Surfactant/biosurfactant mixing: Adsorption of saponin/nonionic surfactant mixtures at the air-water interface

Transitioning from Pickering emulsions to Pickering emulsion hydrogels: A potential advancement in cosmeceuticals

Cosmeceuticals, focusing on enhancing skin health and appearance, heavily rely on emulsions as one of the common mediums. These emulsions pose a challenge due to their dependence on surfactants which are essential for stability but are causing concerns about environmental impact as well as evolving consumer preferences. This has led to research focused on Pickering emulsions (PEs), which are colloidal particle-based emulsion alternatives. Compared to conventional emulsions, PEs offer enhanced stability and functionality in addition to serving as a sustainable alternative but still pose challenges such as rheological control and requiring further improvement in long-term stability, whereby the limitations could be addressed through the introduction of a hydrogel network. In this review, we first highlight the strategies and considerations to optimize active ingredient (AI) absorption and penetration in a PE-based formulation. We then delve into a comprehensive overview of the potential of Pickering-based cosmeceutical emulsions including their attractive features, the various Pickering particles that can be employed, past studies and their limitations. Further, PE hydrogels (PEHs), which combines the features between PE and hydrogel as an innovative solution to address challenges posed by both conventional emulsions and PEs in the cosmeceutical industry is explored. Moreover, concerns related to toxicity and biocompatibility are critically examined, alongside considerations of scalability and commercial viability, providing a forward-looking perspective on potential future research directions centered on the application of PEHs in the cosmeceutical field.

Glycolipids biosurfactants production using low-cost substrates for environmental remediation: progress, challenges, and future prospects

The production of renewable materials from alternative sources is becoming increasingly important to reduce the detrimental environmental effects of their non-renewable counterparts and natural resources, while making them more economical and sustainable. Chemical surfactants, which are highly toxic and non-biodegradable, are used in a wide range of industrial and environmental applications harming humans, animals, plants, and other entities. Chemical surfactants can be substituted with biosurfactants (BS), which are produced by microorganisms like bacteria, fungi, and yeast. They have excellent emulsifying, foaming, and dispersing properties, as well as excellent biodegradability, lower toxicity, and the ability to remain stable under severe conditions, making them useful for a variety of industrial and environmental applications. Despite these advantages, BS derived from conventional resources and precursors (such as edible oils and carbohydrates) are expensive, limiting large-scale production of BS. In addition, the use of unconventional substrates such as agro-industrial wastes lowers the BS productivity and drives up production costs. However, overcoming the barriers to commercial-scale production is critical to the widespread adoption of these products. Overcoming these challenges would not only promote the use of environmentally friendly surfactants but also contribute to sustainable waste management and reduce dependence on non-renewable resources. This study explores the efficient use of wastes and other low-cost substrates to produce glycolipids BS, identifies efficient substrates for commercial production, and recommends strategies to improve productivity and use BS in environmental remediation.

Development and stability of intimate soap formulations using Sapindus saponaria L. extract as a natural surfactant

The use of synthetic surfactants reflects the high demand in the hygiene and cleaning sector for products with low-cost and good-effectiveness. These ingredients are the main components of intimate soap formulations. Sapindus saponaria L. is a plant rich in saponins, with the potential to be used as a natural surfactant due to its amphiphilic character and its foam-forming properties. Therefore, this study aimed to develop intimate soap formulations using S. saponaria extract as a natural surfactant and analyze its stability and surfactant characteristics. Preliminary and accelerated stability parameters, rheological characteristics, surface tension, foaming power, foam stability and emulsification potential were evaluated. The formulations were stable at a pH suitable for the intimate region (4.0 to 4.5), the presence of S. saponaria extract provided greater reduction of surface tension, better foaming and foam stability and greater emulsification power, desirable characteristics for an intimate liquid soap. These results demonstrate that the incorporation of S. saponaria extract into liquid soap formulations is an excellent option as a natural surfactant to reduce the use of synthetic anionic surfactants such as SLES.

Growth of alfalfa in the presence of metabolites from a dark septate endophyte strain Alternaria sp. 17463 cultured with a nonionic surfactant and emulsifier

AIM

Dark septate endophytes (DSE) were widely used in the agriculture and ecological restoration. The objective of this work was to assess the effect of culture media nonionic surfactant and emulsifier on the biomass and metabolites of DSE strain Alternaria sp. 17463.

