Surfactant Interactions Research Articles

A win-win scenario for antibacterial activity and skin mildness of cationic surfactants based on the modulation of host-guest supramolecular conformation

The commercial cationic surfactants (CSAa) with quaternary ammonium (QA) groups have proved to be broad-spectrum bactericide against bacteria, fungi, and viruses. Nevertheless, they inevitably exhibit potent irritation on the skin. In this work, we systematically investigated the regulatory mechanism of the host-guest supramolecular conformation with β-cyclodextrin (β-CD) on the bactericidal performance and skin irritation of CSAa with different head groups and chain lengths. When the ratio of incorporated β-CD is not greater than 1:1, the bactericidal efficiency of CSAa@β-CD (n > 12) remained above 90 % due to the free QA groups and hydrophobic fraction that can act on negatively charged bacterial membranes. And once the ratio of β-CD exceeded 1:1, the β-CD attracted to the bacterial surface by hydrogen bonding might prevent CSAa@β-CD from acting on bacteria, resulting in a decrement in antibacterial performance. Even so, the antibacterial activity of CSAa with long alkyl chains (n = 16, 18) was independent from the complexation of β-CD. Accordingly, both the zein solubilization assay and the neutrophil migration assay on zebrafish skin evidenced that β-CD attenuated the interaction of surfactant with skin model proteins and the inflammatory effect on zebrafish, thereby enhancing skin mildness. In this way, we hope to create a simple but effective brainpower using the host-guest approach to guarantee both bactericidal efficiency and skin mildness without modifying the chemical structure of these commercial biocides.

Rock–Fluid Interactions of Alkyl Ether Carboxylate Surfactants with Carbonates: Wettability Alteration, ζ-Potential, and Adsorption

This work evaluated the rock–fluid interactions of two linear alkyl ether carboxylate (AEC) surfactants C11E11A and C12E7A in carbonates: wetting ability, ζ-potential, and adsorption capacity. Contact angle measurements showed that the ability of AECs to hydrophilize the surface is strongly affected by the ethylene oxide (EO) chain length and the presence of electrolytes. An AEC with a shorter EO chain C12E7A demonstrated a better wetting ability and decreased the contact angle value on the limestone surface from 113 to 27 ± 11° in deionized (DI) water and until 17 ± 5° in 5 wt % NaCl. The mechanism of surfactant action was assessed through thermodesorbed hydrocarbon analysis and organic matter characterization with the help of the Rock-Eval (RE) pyrolysis technique for the first time. The analysis results revealed that all surfactant compositions partially removed free oil and heavy oil components from limestone samples. Also, the presence of C12E7A molecules was detected in the samples after surfactant treatment that indicates that a better wetting ability is achieved by the combination of washing hydrocarbons and adsorption of surfactants on clean sites. The combination of ζ-potential measurements and static adsorption test on crushed limestone demonstrated that the adsorption of AECs in deionized water is not governed by electrostatic interactions and mainly occurs due to hydrogen bonding. Salinity has a significant effect on the adsorption behavior of AECs and leads to the partial destruction of hydrogen bonds and the shift from monomolecular adsorption in DI water to polymolecular adsorption in brines. The adsorption of C11E11A achieved ∼9 mg/g-rock and was higher than that of C12E7A, showing a maximum value of ∼4 mg/g-rock. This work provides a set of experiments that characterize the behavior of AECs during interactions with carbonate rock and describes a novel approach of the wettability shift mechanism assessment through RE pyrolysis.

Review: Implementing the hydrophilic–lipophilic deviation model when formulating detergents and other surfactant‐related applications

