was used to induce controlled changes in stress and strain to determine whether rabbit detrusor smooth muscle (rDSM) is best described as viscoelastic or viscoelastic plastic. Using sequential ramp loading and unloading cycles, stress-strain and stiffness-stress analyses revealed that rDSM displayed reversible viscoelasticity, and that the viscous component was responsible for establishing a high stiffness at low stresses that increased only modestly with increasing stress compared with the large increase produced when the viscosity was absent and only pseudoelasticity governed tissue behavior. The study also revealed that rDSM underwent softening correlating with plastic deformation and creep that was reversed slowly when tissues were incubated in a Ca2+-containing solution. Together, the data support a model of DSM as a viscoelastic-plastic material, with the plasticity resulting from motor protein activation. This model explains the mechanism of intrinsic bladder compliance as "slipping" cross bridges, predicts that wall tension is dependent not only on vesicle pressure and radius but also on actomyosin cross-bridge activity, and identifies a novel molecular target for compliance regulation, both physiologically and therapeutically.

Kinetics of enzyme-mediated hydrolysis of lipid vesicles

Membrane enzymatic reactions can now be experimentally studied at the level of single sub-100nm lipid vesicles. To interpret such experiments, we scrutinize theoretically various aspects of the hydrolysis of vesicles by single enzyme molecules and enzyme (e.g., PLA2) supplied with the constant rate. Using the mean-field kinetic model, we illustrate the shape of the corresponding kinetics and the dependence of the time scale of the reaction on the vesicle radius. Stochastic effects are illustrated as well. In addition, we discuss the likely mechanisms of the reaction-induced pore formation and bilayer rupture.

Long-range hydrodynamic effect due to a single vesicle in linear flow

Vesicles are involved in a vast variety of transport processes in living organisms. Additionally, they serve as a model for the dynamics of cell suspensions. Predicting the rheological properties of their suspensions is still an open question, as even the interaction of pairs is yet to be fully understood. Here we analyse the effect of a single vesicle, undergoing tank-treading motion, on its surrounding shear flow by studying the induced disturbance field , the difference between the velocity field in its presence and absence. The comparison between experiments and numerical simulations reveals an impressive agreement. Tracking ridges in the disturbance field magnitude landscape, we identify the principal directions along which the velocity difference field is analysed in the vesicle vicinity. The disturbance magnitude is found to be significant up to about 4 vesicle radii and can be described by a power law decay with the distance d from the vesicle . This is consistent with previous experimental results on the separation distance between two interacting vesicles under similar conditions, for which their dynamics is altered. This is an indication of vesicles long-range effect via the disturbance field and calls for the proper incorporation of long-range hydrodynamic interactions when attempting to derive rheological properties of vesicle suspensions.

Selective flow-induced vesicle rupture to sort by membrane mechanical properties.

Vesicle and cell rupture caused by large viscous stresses in ultrasonication is central to biomedical and bioprocessing applications. The flow-induced opening of lipid membranes can be exploited to deliver drugs into cells, or to recover products from cells, provided that it can be obtained in a controlled fashion. Here we demonstrate that differences in lipid membrane and vesicle properties can enable selective flow-induced vesicle break-up. We obtained vesicle populations with different membrane properties by using different lipids (SOPC, DOPC, or POPC) and lipid:cholesterol mixtures (SOPC:chol and DOPC:chol). We subjected vesicles to large deformations in the acoustic microstreaming flow generated by ultrasound-driven microbubbles. By simultaneously deforming vesicles with different properties in the same flow, we determined the conditions in which rupture is selective with respect to the membrane stretching elasticity. We also investigated the effect of vesicle radius and excess area on the threshold for rupture, and identified conditions for robust selectivity based solely on the mechanical properties of the membrane. Our work should enable new sorting mechanisms based on the difference in membrane composition and mechanical properties between different vesicles, capsules, or cells.

Application of small-angle X-ray scattering to the characterization and quantification of the drug transport nanosystem based on the soybean phosphatidylcholine

Phospholipid transport nanosystem (PTNS) for drug delivery is based on soybean phosphatidylcholine. The morphology of PTNS is investigated by means of small-angle X-ray scattering. The obtained results allow one to answer the key question from the viewpoint of organization of drug incorporation whether the PTNS nanoparticles have a structure of micelles or vesicles. It is demonstrated that PTNS is a vesicular system with an average vesicle radius of 160±2Å.

PH‐Responsive and CO2‐responsive vesicles can be formed by N‐decylimidazole

Responsive vesicles have attracted great attention because they can undergo reversible changes in response to external stimuli and possess prospective applications in different environments. A pH‐responsive and CO2‐responsive vesicle formed by N‐decylimidazole was prepared. By dynamic light scattering (DLS) and transmission electron microscopy (TEM), it is shown that spherical vesicles are formed spontaneously in N‐decylimidazole aqueous solution at pH 5.8∼6.2. By HCl/NaOH adjustment, the vesicle radius increases from 73.8 to 100.8 nm as the solution pH increases from 5.8 to 6.2. By CO2/Ar adjustment, the vesicles also can be formed in N‐decylimidazole aqueous solution at suitable pH. The CO2‐responsive vesicle can be repeatedly formed without change of vesicle size.Practical applications: The vesicles can be spontaneously formed in N‐decylimidazole aqueous solution at pH 5.8∼6.2 either by HCl/NaOH adjustment or CO2/Ar stimuli. Therefore, they can be used as pH‐responsive or CO2‐responsive vesicles for potential applications in drug‐delivery, size‐selective release, biochemical reactions, and so on.In order to fabricate pH‐responsive and CO2‐responsive vesicles, the authors studied vesicle formation using N‐decylimidazole, by HCl/NaOH or CO2/Ar adjustment. These vesicles have potential applications in drug delivery and other biochemical applications.

