Long-Lived and Thermoresponsive Emulsion Foams Stabilized by Self-Assembled Saponin Nanofibrils and Fibrillar Network

Preparation, design, identification and application of self-assembly peptides from seafood: A review

Hydrogels formed by self-assembling peptides with low toxicity and high biocompatibility have been widely used in food and biomedical fields. Seafood contains rich protein resources and is also one of the important sources of natural bioactive peptides. The self-assembled peptides in seafood have good functional activity and are very beneficial to human health. In this review, the sequence of seafood self-assembly peptide was introduced, and the preparation, screening, identification and characterization. The rule of self-assembled peptides was elucidated from amino acid sequence composition, amino acid properties (hydrophilic, hydrophobic and electric), secondary structure, interaction and peptide properties (hydrophilic and hydrophobic). It was introduced that the application of hydrogels formed by self-assembled peptides, which lays a theoretical foundation for the development of seafood self-assembled peptides in functional foods and the application of biological materials.

A natural food-grade supramolecular self-assembly system for creation of hierarchically structured hydrogels

We develop a novel hierarchically structured hydrogel by the supramolecular self-assembly of all-natural food-grade building blocks, glycyrrhizic acid (GA) and carrageenan (CG). The co-assembled GA-CG hydrogel system displays an unusual structural transition with the appearance from opacity to translucence and then to opacity, as a function of the concentration of metal ions. The unique GA-CG supramolecular hydrogel system can serve as solid, edible, and responsive active cargo delivery platforms for food and biomedical applications.

Harnessing Glycolipids for Supramolecular Gelation: A Contemporary Review

Within the scope of this review, our exploration spans diverse facets of amphiphilic glycolipid-based low-molecular-weight gelators (LMWGs). This journey explores glycolipid synthesis, self-assembly, and gelation with tailorable properties. It begins by examining the design of glycolipids and their influence on gel formation. Following this, a brief exploration of several gel characterization techniques adds another layer to the understanding of these materials. The final section is dedicated to unraveling the various applications of these glycolipid-based supramolecular gels. A meticulous analysis of available glycolipid gelators and their correlations with desired properties for distinct applications is a pivotal aspect of their investigation. As of the present moment, there exists a notable absence of a review dedicated exclusively to glycolipid gelators. This study aims to bridge this critical gap by presenting an overview that provides novel insights into their unique properties and versatile applications. This holistic examination seeks to contribute to a deeper understanding of molecular design, structural characteristics, and functional applications of glycolipid gelators by offering insights that can propel advancements in these converging scientific disciplines. Overall, this review highlights the diverse classifications of glycolipid-derived gelators and particularly emphasizes their capacity to form gels.

Bioactive foamulsion gels: a unique structure prepared with gellan gum and Acanthophyllum glandulosum extract

BACKGROUND

Foamulsions have become increasingly popular in the food industry due to their ability to enhance the textural, sensory and health-promoting properties of food products. This study was therefore aimed to design and prepare a novel gelled structure, foamulsion gel containing 0-600 g L-1 oil, with gellan gum (GG; 7, 10 and 13 g L-1) and saponin-rich antioxidant Acanthophyllum glandulosum extract (AGE; 2, 6 and 10 g L-1).

RESULTS

The interaction between components was confirmed by infrared spectroscopy. The overrun and porosity of the foamulsion gels increased with antioxidant AGE (1.30 times) and reduced with oil (up to ca 70% and 30%, respectively) and GG levels. The systems were highly stable, and no water or oil was released during the physical stability experiments. Microscopic images showed that the size of air cells was significantly larger than that of oil droplets. The foamulsion gels based on 13 g L-1 GG and 10 g L-1 AGE had markedly higher elastic (G') and viscous (G'') moduli than other samples, and exhibited an elastic and solid-like behavior (G' > G''). The highest gel firmness was found in oil-free sample, and the presence of oil resulted in a lower firmness induced by the larger size and lubrication effect of oil droplets.

CONCLUSION

As a result, the interactions between AGE, GG and oil could lead to the creation of new aerated structures known as bioactive foamulsion gels. These gels exhibit excellent foamability, stability and viscoelasticity and may find applications in the development of novel, healthy and low-calorie aerated foods. © 2024 Society of Chemical Industry.

