Low Molecular Weight Surfactants Research Articles

Carbon quantum dot-based fluorescent vesicles and chiral hydrogels with biosurfactant and biocompatible small molecule.

In recent years, it is heartening to witness that carbon quantum dots (CQDs), a rising star in the family of carbon nanomaterials, have displayed tremendous applications in bioimaging, biosensing, drug delivery, optoelectronics, photovoltaics and photocatalysis. However, the investigations toward self-assembly of CQDs are still in their infancy. The participation of CQDs can bring additional functions to supramolecular self-assemblies, with photoluminescent property as the most exciting aspect. Here, we introduce CQDs into two types of classic colloidal systems containing low molecular weight surfactant and gelator to construct fluorescent vesicles and chiral hydrogels. The CQD-based vesicles were constructed through electrostatic interaction between the positively charged CQDs with peripherally substituted imidazolium cations and a negatively-charged biosurfactant, i.e., sodium deoxycholate (NaDC). The chiral hydrogels were prepared by increasing the concentration of NaDC and addition of a tripeptide (glutathione, GSH). It was found that both the hydrogels and corresponding xerogels are highly photoluminescent. A solid sensing system was prepared by coating a uniform layer of the hydrogel onto the silica gel plates by doctor blade technique followed by air-drying, which was then utilized to semiquantitatively detect Cu2+ in aqueous solutions.

Mezcla de datos de reometría para la curva de flujo de emulsión viscosa de Caballa (Scomber scombrus)

Esta contribución contiene datos asociados con el artículo de investigación titulado "Caracterización reométrica de la emulsión de Caballa (Scomber Scombrus)" (Jaimes et al., 2012) Caballa es un pescado donde la mayoría de sus emulsiones contienen emulsionantes, como proteínas o tensioactivos de bajo peso molecular, sustancias con actividad superficial que tienen la propiedad de ser absorbidas en la interfaz formando una capa que envuelve la gota, por lo tanto, la superficie de tensión entre ambos fluidos se reducen significativamente, lo que facilita la formación de la emulsión y la prolonga. Aquí se presentan los datos de caracterización reológica de una emulsión Scomber Scombrus que se exponen mediante una reometría de mezcla que muestra el consumo de energía de la emulsión durante la mezcla con el agitador de ancla y el agitador de tipo cinta helicoidal.

A review of shampoo surfactant technology: consumer benefits, raw materials and recent developments.

Surfactants form the core of all shampoo formulations, and contribute to a wide range of different benefits, including cleansing, foaming, rheology control, skin mildness and the deposition of benefit agents to the hair and scalp. The purpose of this review was to assist the design of effective, modern, shampoo surfactant technologies. The mechanisms through which surfactants help deliver their effects are presented, along with the appraisal techniques through which surfactant options can be tested and screened for product development. The steps that should be taken to select the most appropriate blend of surfactants are described, and useful information on the most widely used surfactants is provided. The review concludes with an examination of recent developments in 'greener' surfactants, 'sulphate-free' technologies and structured liquid phases for novel sensory properties and for suspending benefit agents.

Competitive adsorption of lysozyme and non-ionic surfactants (Brij-35 and pluronic P123) from a mixed solution at water-air and water-xylene interfaces

The adsorption of lysozyme in the presence of high molecular weight (pluronic P123) and low molecular weight (Brij-35) non-ionic surfactants was studied at liquid-liquid and liquid-air interfaces. Using tritium-labeled compounds and liquid scintillation spectrometry of tritium, we investigated the competitive adsorption of lysozyme-pluronic P123 and lysozyme-Brij-35 at the aqueous-xylene interface. The substitution of protein by both polymer and low molecular weight surfactant was observed, while the presence of lysozyme does not influence the behavior of non-ionic molecules. We found that the ionic strength of the aqueous phase does not influence the strength of the effect, while it has a significant influence on the rate of diffusion and penetration of the adsorption layer by free protein. The thermodynamics of the competitive adsorption was described by the model suggested by Fainerman and co-authors, and the obtained parameters were used to describe the interfacial tension isotherms of the respective mixtures at the aqueous-air interface. Thus, the adsorption of each component of the mixture (protein and non-ionic surfactant) at the aqueous-air interface was revealed.

