Temperature-sensitive nonionic vesicles prepared from Span 80 (sorbitan monooleate)

Different types of nonionic vesicles were prepared from commercial Span 80 (also called sorbitan monooleate), as an inexpensive, biocompatible alternative to conventional phospholipid-based vesicles (liposomes). The vesicles were characterized by different techniques and comparison was made with vesicles formed from POPC (1-palmitoyl-2-oleoyl- sn-glycero-3-phosphocholine) or DOPC (1,2-dioleoyl- sn-glycero-3-phosphocholine). Dynamic light scattering measurements, electron microscopy analyses, and two types of fusion assays indicate that Span 80 vesicles are stable for at least 7 days at 4 or 25 degrees C, while storage at 42 degrees C causes irreversible vesicle fusion. This indicates that Span 80 vesicles are thermoresponsive with vesicle fusion occurring at elevated temperature. This property may be related to headgroup dehydration and is certainly not directly linked to the phase transition temperature (Tm) of the vesicles, since the Tm is below -30 degrees C, as determined by differential scanning calorimetry (DSC). The measured Tm value for Span 80 vesicles is lower than in the case of DOPC or POPC, correlating with a higher fluidity of Span 80 vesicles as compared to POPC or DOPC vesicles, as determined with DPH (1,6-diphenyl-1,3,5-hexatriene) as fluorescent membrane probe. High fluidity correlates with increased leakage of entrapped water-soluble dye molecules. Addition of cholesterol and soybean phosphatidylcholine lowers the extent of leakage, allowing a tuning of the bilayer permeability.     

Analysis of sorbitan ester surfactants. Part I: High performance liquid chromatography

Sorbitan ester surfactants are very complicated mixtures. An improved and simple reversed phase high performance liquid chroma tographic (HPLC) method employing a C₁₈ column has been developed for the rapid separation of sorbitan ester surfactants and the quantitative determination of the distribution of sorbitan mono-, di-, tri-, and tetraester fractions. The sorbitan ester distribution of the six Span and Arlacel surfactants studied was calculated using relative response factors obtained from analysis of pure glycerides of fatty acids. The effects of mobile phase composition on the accuracy and reliability of the distribution values calculated for the sorbitan esters were investigated.     

Effects of sorbitan monooleate on the interactions between cyclopentane hydrate particles and water droplets

The effects of a typical anti-agglomerant, sorbitan monooleate (Span80), on the interactions between cyclopentane (CyC5) hydrate particles and water droplets were investigated using a micromechanical force (MMF) apparatus. The concentration of Span80 in CyC5 was ranged from 0.01?wt% to 1?wt%, and the experimental temperature was set at 1.5°C and 7°C, respectively. The results indicate that the absorption of Span80 on the droplet surface can render the interfaces more stable, preventing hydrate agglomeration. When the preload/contact force exceeds the strength of the interface (相似文献   

Understanding the role of surfactants on the preparation of ZnS nanocrystals

We have synthesized surface modified ZnS nanoparticles of size 2-3 nm using non-ionic surfactant-stabilized reverse emulsions. The non-ionic surfactants in the Span series, i.e. sorbitan monolaurate (Span 20) and sorbitan monooleate (Span 80) of hydrophilic-lipophilic balance (HLB) values of 8.6 and 4.3, respectively, have been used for the stabilization of emulsions. The role of these surfactants in controlling the size and properties of the ZnS nanoparticles has been discussed. The triethylamine (TEA) has been proved to be the effective surface modifying (capping) agent for the preparation of free-standing ZnS nanoparticles. The Span 20 with the higher HLB value of 8.6 has been found to be highly suitable in synthesizing TEA-capped ZnS nanoparticles of smaller size and higher photophysical characteristics compared to that of the Span 80 of lower HLB value of 4.3. A mechanism for the formation of TEA-capped ZnS nanoparticles from the surfactant-stabilized reverse emulsions has been proposed.     

淀粉/丙烯酸反相乳液体系的稳定性研究

以丙烯酸(AA)单体的水溶液为水相,液体石蜡为油相,失水山梨醇三油酸酯(Span 85)和辛基苯基聚氧乙烯醚(Opan 10)为复合乳化剂,合成了淀粉/丙烯酸反相乳液;考察了乳化剂亲水亲油平衡值(HLB值)、油水比、乳化剂用量、单体浓度、温度对乳液稳定性和类型的影响.结果表明,合成淀粉/丙烯酸稳定反相乳液体系的适宜条件...     

