Surface Tension Of Surfactant Research Articles

Effects of surface tension and contact angle on pore structure development of coal samples under chemical solution erosion

To explore the influence of surfactant concentration on the pore structure and permeability of coal samples during the chemical enhancement of coalbed methane production, different kinds and different concentrations of surfactants were added to the chemical solution, and the coal samples were soaked. Methods such as low-field nuclear magnetic resonance testing (NMR), fractal theory, permeability testing, surface tension testing, and contact angle testing were employed to analyze the variation patterns of coal sample pore structure, fractal characteristics, and permeability, and to explore the correlation between surface tension, contact angle, and the degree of pore structure development. The results show that the increase in total porosity of coal samples, the increase in the seepage pore porosity, the decrease in Dt, and the growth rate of permeability increase with the increase in surfactant concentration, and are negatively correlated with the surface tension of the solution and the contact angle of the coal-solution interface, while the decrease in Ds is not significantly correlated with surfactant concentration, surface tension, or contact angle. In terms of the erosion effect of a chemical solution on coal samples, the influence of contact angle is greater than that of surface tension, while surface tension has the greatest impact on the development of adsorption pores. By adding different surfactants, the surface tension of the chemical solution and the contact angle of the coal-solution interface can be controlled, further promoting the erosion of coal samples, which is of positive significance for the chemical enhancement of coalbed methane production.

Activation of alveolar epithelial ER stress by β-coronavirus infection disrupts surfactant homeostasis in mice: implications for COVID-19 respiratory failure.

COVID-19 syndrome is characterized by acute lung injury, hypoxemic respiratory failure, and high mortality. Alveolar type 2 (AT2) cells are essential for gas exchange, repair, and regeneration of distal lung epithelium. We have shown that the causative agent, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and other members of the β-coronavirus genus induce an endoplasmic reticulum (ER) stress response in vitro; however, the consequences for host AT2 cell function in vivo are less understood. To study this, two murine models of coronavirus infection were used-mouse hepatitis virus-1 (MHV-1) in A/J mice and a mouse-adapted SARS-CoV-2 strain. MHV-1-infected mice exhibited dose-dependent weight loss with histological evidence of distal lung injury accompanied by elevated bronchoalveolar lavage fluid (BALF) cell counts and total protein. AT2 cells showed evidence of both viral infection and increased BIP/GRP78 expression, consistent with activation of the unfolded protein response (UPR). The AT2 UPR included increased inositol-requiring enzyme 1α (IRE1α) signaling and a biphasic response in PKR-like ER kinase (PERK) signaling accompanied by marked reductions in AT2 and BALF surfactant protein (SP-B and SP-C) content, increases in surfactant surface tension, and emergence of a reprogrammed epithelial cell population (Krt8+ and Cldn4+). The loss of a homeostatic AT2 cell state was attenuated by treatment with the IRE1α inhibitor OPK-711. As a proof-of-concept, C57BL6 mice infected with mouse-adapted SARS-CoV-2 demonstrated similar lung injury and evidence of disrupted surfactant homeostasis. We conclude that lung injury from β-coronavirus infection results from an aberrant host response, activating multiple AT2 UPR stress pathways, altering surfactant metabolism/function, and changing AT2 cell state, offering a mechanistic link between SARS-CoV-2 infection, AT2 cell biology, and acute respiratory failure.NEW & NOTEWORTHY COVID-19 syndrome is characterized by hypoxemic respiratory failure and high mortality. In this report, we use two murine models to show that β-coronavirus infection produces acute lung injury, which results from an aberrant host response, activating multiple epithelial endoplasmic reticular stress pathways, disrupting pulmonary surfactant metabolism and function, and forcing emergence of an aberrant epithelial transition state. Our results offer a mechanistic link between SARS-CoV-2 infection, AT2 cell biology, and respiratory failure.