AbstractWhen designing surfactant formulations using ionic and nonionic surfactants, the hydrophile lipophile balance (HLB) is a generalized surfactant characterization parameter that has shown to be useful when designing surfactant formulations, in the case of both ionic and nonionic surfactants (Davies' and Griffin's methods). Microemulsion phase behavior studies have been extensively used to optimize surfactant formulations, but these studies can cover a very wide phase space and can often encounter troublesome non‐equilibrium issues such as coacervation. Detailed phase behavior studies can be time‐consuming and difficult to apply beyond the specific surfactant‐oil system studied. The hydrophilic–lipophilic deviation (HLD) provides a method to help expedite surfactant formulation research by reducing the number of phase behavior studies required to optimize a given formulation. Detergency experiments have indicated that there is an optimal range of HLD for a given fabric surface. This appears to apply to other applications, as well, for example, surfactant formulations used in enhanced oil recovery have been optimized using the HLD method. These studies found that the HLD can reflect total oil recovery, even if the surfactants were derived from different alcohol feedstocks (e.g., HLD of 0 would describe optimum conditions regardless the type of surfactant). Also with additional parameterization, the HLD method can also be applied to non‐ideal surfactant mixtures, specifically ionic/nonionic blends. Overall, the HLD framework has shown to be an effective screening tool for a wide range of surfactant‐related applications when appropriate experiments, assumptions, and understanding of surfactant and oil interactions are used to generate the HLD parameters.

Study of Chelating Agent—Surfactant Interactions on the Interphase as Possibly Useful for the Well Stimulation

Chelating agents’ application for EOR and well stimulation is fast growing nowadays. However, reagents of this class have some drawbacks, with high values of interfacial tension (IFT) being among them. IFT may be lowered with the addition of surfactants; however, the simultaneous application of chelating agents and surfactants has not yet been widely studied. This paper focuses on the experimental and theoretical investigation of the interaction between chelating agent (ethylenediaminetetraacetic acid, EDTA) and surfactants of anionic and cationic types (sodium dodecyl sulfate, SDS, and dodecyl trimethynlammonium bromide, DTAB). IFT measurement was performed at ambient conditions, with normal octane being as the reference hydrocarbon to eliminate the temperature and salinity effects and compare surfactant-containing systems. The experimental results show that chelating agents’ addition to the solutions of surfactants leads to a decrease in IFT value. Moreover, surfactants’ critical micelle concentration is lowered, whereas their effectiveness and efficiency are increased, which points to the salting-out nature of chelating agents. Molecular dynamics reveal that chelating agent addition causes closer packing of surfactant layer, the decrease in head groups’ hydration, and, at least in the case of SDS, specific surfactant–chelating agent attractive interaction. These molecular-level insights, experimental dependencies, and the combined methodology may be useful for the proper selection of fluids for real-field operations.

Molecular interaction of di-ester bonded cationic Gemini surfactants with pepsin: in vitro and in silico perspectives

The implications of surfactant–enzyme/protein interactions in a variety of fields, including biotechnology, cosmetics, paints and pharmaceuticals, have attracted a lot of attention in contemporary studies. Herein, we have employed several in vitro and in silico techniques such as excitation and absorption spectroscopies, circular dichroism and FT-IR spectroscopies, density functional and molecular dynamics simulations to understand the interaction behavior of oxy-diester-based green cationic Gemini surfactants, N1,N1,N14,N14-tetramethyl-2,13-dioxo-N1,N14-dialkyl-3,6,12-tetraoxateradecane-1,14-diaminiumdichloride (abbreviated as Cm-E2O2-Cm, where ‘m’ stands for alkyl chain length, m = 12 and 14) with one of the main digestive proteins, pepsin. The spectroscopic techniques confirm the static quenching effect of surfactants on pepsin. The calculated physical parameters (Ksv , Kb and ΔG) and their order reveal the distinguished implications for the surfactants’ chain lengths. The spontaneity of interaction was also confirmed by negative Gibbs free energy change values. The extrinsic spectroscopic study with pyrene as fluorescence probe, FT-IR and CD techniques indicated a potential conformational change in pepsin induced by the Gemini surfactants. DFT, docking and MD simulations provided the theoretical understanding regarding the quantum mechanical environment, location of binding and stability of the protein–surfactant complexation in energy terms. We believe this study will be a humble addition to our existing knowledge in the field of protein–surfactant interactions. Communicated by Ramaswamy H. Sarma

Charge controlled interactions between DNA-modified silica nanoparticles and fluorosurfactants in microfluidic water-in-oil droplets.

