Search Results (256)

Microbial biosurfactants (mBSs) are bioactive molecules with diverse applications, notably as antimicrobial agents against antibiotic-resistant pathogens. Produced by bacteria and yeasts, mBSs are classified as glycolipids, lipopeptides, polymeric, and particulate types. The global rise in multidrug-resistant organisms, such as Escherichia coli, Klebsiella pneumoniae, Salmonella typhimurium, Pseudomonas aeruginosa, and Acinetobacter baumannii, underscores the urgent need for new antimicrobial strategies. mBSs disrupt microbial growth by interacting with the lipid components of pathogens, offering promising alternatives to conventional antibiotics. This review highlights the sources, chemical structures, and properties of mBSs, their antimicrobial activities, synergistic effects with antibiotics, and structure–activity relationships. Special emphasis is placed on surfactant modification, where targeted changes—such as valine substitution in surfactin—significantly lower critical micelle concentrations (CMC) and enhance antimicrobial potency. Such rational engineering demonstrates how biosurfactants can be tailored for improved biomedical performance while minimizing cytotoxicity. In parallel, artificial intelligence (AI) algorithms, including artificial neural networks and genetic algorithms, optimize yields, predict substrate suitability from agricultural residues, and guide microbial strain engineering. AI models can predict interfacial behavior and synchronize fermentation with purification. Advancing the understanding of mBS interactions with microbial membranes, combined with modification strategies and AI-guided optimization, is essential for developing targeted therapies against resistant infections. Future research should integrate these approaches to engineer novel derivatives, reduce costs, and validate clinical potential through comprehensive in vivo studies. Full article

Surfactants are commonly employed in cleaning, cosmetic, and pharmaceutical formulations due to their ability to lower surface tension and facilitate the formation of emulsions, foams, and dispersions. Recent research highlights the advantages of synergistic interactions between anionic and nonionic surfactants to improve overall performance. In this study, the physicochemical properties and performance of binary mixtures of the anionic surfactant sodium lauryl sulfate (SLS) and the amphoteric surfactant lauryl dimethyl amine oxide (LDAO) at varying ratios (100% SLS, 90:10, 80:20, 70:30, 60:40, and 50:50) were investigated. Key parameters analysed included critical micelle concentration (CMC), surface tension (γ), foam volume, and potential irritability, assessed via the Zein test. The results revealed a clear synergistic effect between SLS and LDAO: all mixtures showed reduced CMC and minimum surface tension compared to the individual surfactants, while exhibiting enhanced foam volume and stability. Regarding irritability, increasing LDAO content consistently led to decreased protein denaturation, indicating lower irritancy levels. Furthermore, the results obtained in the Zein test confirmed that mixtures induced less protein denaturation than the sum of their individual surfactant components, with formulations ranging from moderately to non-irritating. The results obtained indicate that the more stable mixed micelle systems (SLS + LDAO) might improve the performance of cleaning formulations (γ, CMC, foam) while reducing the irritability. Full article

Bacterial biosurfactants have potential applications in green cleaning due to their environmental friendliness. Among all isolated bacterial strains in this study, strain N33 exhibited the most potent oil-displacing activity and was identified as Pseudomonas aeruginosa. Its biosurfactant yield was approximately 550 mg/L, and structural characterization revealed it to be a glycolipid-type biosurfactant. The oil-displacing ring diameters of the biosurfactant against vegetable oil, paraffin oil, and crude oil reached 6.3 ± 0.3 cm, 5.8 ± 0.2 cm, and 3.8 ± 0.5 cm, respectively. Its critical micelle concentration (CMC) was determined to be 150 mg/L, with a corresponding surface tension of 39.55 mN/m. Notably, this bacterial biosurfactant significantly improved interfacial wettability, reducing the contact angles of vegetable oil, paraffin oil, and crude oil on oil-wetted glass slides from 93.0°, 99.0°, and 98.8° to 10.0°, 15.0°, and 19.0°, respectively. The emulsification efficiency for the three oils was 80%, 57%, and 10%, respectively. Furthermore, capillary oil removal assays verified that the biosurfactant could efficiently strip oil films from the inner walls of capillaries. These findings demonstrate that the biosurfactant produced by P. aeruginosa strain N33 possesses considerable oil-removal efficacy, thereby providing a novel candidate for the research, development, and application of green detergents. Full article