Preparation of hemispherical polyimide particles by inverse emulsion technique from poly(amic acid) ammonium salts

Nonspherical polymer particles have attracted increasing attention recently. In this paper, micron-scale hemispherical polyimide (PI) particles were fabricated using water-soluble poly(amic acid) ammonium salts (PAAS) by a novel inverse emulsion technique. In the process, liquid paraffin was used as a continuous phase, the mixed solution of PAAS and water as a dispersed phase and sorbitan monooleate (Span80) as a surfactant. The research suggested that water as a stabilizing agent played an important role in forming stable emulsion. As the amount of water increased, stability of the emulsion increased gradually and morphology of PI particles transformed from sphere to ellipsoid, and finally to hemisphere. The concentration of PAAS solution and Span80 both affected the shape of particles, which changed from spherical to hemispherical by increasing the PAAS/Span80 concentration. The mechanism of forming hemispherical PI particles was discussed based on interfacial tension and interfacial free energy changes. Via adjusting the composition of the system to change the corresponding interfacial tension, we could get the particles with different morphologies. Furthermore, the change in structure characterized by FT-IR spectroscopy demonstrated that PAAS had been converted to PI after adding the dehydrating agent to the emulsion. And TGA results showed that the obtained PI particles had excellent thermal stability.     

Nonlinear viscoelasticity of sorbitan tristearate monolayers at liquid/gas interface

The interfacial rheology of sorbitan tristearate monolayers formed at the liquid/air interface reveal a distinct nonlinear viscoelastic behavior under oscillatory shear usually observed in many 3D metastable complex fluids with large structural relaxation times. At large strain amplitudes (gamma), the storage modulus (G') decreases monotonically whereas the loss modulus (G') exhibits a peak above a critical strain amplitude before it decreases at higher strain amplitudes. The power law decay exponents of G' and G' are in the ratio 2:1. The peak in G' is absent at high temperatures and low concentration of sorbitan tristearate. Strain-rate frequency sweep measurements on the monolayers do indicate a strain-rate dependence on the structural relaxation time. The present study on sorbitan tristearate monolayers clearly indicates that the nonlinear viscoelastic behavior in 2D Langmuir monolayers is more general and exhibits many of the features observed in 3D complex fluids.     

Micromechanical adhesion force measurements between tetrahydrofuran hydrate particles

Adhesion forces between tetrahydrofuran (THF) hydrate particles in n-decane were measured using an improved micromechanical technique. The experiments were performed at atmospheric pressure over the temperature range 261-275 K. The observed forces and trends were explained by a capillary bridge between the particles. The adhesion force of hydrates was directly proportional to the contact force and contact time. A scoping study examined the effects of temperature, anti-agglomerants, and interfacial energy on the particle adhesion forces. The adhesion force of hydrates was found to be directly proportional to interfacial energy of the surrounding liquid, and to increase with temperature. Both sorbitan monolaurate (Span20) and poly-N-vinyl caprolactam (PVCap) decreased the adhesion force between the hydrate particles.     

Application of liquid chromatography in polymer non-ionic antistatic additives analysis

This article investigates the applicability of HPLC-UV, ultra performance LC-evaporative light-scattering detection (UPLC-ELSD), HPLC-ESI(+)-MS and HPLC-hybrid linear ion trap (LTQ) Orbitrap MS for the analysis of different non-ionic antistatic additives, Span 20, Span 60, Span 65, Span 80, Span 85 (sorbitan fatty acid esters), Atmer 129 (glycerol fatty acid ester) and Atmer 163 (ethoxylated alkylamine). Several alkyl chain length or different degrees of esterification of polyol derivatives can be present in commercial mixtures of these polymer additives. Therefore, their identification and quantification is complicated. Qualitative composition of the studied compounds was analysed by MS. HPLC-UV, UPLC-ELSD and HPLC-LTQ Orbitrap MS methods were applied to the quantitative determination of the different Spans, Atmer 129 and Atmer 163, respectively. Quality parameters of these methods were established and no derivatization was necessary.     