METHODS AND RESULTS

Changes in the composition of DSE metabolites following the addition of Tween 80 during liquid culture of a DSE fungus were analyzed and used in growth tests of alfalfa.Shaking flask fermentation was carried out and the surfactant was fed to the fungus during the fermentation. The residual sugar content and pH declined significantly in the medium and the biomass of DSE increased by 7.27% over controls with no surfactant. Metabolomic analysis showed that adding the surfactant significantly increased the content of 63 metabolites (P < 0.05). These include lipids and lipid-like molecules, organooxygen compounds, amino acids and organic acids, and flavonoids. Enrichment analysis of metabolic pathways indicates that surfactant addition promoted carbohydrate metabolism and amino acid synthesis. A plant hydroponic experiment indicated that these changes in metabolites altered the root structure of alfalfa seedlings. They also promoted significant increases in root length and root surface area, and increased alfalfa total biomass by 50.2%.

CONCLUSIONS

The addition of the surfactant promoted sugar utilization by the DSE fungus and increased the synthesis of lipids and amino acids, resulting in the ability of the fungal metabolites to change root structure and promote plant growth.

Synergism of Surfactant Mixture in Lowering Vapor-Liquid Interfacial Tension

Through employing molecular dynamics, in this work, we study how a two-component surfactant mixture cooperatively reduces the interfacial tension of a flat vapor-liquid interface. Our simulation results show that in the presence of a given insoluble surfactant, adding a secondary surfactant would either further reduce interfacial tension, indicating a positive synergistic effect, or increase the interfacial tension instead, indicating a negative synergistic effect. The synergism of the surfactant mixture in lowering surface tension is found to depend strongly on the structure complementary effect between different surfactant components. The synergistic mechanisms are then interpreted with minimization of the bending free energy of the composite surfactant monolayer via cooperatively changing the monolayer spontaneous curvature. By roughly describing the monolayer spontaneous curvature with the balanced distribution of surfactant heads and tails, we confirm that the positive synergistic effect in lowering surface tension is featured with the increasingly symmetric head-tail distributions, while the negative synergistic effect is featured with the increasingly asymmetric head-tail distributions. Furthermore, our simulation results indicate that minimal interfacial tension can only be observed when the spontaneous curvature is nearly zero.

Microbial Biosurfactant as an Alternate to Chemical Surfactants for Application in Cosmetics Industries in Personal and Skin Care Products: A Critical Review

Cosmetics and personal care items are used worldwide and administered straight to the skin. The hazardous nature of the chemical surfactant utilized in the production of cosmetics has caused alarm on a global scale. Therefore, bacterial biosurfactants (BS) are becoming increasingly popular in industrial product production as a biocompatible, low-toxic alternative surfactant. Chemical surfactants can induce allergic responses and skin irritations; thus, they should be replaced with less harmful substances for skin health. The cosmetic industry seeks novel biological alternatives to replace chemical compounds and improve product qualities. Most of these chemicals have a biological origin and can be obtained from plant, bacterial, fungal, and algal sources. Various biological molecules have intriguing capabilities, such as biosurfactants, vitamins, antioxidants, pigments, enzymes, and peptides. These are safe, biodegradable, and environmentally friendly than chemical options. Plant-based biosurfactants, such as saponins, offer numerous advantages over synthetic surfactants, i.e., biodegradable, nontoxic, and environmentally friendly nature. Saponins are a promising source of natural biosurfactants for various industrial and academic applications. However, microbial glycolipids and lipopeptides have been used in biotechnology and cosmetics due to their multifunctional character, including detergency, emulsifying, foaming, and skin moisturizing capabilities. In addition, some of them have the potential to be used as antibacterial agents. In this review, we like to enlighten the application of microbial biosurfactants for replacing chemical surfactants in existing cosmetic and personal skincare pharmaceutical formulations due to their antibacterial, skin surface moisturizing, and low toxicity characteristics.

Eco-friendly scouring of cotton knit fabrics with enzyme and soapnut: An alternative to conventional NaOH and synthetic surfactant based scouring