Nanomanufacturing through microfluidic-assisted nanoprecipitation: Advanced analytics and structure-activity relationships

We have employed microfluidics (cross-shaped chip) for the preparation of drug-loaded poly(lactic acid-co-glycolic acid) (PLGA) nanoparticles. The polymer precipitates from an acetone solution upon its controlled laminar mixing (flow focusing) with an aqueous solution of a surfactant, allowing for an operator-independent, up-scalable and reproducible preparative process of nanoformulations.Firstly, using PEGylated surfactants we have compared batch and microfluidic processes, and showed the superior reproducibility of the latter and its strong dependency on the acetone/water ratio (flow rate ratio). We have then focused on the issue of purification from free surfactant, and employed advanced characterization techniques such as flow-through dynamic light scattering as the in-line quality control technique, and field flow fractionation (FFF) with dynamic and static light scattering detection, which allowed the detection of surfactant micelles in mixture with nanoparticles (hardly possible with stand-alone dynamic light scattering). Finally, we have shown that the choice of polymer and surfactant affects the release behaviour of a model drug (paclitaxel), with high molecular weight PLGA (RG756) and low molecular weight surfactant (tocopheryl poly(ethylene glycol) 1000 succinate, TPGS) apparently showing higher burst and accelerated release.

Influence of hydroxypropyl methylcellulose, methylcellulose, gelatin, poloxamer 407 and poloxamer 188 on the formation and stability of soybean oil-in-water emulsions

Macromolecules of polysaccharides, proteins and poloxamers have a hydrophobic portion and a hydrophilic one that can be used as emulsifiers. Parts of these emulsifiers are safe pharmaceutical excipients, which can replace the irritant low molecular weight surfactants to formulate emulsions for the pharmaceutical field. This project focused on preparing O/W emulsions stabilized with polymers for pharmaceuticals such as polysaccharides, proteins and poloxamers, including hydroxypropyl methylcellulose (HPMC), methylcellulose (MC), gelatin, poloxamer 407 (F127) and poloxamer 188 (F68). Emulsion physical stability was assessed by centrifugation, autoclaving sterilization and droplet size measurements. The stabilization mechanisms of emulsions were determined by interfacial tension and rheological measurements. Results stated that the efficacy of these polymers for pharmaceuticals stabilized emulsions was sorted in the order: F127 > F68 > HPMC > MC > Gelatin.

The effect of surfactant crystallization on partial coalescence in O/W emulsions

Partial coalescence is a ubiquitous instability in emulsions whose dispersed phase is partially crystallized. When emulsions are stabilized with proteins, interfacial stiffness and long-range repulsive surface forces hinder this type of instability. The addition of low molecular weight surfactants modifies the interfacial properties and surface forces, generally promoting partial coalescence. In the present work, various surfactants (Tween® 80, palmitic acid and monoglycerides) differing in their crystallization temperature were probed for their ability to induce partial coalescence in model O/W emulsions stabilized by sodium caseinate. The initially fluid emulsions were submitted to a tempering cycle leading to the gelation of the system. The extent of partial coalescence was evaluated by measuring the bulk storage modulus. DSC was used to determine the melting range of the oil phase and surfactants, while polarized microscopy, Raman imaging, and surface rheology measurements were performed to characterize the oil/water interface. The experimental conditions in terms of droplet size, surfactant-to-protein molar ratio and tempering history favoring partial coalescence were first explored in presence of Tween® 80. We show that partial coalescence is rather marginal when crystallizable surfactants are added, and pronounced with liquid surfactants. The phenomena underlying this result, especially interfacial crystallization of surfactants, are evidenced and discussed.