Surface activity, foamability, and foam stability of binary mixed systems based on siloxane-based Gemini and hydrocarbon surfactants

Aiming to explore the potential of siloxane-based Gemini surfactants in the development of environmentally friendly foam extinguishing agent to address the pollution caused by traditional fluorinated ones. A crucial step is to study the performance of binary mixed systems of siloxane-based Gemini and hydrocarbon surfactants in terms of surface activity, foamability, and foam stability. In this study, binary mixed systems of two types of siloxane-based Gemini surfactants and one siloxane surfactant with four different hydrocarbon surfactants are prepared. Parameters such as surface tension, foam height, drainage time, and coarsening rate are tested. The results show that the siloxane-based Gemini surfactant HY-4000 with double silane chains could effectively reduce the surface tension of hydrocarbon surfactants. In addition, the two types of Gemini surfactants performed better in enhancing the foamability of hydrocarbon surfactants. The siloxane OFX0193 even inhibits the foaming of cationic hydrocarbon surfactant CATC. Besides the HY-4000/APG0180 mixed system, the binary mixed systems of three silicone surfactants with AOS and APG0180 exhibit better foam stability, particularly the systems containing TEGO4100. For the coarsening process of foam bubbles, we develop a predictive model based on previous studies, where the relationship between bubble area and time follows a power function law. The findings of this study could provide guidance for the development of green foam extinguishing agent with siloxane-based Gemini and hydrocarbon surfactants as core components.

Investigations on the performance of xanthan gum as a foam stabilizer and assessment of economic and environmental impacts of foam concrete production

The properties of foam concrete are greatly influenced by the quality of the foam used. The stability of the foam is a vital property that needs dire attention when selecting surfactant. This paper evaluates the role of Xanthan gum (XG) as an additive in the performance improvement of foam produced with two different surfactants, viz., Hingot (Natural surfactant) and Nonylphenol ethoxylate (NPE) (Synthetic surfactant). Different characteristics of foam and surfactant, such as initial foam density, foam drainage, foam bubble microstructure, surface tension, and viscosity of surfactants, are experimentally evaluated. Addition of XG results in a 10-fold increment in viscosity for both Hingot and NPE surfactant solutions. The above enhancement in viscosity results in a substantial reduction in bubble size and an increment in lamella thickness. Further, the reduced surface tension of Hingot surfactant also contributes to a significant reduction in the rate of bubble coalescence. Having studied the surfactant and foam behaviour, the next phase comprises studies on the influence of XG on consistency, setting behaviour, compressive strength, and thermal conductivity of foam concrete with two different densities, viz., 1000 kg/m3 and 1500 kg/m3. Results show that the addition of XG results in a reduction in consistency and an increase in demoulding time of foam concrete. Besides improvement in foam performance, a substantial increase in compressive strength and reduction in thermal conductivity of FC is also observed due to XG addition, indicating that foam bubble microstructure has a significant impact. The last phase involves the life cycle assessment (LCA) of the FC produced with the aforementioned surfactants, which is the first of its kind study that considers the impact of surfactants across various environmental categories. Results of the LCA analysis show that the total cumulative energy demand of preparation of 1 kg of Hingot solution is less than that of 1 kg of NPE surfactant solution. The environmental impact analysis also favours Hingot as a sustainable and economical alternative to NPE surfactant. Results of LCA analysis of FC indicate that foam concrete with 1000 kg/m3 performs better than AAC block and conventional clay brick. Furthermore, the studies highlighted that there is more scope for improving the performance of LCA of FC through using various mineral admixtures as replacement for cement.

Effect of surfactant surface and interfacial tension reduction on infiltration into hydrophobic porous media

Surfactant molecules increase the infiltration rate into hydrophobic porous media by lowering the infiltrating water's surface tension and the interfacial tension between hydrophobic surfaces and water molecules. We investigated the relative effect of these rate-limiting processes on the infiltration rate of aqueous surfactant solution into hydrophobic porous media. Two surfactants at various concentrations were applied at a constant pressure head to 1D columns filled with hydrophobic soil, and water was applied at the same pressure head to columns filled with surfactant-pretreated hydrophobic soil. Based on the measured contact angle, surfactant pretreatment significantly reduced the hydrophobic soil's interfacial surface tension, which increased the infiltration rate compared to the direct aqueous surfactant application to the hydrophobic soil. The latter's slower infiltration rate was attributed to the depletion of surfactant molecules due to its adsorption to the hydrophobic molecules near the advancing wetting front, yielding an increase in the surface tension of the infiltrating solution. Surfactant pretreatment increased the opportunity time for surfactant adsorption to the hydrophobic molecules, resulting in interfacial tension reduction and infiltration rate increase. Diffusion-limited surfactant adsorption on the hydrophobic surfaces, leading to reduced interfacial tension between the surface and infiltrating liquid, had a greater impact on limiting infiltration into hydrophobic porous media compared to the reduction in surface tension of the infiltrating liquid due to surfactant presence.