Microfluidic droplets are an important tool for studying and mimicking biological systems, e.g., to examine with high throughput the interaction of biomolecular components and the functionality of natural cells, or to develop basic principles for the engineering of artificial cells. Of particular importance is the approach to generate a biomimetic membrane by supramolecular self-assembly of nanoparticle components dissolved in the aqueous phase of the droplets at the inner water/oil interface, which can serve both to mechanically reinforce the droplets and as an interaction surface for cells and other components. While this interfacial assembly driven by electrostatic interaction of surfactants is quite well developed for water/mineral oil (W/MO) systems, no approaches have yet been described to exploit this principle for water/fluorocarbon oil (W/FO) emulsion droplets. Since W/FO systems exhibit not only better compartmentalization but also gas solubility properties, which is particularly crucial for live cell encapsulation and cultivation, we report here the investigation of charged fluorosurfactants for the self-assembly of DNA-modified silica nanoparticles (SiNP-DNA) at the interface of microfluidic W/FO emulsions. To this end, an efficient multicomponent Ugi reaction was used to synthesize the novel fluorosurfactant M4SURF to study the segregation and accumulation of negatively charged SiNP-DNA at the inner interface of microfluidic droplets. Comparative measurements were performed with the negatively charged fluorosurfactant KRYTOX, which can also induce SiNP-DNA segregation in the presence of cations. The segregation dynamics is characterized and preliminary results of cell encapsulation in the SiNP-DNA functionalized droplets are shown.

A Review on Interactions between Amino Acids and Surfactants as Well as Their Impact on Corrosion Inhibition.

Amino acid-surfactant interactions are central to numerous studies because of their increased effectiveness in chemical, biological, household and industrial use. This review will focus on the impact and effect of the physicochemical properties, temperature, pH, and surfactant chain length of the amino acid for detailed exploration of amino acids and surfactants in aqueous medium. The impact of cosolvent on self-aggregation, critical micelle concentration (CMC), and binding affinity with other biomolecules, as well as amino acid-surfactant interactions, are the epicenters. The results show that increasing the temperature causes negative enthalpy for ionic surfactants and micellization, implying that micellization and amino acids are thermodynamically spontaneous and exothermic, accompanied by positive entropy. As these physicochemical studies are additive, the amino acid and ionic surfactant interactions provide clues on protein unfolding and denaturation under different media, which further changes with a change in physiological conditions like pH, cosolvent, chain length, and temperature. On varying the pH, the net charge of the amino acid also changes and, subsequently, the binding efficiency of the amino acids to the surfactants. The presence of cosolvent causes a lowering in the hydrophobic chain, which changes the surfactant's CMC. At a reduced CMC, the hydrophobic characteristic of amino acid-surfactant associations is amplified, leading to rapid denaturation of proteins that act as propulsion under the influence of extended chain surfactants. Amino acids are one of the most intriguing classes of chemicals that produce high inhibitory efficacy. Amino acids are also a component of proteins and therefore, found in a significant part of the human body, further making them a promising candidate as corrosion inhibitors. In this review article, authors have also focused on the collection and investigation for application of amino acid-surfactant interactions in corrosion inhibition. Various predictive studies/in silico studies are also reported by many research groups, such as density functional theory (DFT) calculations and molecular dynamics simulations to obtain tentative electronic, structural, and physiochemical characteristics like energies of the highest occupied molecular orbitals and lowest unoccupied molecular orbitals, binding energy, Gibb's free energy, electronegativity, polarizability, and entropy. In silico studies are helpful for the mechanism predictions of the process occurring on metal surfaces.