Cubosomes from hierarchical self-assembly of poly(ionic liquid) block copolymers

Cubosomes are micro- and nanoparticles with a bicontinuous cubic two-phase structure, reported for the self-assembly of low molecular weight surfactants, for example, lipids, but rarely formed by polymers. These objects are characterized by a maximum continuous interface and high interface to volume ratio, which makes them promising candidates for efficient adsorbents and host-guest applications. Here we demonstrate self-assembly to nanoscale cuboidal particles with a bicontinuous cubic structure by amphiphilic poly(ionic liquid) diblock copolymers, poly(acrylic acid)-block-poly(4-vinylbenzyl)-3-butyl imidazolium bis(trifluoromethylsulfonyl)imide, in a mixture of tetrahydrofuran and water under optimized conditions. Structure determining parameters include polymer composition and concentration, temperature, and the variation of the solvent mixture. The formation of the cubosomes can be explained by the hierarchical interactions of the constituent components. The lattice structure of the block copolymers can be transferred to the shape of the particle as it is common for atomic and molecular faceted crystals.

Characterization of O/W Emulsions Prepared by PEG-Diisostearate Amphiphilic Random Copolymer.

We have characterized an emulsion system stabilized by an amphiphilic random copolymer, methoxy polyethylene glycol-23 methacrylate/glyceryl diisostearate methacrylate copolymer (MPM-GDM). The combined results of the static surface tension and transmission electron microscopy with freeze-fracture technique (FF-TEM) suggested that this copolymer forms aggregates in aqueous solutions. The membrane emulsification method produced an oil-in-water (O/W) emulsion in the mixture of squalane, water, and MPM-GDM, where the squalane concentration was set at 10 - 60 wt% and the MPM-GDM concentration was either 1 or 5 wt%. The prepared emulsion was stable against coalescence due to the formation of an adsorption layer of MPM-GDM. Based on the FF-TEM results, it is confirmed that a relatively large island-like structure is formed on the emulsion droplet surface. Furthermore, MPM-GDM can act as a thickening agent of the continuous liquid phase, which enhances the stability against creaming. The cooperative two effects improve the stability of the emulsion system without adding co-stabilizer such as low molecularweight surfactants.

Copolymer based on lauryl methacrylate and poly(ethylene glycol) methyl ether methacrylate as amphiphilic macrosurfactant: Synthesis, characterization and their application as dispersing agent for carbon nanotubes

The use of amphiphilic macrosurfactants as emulsifying agents has shown to have higher efficiency than that of low molecular weight surfactants. Compared to traditional surfactants, polymeric surfactants have lower critical micelle concentrations and lower diffusion coefficients. In this paper, we present a well defined copolymer based on lauryl methacrylate and poly(ethylene glycol) methyl ether methacrylate, prepared by solution radical copolymerization. The product was characterized by NMR and FTIR spectroscopies and the weight-average molecular weight and polydispersity index were analyzed by SEC. The thermal transitions and decomposition temperatures of the copolymers were determined by DSC and TGA, respectively. Due to the hydrophobic and hydrophilic nature of the monomer units, emulsification studies were performed. DLS experiments showed different sizes of the formed micelles depending on solvent polarity due to polymer-polymer or polymer-solvent interactions. Rheological characterization was undertaken to study the viscoelastic properties of the dispersed systems. Finally, two types of experiments to evaluate the polymer abilities as surfactant have been carried out. Firstly, the amphiphilic characteristics of this material allowed the incorporation of small amounts of an organic solvent in water forming only one phase, as well as the incorporation of small amounts of water in the organic solvent forming an emulsified phase. Then, the amphiphilic properties of this macrosurfactant have been fully exploited in order to form highly stable dispersions of carbon nanotubes in water.