Effect of hydrophobic chain length on the properties of polycarboxylate polymeric surfactants

In this work, a series of polycarboxylate polymeric surfactants were designed and synthesized from acrylate monomers with different alkyl chain lengths (alkyl chain lengths of 1, 4, 6, 12, 18), epoxy succinic acid (ESA), acrylic acid (AA) and 2-acrylamide-2-methylpropane sulfonic acid (AMPS). Their structures were confirmed by FT-IR, 1H NMR and GPC. A series of surfactant parameters, including critical micelle concentration (CMC), minimum surface tension, surface tension reduction at critical micelle concentration (Πcmc), surface tension reduction efficiency (pC20), etc, were obtained by surface activity test. The results showed that with the increase of the alkyl chain length of acrylate, surface tension and CMC of polycarboxylate polymeric surfactants gradually decreased. When the alkyl chain length of acrylate monomer was 12, the surface tension of polycarboxylate polymeric surfactants was the lowest, which was 32.6 mN/m. The results of TG, DLS and TEM showed that with the increased of the alkyl chain length of the acrylate, the micellar size of polycarboxylate polymeric surfactants decreased regularly. Meanwhile, the foaming, wetting and emulsifying properties of polycarboxylate polymeric surfactants were positively correlated with the alkyl chain length of the acrylate. The dispersing ability of polycarboxylate polymeric surfactants for calcium carbonate was 101.5 mg/g, which can dispersed Fe2O3 fouling to less than 1 μm under the condition of 0.6 g/L.

Effect of foam temperature on foam stability of foamed concrete and stabilization mechanisms

In this study, a novel method for increasing foam stability based on adjusting the temperature of surfactant solution used to prepare foam (foam temperature) is presented. The effect of foam temperature on the compressive strength, and stability of the foamed concrete was studied. Meanwhile, laser displacement sensors, X-ray computed tomography, automated surface tensiometer, and electron microscopy were adopted to explore the action mechanisms. Experimental results reveal that the method of adjusting the proper foam temperature can decrease the surface tension of surfactant, reduce the diameters of bubbles, and retard bubble coarsening, thus enhancing the foam stability. The fresh foamed concrete with a foam temperature at 20 °C displays the highest stability level. The foamed concrete with a foam temperature at 20 °C possesses a more uniform pore structure, which explains the reasons for the better properties of foamed concrete.

Interfacial and micellar synergistic interactions between a phosphonium surface active ionic liquid and TX-100 nonionic surfactant: Surface tension and 1H NMR investigations

The adsorption and self-aggregation behaviors of a mixed system made of a cationic surface active ionic liquid (SAIL), dodecyltriphenylphosphnium bromide (C12TPB), and a nonionic surfactant, polyoxyethylene p-tertoctylphenyl ether (TX-100), were investigated in aqueous solution using tensiometry and 1H NMR measurements. From the surface tension data, relevant physico-chemical parameters were determined for different proportions of the components: critical micelle concentration (cmc), surface saturation adsorption, minimum surface area per surfactant molecule and surface tension at the cmc. The obtained data were treated through different theoretical models, namely those of Clint, Rubingh, Maeda and Rosen, which allow the determination of key thermodynamic properties. The results revealed, in both the mixed micelles and surface monolayer, the existence of a non-ideal behavior due to rather strong attractive links, confirmed by the 1H NMR data analysis. They are attributed mainly, besides the hydrophobic interaction, to firstly the ion–dipole interaction and the complex formation between the polyoxyethylene head of TX-100 and the quaternary phosphonium group of C12TPB, and secondly to an intermolecular π-π stacking and a hydrogen-bonds formation between the protons in α position of the phosphonium and the oxygen atoms of polyoxyethylene units of TX-100, giving rise to a strong synergism.