Interaction between surfactants of different classes and nanofiltration membranes

The presence of surfactants in aquatic environments may alter the water quality parameters. Nanofiltration is a promising technique that can separate surfactants from water with high rejections. Nevertheless, negative charges on nanofiltration membranes could facilitate the occurrence of electrostatic interactions between the charged surfactants and the surface of these membranes, increasing the membrane-fouling tendency. In this work, the interaction of surfactants commonly found in residential laundry wastewater with membranes used in nanofiltration was investigated. For this purpose, the surface, and transport properties of four commercial membranes were analyzed. The zeta potential of the NF90 membrane in the presence of individual and mixture of surfactants was performed to evaluate the effect of adsorption of these surfactants on the performance of the membrane. Additionally, a central composite rotatable design (CCDR) and response surface model were applied to investigate the simultaneous effect of the initial concentration of CTAB and SDS ([CTAB + SDS]0) and pH on the NF90 permeate fluxes and rejections. It was shown that surfactant adsorption varies with the type of surfactant and membrane. Moreover, adsorption played an important role in NF90 membrane fouling, mainly for the cationic surfactant in individual solutions and in the mixture of surfactants. Besides adsorption, pore blocking may have affected the performance of nanofiltration for higher concentrations of surfactants. Finally, by the application of the central composite rotatable design (CCDR), it was possible to find the best conditions of pH and initial concentration of surfactants for achieving higher fluxes and rejections by the NF90 membrane.

Fourier transform infrared spectroscopy in surfactant science: A personal view

AbstractThe overall goal of this review paper on Fourier transform infrared spectroscopy (FT‐IR) is to provide non‐specialists and spectroscopists alike a motivational introduction to how this technique may be used to obtain unique structural information on a wide range of surfactant‐based systems. Two main topics are addressed—The structures of surfactant aggregates in solution and the interactions of surfactants in solution with solid surfaces. Infrared spectra can yield insights into the interactions of surfactants in mixed micelles as well as in microemulsions. The structures of adsorbed surfactant layers and their kinetics of formation may be elucidated from FT‐IR spectra obtained using attenuated total reflectance sampling techniques. Insights into the detergency process of solid oily soils may also be obtained from the spectra of phases formed at the soil‐surfactant solution interface. Future work in applying FT‐IR to the development of the hydrophilic–lipophilic difference + net average curvature (HLD‐NAC) framework is proposed. Spectral interpretation principles examined in many examples, particularly regarding surfactant hydration and the loci of oil solubilization, could be used in the further development of HLD‐NAC through application to some microemulsion systems that have recently been reported.

Interactions of Surfactants with the Bacterial Cell Wall and Inner Membrane: Revealing the Link between Aggregation and Antimicrobial Activity.

Surfactants with their intrinsic ability to solubilize lipid membranes are widely used as antibacterial agents, and their interactions with the bacterial cell envelope are complicated by their differential aggregation tendencies. We present a combined experimental and molecular dynamics investigation to unravel the molecular basis for the superior antimicrobial activity and faster kill kinetics of shorter-chain fatty acid surfactant, laurate, when compared with the longer-chain surfactants studied in contact time assays with live Escherichia coli (E. coli). From all-atom molecular dynamics simulations, translocation events across peptidoglycan were the highest for laurate followed by sodium dodecyl sulfate, myristate, palmitate, oleate, and stearate. The translocation kinetics were positively correlated with the critical micellar concentration, which determined the free monomer surfactant concentration available for translocation across peptidoglycan. Interestingly, aggregates showed a lower propensity to translocate across the peptidoglycan layer and longer translocation times were observed for oleate, thereby revealing an intrinsic sieving property of the bacterial cell wall. Molecular dynamics simulations with surfactant-incorporated bacterial inner membranes revealed the greatest hydrophobic mismatch and membrane thinning in the presence of laurate when compared with the other surfactants. The enhanced antimicrobial efficacy of laurate over oleate was further verified by experiments with giant unilamellar vesicles, and electroporation molecular dynamics simulations revealed greater inner membrane poration tendency in the presence of laurate when compared with the longer-chain surfactants. Our study provides molecular insights into surfactant translocation across peptidoglycan and chain length-induced structural disruption of the inner membrane, which correlate with contact time kill efficacies observed as a function of chain length with E. coli. The insights gained from our study uncover unexplored barrier properties of the bacterial cell envelope to rationalize the development of antimicrobial formulations and therapeutics.