Modeling curvature-dependent subcellular localization of the small sporulation protein SpoVM in Bacillus subtilis.

Recent in vivo experiments suggest that in the bacterium, Bacillus subtilis, the cue for the localization of the small sporulation protein, SpoVM, an essential factor in spore coat formation, is curvature of the bacterial plasma membrane. In vitro measurements of SpoVM adsorption to vesicles of varying sizes also find high sensitivity of adsorption to vesicle radius. This curvature-dependent adsorption is puzzling given the orders of magnitude difference in length scale between an individual protein and the radius of curvature of the cell or vesicle, suggesting protein clustering on the membrane. Here we develop a minimal model to study the relationship between curvature-dependent membrane adsorption and clustering of SpoVM. Based on our analysis, we hypothesize that the radius dependence of SpoVM adsorption observed in vitro is governed primarily by membrane tension, while for in-vivo localization of SpoVM, we propose a highly sensitive mechanism for curvature sensing based on the formation of macroscopic protein clusters on the membrane.

Fluctuation dynamics of bilayer vesicles with intermonolayer sliding: Experiment and theory

The presence of coupled modes of membrane motion in closed shells is extensively predicted by theory. The bilayer structure inherent to lipid vesicles is suitable to support hybrid modes of curvature motion coupling membrane bending with the local reorganization of the bilayer material through relaxation of the dilatational stresses. Previous experiments evidenced the existence of such hybrid modes facilitating membrane bending at high curvatures in lipid vesicles [Rodríguez-García, R., Arriaga, L.R., Mell, M., Moleiro, L.H., López-Montero, I., Monroy, F., 2009. Phys. Rev. Lett. 102, 128201.]. For lipid bilayers that are able to undergo intermonolayer sliding, the experimental fluctuation spectra are found compatible with a bimodal schema. The usual tension/bending fluctuations couple with the hybrid modes in a mechanical interplay, which becomes progressively efficient with increasing vesicle radius, to saturate at infinity radius into the behavior expected for a flat membrane. Grounded on the theory of closed shells, we propose an approximated expression of the bimodal spectrum, which predicts the observed dependencies on the vesicle radius. The dynamical features obtained from the autocorrelation functions of the vesicle fluctuations are found in quantitative agreement with the proposed theory.

Dynamics of intermittent force fluctuations in vesicular nanotubulation.

Irregular force fluctuations are seen in most nanotubulation experiments. The dynamics behind their presence has, however, been neither commented upon nor modeled. A simple estimate of the mean energy dissipated in force drops turns out to be several times the thermal energy. This coupled with the rate dependent nature of the deformation reported in several experiments point to a dynamical origin of the serrations. We simplify the whole process of tether formation through a three-stage model of successive deformations of sphere to ellipsoid, neck-formation, and tubule birth and extension. Based on this, we envisage a rate-softening frictional force at the neck that must be overcome before a nanotube can be pulled out. Our minimal model includes elastic and visco-elastic deformation of the vesicle, and has built-in dependence on pull velocity, vesicle radius, and other material parameters, enabling us to capture various kinds of serrated force-extension curves for different parameter choices. Serrations are predicted in the nanotubulation region. Other features of force-extension plots reported in the literature such as a plateauing serrated region beyond a force drop, serrated flow region with a small positive slope, an increase in the elastic threshold with pull velocity, force-extension curves for vesicles with larger radius lying lower than those for smaller radius, are all also predicted by the model. A toy model is introduced to demonstrate that the role of the friction law is limited to inducing stick-slip oscillations in the force, and all other qualitative and quantitative features emerging from the model can only be attributed to other physical mechanisms included in the deformation dynamics of the vesicle.

Size control of surfactant vesicles made by a mixture of cationic surfactants and organic derivatives.

Spontaneous size-controllable vesicles that are prepared by a mixture of surfactants with different alkyl chain lengths (n-alkyltrimethylammonium bromide, C(n)TAB) and an organic derivative (5-methyl salicylic acid, 5mS) in aqueous solution have been investigated. When the organic derivative 5mS is mixed with the C(n)TAB surfactants in aqueous solution, the surfactant vesicles are spontaneously formed above a certain 5mS concentration. Small angle neutron scattering reveals that the core radius of surfactant vesicles is clearly increased from ca. 31 nm to ca. 97 nm with the alkyl chain length of surfactants while the bilayer thickness of the vesicles is nearly constant. The structure of surfactant vesicles maintains against temperature change ranging from 30 degrees C to 45 degrees C, showing no structural change. These results can provide thermally stable surfactant vesicles with various sizes and constant bilayer thickness that may possess a different permeability and may allow the surfactant vesicle to be used in gene or drug delivery for a variety of goods.