Small-Angle Neutron Scattering Study of Nonionic Surfactant Micelles and Phase Transitions in w/o Microemulsion

The structure of micelles formed by a four component water-in-oil nonionic microemulsion surfactant polyoxyethene (20) sorbitan monoleate (Tween 80), sorbitan monolaurate (Span 20) at ethyl oleate and deuterated water interface have been probed by small-angle neutron scattering (SANS). The total surfactant concentration in each of the samples studied (Tween 80: Span 20) is fixed at 3:2. The deuterated water content is variable at 5–60% w/w. The experimental SANS data from all the seven samples are fit well by spherical micelles interacting with hard sphere potential. Increased deuterated water leads to spherical to lamellar and rod-like micelle geometry featured in the SANS scattering data. The observed change in micelle geometry supports the characterization of phase transition between the self-assembled micelles of the nonionic microemulsion.      

Poly(methyl methacrylate) hollow particles by water-in-oil-in-water emulsion polymerization

Poly(methyl methacrylate) particles having hollow structures were produced by water-in-oil-in-water (W/O/W) emulsion polymerization where sorbitan monooleate (Span80) was used as a primary surfactant and sodium laurylsulfate and Glucopen (APG, polypeptide derivative) were used as secondary surfactants. Urethane acrylate having a molecular structure with a hard segment in the molecular backbone, a long soft segment in the middle, and vinyl groups at both ends was employed as a reactive viscosity enhancer. At low concentration of urethane acrylate, only a few particles contained a void in the polymer phase. However, as the concentration of urethane acrylate increased, the number of the particles containing the void increased. This was because urethane acrylate increased the viscosity of the monomer mixture and helped to form the stable W/O/W emulsion droplets, which possibly restricted droplet coalescence during emulsion polymerization. Moreover, at high concentration of urethane acrylate (above 7 wt%), multi-hollow-structured particles were obtained. It is believed that the increase in the lyophilicity of the monomer mixture caused by urethane acrylate led to stronger interfacial activity of the primary surfactant (Span80) and finally resulted in many internal aqueous droplets. Received: 31 July 1998 Accepted: 13 October 1998     

Synthesis of zinc borate by inverse emulsion technique for lubrication

Lubricating oil additives based on boron compounds are promising materials for lubrication due to their tribological advantages such as antiwear efficiency, good film strength, and high temperature resistance. This article deals with the preparation of zinc borate particles that are well dispersed and colloidally stabilized in mineral oil. This method starts with preparing two inverse emulsions (water-in-oil) with sorbitan monostearate (Span 60) as a surfactant, light neutral oil as a continuous phase, and the aqueous solutions of borax decahydrate (Na₂B₄O₇·10H₂O) and zinc nitrate (Zn(NO₃)₂·6H₂O) as the dispersed phases. The produced particles were zinc borate crystals having both rod-like and spherical morphologies, and the diameters of spherical particles were changing between 20 and 30 nm. FTIR spectra of the obtained particles showed the characteristic peaks of trihedral borate (B(3)-O) and tetrahedral borate (B(4)-O) groups as well as the specific peaks of the sorbitan monostearate. TG showed 30.42% and 22.08% mass loss at 600 °C for the samples prepared by inverse emulsion and precipitation techniques, respectively. The endothermic peak at 50 °C is observed due to the melting of sorbitan monostearate and the heat of melting is evaluated as −3.50 J/g. Tribological studies revealed that sorbitan monostearate not only outperformed as a dispersing agent of inorganic particles, but also it proved to be an anti-wear agent. Zinc borate produced by precipitation decreased the wear scar diameter from 1.402 to 0.639 mm and the friction coefficient from 0.099 to 0.064. The inverse emulsion was effective in decreasing wear scar diameter and the friction coefficient by lowering them to 0.596 and 0.089 mm, respectively.     