Isolation of essential oil from Mosla chinensis Maxim by surfactant-enzyme pretreatment in high-solid system and evaluation of its biological activity

Plant essential oil (EO) is an important natural active product, and the development of efficient and green EO separation technique has been one of the research hotspots. In this work, surfactant-enzyme pretreatment in high-solid system followed by microwave-assisted hydrodistillation (SEHS-MHD) was developed for the isolation of EO from Mosla chinensis Maxim. Through kinetic curve fitting, pretreatment of raw materials with combined enzyme (cellulase and hemicellulase of 1:1 in activity value) and surfactant (tween-20) in high-solid system (20% solid content) could provide a higher yield of EO. Compared with other reference methods, the yield of EO obtained by SEHS-MHD was significantly increased, which was mainly due to the synergistic interaction of enzyme and surfactant in the high-solid system. The results of gas chromatography-mass spectrometer analysis showed that the main components of M. chinensis EO were thymol and carvacrol, the contents of which were 75.38% and 17.20%, respectively. Additionally, the inhibitory enzyme activity and antifungal activity of M. chinensis EO were evaluated, the results of which indicated that EO had no obvious inhibitory activity on α-amylase and acetylcholinesterase, but had spectral antifungal activity. In general, the SEHS-MHD developed in this work is a potential and powerful alternative to traditional techniques for the sufficient isolation of EO from natural plant and crop materials. • Surfactant and enzyme were combined to pretreat raw materials in high-solid system. • Synergistic interaction of surfactant and enzyme in high-solid system was produced. • Kinetics and composition of essential oils under various conditions were studied. • Essential oil showed excellent inhibitory activity against plant pathogenic fungi.

Random Heteropolymer Excipients Improve the Colloidal Stability of a Monoclonal Antibody for Subcutaneous Administration.

Developing stable high concentration monoclonal antibody (mAb) formulations is increasingly important to move toward subcutaneous (SC) administration for better patient experience. Challenges stemming from protein-protein interactions in these crowded solutions, such as colloidal instability, limit the feasibility of some formulations because of concerns of safety, product quality, and/or manufacturability. Herein, we report novel random heteropolymer excipients that improve the colloidal stability of a high concentration mAb formulation for SC administration. A library of polymers was synthesized and screened by a high-throughput, absorbance-based assay. The lead polymers were selected and characterized for their ability to alter the precipitation kinetics of a mAb in physiologically relevant conditions using two model systems. Biophysical testing via surface tension measurements, isothermal titration calorimetry (ITC), microscale thermophoresis (MST), and intrinsic fluorescence quenching indicated that the polymers delayed onset of mAb precipitation from a combination of surfactant behaviour and interactions with the protein to prevent protein-protein interactions leading to colloidal instability. The random heteropolymers described are a new class of excipients that may enable development of SC mAb formulations previously inaccessible to patients.

Meso- and Macroporous Polymer Gels for Efficient Adsorption of Block Copolymer Surfactants.

An understanding of surfactant adsorption at solid-liquid interfaces is important for solving many technological problems. This work evaluates surfactant adsorption abilities of high surface area (200-600 m2/g), high porosity (>90%), hierarchically structured open pore polymer gels. Specifically, the interactions of a nonionic block copolymer surfactant, poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO), with three polymer gels, namely, syndiotactic polystyrene (sPS), polyimide (PI), and polyurea (PUA) offering different surface energy values, are evaluated at surfactant concentrations below and well above the critical micelle concentration (CMC). Two distinct surfactant adsorption behaviors are identified from the surface tension and nuclear magnetic resonance data. At concentrations below CMC, the surfactant molecules adsorb as a monolayer on polymer strands, inferred from the Langmuir-type adsorption isotherm, with the adsorbed amount increasing with the specific surface area of the polymer gel. The study reports for the first time that the gels show a strong surfactant adsorption above CMC, with the effective surfactant concentration in the gel reaching several folds of the CMC values. The effective surfactant concentration in the gel is analyzed using surfactant micelle size, polymer surface energy, and pore size of the gel. The findings of this study may have strong implications in liquid-liquid separation problems and in the removal of small dye molecules, heavy metal ions, and living organisms from aqueous streams.

Probing Molecular Interactions of Antibody Drugs, Silicone Oil, and Surfactant at Buried Interfaces In Situ.