Background/Objectives: Polysorbate 80 (PS80), a complex surfactant mixture, is widely recognized for its ability to enhance drug permeation across the blood–brain barrier (BBB). While this effect is generally attributed to the combined actions of its components, the specific contribution and potential selectivity of individual minor components remain poorly understood. This study therefore aimed to isolate and compare the primary minor components of PS80 to determine whether they uniformly enhance BBB permeation or exhibit drug-specific functions. Methods: In this research, four primary minor components of PS80—polyoxyethylene sorbitan monooleate (PSM), polyoxyethylene isosorbide monooleate (PIM), polyoxyethylene sorbitan dioleate (PSD), and a polyethylene glycol/polyoxyethylene sorbitan/polyoxyethylene isosorbide mixture (PEG/PS/PI mixture)—were isolated using preparative liquid-phase chromatography. Drug-loaded formulations were then prepared using the solvent evaporation method incorporating five model drugs: 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindotricarbocyanine iodide (DiR, MW = 1013.39 Da), donepezil (MW = 379.49 Da), nimodipine (MW = 418.44 Da), chlorogenic acid (MW = 354.31 Da), and paclitaxel (MW = 853.92 Da). The permeability of these formulations across the BBB was evaluated in BALB/c mice after intravenous administration. Brain distribution of the lipophilic dye DiR was assessed using fluorescence imaging, whereas brain homogenate concentrations of therapeutic drugs were quantified by UPLC-MS/MS. Results: Results revealed that the enhancement of brain delivery was dependent on both the specific minor component and the drug. The PEG/PS/PI mixture specially enhanced the brain homogenate concentration of donepezil to 11.8 ± 1.2 ng/mL, representing a 6.9-fold enhancement, while PIM micelles increased the delivery of DiR, donepezil, and nimodipine. In contrast, PSM and PSD micelles improved transport of only DiR and donepezil. The broad performance of PIM suggests a more flexible formulation—a hypothesis that warrants further validation. Conversely, none of the different minor components enhanced the delivery of chlorogenic acid or paclitaxel, underscoring the critical role of specific drug–component interactions. Conclusions: This component-resolved insight challenges the conventional perception of PS80 and provides a rational framework for engineering precision brain-targeted delivery systems by selecting functional minor components. Full article

This study systematically compares how three counterions (Na⁺, K⁺, NH₄⁺) regulate the interfacial properties, foaming behavior, and foam stability of lauroyl glutamate (LG) surfactants, and further examines how added NaCl modifies these properties in the sodium salt (SLG). The three counterions induce only slight variations in surface activity and foam generation. Their influence is more evident in foam stability, with the sodium salt exhibiting enhanced stability across a wider concentration range. For SLG, NaCl addition markedly lowers the critical micelle concentration and induces concentration-dependent changes in foaming behavior: 1% NaCl enhances foam generation, while higher salt levels diminish this effect. Foam stability is strongly affected in the sub-cmc regime, with 3% NaCl producing the most stable foams. Surfactant concentration and salt content are the main factors affecting foam performance. Full article

This study elucidates the interfacial adsorption behavior of a series of short-chain extended anionic surfactants C₈P_xE_yC (sodium ethylhexyl polyoxypropylene x-polyoxyethylene y-carboxylate) on quartz surfaces, with a focus on the regulatory role of polyoxyethylene (EO) and polyoxypropylene (PO) groups. The results indicate that there is a two-stage adsorption process for C₈P_xE_yC molecules on the quartz surface. In the first adsorption stage, C₈P_xE_yC molecules adsorb at the interface primarily via hydrogen bonding with their hydrophobic tails oriented to water and thereby reducing quartz hydrophilicity before the critical micelle concentration (CMC). The second adsorption stage appears at the CMC, and a saturated monolayer forms via hydrogen bonding. When further increasing the concentration, C₈P_xE_yC molecules interact with the pre-adsorbed monolayer by hydrophobic interactions to establish a loose bilayer structure. As the hydrophilic heads of C₈P_xE_yC orient to water, the surface hydrophilicity of quartz enhances after CMC. The PO/EO chain length critically governs the adsorption behavior of C₈P_xE_yC. Specifically, longer PO chains enhance the molecular size and hydrophobicity of C₈P_xE_yC, leading to a decreased saturation adsorption amount. Conversely, longer EO chains improve the hydrophilicity of C₈P_xE_yC, promoting C₈P_xE_yC molecules to stay in water and consequently decreasing the interfacial adsorption amount of C₈P_xE_yC. This structure–activity relationship of C₈P_xE_yC molecules guides the design of extended surfactants for applications requiring precise wettability control. Full article