Studies on crystallinity state of puerarin loaded solid lipid nanoparticles prepared by double emulsion method

In this work, solid lipid nanoparticles (SLN) have been prepared from water-in-oil-in-water double emulsion, using monocaprate as solid lipid, sorbitan monooleate (Span 80) and polyoxyethylene sorbitan monolaurate (Tween 20) as emulsifier, and puerarin as target drug. The morphology of SLN with drug loaded or not was investigated by the transmission electron microscope (TEM). The crystal order and structure of particles were studied by differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD), respectively. The results indicate that the diameters of SLN with puerarin inside are larger than those without drugs. The analysis of WAXD and DSC shows that the state of crystallinity SLN prepared by double emulsion method was worse than that of SLN prepared by microemulsion. And also the drug-loaded SLN presents a less ordered crystallinity than the drug-free SLN. But both the drug-free and drug-loaded SLN exist in an amorphous state. The reasons of the phenomenon have been discussed.     

Aerosol assisted synthesis of silica/phenolic resin composite mesoporous hollow spheres

Hollow spheres of phenolic resin/silica composite are synthesized by macroscopic phase separation of a sorbitan monooleate surfactant Span 80 during aerosol-assisted spraying. The cavity can be evolved from multiple compartments to single hollow cavity with the increase of Span 80 content. The composite shell becomes mesoporous due to the release of small molecules after thermal treatment above 350 °C. After further thermal treatment at a higher temperature for example 900 °C in nitrogen or 1,450 °C in argon, the carbon/silica composite hollow spheres or crystalline silicon carbide hollow spheres are derived, respectively. Compared to the pure phenolic resin-based carbon spheres, thermal stability of the carbon-based composite spheres in air is essentially improved by the introduction of inorganic component silica. The carbon-based composite hollow spheres combine both performances of easy mass transportation through macropores and high specific surface area of mesopores, which will be promising to support catalysts for fuel cells. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Effects of surfactants on the morphology of composite polymer particles produced by two‐stage seeded emulsion polymerization

Poly(methyl methacrylate) (PMMA)–polystyrene (PS) composite polymer particles were synthesized in the presence of a surfactant by two‐stage seeded emulsion polymerization. The first stage was the synthesis of PMMA particles by soapless emulsion polymerization; the second stage was the synthesis of the PMMA–PS composite polymer particles with the PMMA particles as seeds. In the second stage of the reaction, three kinds of surfactants—sodium laurate sulfate (SLS), polyoxyethylene (POE) sorbitan monolaurate (Tween 20), and sorbitan monolaurate (Span 20)—were used to synthesize the PMMA–PS composite particles. Both the properties and concentrations of the surfactants influenced the morphology of the composite particles significantly. Core–shell composite particles, with PS as the shell and PMMA as the core, were synthesized in the presence of a low concentration of the hydrophilic surfactant SLS. This result was the same as that in the absence of the surfactant. However, a low concentration of Tween 20 led to composite particles with a core/strawberry‐like shell morphology; the core region was a PS phase, and the strawberry‐like shell was a PS phase dispersed in a PMMA phase. With an increase in the concentration of SLS, the morphology of the composite particles changed from core (PMMA)–shell (PS) to core (PS)–shell (PMMA). Moreover, the effects of a high concentration of Tween 20 or Span 20 on the morphology of the PMMA–PS composite particles were investigated in this study. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2224–2236, 2005     

Characterizing colloidal behavior of non-ionic emulsifiers in non-polar solvents using electrical impedance spectroscopy

Colloidal behavior of a widely used non-ionic emulsifier, sorbitan monooleate (Span80), was investigated in non-polar solvents (cyclohexane and xylene) using electrical impedance spectroscopy (EIS). The electrical characteristics of the colloidal mixtures were measured with frequency scans ranging from 1 Hz to 200 kHz. The conductances at low frequencies were found to increase with an increase in Span80 concentration. The source of conductivity for non-polar solvents using non-ionic emulsifiers is usually attributed to ionic impurities either in the Span80 or in the non-polar solvents. The measured electrical characteristics for pure Span80 and pure non-polar solvents revealed that the source of ionic conduction is impurities in Span80. It was confirmed that the ionic impurities in the non-polar solvents are in form of aggregate of ions, ion-pairs, and triple ions which is unaffected with the emulsifier concentration. Analyses using equivalent electrical circuits confirmed that the critical Maxwell-Wagner frequency is 0.6–1.8 Hz for the mixtures. The conductance-concentration profiles for the mixtures at 1 Hz showed transitions from a square root to a linear concentration dependence at the CMC. This indicated that the dissociation model holds below the CMC, while the fluctuation model applies above the CMC. The conductance profiles enabled estimates of the relative hydrophilic core radius and the fraction of charged micelles in both non-polar solvents. Figure

