Small Surfactant Research Articles

Surfactant spreading on liquid films in the Stokes regime

Characterizing the spreading of surfactants on the surface of a liquid film is central to our understanding of natural and technological processes ranging from cell propulsion and drug delivery in pulmonary airways to cleaning food processing surfaces. In this work, we analyze the spreading dynamics of a drop of insoluble surfactants in a perfectly viscous (i.e., Stokes) regime. Using simple scaling arguments, we estimate that the size of a small surfactant drop grows as a power-law with time with an exponent of 1/3. The estimated scaling is then corroborated and better characterized using direct numerical simulations. Furthermore, the simulation results help establish the transition from the initial 1/3 scaling with time to the later 1/4 scaling that is expected when the spreading drop grows larger than the film thickness.

α-Cyclodextrin-based poly(pseudo)rotaxane for antifungal drug delivery to the vaginal mucosa

This work aimed to evaluate poly(pseudo)rotaxanes (PPRs) potential for vaginal antifungal delivery. For this, PPRs containing terbinafine (TB) 2 % were obtained using two small surfactants, Kolliphor® RH40 and Gelucire® 48/16, and different α-cyclodextrin (α-CD) concentrations (5 and 10 %). PPRs were characterized by their physicochemical characteristics, irritation, and mucoadhesion capabilities. Formulations' performance was assessed in a vertical penetration model, which uses ex vivo entire porcine vagina. Conventional penetration experiments with excised vaginal tissue were performed as a control. Results showed all formulations were non-irritant according to the HET-CAM test. Furthermore, PPRs with 10 % αCD showed superior mucoadhesion (p < 0.05). Conventional horizontal penetration studies could not differentiate formulations (p > 0.05). However, PPRs with 10 % αCD presented a better performance in vertical ex vivo studies, achieving higher drug penetration into the vaginal mucosa (p < 0.05), which is probably related to the formulation's prolonged residence time. In addition, the antifungal activity of the formulations was maintained against Candida albicans and C. glabrata cultures. More importantly, the formulation's viscosity and drug delivery control had no negative impact on the antifungal activity. In conclusion, the best performance in a more realistic model evidenced the remarkable potential of PPRs for vaginal drug delivery.

Effect of a soluble surfactant on the linear stability of two-phase flows in a finite-length channel

We study numerically the effect of a soluble surfactant on the stability of two-phase flow in a finite-length microchannel. The two streams drag the surfactant molecules toward the downstream end of the interface against the action of the Marangoni stress. The sharp reduction of the interfacial tension at that end enhances the interface deformation and considerably destabilizes the system, translating into a sharp reduction of the critical capillary number even for very small surfactant volume concentrations.

Effect of small molecular surfactants on physical, turbidimetric, and rheological properties of Pickering nanoemulsions stabilized with whey protein isolate

In the present study, Pickering nanoemulsions (oil-in-water) co-stabilized with whey protein isolate (WPI) and three types of small molecular surfactants were prepared. Hexadecyltrimethylammonium (CTAB), sodium dodecyl sulfate (SDS), and Tween 20 were used as cationic, anionic, and nonionic surfactants, respectively. To investigate effects of small molecular surfactants on physical stability, turbidimetric, and rheological properties of protein-stabilized Pickering nanoemulsions, various treatments mimicking food processing including pH, heat, freeze-thaw, and salt were applied. Results revealed that the droplet size and polydispersity index of the nanoemulsion prepared with WPI alone were increased after heat treatment or at pH condition near the isoelectric point of WPI, indicating a low physical stability. However, nanoemulsions prepared with WPI-SDS or WPI-CTAB maintained their initial state even after heat treatment including autoclave. Furthermore, there was no significant change in the droplet size of the nanoemulsion prepared with WPI-Tween after freeze-thaw and salt treatments. Although Pickering nanoemulsion stabilized with both WPI and SDS had the highest viscosity, Turbiscan stability index (TSI) was the highest. However, the TSI of the nanoemulsions added with CTAB or Tween 20 was lower than that of the nanoemulsions prepared with WPI alone, confirming that the storage stability of protein-stabilized Pickering nanoemulsion was improved by adding small molecular surfactants.