The chirality transfer from chiral domains to achiral molecules is an important theoretical and applicative issue. In this work, we have investigated the interaction between two anionic chiral surfactants bearing a proline residue as hydrophilic head and the cationic, achiral porphyrin Zn(II) [5-{4-(3-trimethylammonium)propyloxyphenyl}-10,15,20-triphenylporphyrinyl]chloride to assess the effects of the structural variations in both units on the chirality transfer efficiency and amplification. We showed that the efficiency of transferring molecular information depends on the surfactant’s features, namely the chiral configuration of the polar head, the length of the aliphatic chain, and the aggregation state. At the same time, the presence of a coordinated metal and the peripheral charged group on the porphyrin macrocycle are key factors. In detail, the study of the hetero-aggregates formed at a surfactant concentration below the critical micellar concentration (cmc) indicates that the chirality depends on the synergy of hydrophobic effect, coordination interaction, and electrostatic forces. If the surfactant concentration is higher than the cmc, at a low concentration, porphyrins are included in micelles as monomers. Under these conditions, no chirality transfer is evident. When the porphyrin is in excess with respect to the micelles, an efficient asymmetry induction is again observed, transmitted from the chiral polar head to the porphyrin oligomers included in the micelle, through the polar heads and the hydrocarbon chains of the surfactants. Full article

Addressing the issues of low permeability, stress sensitivity in CBM reservoirs, and severe reservoir damage from traditional fracturing fluids, we prepared a Gemini surfactant (designated GEM-CBM) for CBM development using ethanolamine, epichlorohydrin, and alkylamidopropyl dimethylamine as feedstocks. On this basis, we further developed a clean fracturing fluid system. The synthesis process of GEM-CBM was optimized via single-factor and orthogonal experiments. The surface activity of GEM-CBM was assessed through surface tension measurements, whereas the sand-carrying capacity, the rheological properties, gel-breaking performance, and reservoir compatibility were comprehensively examined. The optimal conditions for GEM-CBM are listed as follows: the molar ratio of intermediate to alkylamidopropyl dimethylamine being 1:2.2, reacted at 80 °C for 20 h, with a conversion rate of 96.5%. FTIR verified the existence of characteristic functional groups, and EA results matched the theoretical molecular composition. GEM-CBM has good performance, with a critical micelle concentration (CMC) of 19.0 μmol/L and a surface tension at CMC (γCMC) of 37.44 mN/m. The optimized clean fracturing fluid (formulation: 2.3% GEM-CBM + 0.3% Tween-80 + simulated formation water with 150,000 mg/L mineralization) exhibited a viscosity of 82 mPa·s (66.7% viscosity retention rate) after being subjected to 100 min of shearing at 90 °C and 170 s⁻¹. At 90 °C, the proppant settlement velocity was less than 0.15 mm/s, and complete gel breaking was achieved within 30 min without residues. For coal cores from the Qinshui Basin, the permeability recovery rate reached 78.6%. The permeability recovery rate of coal cores from the Qinshui Basin reached 78.6%. This fracturing fluid realizes viscosity enhancement and sand carrying via the worm-like micellar network formed by GEM-CBM, inducing minimal damage to CBM reservoirs and offering technical support for efficient CBM extraction. Full article

Background: Epigallocatechin-3-gallate (EGCG), a potent green tea polyphenol, possesses significant therapeutic potential, but its clinical application is limited by poor gastrointestinal stability and low oral bioavailability. To address this, a novel herbal nanomedicine-based delivery system was developed utilizing D-α-tocopheryl polyethylene glycol succinate (TPGS) and Poloxamer 407. Objectives: This study aims to develop and characterize EGCG-loaded TPGS/Poloxamer 407 micelles, evaluating their physicochemical properties, storage stability, in vitro drug release profile, in vivo oral bioavailability, and preliminary tolerability observation. Methods: The micelles were prepared using the film hydration method followed by lyophilization. Results: The optimized 2:2 TPGS-to-poloxamer 407 weight ratio yielded EGCG-loaded micelles, displaying a mean particle size of 15.4 nm, a polydispersity index (PDI) of 0.16, a zeta potential of −17.7 mV, an encapsulation efficiency of 82.7%, and a drug loading capacity of 7.6%. The critical micelle concentration (CMC) was determined to be 0.00125% w/v. Transmission electron microscopy (TEM) confirmed the micelles’ uniform spherical morphology. In vitro release studies demonstrated a sustained release profile in both simulated gastric and intestinal fluids. EGCG formulation remained stable for at least six months when stored at 4 °C. No adverse clinical signs were noted during the 28-day tolerability observation. In vivo pharmacokinetic evaluation in mice revealed a significant elevation in oral bioavailability, achieving a 2.27-fold increase in area under the curve (AUC) and a 1.8-fold increase in peak plasma concentration (Cmax) compared to free EGCG. Conclusions: Collectively, these findings underscore the potential of the TPGS/poloxamer 407-based micelle system as a promising oral delivery platform for EGCG, enhancing its stability and pharmacokinetic performance. Full article