Fabrication and characterization of novel thermoresponsive emulsion gels and oleogels stabilizied by assembling nanofibrous from dual natural triterpenoid saponins

Novel thermoresponsive emulsion gels and oleogels were fabricated by assembling nanofibrous from natural triterpenoid Quillaja saponin (QS) and glycyrrhizic acid (GA). The viscoelasticity of QS-coated emulsion was observed to be remarkably improved by GA and thus obtain the advantages of excellent gelatinous, thermoresponsive and reversible manner due to the viscoelastic texture from GA nanofibrous as scaffolds in continuous phase. In the gelled emulsions, the phase transition of the GA fibrosis network structure upon heating and cooling was attributed to a thermal sensitivity, whereas interface-induced fibrosis assembly of amphiphilic QS endowed the formation of stable emulsion droplets. Then these emulsion gels were further used as an effective template to fabricate soft-solid oleogels with high oil content of 96%. These findings open up new opportunities for the use of all-natural and sustainable ingredients to develop smart soft materials for replace trans and saturated fats in food industry and other fields.

Injectable Self-Healing Adhesive Natural Glycyrrhizic Acid Bioactive Hydrogel for Bacteria-Infected Wound Healing

Bioactive hydrogels self-assembled from naturally occurring herbal small molecules are attracting growing interest for applications in wound healing, due to their versatile intrinsic biological activities, excellent biocompatibility, as well as facile, sustainable, and eco-friendly processes. However, the development of supramolecular herb hydrogels with sufficient strength and multifunctionality as an ideal wound dressing in clinical practice remains a challenge. In this work, inspired by the efficient clinic therapy and directed self-assembly of natural saponin glycyrrhizic acid (GA), we create a novel GA-based hybrid hydrogel to promote full-thickness wound healing and bacterial-infected wound healing. This hydrogel possesses excellent stability and mechanical performance and multifunctional properties, including injectable, shape-adaptation and remodeling, self-healing, and adhesive abilities. This is attributed to the hierarchical dual-network that comprises the self-assembled hydrogen-bond fibrillar network of aldehyde-contained GA (AGA) and the dynamic covalent network through Schiff base reaction between AGA and a biopolymer carboxymethyl chitosan (CMC). Notably, benefiting from the inherent strong biological activity of GA, the AGA-CMC hybrid hydrogel exhibits unique and significant anti-inflammation effects and antibacterial ability, especially toward the Gram-positive Staphylococcus aureus (S. aureus). In vivo experiments demonstrate that the AGA-CMC hydrogel promotes uninfected skin wound healing and S. aureus-infected skin wound healing by enhancing the formation of granulation tissue, facilitating collagen deposition, reducing bacterial infection, and downregulating inflammatory response. This study highlights the design of new and multifunctional bioactive herb hydrogels from natural drug-food homologous small molecules, which can serve as a promising wound-healing dressing for biomedical applications.

Self-assembled glycyrrhetinic acid derivatives for functional applications: a review

Glycyrrhetinic acid (GA), a famous natural product, has been attracting more attention recently because of its remarkable biological activity, natural sweetness, and good biocompatibility. In the past few years, a considerable amount of literature has grown up around the theme of GA-based chemical modification to broaden its functional applications. Promising structures including gels, micelles, nanoparticles, liposomes, and so forth have been constantly reported. On the one hand, the assembly mechanisms of various materials based on GA derivatives have been elucidated via modern analytical techniques. On the other hand, their potential application prospects in edible additives, intelligent drug delivery, and other fields have been investigated fully due to availability, biocompatibility, and controllable degradability. Inspired by these findings, a systematic summary and classification of the materials formed by GA derivatives seems necessary and meaningful. This review sums up the new functional applications of GA derivatives for the first time and provides better prospects for their application and development.

Stable O/W emulsions and oleogels with amphiphilic konjac glucomannan network: preparation, characterization, and application

BACKGROUND

The stabilization of oil-in-water (O/W) emulsions has long been explored. Assembly of polymer networks is an effective method for stabilizing O/W emulsions. Konjac glucomannan (KGM) is a plant polysaccharide and the network of KGM gel is a good candidate for stabilizing O/W emulsions based on its high viscosity and thickening properties. However, natural KGM has strong hydrophilicity and is not able to offer interfacial activity. Octenyl succinic anhydride (OSA) is a hydrophobic molecule, which is widely used as thickener and stabilizer in food emulsions. In this work, the amphiphilic biopolymer (OSA-KGM) was fabricated by modifying the KGM with OSA. Furthermore, OSA-KGM biopolymer was used to prepare O/W emulsions, which were then freeze-dried and used to prepare oleogels as fat substitute for bakery products.