Synergistic effect and performance characterization of an efficient environmental-friendly Camellia oleifera saponins based foamed cleaning agents

Foamed cleaning agents mainly consist of synthetic surfactants. However, the widespread use of petroleum-based surfactants not only consumes non-renewable resources but also causes harm to the environment. It is necessary to develop surfactants with higher biodegradability and lower toxicity to obtain a recipe for an environment friendly foamed cleaning agent. Camellia oleifera saponins (TS) was prepared and mixed with a zwitterionic surfactant (dodecyl dimethyl sulfopropyl betaine, SB12-3). The equilibrium surface tension of single surfactants and their binary mixtures in the air/water system was measured using Wilhelmy method. The interaction and thermodynamic parameters of different mixtures were calculated via the regular solution model. The parameters showed that the mixtures displayed a synergistic effect, and the optimum molar ratio of TS/SB12-3 was determined to be 5/95. The mixture had the shortest wetting time (13 s), the smallest contact angle (32.4°), and the lowest surface tension (32.2 mN/m). Furthermore, the addition of TS significantly improved the emulsifying and foam properties. Cleaning experiments were completed by applying foamed surfactant solutions with different liquid fractions (ε) prepared by the double syringe technique on oil-contaminated glass substrates. The foamed surfactant solutions of the mixture were cleaner than those of TS or SB12-3 at all ε. The maximum oil area removal efficiency of the mixture was 94.9% at ε = 15%. The mixture exhibits a better cleaning efficiency than that of single surfactants. This study provides a new way for the utilization of Camellia oleifera cake.

Platform for Exposing Aerosolized Substances to Lung Surfactant and Alveolar Cells at the Air-Liquid Interface

Lung surfactant lowers surface tension in the alveoli, playing a critical role in lung function and immune defense. Inhaled aerosol particles may induce adverse health effects via the interruption of lung surfactant surface tension. Previous generations of surfactometers have been developed and used to characterize surfactants and their response to various exposures. However, these devices do not allow for simultaneous exposure with multiple aerosols, the incorporation of multiple aerosolization methods, or the co-exposure scenario involving both lung surfactant fluid and pulmonary cells/tissues. Herein, we introduce a new configuration, termed the aerosol exposure surfactometer (AESM), that addresses all of these limitations. The results indicate correlation of surface tension changes in concordance with aerosol properties while preventing unwanted cell death. Further investigation using this method may elucidate mechanisms of pathogenesis related to surfactant dysfunction and provide the foundation for predictive models.

Droplet splash and spread on superhydrophobic lotus leaves: Direct regulation by tuning the chain length of surfactant

Impact and spread of droplet on superhydrophobic surface are ubiquitous in inkjet printing, pesticide spraying, paint coating, and other fields. However, due to the extremely water-repellent properties of superhydrophobic surface, droplets frequently splash or roll off, causing great waste and serious environmental problems. Thus, searching for an effective strategy to regulate the droplet splash and spread on superhydrophobic surfaces is of remarkable significance. To address the above issues, herein, we demonstrate the controllable regulation on superhydrophobic lotus leaf surface by tuning the double-chain length of surfactants. The outcomes indicate different regularities for droplet splash in a short time (~10 ms) and spread in a relatively long period (~100 s). It can be concluded that dynamic surface tension of surfactant, diffusion rate of surfactant from the bulk to the interface, and assembly disaggregation rate dominate the impact process, whereas the adsorption kinetic and effectiveness of surfactant along with the spreading driving force determine the wetting transition. Surfactant owning suitable hydrophilic and hydrophobic ratio, fast diffusion rate, and unstable assembly could inhibit droplet splash and improve spreading pronouncedly, thereby enhancing the droplet deposition on superhydrophobic surfaces. This study makes original contribution to screen suitable surfactants from the structural aspects, especially double-chain length, which has not been treated in much detail to date. Our work not only creates a big impetus in illuminating the mechanism of surfactant molecular structure on droplet deposition processes but also greatly expands the applications of surfactant in many fields.