Antibody drugs have been rapidly developed to cure many diseases including COVID-19 infection. Silicone oil is commonly used as a lubricant coating material for devices used in the pharmaceutical industry to store and administer antibody drug formulations. However, the interaction between silicone oil and antibody molecules could lead to the adsorption, denaturation, and aggregation of antibody molecules, impacting the efficacy of antibody drugs. Here, we studied the molecular interactions between antibodies and silicone oil in situ in real time. The effect of the surfactant on such interactions was also investigated. Specifically, the adsorption dynamics of a bispecific antibody (BsAb) onto a silicone oil surface without and with different concentrations of the surfactant PS80 in antibody solutions were monitored. Also the possible lowest effective PS80 concentrations that can prevent the adsorption of BsAb as well as a monoclonal antibody (mAb) onto silicone oil were measured. It was found that different concentrations of PS80 are required for preventing the adsorption of different antibodies. Both BsAB and mAB denature on silicone oil without a surfactant. However, for a low surfactant concentration in the solution, although the surfactant could not completely prevent the antibody from adsorption, it could maintain the native structures of adsorbed BsAb and mAb antibodies on silicone oil. This is important knowledge, showing that to prevent antibody aggregation on silicone oil it is not necessary to add surfactant to a concentration high enough to completely minimize protein adsorption.

Obtaining Bioemulsions Structured as "Networks" by Innovative Technologies

New bioemulsions structured like “networks” were created by innovative technologies based on: elastin/zinc hydroxide/ (bolaamphiphiles mixture: bis [2-butyl (sodium bis-thioacetate) sodium dicarboxylate 1,10 decanediyl ester] and/or sucrose diester)/ acetic acid/water, for improved surface properties development with applications in leather industry. We used in this research two “bolaamphiphiles”. Bolaamphiphilic molecules contain a hydrophobic skeleton (e.g., one, two, or three alkyl chains, a steroid, or a porphyrin) and two water-soluble groups on both ends. The interaction of surfactants with biopolymers in aqueous medium results in the formation of different association structures. There are various morphologies of biopolymer-surfactant association complexes depending on the molecular structure of the biopolymer and surfactant, on the nature of interaction forces between solvents and surfactant or biopolymer. The innovation consists in the technologies for obtaining novel micro and nanostructured bioemulsions, and the compatibilisation with film forming polymers for leather surface finishing. Elastin/zinc hydroxide micro and nanocomposites have been stabilized with bolaamphiphilic surfactants mixture: bis [2-butyl (sodium bis-thioacetate) sodium dicarboxylate 1,10 decanediyl ester and sucrose diester in a 1:1 acetic acid/water ratio, to increase the uniformity of nanocomposites. Micro and nanostructured composites like “networks” developed as a result of biopolymer-surfactants interactions for elastin/zinc hydroxide/surfactants mixture couple in acetic acid/water system are reported by SEM microscopy and DLS analysis. A special class of micro and nanoarchitectures is represented by structures organized as “network” assemblies. The novel micro and nanocomposites can provide the hybrid film with increased resistance to rubbing and water, and to deformation. Environmentally-friendly substrates with smart multifunctional features can be obtained for various applications.

Interaction of surfactants with phospholipid vesicles in the low concentration regime

The interactions between diluted phospholipid vesicles (0.3 μM - 40 μM) and surfactants (around their cmc) have been investigated as model of the phenomena taking place when enveloped viruses are challenged by detergent formulations such as mouthwashes or dishwashing liquids. We have used negatively charged Small Unilamellar Vesicles (SUVs) to simulate the negatively charged viral envelope and surfactants with different charges: the anionic Sodium Dodecyl Sulphate (SDS), the cationic Cetylpyridinium Chloride (CPC) and the non-ionic Octaethylene glycol monodecyl ether (C10E8). Dynamic and Electrophoretic Light Scattering have been used to probe variations in size and surface charge of the vesicles. The surfactants effect on the membrane permeability was investigated by measuring the fluorescence of SUVs secluding the fluorophore calcein. All the surfactants perturb the bilayer inducing graded dye leakage. Irrespective of the chemical nature of the surfactant, the membrane leakage follows the same sigmoidal master curve when it is plotted against the ratio surfactant concentration/cmc. The membrane leakage is negligible below cmc/2 and above such a value increases up to the cmc where all the dye has been fully released. For ionic SDS and CPC the dependence of leakage halftime on such a scaled concentration is the same irrespective of the charge of the surfactant and the vesicles. The nonionic surfactant C10E8 induces the dye release from the SUV two orders-of-magnitude faster than the ionic surfactants. These results show that the rate-determining parameter for the permeabilization of the lipid bilayers is the electrostatic penalty to the flip-flop required to transport the surfactant inside the vesicle.