RESULTS

OSA-KGM had advanced hydrophobicity with water contact angle 81.13° and adsorption behavior at the oil-water interface, with interfacial tension decreasing from 18.52 to 13.57 mN m^-1 within 1 h. The emulsification of OSA-KGM remarkably improved the stability of emulsions without phase separation during storage for 31 days. Oleogels with OSA-KGM showed good thixotropic and structure recovery properties (approximately 100%) and low oil loss (from 69.5% to 50.4%). Cakes made from oleogels had a softer texture than cakes made from peanut oil and margarine.

CONCLUSION

Amphiphilic biopolymer OSA-KGM shows advanced interfacial activity and hydrophobicity. This paper provides an insight into preparing stable O/W emulsions with a new biopolymer and oleogels potentially applied as fat substitute in bakery products. © 2022 Society of Chemical Industry.

Heat- and shear-reversible networks in food: A review

While nature behaves like an irreversible network with respect to entropy and time, certain systems in nature exist that are, to some extent, reversible. The property of reversibility imparts unique benefits to systems that possess them, making them suitable for designing self-healing, stimuli-responsive, and smart materials that can be used in widely divergent fields. Reversible networks are currently being exploited for applications in tissue engineering, drug delivery, and soft robotics. They are also being utilized as low-calorie fat mimetics with melt-in-your-mouth textures, as well as being explored as potential scaffolds for three-dimensional (3D) printable food, among other applications. This review aims to gather representative examples of heat- and shear-reversible networks in the food science literature from the last 30 or so years, in other words, reversible food gels made either from linear biopolymers or from colloidal, particulate dispersions, including those that have been modified specifically to induce reversibility. An overview of the network mechanisms involved that impart reversibility, including a discussion of the strength and range of forces involved, will be highlighted. A model that explains why certain networks are thermoreversible while others are shear-reversible, and why others are both, will also be proposed. A fundamental understanding of these mechanisms will prove invaluable when designing reversible networks in the future, making possible the precise control of their properties, thus fostering innovative applications within the food industry and beyond.

Robust and highly adaptable high internal phase gel emulsions stabilized solely by a natural saponin hydrogelator glycyrrhizic acid

Herein, we report a new class of high internal phase gel emulsions (gel-HIPEs) that are mechanically robust, adaptable, and processable. They can be synthesized facilely by using the natural food-grade saponin glycyrrhizic acid (GA) as the sole stabilizer, which is shown to be versatile for various oils. The structural properties of these HIPEs including appearance, viscoelasticity and processability are well controlled by simply changing the concentration of GA nanofibrils. When the GA nanofibril concentration exceeds 0.3 wt%, the unique gel-HIPEs can be produced through the formation of fibrillar hydrogel networks in the continuous phase. When the nanofibril concentration only increases to 5 wt%, it is surprising to see that these gel-HIPEs display an extremely high mechanical strength, and the storage moduli as well as the yield stress values can reach 408.5 kPa and 3340 Pa (or even more), respectively. We conjecture that such remarkable mechanical performance is mainly attributed to the highly viscoelastic GA nanofibrillar networks in the continuous phase of gel-HIPEs, which can actively trap the nanofibril-coated emulsion droplets and thus strengthen the gel matrix. Consequently, the robust gel-HIPEs can be used as a solid template to fabricate stable porous materials without the need for crosslinking of the continuous phase, and the open- and closed-cell foam microstructures are controlled by the nanofibril concentration. Furthermore, the nanofibril-based HIPEs are promising long-term delivery vehicles with controlled-release properties for lipophilic active cargoes, since the strong fibrillar networks at the droplet surfaces and in the continuous phase can effectively retard the active release.