The steroid mometasone alters protein containing lung surfactant monolayers in a concentration-dependent manner

Mometasone is an investigational anti-inflammatory steroidal drug to treat inflammation via pulmonary administration. For steroid drugs to be effective they need to be adsorbed by lung surfactants, a thin monolayer at the air-water interface in alveoli that reduces surface tension. Information on the molecular-level interactions of the drug with lung surfactants is useful to understand the mechanism of adsorption. In this study, we use coarse-grained molecular dynamics simulation to understand the concentration-dependent effect of mometasone on a lung surfactant monolayer (LSM) composed of lipids and surfactant proteins, under two different breathing conditions (exhalation, at surface tension 0 mNm−1 and inhalation, surface tension 20–25 mNm-1). A series of fixed-APL and fixed-surface tension simulations were used to demonstrate that in the absence of drugs, the model LSM reproduces the surface tensions for the compressed and expanded states, as well as compressibility at different surface tensions. In-depth analysis of simulations of a LSM in the presence of five different drug concentrations shows that mometasone alters the structure and dynamics of the LSM in a concentration-dependent manner. Mometasone induces a collapse in the monolayer that is affected by the surfactant protein and surface tension. Overall, these findings suggest that the surfactant proteins, surface tension and drug concentration are all critical components affecting monolayer stability and drug adsorption. The outcomes of this study may be beneficial for a more in-depth understanding of how mometasone is adsorbed by lung surfactants.

Effects of nonionic surfactant source and surface tension on in vitro fermentation characteristics of cereal straws

This study investigated the in vitro fermentation of three cereal straws (corn stover, wheat straw, and rice straw) with culture media containing two nonionic surfactants (alkyl polyglycoside and Tween 80) and variable surface tension (42, 48, and 54 mN/m) in a 2 × 3 factorial arrangement. The in vitro dry matter degradation of rice straw and corn straw linearly (P < 0.05) decreased with increasing culture media surface tension. Ammoniacal nitrogen and microbial crude protein production were not influenced by nonionic surfactant sources or surface tension; however, the ammoniacal nitrogen concentration of wheat straw linearly (P = 0.01) increased with increasing culture media surface tension. Decreasing the surface tension linearly (P < 0.05) increased the microbial membrane permeability and the ratio of acetate to propionate in rice straw and corn stover. The molar proportion of propionate in rice straw (P = 0.03) and corn stover (P = 0.02) linearly decreased as surface tension decreased. This study highlights the potential of nonionic surfactants as feed additives, and their ability to modulate the surface tension of rumen fluid should be more carefully considered.

Molecular and biophysical basis for the disruption of lung surfactant function by chemicals

With the intention to move away from animal testing for the toxicological evaluation of chemicals comes the need to develop new approach methodologies which are mechanism-anchored and target relevant key events leading to an adverse outcome. To date, no validated alternative methods are available for studying the acute inhalation toxicity potential of airborne chemicals but the constrained drop surfactometer measuring the surface tension of a drop of lung surfactant presents as a promising candidate. Indeed, the correlation of the increase in minimum surface tension of lung surfactant in vitro with changes in the breathing patterns of mice after inhalation of test compounds has been shown in multiple studies. However, the causal factors leading to lung surfactant inactivation remain speculative. This paper combines molecular and biophysical methods (constrained drop and captive bubble surfactometers, Langmuir-Blodgett balance, epifluorescence microscopy, cryogenic transmission electron microscopy, and differential scanning calorimetry) applied to purified porcine lung surfactant and dipalmitoylphosphatidylcholine interfacial films to gain insights into the disruption of lung surfactant function by three chemicals known to show acute inhalation toxicity (trimethoxyoctylsilane, methyl 3-oxo-2-pentylcyclopentaneacetate, and diisopentyl ether). The results of this study suggest that the test chemicals intercalate between the phospholipids at the air-liquid interface, reduce the stability of the films, and decrease the cohesivity of interface-associated multilayered structures thereby perturbing the lung surfactant surface activity. These findings contribute to a better understanding of chemically-induced lung surfactant function disruption.

Impact of Surfactants on the Functionality of Prefilled Syringes

Previous studies revealed the impact of formulation factors (excipients and pH) on the functionality of prefilled syringes. Surfactant, a critical formulation component for therapeutic proteins and antibodies, aids in minimizing protein adsorption onto interfaces and reduces protein aggregation or particulate formation. This study evaluated the impact of different surfactants and protein concentration on the functionality of prefilled syringes. Syringes filled with solution formulations with different surfactants were stored at various temperatures and evaluated at selected time points. Upon thermal stress, polysorbate 80 and dodecyl-β-d-maltoside containing formulations showed significantly greater increase in glide force when compared with poloxamer 407 containing formulations. In contrast, syringes filled with poloxamer 188 containing formulations did not show any increase in glide force under the same conditions. Based on the results from this study, the increase in syringe glide force was inversely correlated with hydrophobic-lipophilic balance values and surface tension of different surfactants. The mechanism of increase in glide force was primarily the change of silicone oil coverage and lubricity in the barrel of syringes.