CMC determination of non-ionic emulsifier in non-polar solvents     

Minimum Evaporation Model of Dermatological Delivery Systems. Lamellar Liquid Crystal Formulations Containing Brazilian Nut (Bertholletia excelsa HBK) Vegetable Oil and Guarana Glycolic Extract

Formulations with lyotropic liquid crystals were prepared from a Brazilian nut vegetable oil, guarana extract and combination of sorbitan monooleate (Span 80) and sorbitan monolaurate ethoxylate EO 20 (Tween 20) in the ratio 1:3 (surfactant component) and their physical–chemical aspects and rheological properties were determined. Compositions with liquid crystals were found in the pseudoternary diagram in a surfactant range of 70–90% and polarized light microscopy, small-angle x-ray scattering (SAXS) showed them to be lamellar. The preparations were furthermore characterized rheologically by shear stress shear rate sweeps finding plastic and pseudoplastic behavior without thixotropy. Electric conductivity and pH measurements demonstrated a potential for future application as dermatological delivery system of the active compounds in the Bertholletia excelsa and Paullinia cupana.      

Cationic liposomes modified with non-ionic surfactants as effective non-viral carrier for gene transfer

A defined change in formulation components affects the physical and chemical characteristics of cationic liposomes (CLs) carriers in many ways. Therefore, a great degree of control can be exercised over the structure by modifying the CLs with various materials, leading to new innovations for carrier improvement. In the present study, surface modifications of cationic liposomes with non-ionic surfactants—sorbitan monoesters serials (Span 85, 80, 40 and 20) were carried out for developing a new gene transfer carrier. Span modified cationic liposomes (Sp-CLs) were prepared by reverse phase evaporation method (RPV) and self-assemble complexes of antisense oligonucleotides/surfactant modifying cationic liposomes were prepared by auto-coacervation through electrostatic effect. Characterization of Sp-CLs and the self-assembled complex was performed by electron microscope, particle size, zeta potential, turbidity and agarose electrophoresis. Furthermore, in vitro cellular uptake experiment showed that Span plays a role in enhancing the cellular uptake of encapsulated oligonucleotides mediated by Sp-CLs by the endocytosis-dependent route. CLs modified with Span 40 significantly facilitated the cellular uptake by COS-7 cells and HeLa cells; also showed some positive effect on gene expression. That suggests it is a potential non-viral carrier for efficient gene transfer.     

Spectrophotometric determination of sulfate by solvent extraction with the non-ionic surfactant span 20 and crystal violet

The sulfate ion is extracted into toluene with Span 20 (sorbitan monolaurate) and crystal violet. The calibration graph is linear over the range 2.5 × 10^-5–2.5 × 1O^-4 mol l^-1 sulfate (2.4–24 mg l^-1) in the aqueous phase when the extracted crystal violet is measured at 600 nm. The method is applied to natural waters.     

Effect of Neck Formation on the Measurement of Dynamic Interfacial Tension in a Drop Volume Tensiometer

Dynamic interfacial tension values obtained by drop volume tensiometry will be affected under certain experimental conditions by the formation of a neck between the drop and the capillary tip. This phenomenon must be accounted for to obtain accurate values of interfacial tension. In this work, neck formation for a water–mineral oil system is studied under conditions where hydrodynamic effects can be neglected. A model originally developed for the determination of the surface tension of a suspended drop is modified for application to dynamic interfacial tensions of surfactant-containing liquids. The model relates apparent values of interfacial tension calculated from drops possessing necks to actual values. Experiments with Span 80 (sorbitan monooleate) and sodium dodecyl sulfate (SDS) surfactants in a mineral oil–water system are used to test the validity of the developed model. For the small tip diameter used, good agreement is obtained for Span 80 up to the critical micelle concentration, and for low concentrations of SDS, when the surfactant adsorption is diffusion-limited. In both cases, the neck diameter of the growing drop can be considered constant over the range of dynamic interfacial tensions tested.