Tailoring structure and properties of long-lived emulsion foams stabilized by a natural saponin glycyrrhizic acid: Role of oil phase

Novel supramolecular nanofibrils assembled from food-grade saponin glycyrrhizic acid (GA) are effective building blocks to make complex multiphase systems, e.g., emulsion foams. In this work, the effects of different oil phases (castor oil, sunflower oil, dodecane, and limonene) on the formation, stability and structural properties of long-lived emulsion foams prepared by GA nanofibrils (GNs) were investigated. The obtained results showed that soft-solid emulsion foams (4 wt% GNs) can be fabricated, independently of oil phase, and their structural properties, viscoelasticity, and tribological properties can be well tuned by oil phase polarity. Compared to the GNs aqueous foams, the presence of jammed emulsion droplets in the liquid channels and at the surfaces of bubbles can provide a higher bubble stability for emulsion foams. For more polar oil phase (castor oil), GNs showed a higher affinity to the oil-water interface with a lower interfacial tension, thus forming smaller oil droplets and bubbles, which leads to the higher mechanical strength, denser network microstructures, and lower friction coefficients of emulsion foams. However, the limonene foam exhibited weak storage stability and rheological properties, as well as the relatively low lubrication, which may be related to the formation of oil droplet aggregates and clusters induced by the volatility of limonene. GN-based emulsion foams are thermoresponsive, independently of oils, and the temperature-switchable process for the destabilization and regeneration of foams can be controlled and repeated. These emulsion foams based on natural saponin nanofibrils with tunable properties have potential sustainable applications in foods, pharmaceuticals, and personal care products.

Recent Advances and Applications of Plant-Based Bioactive Saponins in Colloidal Multiphase Food Systems

The naturally occurring saponins exhibit remarkable interfacial activity and also possess many biological activities linking to human health benefits, which make them particularly attractive as bifunctional building blocks for formulation of colloidal multiphase food systems. This review focuses on two commonly used food-grade saponins, Quillaja saponins (QS) and glycyrrhizic acid (GA), with the aim of clarifying the relationship between the structural features of saponin molecules and their subsequent self-assembly and interfacial properties. The recent applications of these two saponins in various colloidal multiphase systems, including liquid emulsions, gel emulsions, aqueous foams and complex emulsion foams, are then discussed. A particular emphasis is on the unique use of GA and GA nanofibrils as sole stabilizers for fabricating various multiphase food systems with many advanced qualities including simplicity, ultrastability, stimulability, structural viscoelasticity and processability. These natural saponin and saponin-based colloids are expected to be used as sustainable, plant-based ingredients for designing future foods, cosmetics and pharmaceuticals.

A novel strategy to fabricate stable oil foams with sucrose ester surfactant

HYPOTHESIS

Can a mixture of sucrose ester surfactant in vegetable oil be aerated to yield stable oleofoams? Is foaming achievable from one-phase molecular solutions and/or two-phase crystal dispersions? Does cooling a foam after formation induce surfactant crystallisation and enhance foam stability?

EXPERIMENTS

Concentrating on extra virgin olive oil, we first study the effect of aeration temperature and surfactant concentration on foamability and foam stability of mixtures cooled from a one-phase oil solution. Based on this, we introduce a strategy to increase foam stability by rapidly cooling foam prepared at high temperature which induces surfactant crystallisation in situ. Differential scanning calorimetry, X-ray diffraction, infra-red spectroscopy, surface tension and rheology are used to elucidate the mechanisms.

FINDINGS

Unlike previous reports, both foamability and foam stability decrease upon decreasing the aeration temperature into the two-phase region containing surfactant crystals. At high temperature in the one-phase region, substantial foaming is achieved (over-run 170%) within minutes of whipping but foams ultimately collapse within a week. We show that surfactant molecules are surface-active at high temperature and that hydrogen bonds form between surfactant and oil molecules. Cooling these foams substantially increases foam stability due to both interfacial and bulk surfactant crystallisation. The generic nature of our findings is demonstrated for a range of vegetable oil foams with a maximum over-run of 330% and the absence of drainage, coalescence and disproportionation being achievable.

Large amplitude oscillatory shear (LAOS) for nonlinear rheological behavior of heterogeneous emulsion gels made from natural supramolecular gelators