Surface properties and microemulsion of anionic/nonionic mixtures based on sulfonate Gemini surfactant in the presence of NaCl

The mixing properties of anionic/nonionic surfactant mixtures in the presence of inorganic salts are essential to the industrial application. The equilibrium and dynamic surface tension of the sulfonate Gemini surfactant (SGS12) and alkyl glycoside (APG0810) mixtures were examined using the plate method and drop-shape analysis. Moreover, the Winsor phase diagram and solubility properties of the microemulsion were studied using the salinity scan. Results show that the critical micelle concentration (cmc) of the SGS12/APG0810 mixtures was intermediate between those of the two single surfactants in the presence of NaCl. For the SGS12/APG0810 mixtures, the absolute value of interaction parameters increased as the APG0810 content increased at cNaCl = 0.01 or 0.1 mol/L. The formation of the mixed micelles was spontaneous. At cNaCl = 0.01 mol/L, the initial adsorption (t → 0) of surfactant molecules from the bulk phase to the surface was diffusion-controlled. The salinity scan experiments showed that the optimal solubilization parameters of the SGS12/APG0810 microemulsion decrease with the decrease of the molar fraction of SGS12. However, the concentration range of inorganic salt between the formation and disappearance of Winsor III broadened with the decline in SGS12 content. The impact of temperature on the volume fraction of the middle-phase microemulsion (MPM) was ignorable, indicating the high stability of MPM at the temperature range of 30.0 °C ~ 80.0 °C. At 30.0 ± 0.1 °C, the hydrodynamic diameter of the SGS12/APG0810 MPM was about 28.0 nm, and the number of microemulsion droplets decreased with the increase of APG0810 content. When the total mass fraction of surfactant and cosurfactant was 15%, wNaCl = 5% (brine), Km = 1:3 and Vo/Vw = 1, the interfacial tension between crude oil and the SGS12/APG0810 MPM reached the order of 10−3mN/m. At nSGS12:nAPG0810 = 7:3, the lowest interfacial tension was 9 × 10−4 mN/m. For the SGS12/APG0810 (7:3) mixture, the addition of n-butanol induced the formation of MPM. The concentration range of n-butanol between the formation and the disappearance of Winsor III first increased and then decreased with the increase of surfactant concentration.

Usage of Inhaled Nitric Oxides in Cases of Eisenmenger Syndrome

Eisenmenger Syndrome is congenital heart disease with pulmonary hypertension and shunting turning from right to left. The resistance of pulmonary vascular more than 7.5 mmHg/L/min. The right ventricle and pulmonary artery always enlarge. Physiological effects of inhaled nitric oxide therapy cause selective pulmonary vasodilation: Hypoxia alveoli causes reversible vasoconstriction, thereby increasing pulmonary wedge pressure. Inhaled nitric oxide can lower it. Moderate cardiac output and systematic arterial pressure are not affected; Selective in pulmonary because it is activated by hemoglobin; Selective vasodilation in the ventilated area, local hypoxia alveoli constricts the surrounding vascular tissue and redistributes blood flow to the ventilated lungs better and higher intraalveolar oxygen pressure. Inhaled nitric oxide enhances this mechanism by increasing blood flow through a well-ventilated lung; Bronchodilators; Pulmonary surfactant, The combination of high concentrations of inspired oxygen and high concentrations of Inhaled nitric oxide reduces the minimum surfactant surface tension.

Dynamic Surface Tension of Surfactants in the Presence of High Salt Concentrations

We study the influence of high NaCl concentrations on the equilibrium and dynamic surface tensions of ionic (CTAB) and nonionic (Tween 80) surfactant solutions. Equilibrium surface tension measurements show that NaCl significantly reduces the critical micellar concentration (CMC) of CTAB but has no effect on the CMC of Tween 80. Dynamic surface tension measurements allow comparing the surface tension as a function of time for pure surfactant solutions and in the presence of NaCl. For the ionic surfactant, the dynamics agree with the usual diffusion-limited interfacial adsorption kinetics; however, the kinetics become orders of magnitude slower when NaCl is present. Sum-frequency generation spectroscopy experiments and the equilibrium adsorption measurements show that the presence of NaCl in CTAB solution leads to the formation of ion pairs at the surface, thereby neutralizing the charge of the head group of CTAB. This change, however, is not able to account for the slowing down of adsorption dynamics; we find that it is rather the decreases in the monomer concentration (CMC) in the presence of salt which has the major influence. For the nonionic surfactant, the kinetics of interfacial tension is seen to be already very slow, and the addition of salt does not influence it further. This also correlates very well to the very low CMC of Tween 80.