Constructing a molecular theory of self-assembly: Interplay of ideas from surfactants and block copolymers

Low molecular weight surfactants and high molecular weight block copolymers display analogous self-assembly behavior in solutions and at interfaces, generating nanoscale structures of different shapes. Understanding the link between the molecular structure of these amphiphiles and their self-assembly behavior has been the goal of theoretical studies. Despite the analogies between surfactants and block copolymers, models predicting their self-assembly behavior have evolved independent of one another, each overlooking the molecular feature considered critical to the other. In this review, we focus on the interplay of ideas pertaining to surfactants and block copolymers in three areas of self-assembly. First, we show how improved free energy models have evolved by applying ideas from surfactants to block copolymers and vice versa, giving rise to a unitary theoretical framework and better predictive capabilities for both classes of amphiphiles. Second we show that even though molecular packing arguments are often used to explain aggregate shape transitions resulting from self-assembly, the molecular packing considerations are more relevant in the case of surfactants whereas free energy criteria are relevant for block copolymers. Third, we show that even though the surfactant and block copolymer aggregates are small nanostructures, the size differences between them is significant enough to make the interfacial effects control the solubilization of molecules in surfactant micelles while the bulk interactions control the solubilization in block copolymer micelles. Finally, we conclude by identifying recent theoretical progress in adapting the micelle model to a wide variety of self-assembly phenomena and the challenges to modeling posed by emerging novel classes of amphiphiles with complex biological, inorganic or nanoparticle moieties.

Competition of Thermomyces lanuginosus lipase with its hydrolysis products at the oil–water interface

Lipase–catalyzed hydrolysis of triglycerides yields glycerol and free fatty-acids, provided that the enzyme is non-regioselective. For an Sn-1,3 regioselective enzyme, such as lipase from Thermomyces lanuginosus, the final product is no longer glycerol but Sn-2 monoglyceride instead. However, surface active molecules generated by lipolysis may have a detrimental effect on the interfacial biocatalysis since it is known that low molecular weight surfactants can displace proteins from interfaces. By using drop profile analysis tensiometry, we evaluated the interfacial properties of the lipase–generated molecules and their competitive effect on the adsorption behavior of the lipase and on the proceeding lipolysis. Our results show that even at concentration ratios of 8.64×10−4M (Sn-2 monoglyceride) to 2.5×10−7M (lipase), the final interfacial pressure values are very similar as for the system containing the lipase alone (i.e. ∼26 mN/m). This is a strong indication that monoglycerides, as the most interfacially active products generated during regioselective lipolysis, are expelled from the oil–water interface by the lipase. We attribute this effect to intermolecular lipase–lipase interactions, resulting in a low desorption probability of the lipase. For low oleic acid concentrations, the interfacial tension is solely determined by the lipase, while for higher concentrations, lipase and oleic acid both contribute to the tension values. We propose a hypothesis based on the preferential interaction of oleic acid molecules with hydrophobic sites on the lipase. The pH dependence of the adsorption rate and the interfacial activity of the lipase were also investigated.

Forced dewetting dynamics of high molecular weight surfactant solutions

The dewetting behavior of surfactant solutions differs from pure liquids due to the possibility of generating Marangoni stresses near the receding contact line. Specifically, for surfactant solutions the dynamic receding contact angle decreases much stronger with increasing dewetting speed than of pure liquids with similar viscosity and surface tension. To gain a better understanding of the correlation between the dynamics of dewetting and the properties of the surfactants (e.g. surface activity, micelle formation, surface rheology) we compare high molecular weight surfactants to low molecular weight surfactants. We investigate the forced wetting of aqueous solutions of Pluronic F-127 (a {poly-ethylene-oxide}-{poly-propylene-oxide}-{poly-ethylene-oxide} triblock copolymer), with a molecular weight of Mw=12kg/mol, roughly 50 times larger than an average size surfactant, like cetyltrimethylammonium bromid (CTAB). Pluronic F-127 is more surface active than CTAB and already a nanomolar concentration affects the surface tension. Similar to smaller surfactants Pluronic F-127 decreases the dynamic receding contact angle. However, the change in the dynamic receding contact angle is more pronounced. In case of Pluronic F-127 already concentrations below 0.1 %CMC (critical micelle concentration) led to a substantial decrease in dynamic receding contact angle. With a combination of dewetting experiments, surfaces rheology and bulk measurements of aggregate concentrations, we show that the concentration of full surface coverage (CFSC) is the relevant concentration scale. Only in the case of low molecular weight surfactant this concentration is close to the critical micelle concentration (CMC). In the case of Pluronic F-127 the CFSC and the CMC differ by about three orders of magnitude.