Emulsion Stabilization by Cationic Lignin Surfactants Derived from Bioethanol Production and Kraft Pulping Processes.

Oil-in-water bitumen emulsions stabilized by biobased surfactants such as lignin are in line with the current sustainable approaches of the asphalt industry involving bitumen emulsions for reduced temperature asphalt technologies. With this aim, three lignins, derived from the kraft pulping and bioethanol industries, were chemically modified via the Mannich reaction to be used as cationic emulsifiers. A comprehensive chemical characterization was conducted on raw lignin-rich products, showing that the kraft sample presents a higher lignin concentration and lower molecular weight. Instead, bioethanol-derived samples, with characteristics of non-woody lignins, present a high concentration of carbohydrate residues and ashes. Lignin amination was performed at pH = 10 and 13, using tetraethylene pentamine and formaldehyde as reagents at three different stoichiometric molar ratios. The emulsification ability of such cationic surfactants was firstly studied on prototype silicone oil-in-water emulsions, attending to their droplet size distribution and viscous behavior. Among the synthetized surfactants, cationic kraft lignin has shown the best emulsification performance, being used for the development of bitumen emulsions. In this regard, cationic kraft lignin has successfully stabilized oil-in-water emulsions containing 60% bitumen using small surfactant concentrations, between 0.25 and 0.75%, which was obtained at pH = 13 and reagent molar ratios between 1/7/7 and 1/28/28 (lignin/tetraethylene pentamine/formaldehyde).

Oil-in-water high-internal-phase poly(styrene-acrylate) Pickering emulsions and their applications as waterborne damping coatings

Herein, we report the synthesis of a series of oil-in-water high-internal-phase Pickering emulsions (HIPEs) within styrene and acrylate as monomer and oil phases, using composite stabilizers containing hydrophobic modified diatomite particles and small molecular surfactants. Internal-phase HIPE levels of up to 80 wt% were achieved, which was far higher than those of conventional emulsions. Meanwhile, the mechanical performance, thermal stabilities, and damping capacities of polymer films prepared using these HIPEs were superior to those of polymer films prepared using conventional emulsions. Synergistic emulsification of the composite stabilizer was found to be crucial for stabilizing the emulsion during HIPE synthesis and for improving the mechanical and damping performance of the polymer films.

Hyperbranched ionic surfactants with polyether skeleton: Synthesis, properties and used as stabilizer for emulsion polymerization

A versatile strategy involves anionic ring-opening polymerization (AROP) and thiol-ene reaction was contributed for the construction of hyperbranched ionic surfactants. A series of hyperbranched surfactants composed of polyether skeleton and various ionic side groups such as anion, cation and zwitterion were synthesized and labeled as HPEanionic, HPEcationic and HPEzwitterionic, respectively. The chemical structures of all the intermediate and final products were verified by means of fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. The surface and interfacial tension reduction performances of three obtained ionic surfactants were systematically investigated. And the results confirmed all the resultant surfactants could effectively reduce the surface and interfacial tension of the solution, and the CMC values were all determined approximately to 0.1 mg/mL. Meanwhile, three surfactants exhibit relatively low Krafft temperatures (below 6 ℃) and good wettability to oil-wetted surface. To further explore their promising applications, HPEanionic was proposed for use as a stabilizer in emulsion polymerization. Dynamic light scattering (DLS) measurements as well as transmission electron microscope (TEM) observation confirmed well-defined latex was obtained indeed. Moreover, as compared to latex synthesized by using the traditional small molecule compound surfactants, latex synthesized using HPEanionic as stabilizer exhibit improved tolerance to salinity. This beneficial result is probably caused by the special hyperbranched structure of HPEanionic, which contributes both electrostatic repulsion and steric hindrance drive force for the stabilization of latex particles.