Pulmonary surfactant and drug delivery: Vehiculization of a tryptophan-tagged antimicrobial peptide over the air-liquid interfacial highway

This work evaluates interaction of pulmonary surfactant (PS) and antimicrobial peptides (AMPs) in order to investigate (i) if PS can be used to transport AMPs, and (ii) to what extent PS interferes with AMP function and vice versa. This, in turn, is motivated by a need to find new strategies to treat bacterial infections in the airways. Low respiratory tract infections (LRTIs) are a leading cause of illness and death worldwide that, together with the problem of multidrug-resistant (MDR) bacteria, bring to light the necessity of developing effective therapies that ensure high bioavailability of the drug at the site of infection and display a potent antimicrobial effect. Here, we propose the combination of AMPs with PS to improve their delivery, exemplified for the hydrophobically end-tagged AMP, GRR10W4 (GRRPRPRPRPWWWW-NH2), with previously demonstrated potent antimicrobial activity against a broad spectrum of bacteria under various conditions. Experiments using model systems emulating the respiratory interface and an operating alveolus, based on surface balances and bubble surfactometry, served to demonstrate that a fluorescently labelled version of GRR10W4 (GRR10W4-F), was able to interact and insert into PS membranes without affecting its biophysical function. Therefore, vehiculization of the peptide along air–liquid interfaces was enabled, even for interfaces previously occupied by surfactants layers. Furthermore, breathing-like compression-expansion dynamics promoted the interfacial release of GRR10W4-F after its delivery, which could further allow the peptide to perform its antimicrobial function. PS/GRR10W4-F formulations displayed greater antimicrobial effects and reduced toxicity on cultured airway epithelial cells compared to that of the peptide alone. Taken together, these results open the door to the development of novel delivery strategies for AMPs in order to increase the bioavailability of these molecules at the infection site via inhaled therapies.

Design of a biomimetic, small-scale artificial leaf surface for the study of environmental interactions.

The cuticle with its superimposed epicuticular waxes represents the barrier of all aboveground parts of higher plant primary tissues. Epicuticular waxes have multiple effects on the interaction of plants with their living and non-living environment, whereby their shape, dimension, arrangement, and chemical composition play significant roles. Here, the ability of self-assembly of wax after isolation from the leaves was used to develop a small-scale wax-coated artificial leaf surface with the chemical composition and wettability of wheat (Triticum aestivum) leaves. By thermal evaporation of extracted plant waxes and adjustment of the evaporated wax amounts, the wettability and chemical character of the microstructure of the surface of wheat leaves were transferred onto a technical surface. For the use of these artificial leaves as a test system for biotic (e.g., germination of fungal pathogens) and non-biotic (e.g., applied surfactants) interactions on natural leaf surfaces, the chemical composition and the wetting behavior should be the same in both. Therefore, the morphology, chemistry, and wetting properties of natural and artificial surfaces with recrystallized wax structures were analyzed by scanning electron microscopy, gas chromatography–mass spectrometry, and by the determination of water contact angles, contact angle hysteresis, and tilting angles. Wheat leaves of different ages were covered exclusively with wax platelets. The extracted wheat wax was composed of alcohols, aldehydes, esters, and acids. The main component was 1-octacosanol. The waxes recrystallized as three-dimensional structures on the artificial surfaces. The three tested wetting parameters resembled the ones of the natural surface, providing an artificial surface with the chemical information of epicuticular waxes and the wetting properties of a natural leaf surface.