This article focuses on the utilization of the supramolecular self-assembly of renewable materials derivatives to obtain functional compounds. Novel bio-based amphiphile molecules (CALAH and PALAH) were synthesized through a tailored process, involving Williamson ether synthesis and amidation reactions, employing renewable amino acid and cashew nut shell liquid (CNSL) derivatives as essential reactants. Their molecular structures were confirmed by nuclear magnetic resonance (NMR), high-resolution mass spectrometry (HRMS), and Fourier-transform infrared spectroscopy (FT-IR). Notably, these compounds self-assemble into nanofibers that organize into a fibrous network, unexpectedly exhibiting two distinct morphologies: curved and rigid nanostructures. These structures were characterized by scanning electron microscopy (SEM), and their formation mechanisms were elucidated through temperature-dependent NMR studies and density functional theory (DFT) calculations. The sodium salts of the compounds (PALA and CALA) exhibited fundamental surfactant properties, exhibiting a hydrophilic lipophilic balance (HLB) value of 13.7 and critical micelle concentration (CMC) values of 1.05 × 10⁻⁵ M and 4.10 × 10⁻⁶ M. They also demonstrated low cytotoxicity, suggesting potential suitability in consumer applications. Furthermore, the compounds exhibited multi-functional performance as effective inhibitors of Staphylococcus aureus and efficient adsorbents for gaseous pollutants. Full article

The impact of counterion structure, especially variations in constitutional and stereochemical isomers, on the properties and performance of AABSs remains under-explored. This study investigates how structural variations, particularly the stereochemistry of diammonium cyclohexane (DACH) counterions, influence the self-assembly behavior of AABSs. Four AABSs: undecanoyl-glycine, -L-alanine, -L-valine, and -L-leucine, were paired with six DACH counterions representing cis/trans isomers of 1,2-, 1,3-, and 1,4-DACH. Critical micelle concentrations (CMCs) were determined via conductimetry, and micellar sizes were measured using dynamic light scattering. The degree of counterion binding (β) was calculated to probe micelle stability, while geometry-optimized structures of the DACH isomers were obtained using density functional theory. Lastly, pH measurements were taken to probe the protonation of DACH counterions at their natural pH, where both the DACH counterion and AABS headgroups intrinsically behave as buffers. Results indicate that while surfactant hydrophobicity primarily dictates CMC in other AABS/DACH combinations, trans-1,3-DACH leads to consistently higher CMCs. This deviation likely arises from its structural conformation, which positions the amine groups an intermediate distance of ~4.4–4.5 Å apart, allowing a small fraction of divalently charged counterions to form strong electrostatic bridging pockets at the micelle interface. These interactions dominate over headgroup effects, leading to elevated and surfactant-independent CMC values. Regarding size and other unusual trends in the systems, cis- isomers formed slightly larger micelles, and trans-1,4-DACH induces abnormal aggregation in undecanoyl-glycine leading to temperature dependent gel formation. These findings highlight the significant influence of counterion structure on AABS behavior and support counterion design as a strategy for enhancing surfactant performance in sustainable applications. Full article

Understanding adsorption and interfacial properties of surface-active agents at interfaces is crucial to the formation and stability of colloidal systems such as emulsions and foams. In this work, interfacial tension and viscoelasticity of saponin at the β-pinene/water interface were studied using drop tensiometry and dilational rheology measurement. For comparison, saponin at the air/water interface was also evaluated. Both saponin and β-pinene are bio-based, eco-friendly, and abundant in plants, trees, and agricultural wastes. Results showed that dynamic interfacial tensions σ(t) of saponin adsorbed at β-pinene/water and air/water interfaces could be well described by the Ward and Tordai model, suggesting that the saponin adsorption kinetics at both interfaces are controlled by a kinetically limited mechanism. The equilibrium interfacial pressure π_e data prior to critical micelle concentration (cmc) were adequately fitted by the Gibbs adsorption isotherm. At the β-pinene/water interface, a higher cmc and a larger area per molecule, but a lower π_e, were observed compared to the air/water interface. Interestingly, the dilational moduli of saponin at β-pinene/water increased with increasing oscillating frequency, but with less significant frequency dependence than their counterparts at the air/water interface. The dilational moduli of saponin at β-pinene/water passed through a minimum with increasing saponin bulk concentration, while the air/water interface exhibited a strikingly different trend in terms of concentration dependence and a higher magnitude for the dilational moduli. The correlation between adsorption behaviors and dilational properties of saponin at the two interfaces is discussed. Fundamental knowledge gained from this study will be beneficial for the rational development of new biocompatible emulsions and foam products for more sustainable applications. Full article