MAPPING OIL SPILLS ON SEA SURFACE FROM SENTINEL 2 IMAGES USING PRINCIPAL COMPONENTS AND CATEGORICAL BOOSTING

Abstract. A large oil spill in Iloilo Straight that occurred on July 3, 2020, as well as a possible deliberate, small but frequent oil spill and surfactant contamination in Manila Bay, were mapped. The method employs the Sentinel 2-1C image, which is transformed into principal components to reveal the presence of oil spills and possibly surfactants. Additionally, a gradient boosting algorithm was trained to discriminate between pixels that were contaminated with oil and those that were not. The multi-band image with three principal components with a 99% cumulative explained variance ratio highlights the occurrence of an oil spill in Iloilo Straight. Further, the classified image produced by pixel-based classification clearly distinguishes between water and oil pixels in the said area. The methodology was applied to a Sentinel 2-1C image of Manila Bay, with pixels observed/identified as oil and classified as well. The highest density of supposedly oil-contaminated pixels (large or small but frequent) was observed on the eastern side of Manila Bay (Bataan). While there were no documented oil spills concurrent to the satellite image used, historical reports on the area indicate that the likelihood of an oil spill is extremely high due to the massive amount of shipping activity. Pixels supposedly contaminated by oil spills also occur in areas near ports where oil spills could occur as a result of ship operations. Pixels with the same properties as oil contamination are also visible in areas adjacent to fishponds and aquaculture, where phytoplankton and fish contribute to surfactant contamination.

Effect of protein complexation by pectin and small molecular surfactants

Effect of protein complexation by pectin and small molecular surfactants

Back Cover: Cooperative organizations of small molecular surfactants and amphiphilic block copolymers: Roles of surfactants in the formation of binary co‐assemblies

The binary co-assembly systems consisting of amphiphilic block copolymers and surfactants have provided us a versatile platform for materials design and structural regulation. In this review (Article number 2021, e49), Shi, Li, and co-workers comprehensively discussed the main three amphiphilic co-assembly systems and their potential biological applications.

Dextran-Coated Latex Nanoparticles via Photo-RAFT Mediated Polymerization Induced Self-Assembly.

Polysaccharide coated nanoparticles represent a promising class of environmentally friendly latex to replace those stabilized by small toxic molecular surfactants. We report here an in situ formulation of free-surfactant core/shell nanoparticles latex consisting of dextran-based diblock amphiphilic copolymers. The synthesis of copolymers and the immediate latex formulation were performed directly in water using a photo-initiated reversible addition fragmentation chain transfer-mediated polymerization induced self-assembly strategy. A hydrophilic macromolecular chain transfer-bearing photosensitive thiocarbonylthio group (eDexCTA) was first prepared by a modification of the reducing chain end of dextran in two steps: (i) reductive amination by ethylenediamine in the presence of sodium cyanoborohydride, (ii) then introduction of CTA by amidation reaction. Latex nanoparticles were then formulated in situ by chain-extending eDexCTA using 2-hydroxypropyl methacrylate (HPMA) under 365 nm irradiation, leading to amphiphilic dextran-b-poly(2-hydroxypropyl methacrylate) diblock copolymers (DHX). Solid concentration (SC) and the average degree of polymerization -- of PHPMA block (X) were varied to investigate their impact on the size and the morphology of latex nanoparticles termed here SCDHX. Light scattering and transmission electron microscopy analysis revealed that SCDHX form exclusively spherical nano-objects. However, the size of nano-objects, ranging from 20 nm to 240 nm, increases according to PHPMA block length.