Eye-catching, aesthetic fashions often suppress its untold dark story of unsustainable processing including hazardous wet treatment. Considering the risks imposed by conventional cotton scouring and following the trend of scouring with enzymes, this study was undertaken to evaluate the bioscouring of cotton knit fabric involving saponin-enriched soapnut as a natural surfactant, applied from a bath requiring a few chemicals and gentle processing conditions, contributing to the eco-friendliness. The proposed application was compared to synthetic detergent engaged enzymatic scouring as well as the classic scouring with Sodium hydroxide. A cellulolytic pectate lyase enzyme (0.5%-0.8% o.w.f) was applied at 55 °C for 60 min at pH 5-5.5 with varying surfactant concentrations. A low concentration of soapnut extract (1 g/L to 2 g/L) was found sufficient to assist in the removal of non-cellulosic impurities from the cotton fabric after bioscouring with 0.5% o.w.f. enzyme, leading to good hydrophilicity indicated by an average wetting time of 4.86 s at the expense of 3.1%-3.8% weight loss. The scoured fabrics were further dyed with 1% o.w.f. reactive dye to observe the dyeing performance. The treated samples were characterized in terms of weight loss, wettability, bursting strength, whiteness index, and color value. The proposed application confronted level dyeing and the ratings for color fastness to washing and rubbing were 4-5 for all of the samples scoured enzymatically with soapnut. The study was also statistically analyzed and concluded.

Neutron reflection and the thermodynamics of the air-water interface

By means of isotopic substitution, measurements of the neutron reflectivity (NR) from a flat water surface generally give model independent measurements of the amount of a chosen solute at the surface irrespective of whether the layer is a mixture or whether there is any aggregation in the bulk solution. Previously, adsorption at air-water interfaces has been determined by applying the Gibbs equation to surface tension (ST) measurements, which requires assumptions about the composition of the surface and about the activity of the solute in the bulk, which, in turn, means that in practice the surface is assumed to consist of the pure solute or of a mixture of pure solutes, and that the activity of the solute in the bulk solution is known. The use of NR in combination with ST-Gibbs measurements makes it possible to (i) avoid these assumptions and hence understand several patterns of ST behaviour previously considered to be anomalous and (ii) to start to analyse quantitatively the behaviour of mixed surfactants both below and above the critical micelle concentration. These two developments in our understanding of the thermodynamics of the air-water interface are described with recent examples.

Studies on evaluation of surfactant coupled sonication pretreatment on Ulva fasciata (marine macroalgae) for enhanced biohydrogen production

Biohydrogen production from marine macroalgal biomass by advanced pre-treatment strategies is considered a clean energy technology. The present study focuses on investigating the effects of sonication pre-treatment (SP) and saponin coupled sonic pre-treatment (SSP) on Ulva fasciata for enhancing the production of biohydrogen. The SP and SSP were optimized to improve the hydrolysis process during digestion. The optimized time and sonication power were found respectively as 30 min and 200 W. A high concentration of biopolymer release was noticed in SSP than SP at optimized conditions. The surfactant dosage in SSP was optimized at 0.0036 g/g TS. The effect of SSP process was assessed by estimation of COD (Chemical Oxygen Demand) and SCOD (Soluble Chemical Oxygen Demand) release. The study revealed that, at a specific energy of 36,000 KJ/Kg TS, the SCOD release was higher in SSP (1900 mg/L) than SP (1050 mg/L). The SSP process could improve the COD solubilization to 15 % more than the SP. Carbohydrate and protein release are also more in SSP than SP. The use of biosurfactants significantly reduced the energy utilization in the hydrolysis process. The SSP pre-treated Ulva fasciata biomass has yielded a higher biohydrogen of 91.7 mL/g COD which is higher compared to SP (40.5 mL/g COD) and Control (9 mL/g COD).

Self-Assembly of NaOL-DDA Mixtures in Aqueous Solution: A Molecular Dynamics Simulation Study

The self-assembly behaviors of sodium oleate (NaOL), dodecylamine (DDA), and their mixtures in aqueous solution were systematically investigated by large-scale molecular dynamics simulations, respectively. The interaction mechanisms between the surfactants, as well as the surfactants and solvent, were revealed via the radial distribution function (RDF), cluster size, solvent-accessible surface area (SASA), hydrogen bond, and non-bond interaction energy. Results showed that the molecules more easily formed aggregates in mixed systems compared to pure systems, indicating higher surface activity. The SASA values of DDA and NaOL decreased significantly after mixing, indicating a tighter aggregation of the mixed surfactants. The RDF results indicated that DDA and NaOL strongly interacted with each other, especially in the mixed system with a 1:1 molar ratio. Compared to van der Waals interactions, electrostatic interactions between the surfactant molecules were the main contributors to the improved aggregation in the mixed systems. Besides, hydrogen bonds were found between NaOL and DDA in the mixed systems. Therefore, the aggregates in the mixed systems were much more compact in comparison with pure systems, which contributed to the reduction of the repulsive force between same molecules. These findings indicated that the mixed NaOL/DDA surfactants had a great potential in application of mineral flotation.

pH effects on the molecular structure and charging state of β-Escin biosurfactants at the air-water interface