To stimulate the progress of clean fracturing fluid systems, an innovative erucyl ultra-long-chain gemini surfactant (EUCGS) was devised and manufactured during the course of this study. The target product was successfully prepared via a two-step reaction involving erucyl primary amine, 3-bromopropionyl chloride, and 1,3-bis(dimethylamino)propanediol, with an overall yield of 78.6%. FT-IR and ¹H NMR characterization confirmed the presence of C₂₂ ultra-long chains, cis double bonds, amide bonds, and quaternary ammonium headgroups in the product structure. Performance tests showed that EUCGS exhibited an extremely low critical micelle concentration (CMC = 0.018 mmol/L) and excellent ability to reduce surface tension (γCMC = 30.0 mN/m). Rheological property studies indicated that EUCGS solutions gradually exhibited significant non-Newtonian fluid characteristics with increasing concentration, and wormlike micelles with a network structure could self-assemble at a concentration of 1.0 mmol/L. Dynamic rheological tests revealed that the solutions showed typical Maxwell fluid behavior and significant shear-thinning properties, which originated from the orientation and disruption of the wormlike micelle network structure under shear stress. In the presence of 225 mmol/L NaCl, the apparent viscosity of a 20 mmol/L EUCGS solution increased from 86 mPa·s to 256 mPa·s. A temperature resistance evaluation showed that EUCGS solutions had a good temperature resistance at high shear rates and 100 °C. The performance evaluation of fracturing fluids indicates that the proppant settling rate (0.25 cm/min) of the EUCGS-FFS system at 90 °C is significantly superior to that of the conventional system. It features the low dosage and high efficiency of the breaker, with the final core damage rate being only 0.9%. The results demonstrate that the EUCGS achieves a synergistic optimization of high-efficiency interfacial activity, controllable rheological properties, and excellent thermal–salt stability through precise molecular structure design, providing a new material choice for the development of intelligent responsive clean fracturing fluids. Full article

Foam stability plays a critical role in a wide range of industrial and scientific applications. In this study, an innovative method is presented for assessing foam stability through electrical conductivity measurements of liquid films formed within a controlled experimental setup. A modified horizontal glass capillary system with vertically aligned copper electrodes was developed, allowing the continuous monitoring of film drainage and rupture behavior under precise humidity (92% RH) and temperature (30 °C). Experiments were conducted using various concentrations of sodium dodecyl sulfate and Ethylan 1005, with and without NaCl addition. The results demonstrate that film stability increases with higher surfactant concentrations up to a point, beyond which the addition of salt can have either stabilizing or destabilizing effects depending on whether concentration levels are below or above the Critical Micelle Concentration (CMC). At sub-CMC levels, NaCl enhanced film stability by promoting surfactant adsorption and reducing electrostatic repulsion. Conversely, in super-CMC conditions, NaCl led to film destabilization, likely due to changes in interfacial structure and micellar behavior. This approach provides a simple, sensitive, and reproducible technique to quantitatively characterize foam film stability, offering key mechanistic insights and practical guidance for the formulation and optimization of foaming systems across diverse applications. Full article

Biosurfactants (BS) are surface-active compounds synthesized by microorganisms with broad industrial applications. Although BS-producing strains are widely reported, little is known about their production by diazotrophic bacteria. This study investigated, for the first time, the BS produced by Bradyrhizobium sp. ESA 81, a diazotrophic bacterium isolated from the Brazilian semiarid region. The strain was cultivated in the mineral medium using sunflower oil and ammonium nitrate as carbon and nitrogen sources. The compound was chemically characterized using TLC, FAME, FTIR, and mass spectrometry (MALDI-TOF). The results revealed a mixture of glycolipids composed of trehalose linked to fatty acid chains ranging from C9 to C18. The BS exhibited a surface tension of 31.8 mN/m, a critical micelle concentration of 61.2 mg/L, and an interfacial tension of 22.1 mN/m. The BS also showed an emulsification index (EI24) of 55.0%. High stability was observed under extreme conditions of temperature (−20 to 121 °C), pH (2–12), NaCl (5–20%), and sucrose (1–5%). These findings indicate that the trehalolipid BS produced by Bradyrhizobium sp. ESA 81 is a stable and efficient surface-active agent, with promising potential for use in biotechnological and industrial processes. Full article