Freeze-thaw stability and oil crystallization behavior of phospholipids/whey protein-costabilized acidic emulsions with four oil types

The physical properties and freeze-thaw behavior of mayonnaise-like emulsions prepared from 60% (v/v) olive oil (OLO), peanut oil (PNO), palm oil (PO), and coconut oil (CNO) at pH 3.0 using whey protein isolate (WPI) as the stabilizer and soybean lecithin (SL) or egg lecithin (EL) as supplementary surfactants were investigated. For all oil types, the addition of SL or EL decreased emulsion stability due to partial displacement of WPI at the interface. Nevertheless, both surfactants generally improved the emulsion freeze-thaw stability except for OLO emulsion. The thermometry of fat crystal formation in PNO (Tfat = 0.4 °C), PO (Tfat = 6.6 °C) and CNO (Tfat = −1.4 °C) emulsions was higher than that of ice crystal (Tice = −10 °C) formation. On the other hand, ice crystallization occurred prior to fat crystal formation (Tfat = −14 °C) in OLO emulsions. Upon freezing, serum phase ice crystals protruded into OLO emulsion droplets with a mixed SL-protein thin membrane leading to a reduced stability than WPI-alone emulsion. Compared with SL, EL was more capable of facilitating fine fat crystal formation, and partial fat crystallization generally increased emulsion viscosity. Overall, both small surfactants promoted crystallization behavior and freeze-thaw stability of WPI-based PNO, PO, and CNO emulsions; although slightly less effective than EL, SL showed a strong efficacy in the emulsion system.

Early lung carcinogenesis and tumor microenvironment observed by single-cell transcriptome analysis

With the increasing interest in health screening with chest CT Ground-glass nodule (GGN) has become one of the common lung lesions encountered in daily medical practice. Because lung adenocarcinoma in the form of GGN is an ideal model for studying early lung carcinogenesis, 11 GGN and normal lung specimens from 6 never smoker patients were studied by single-cell RNA sequencing. Lung cancer cells showed enrichment of gene sets related to small vesicle processing and surfactant homeostasis compared to non-malignant lung epithelial cells, suggesting the dysregulation of surfactant pathway may be involved in early lung carcinogenesis. Along with cancer-associated fibroblasts showing enrichment of gene sets involved in negative regulation of protein kinase activity and negative regulation of endothelial cell proliferation, tumor microenvironment (TME) was dominated by infiltration of TNFRSF4+/TNFRSF18+/CTLA4+ regulatory T cells (Treg) and depletion of CD8+ cytotoxic T cells (TC) and γδTC. Majority of mucosa-associated lymphoid tissue B cells (BCs) and follicular BCs were detected within tumor tissue, which was associated with CXCL13 overexpressed in intratumoral Tregs and CD4+ memory TCs. Coordination of components of the TME towards immune evasion is governed by Tregs from the onset of lung cancer, requiring unremitting efforts to target and overcome them. This provision of information on changes in cancer cell-specific biomarkers and TME using early lung cancer from never smokers will provide new insight into early lung carcinogenesis and useful targets for treatment.

Improvement of stability and bioaccessibility of β-carotene by curcumin in pea protein isolate-based complexes-stabilized emulsions: Effect of protein complexation by pectin and small molecular surfactants

The impact of different complexes on the properties of β-carotene-loaded emulsions was investigated by measuring the droplet size, encapsulation efficiency, droplet morphology, and physical stability. The photo and thermal stability of β-carotene and its bioaccessibility during digestion were also analyzed. Comparing to the emulsions stabilized by other complexes, the emulsion stabilized by the high methoxyl pectin-rhamnolipid-pea protein isolate-curcumin (HMP-Rha-PPI-Cur) complex had the smallest droplet size (17.53 ± 0.15 μm) and the maximum encapsulation efficiency for curcumin (90.33 ± 0.03 %) and β-carotene (92.16 ± 0.01 %). The emulsion stabilized by the HMP-Rha-PPI-Cur complex exhibited better physical stability against creaming. The retention rate of β-carotene in the HMP-Rha-PPI-Cur complex-stabilized emulsion was 17.75 ± 0.02 and 33.64 ± 0.02 % after UV irradiation and thermal treatment. The HMP-Rha-PPI-Cur complex-stabilized emulsion also had a higher level of free fatty acid released (43.67 %) and higher bioaccessibility of β-carotene (32.35 ± 0.02 %).