Micellization and gelation characteristics of Pluronic P123 and single ester-bonded cleavable cationic gemini surfactant: A potential system for solubilization and release of ibuprofen

We herein report the mixed micelle and monolayer formation of mixtures of a biocompatible and cleavable oxy-diester twin tailed (gemini) surfactant, 2,2′-[(oxybis(ethane-1,2-diyl))bis(oxy)]bis(N-hexadecyl-N,Ndimethyl-2-oxoethanaminium) dichloride (16-E1-16) with the triblock copolymer, P123 (HO(CH2CH2O)20(CH2CH(CH3)O)70(CH2CH2O)20H) using tensiometry, dynamic light scattering (DLS), and rheology. It was observed that P123 and 16-E1-16 have strong interaction and form small mixed micelles with similar micellar composition throughout the bulk mole fraction range with insignificant counterion binding. Besides, P123 and 16-E1-16 mixed surfactant system forms thermodynamically stable mixed monolayer that is rich in P123. Variation of viscosity with shear rate revealed better injectable property of the formulations of binary mixtures of P123 and 16-E1-16 compared to pure P123. Also, below α16-E1-16 = 0.3, all the mixtures were in the form of sol which transform into a weak gel at physiological temperatures making these formulations relevant as injectable delivery system. Solubilization capacity of these mixed micelles towards ibuprofen (IBU) showed that addition of 16-E1-16 to P123 micelles reduces its solubilization capacity but with the advantage of making the formulation injectable due to their favorable shear induced viscosity changes and thermogelation properties. Mixed micelles showed faster drug release rate predominantly following Fickian mechanism with negligible contribution of relaxation process in the release phenomena. There is no report showing interaction of biocompatible and cleavable gemini surfactant 16-E1-16 with P123 in mixed micelle and monolayer formation with detailed rheological, drug encapsulation and release studies even though this amphiphilic system has a potential to act as an injectable drug delivery system.

Technology Focus: Oilfield Chemistry (September 2022)

The technical arena of oilfield chemistry is no longer an area of interest only to production operations. When completions operations (including hydraulic fracturing) yield wells with a low productivity index (PI), all chemical constituents introduced downhole (e.g., drilling, completions, and stimulation) are scrutinized for deleterious interactions with the mineralogy, formation fluids, and one another. Field-relevant work flows and improved test methods are critical to the investigation of root causes for a low PI. Several studies have been published showcasing new additives and fluids that can improve well productivity. However, often the methods to select and optimize these products do not account for the uncertainties and challenges of an actual wellsite (e.g., sample collection and integrity, challenging surface conditions, and representative samples). Operators must challenge themselves first to document and rank the most likely causes of low or declining well productivity using actual well samples and parameters. Then, collaboration with chemical and service providers is used to technically justify (a) the selection and optimization of chemical additives to maintain or stimulate productivity on existing producers and (b) the optimization of additives for future well completions in the same reservoir. The selected papers represent sophisticated work around the phenomena of scale and precipitation that can have dramatic effects on productivity, specifically in shale and tight completions. These papers include comprehensive work flows to analyze recovered samples (to confirm damage identification) as well as improved methods to analyze the concentration of scale inhibitor in produced water with enhanced simplicity and accuracy. The selections also include integrated studies of the phenomena of chemical species at critical interfaces (formation, cement, and casing) that can seed production of damaging deposits, with an eye toward prevention of their effects on productivity. Recommended additional reading at OnePetro: www.onepetro.org. SPE 205284 Surfactant and Friction-Reducer Interaction in High-Salinity Slickwater Fracturing by Abdelrahman Kotb, Texas A&M University, et al. SPE 209507 The Oda Field: From Scale Prediction to Reality—Why Squeezing Was Not Necessary Despite a High Calcium Sulphate Risk by Baard Kaasa, Scale Consult, et al. URTeC 208302 A Flexible Biomimetic Superhydrophobic and Superoleophilic 3D Macroporous Polymer-Based Robust Network for the Efficient Separation of Oil-Contaminated Water by Fahd I. Alghunaimi, Saudi Aramco, et al.