Saponins like β-escin exhibit an unusually high surface activity paired with a remarkable surface rheology which makes them as biosurfactants highly interesting for applications in soft matter colloids and at interfaces. We have applied vibrational sum-frequency generation (SFG) to study β-escin adsorption layers at the air-water interface as a function of electrolyte pH and compare the results from SFG spectroscopy to complementary experiments that have addressed the surface tension and the surface dilational rheology. SFG spectra of β-escin modified air-water interfaces demonstrate that the SFG intensity of OH stretching vibrations from interfacial water molecules is a function of pH and dramatically increases when the pH is increased from acidic to basic conditions and reaches a plateau at a solution pH of > 6. These changes are attributable to the interfacial charging state and to the deprotonation of the carboxylic acid group of β-escin. Thus, the change in OH intensity provides qualitative information on the degree of protonation of this group at the air-water interface. At pH < 4 the air-water interface is dominated by the charge neutral form of β-escin, while at pH > 6 its carboxylic acid group is fully deprotonated and, consequently, the interface is highly charged. These observations are corroborated by the change in equilibrium surface tension which is qualitatively similar to the change in OH intensity as seen in the SFG spectra. Further, once the surface layer is charge neutral, the surface elasticity drastically increases. This can be attributed to a change in prevailing intermolecular interactions that change from dominating repulsive electrostatic interactions at high pH, to dominating attractive interactions, such as hydrophobic and dispersive interactions, as well as, hydrogen bonding at low pH values. In addition to the clear changes in OH intensity from interfacial H₂O, the SFG spectra exhibit drastic changes in the CH bands from interfacial β-escin which we relate to differences in the net molecular orientation. This orientation change is driven by tighter packing of β-escin adsorption layers when the β-escin moiety is in its charge neutral form (pH < 4).

Saponin surfactants used in drug delivery systems: A new application for natural medicine components

Saponins are a group of compounds widely distributed in the plant kingdom. Due to their amphiphilic characteristic structure, saponins have high surface activity and self-assembly property and can be used as natural biosurfactants. Therefore, saponin has become a potential drug delivery system (DDS) carrier and has attracted the attention of many researchers. Increasing studies have found that when drugs combining with saponins, their solubility or bioavailability are improved. This phenomenon may be due to a synergistic mechanism and provides a potentially novel concept for DDS: saponins may be also used for carrier materials. This review emphasized the molecular characteristics and mechanism of saponins as carriers and the research on the morphology of saponin carriers. Besides, the article also introduced the role and application of saponins in DDS. Although there are still some limitations with the application of saponins such as cost, applicability, and hemolysis, the development of technology and in-depth molecular mechanism research will provide saponins with greater application prospects as DDS carriers.

Adsorption and self-assembly properties of the plant based biosurfactant, Glycyrrhizic acid

There is an increased interest in the use of natural surfactant as replacements for synthetic surfactants due to their biosustainable and biocompatible properties. A category of natural surfactants which are attracting much current interest is the triterpenoid saponins; surface active components found extensively in a wide range of plant species. A wide range of different saponin structures exist, depending upon the plant species they are extracted from; but regardless of the variation in structural details they are all highly surface active glycosides. Greater exploitation and application requires a characterisation and understanding of their basic adsorption and self-assembly properties.

HYPOTHESIS

Glycyrrhizic acid, extracted from Licorice root, is a monodesmosidic triterpenoid saponin. It is widely used in cosmetic and pharmaceutical applications due to its anti-inflammatory properties, and is an ingredient in foods as a sweetener additive. It has an additional attraction due to its gel forming properties at relatively low concentrations. Although it has attracted much recent attention, many of its basic surface active characteristics, adsorption and self-assembly, remain relatively unexplored. How the structure of the Glycyrrhizic acid saponin affects its surface active properties and the impact of gelation on these properties are important considerations, and to investigate these are the focus of the study.

EXPERIMENTS

In this paper the adsorption properties at the air-water interface and the self-assembly in solution have been investigated using by neutron reflectivity and small angle neutron scattering; in non-gelling and gelling conditions.

FINDINGS

The adsorption isotherm is determined in water and in the presence of gelling additives, and compared with the adsorption behaviour of other saponins. Gelation has minimal impact on the adsorption; apart from producing a rougher surface with a surface texture on a macroscopic length scale. Globular micelles are formed in aqueous solution with modest anisotropy, and are compared with the structure of other saponin micelles. The addition of gelling agents results in only minimal micelle growth, and the solutions remain isotropic under applied shear flow.