Effect of insoluble surfactants on a thermocapillary flow

The thermocapillary effect, arising flow due to a temperature gradient along a fluid interface, is the dominant effect in some industrial and microfluidic processes and must be studied in order to optimize them. In this work, we analyze how insoluble surfactants adsorbed at the interface can affect such a flow. In particular, we analyze the case where the thermocapillary flow is induced at the air–water interface by locally heating it with an infrared laser, setup that is used to manipulate floating particles through the generated flow. Since water is a polar fluid, the air–water interface is easily polluted by surfactants. We developed a numerical model considering the uncontrolled presence of surfactants, which evidences that the effect of the surface contamination cannot be neglected, even for small surfactants concentration. The results of this numerical model were compared with different experimental measurements: particle tracking velocimetry, convection cell radius measurements, and thermography of the surface. All the experimental observations agree with the numerical model with the initial surface contamination being a fitting parameter. The model was then validated comparing its results with measurements for which a known quantity of surfactant was added to the interface. Finally, an analytical model was developed to explain the effects of the governing parameters, which agrees with the simulations and the experimental results. The developed models give us insight toward the miniaturization of the manipulation platform.

Investigation of pesticide residue removal effect of gelatinized starch using surface-enhanced Raman scattering mapping

This study investigated the effectiveness of gelatinized starch (GS) in the removal of surface and internalized pesticide residues from basil leaves. Surface activity of GS was confirmed by surface tension and fluorescence study. Surface-enhanced Raman scattering (SERS) mapping was applied for in situ and real-time tracking of pesticides over time. Results showed that gelatinized starch has better and safer pesticide removing effect compared to commercial surfactants. Simulation study showed that starch fragment can adjust its three-dimensional conformation according to the size of the guest with ~ four repeating α-1,4-d-glucopyranose residues interacting efficiently with pesticides. However, washing by small molecular weight surfactants will lead to a “secondary contamination” due to its amphilphilic nature and small molecular size, which can escort pesticide deeper into the leaf. Due to the wide availability, easy fabrication, efficient rinsing effect and bio-safety nature, GS should be highly recommended in family practice.

Combination of irreversible electroporation with sustained release of a synthetic membranolytic polymer for enhanced cancer cell killing

Irreversible electroporation (IRE) is used clinically as a focal therapy to ablate solid tumors. A critical disadvantage of IRE as a monotherapy for cancer is the inability of ablating large tumors, because the electric field strength required is often too high to be safe. Previous reports indicate that cells exposed to certain cationic small molecules and surfactants are more vulnerable to IRE at lower electric field strengths. However, low-molecular-weight IRE sensitizers may suffer from suboptimal bioavailability due to poor stability and a lack of control over spatiotemporal accumulation in the tumor tissue. Here, we show that a synthetic membranolytic polymer, poly(6-aminohexyl methacrylate) (PAHM), synergizes with IRE to achieve enhanced cancer cell killing. The enhanced efficacy of the combination therapy is attributed to PAHM-mediated sensitization of cancer cells to IRE and to the direct cell killing by PAHM through membrane lysis. We further demonstrate sustained release of PAHM from embolic beads over 1 week in physiological medium. Taken together, combining IRE and a synthetic macromolecular sensitizer with intrinsic membranolytic activity and sustained bioavailability may present new therapeutic opportunities for a wide range of solid tumors.

Methane Inhalation Protects Against Lung Ischemia-Reperfusion Injury in Rats by Regulating Pulmonary Surfactant via the Nrf2 Pathway.