Effects of Conventional Surfactants on the Activity of Designed Antimicrobial Peptide.

In this article, the interaction between a designed antimicrobial peptide (AMP) G(IIKK)3I-NH2 (G3) and four typical conventional surfactants (sodium dodecyl sulfonate (SDS), hexadecyl trimethyl ammonium bromide (C16TAB), polyoxyethylene (23) lauryl ether (C12EO23), and tetradecyldimethylamine oxide (C14DMAO)) has been studied through surface tension measurement and circular dichroism (CD) spectroscopy. The antimicrobial activities of AMP/surfactant mixtures have also been studied with Gram-negative Escherichia coli, Gram-positive Staphylococcus aureus, and the fungus Candida albicans. The cytotoxicity of the AMP/surfactant mixtures has also been assessed with NIH 3T3 and human skin fibroblast (HSF) cells. The surface tension data showed that the AMP/SDS mixture was much more surface-active than SDS alone. CD results showed that G3 conformation changed from random coil, to β-sheet, and then to α-helix with increasing SDS concentration, showing a range of structural transformation driven by the different interactions with SDS. The antimicrobial activity of G3 to Gram-negative and Gram-positive bacteria decreased in the presence of SDS due to the strong interaction of electrostatic attraction between the peptide and the surfactant. The interactions between G3 and C16TAB, C12EO23, and C14DMAO were much weaker than SDS. As a result, the surface tension of surfactants with G3 did not change much, neither did the secondary structures of G3. The antimicrobial activities of G3 were little affected in the presence of C12EO23, slightly improved by C14DMAO, and clearly enhanced by cationic surfactant C16TAB due to its strong cationic and antimicrobial nature, consistent with their surface physical activities as binary mixtures. Although AMP G3 did not show activity to fungus, the mixtures of AMP/C16TAB and AMP/C14DMAO could kill C. albicans at high surfactant concentrations. The mixtures had rather high cytotoxicity to NIH 3T3 and HSF cells although G3 is nontoxic to cells. Cationic AMPs can be formulated with nonionic, cationic, and zwitterionic surfactants during product development, but care must be taken when AMPs are formulated with anionic surfactants, as the strong electrostatic interaction may undermine their antimicrobial activity.

Regulatory Roles of Human Surfactant Protein B Variants on Genetic Susceptibility to Pseudomonas Aeruginosa Pneumonia-Induced Sepsis.

Wild-type (WT) FVB/NJ and humanized transgenic SP-B-T and SP-B-C mice (expressing either hSP-B C or T allele without mouse SP-B gene) were infected intratracheally with 50 μL (4 × 10 colony-forming units [CFUs]/mouse) Pseudomonas aeruginosa Xen5 or saline, and then killed 24 or 48 h after infection. Bacterial dynamic growths were monitored from 0 to 48 h postinfection by in vivo imaging. Histopathological, cellular, and molecular changes of lung tissues and bronchoalveolar lavage fluid (BALF) were analyzed. Surface tension of surfactants was determined with constrained drop surfactometry. SP-B-C mice showed higher bioluminescence and CFUs, increased inflammation and mortality, the higher score of lung injury, and reduced numbers of lamellar bodies in type II cells compared with SP-B-T or WT (P < 0.05). Minimum surface tension increased dramatically in infected mice (P < 0.01) with the order of SP-B-C > SP-B-T > WT. Levels of multiple cytokines in the lung of infected SP-B-C were higher than those of SP-B-T and WT (P < 0.01). Furthermore, compared with SP-B-T or WT, SP-B-C exhibited lower SP-B, higher NF-κB and NLRP3 inflammasome activation, and higher activated caspase-3. hSP-B variants differentially regulate susceptibility through modulating the surface activity of surfactant, cell death, and inflammatory signaling in sepsis.