Mixtures of saponins and beta-lactoglobulin differ from classical protein/surfactant-systems at the air-water interface

Interactions between surfactants and proteins have been intensively studied in the past because their interactions in food and cosmetic products can tremendously alter the product properties. Recent studies have shown that Quillaja saponins (QS) have very different interfacial properties in comparison to common low-molecular weight surfactants. It was reported that QS forms highly elastic interfacial films, adsorbs more slowly to the interface and cannot as easily be classified as an ionic or non-ionic surfactant. However, the mechanism of interaction between QS and proteins like beta-lactoglobulin (β-LG) is still to be understood. For this purpose the present study aimed to explore the interactions between Quillaja saponin and beta-lactoglobulin in the bulk and at the air/water-interface. At this purpose, interfacial properties were characterized with dynamic interfacial tension, short-term adsorption, shear and dilational oscillation experiments and the results were compared to foam properties. To study molecular interactions fluorescence quenching was analyzed and sequential two-fluid needle experiments were performed to get more insights on depletion of β-LG by QS.The presence of β-LG lowered the dilational viscoelasticity of the mixed films. Although the interfacial film was weakened by β-LG the dilational elasticity was still very high and did not result in reduced foam stability. Interfacial shear results suggest that QS and β-LG can interact at the interface probably through hydrogen bonds and/or hydrophobic interactions. We determined 1.7 binding sites on β-LG in the bulk which are accessible for complex formation for QS by fluorescence quenching experiments. The findings of this work can contribute to a better understanding of the properties of complex systems with mixtures of natural surfactants and proteins.

The Mechanism of Metal Dispersion in the Presence of a Solid-Phase High Molecular Compound

The mechanism of dispersion of metals in the presence of high molecular compounds is shown on the example of grinding high speed R6M5 steel swarf. It was shown that metal pulverization is more energetically favorable in the presence of a mechanically degradable polymer than in the presence of low-molecular weight surfactants.

The effect of ultrasound upon the physicochemical and emulsifying properties of wheat and soy protein isolates

The effect of ultrasound upon the physicochemical and emulsifying performance of wheat protein isolate (WhPI) and soy protein isolate (SPI) was investigated. Protein solutions (0.1–3 wt. %) were sonicated with an acoustic intensity of ∼34 W cm−2 for 2 min. The physicochemical properties were assessed in terms of changes in protein aggregate size, hydrodynamic volume and molecular structure. The emulsifying performance of ultrasound treated WhPI and SPI was compared to their untreated counterparts, and a low molecular weight surfactant, Tween 80, for comparative purposes. Ultrasonic processing significantly reduced the aggregate size of both proteins, whilst no reduction in the primary structure molecular weight profile was observed in both instances, ascribed to insufficient energy to hydrolyse the peptide bond. Emulsions prepared with both untreated proteins yielded submicron emulsion droplets (∼150 nm) at concentrations ≥ 0.75 wt. %. Emulsions fabricated with both sonicated proteins at concentrations <0.75 wt. % demonstrated significantly (P < 0.05) smaller emulsion droplets and long term emulsion stability in comparison to their untreated counterparts. This effect is consistent with the observed reduction in the equilibrium value of interfacial tension between untreated and ultrasound treated proteins.