Methane (CH4) exerted protective effects against lung ischemia-reperfusion (I/R) injury, but the mechanism remains unclear, especially the role of pulmonary surfactant. Therefore, this study aimed to explore the effects of CH4 inhalation on pulmonary surfactant in rat lung I/R injury and to elucidate the mechanism. Rats were randomly divided into three groups (n = 6): the sham, I/R control, and I/R CH4 groups. In the sham group, only thoracotomy was performed on the rats. In the I/R control and I/R CH4 groups, the rats underwent left hilum occlusion for 90 min, followed by reperfusion for 180 min and ventilation with O2 or 2.5% CH4, respectively. Compared with those of the sham group, the levels of large surfactant aggregates (LAs) in pulmonary surfactant, lung compliance, oxygenation decreased, the small surfactant aggregates (SAs), inflammatory response, oxidative stress injury, and cell apoptosis increased in the control group (P < 0.05). Compared to the control treatment, CH4 increased LA (0.42 ± 0.06 vs. 0.31 ± 0.09 mg/kg), oxygenation (201 ± 11 vs. 151 ± 14 mmHg), and lung compliance (16.8 ± 1.0 vs. 11.5 ± 1.3 ml/kg), as well as total antioxidant capacity and Nrf2 protein expression and decreased the inflammatory response and number of apoptotic cells (P < 0.05). In conclusion, CH4 inhalation decreased oxidative stress injury, inflammatory response, and cell apoptosis, and improved lung function through Nrf2-mediated pulmonary surfactant regulation in rat lung I/R injury.

Cooperative organizations of small molecular surfactants and amphiphilic block copolymers: Roles of surfactants in the formation of binary co‐assemblies

AbstractThe construction of highly ordered organizations through self‐assembly is one of the most popular phenomena both in natural and artificial environments. Amphiphilic molecules are the most commonly used building blocks for the self‐assembly, which are conventionally known as amphiphilic low molecular weight surfactants with polar heads and nonpolar tails, or amphiphilic block copolymers (BCPs) consisting of covalently bonded hydrophilic and hydrophobic block chains. Compared with single surfactant self‐assembly system, binary amphiphiles co‐assembly systems composing of both small mass surfactants and amphiphilic BCPs feature high flexibilities and versatilities in materials designing and structure regulation, ascribing to the vast possibilities of intermolecular interactions within the systems and facile component modulations during the assembly processes. The amphiphilic features of the two kinds of molecules endow them with similar self‐assembly behaviors, while the unique and distinct characters of each kind of amphiphiles lead to various complex but highly diversified co‐assembly systems. According to the roles of the surfactant played in the co‐assembly system, in this review, we summarize the binary co‐assembly systems from three distinct types: 1) the co‐micellization system in which the surfactants are added into the BCPs assemblies as a self‐assembly assistant; 2) the co‐emulsification system in which the surfactants work as an emulsion stabilizer to assist and confine the assembly of BCPs in 3D geometries; 3) the co‐templating system where the individual micelles of both surfactant and BCPs are hierarchically arranged and distributed to guide the formation of hierarchical nanomaterials. Following this, the major potential applications of the nanomaterials synthesized from the binary amphiphiles in biological field are described. Finally, we shortly discuss the current challenges and future perspectives of the binary amphiphiles self‐assembly systems.

Surfactant Modeling Using Classical Density Functional Theory and a Group Contribution PC-SAFT Approach

Models for surfactants need to incorporate the amphiphilic character of the molecules to describe key properties such as the adsorption at interfaces and the reduction of interfacial tensions. One possibility is to model the surfactant molecules as heteronuclear chains. Therefore, we revisit the heterosegmented density functional theory and present a theory consistent with the group contribution perturbed-chain statistical associating fluid theory equation of state. The model is used to study water/surfactant and water/surfactant/octane systems with surfactants from the group of polyethylene glycol alkyl ethers, a commonly used group of nonionic surfactants. The model parameters are obtained by fitting to pure component data of small surfactants. Binary interaction parameters are required to model the water/alkane subsystem and to account for the polarity of the head groups of the surfactant. The model is able to reproduce the significant enrichment of surfactant molecules at both vapor–liquid surfaces and liquid–liquid interfaces and the corresponding reduction of interfacial tensions. For liquid–liquid interfaces, the competing solubility of the surfactant in both phases has to be taken into account when searching for an optimal surfactant molecule.