Aqueous dispersions of cross-linked poly-N-vinylcaprolactam stabilized with hydrophobically modified polyacrylamide: synthesis, colloidal stability, and thermosensitive properties

Temperature-responsive nanoparticles of cross-linked poly-N-vinylcaprolactam (microgels), stabilized by high molecular weight emulsifier—monohelic hydrophobically modified polyacrylamide—have been synthesized in oil-in-water emulsion. Nanodispersions of spherical particles of about 100 nm in size rather narrowly distributed as defined by dynamic light scattering and TEM and AFM microscopy were stable in time. Electrokinetic potential, which depended on pH, revealed negative charges on nanoparticle surface arisen from hydrolysis of amide groups of polymer-stabilizer. Due to electrosterical stabilization caused by the adsorption of weakly charged polymeric stabilizer, the prepared dispersions exhibited higher stability against an action of electrolytes as compared with sols stabilized with low molecular weight surfactants. The prepared microgels exhibited high stability at high temperatures.

Influence of formulation on the oxidative stability of water-in-oil emulsions

The oxidation of water-in-oil (W/O) emulsions was investigated, emphasizing the impact of compositional parameters. The emulsions had approximately the same average droplet size and did not show any physical destabilization throughout the study. In the absence of pro-oxidant ions in the aqueous phase, lipid oxidation of the W/O emulsions was moderate at 60°C and was in the same range as that measured for the neat oils. Oxidation was significantly promoted by iron encapsulation in the aqueous phase, even at 25°C. However, iron chelation reduced the oxidation rate. Emulsions based on triglycerides rich in polyunsaturated fatty acids were more prone to oxidation, whether the aqueous phase encapsulated iron or not. The emulsions were stabilized by high- and low-molecular weight surfactants. Increased relative fractions of high molecular weight components reduced the oxidation rate when iron was present.

Ancillary effects of surfactants on filtration of low molecular weight contaminants through cellulose nitrate membrane filters

Abstract Removal of contaminants with low molecular weight ( The ancillary effects created by anionic (sodium dodecyl sulfate, SDS), cationic (hexadecyltrimethyl ammonium bromide, CTAB) and non-ionic (ethoxylated octylphenol, TX-100) surfactants on the mechanism and efficiency of the filtration process were investigated in this study. Methylene blue (MB) and cellulose nitrate membrane (CNM) filters were employed as model retentate and the separation medium. A combination of surface tension, contact angle and charge measurements demonstrated that the addition of surfactants had a remarkable effect on the filtration outcome. The effect depended on both the type and concentration of the surfactant and was manifested mainly through the creation of MB-surfactant entities which acted differently than the MB alone; but more importantly, through the interactions of the surfactant molecules/micelles and the MB-surfactant pairs with the separation membrane.

An evaluation of the adhesion of solid oral dosage form coatings to the oesophagus

There is a requirement for the development of oral dosage forms that are adhesive and allow extended oesophageal residence time for localised therapies, or are non-adhesive for ease of swallowing. This study provides an initial assessment of the in vitro oesophageal retention characteristics of several widely utilised pharmaceutical coating materials. To this end, a previously described apparatus has been used to measure the force required to pull a coated disc-shaped model tablet across a section of excised oesophageal tissue. Of the materials tested, the well-studied mucoadhesive polymer sodium alginate was found to be associated with significant oesophageal adhesion properties that was capable of ‘self-repairing’. Hydroxypropylmethylcellulose exhibited less pronounced bioadhesive behaviour and blending this with plasticiser or with low molecular weight polymers and surfactants did not significantly affect this. Low molecular weight water soluble polymers, were found to behave similarly to the uncoated glass control disc. Polysorbates exhibited bioadhesion behaviour that was majorly influenced by the nature of the surfactant. The insoluble polymer ethylcellulose, and the relatively lipophilic surfactant sorbitan monooleate were seen to move more readily than the uncoated disc, suggesting that these may have a role as ‘easy-to-swallow’ coatings.