The linear and nonlinear rheological behaviors of heterogeneous emulsions gels made from natural glycyrrhizic acid (GA) nanofibrils and sitosterol-oryzanol mixtures (sterols) were investigated using small amplitude oscillatory shear (SAOS) and large amplitude oscillatory shear (LAOS). The nonlinear rheological response was qualitatively analyzed using normalized Lissajous-Bowditch curves. The microstructure of the emulsion gels strongly depended on the concentration of sterols in the oil phase, and showed a percolated segregated network at 10-20 wt% sterols due to the partial coalescence of droplets, and a jamming transition without coalescence at higher sterols concentration of 30 wt%. The microstructure differences led to different linear and nonlinear viscoelastic behaviors of these emulsion gels. SAOS tests showed that the oil phase structuring by the sterols significantly enhance the viscoelasticity of GA nanofibril emulsion gels, and the percolating emulsion gels exhibited higher elasticity than the jammed emulsion gel, as evidenced by a lower damping factor and frequency power-law exponent. The data of crossover strain, phase angle, and the normalized Lissajous-Bowditch curves from LAOS tests further revealed that compared to the samples in a jammed state or without oil phase structuring, the emulsion gels with a percolating segregated network showed higher structural elasticity and thus were more resistant to large deformations, probably due to the slow relaxation of rigid, hydrodynamically interacting clusters of partially coalesced droplets. These findings could potentially aid in the design of novel emulsion gels, based on all-natural and sustainable building blocks, with specific textural and functional properties for foods, cosmetics, and pharmaceutical applications.

Highly stable and thermo-responsive gel foams by synergistically combining glycyrrhizic acid nanofibrils and cellulose nanocrystals

HYPOTHESIS

Natural saponin glycyrrhizic acid (GA) and GA nanofibrils (GNFs) are effective foaming agents for formulation of aqueous food-grade foams. Through the synergistic combination of soft semiflexible GNFs with rigid nanofiller cellulose nanocrystals (CNCs), it should be possible to create advanced composite foams with a more complex structure and diverse properties including high stability and stimuli responsiveness.

EXPERIMENTS

Foams containing mixtures of GNFs and CNCs were prepared, and their formation and stability were investigated. A range of microscopy techniques and small deformation oscillatory shear were adopted to examine the microstructure and viscoelasticity of foams, and a stabilization mechanism for highly stable foams was then established. Further, the temperature-responsive destabilization of foams was evaluated.

FINDINGS

CNCs are homogeneously distributed in the architecture and mechanically reinforce the GNF fibrillar network, leading to a highly viscoelastic composite network in the continuous phase of foams, which is the key factor responsible for their high stability. Such ultra-stable gel foams display tunable thermo-responsive behavior and a rapid on-demand destabilization upon heating by inducing a phase transition of the bulk composite network. Our work opens up new scenarios on the use of a novel combination of all-natural, sustainable nanoscale building blocks to develop aqueous "superfoams" which are highly stable, stimulable and processable.

Glycyrrhizin: An alternative drug for the treatment of COVID-19 infection and the associated respiratory syndrome?

Safe and efficient drugs to combat the current COVID-19 pandemic are urgently needed. In this context, we have analyzed the anti-coronavirus potential of the natural product glycyrrhizic acid (GLR), a drug used to treat liver diseases (including viral hepatitis) and specific cutaneous inflammation (such as atopic dermatitis) in some countries. The properties of GLR and its primary active metabolite glycyrrhetinic acid are presented and discussed. GLR has shown activities against different viruses, including SARS-associated Human and animal coronaviruses. GLR is a non-hemolytic saponin and a potent immuno-active anti-inflammatory agent which displays both cytoplasmic and membrane effects. At the membrane level, GLR induces cholesterol-dependent disorganization of lipid rafts which are important for the entry of coronavirus into cells. At the intracellular and circulating levels, GLR can trap the high mobility group box 1 protein and thus blocks the alarmin functions of HMGB1. We used molecular docking to characterize further and discuss both the cholesterol- and HMG box-binding functions of GLR. The membrane and cytoplasmic effects of GLR, coupled with its long-established medical use as a relatively safe drug, make GLR a good candidate to be tested against the SARS-CoV-2 coronavirus, alone and in combination with other drugs. The rational supporting combinations with (hydroxy)chloroquine and tenofovir (two drugs active against SARS-CoV-2) is also discussed. Based on this analysis, we conclude that GLR should be further considered and rapidly evaluated for the treatment of patients with COVID-19.

Dynamic Assemblies of Molecular Motor Amphiphiles Control Macroscopic Foam Properties

Stimuli-responsive supramolecular assemblies controlling macroscopic transformations with high structural fluidity, i.e., foam properties, have attractive prospects for applications in soft materials ranging from biomedical systems to industrial processes, e.g., textile coloring. However, identifying the key processes for the amplification of molecular motion to a macroscopic level response is of fundamental importance for exerting the full potential of macroscopic structural transformations by external stimuli. Herein, we demonstrate the control of dynamic supramolecular assemblies in aqueous media and as a consequence their macroscopic foam properties, e.g., foamability and foam stability, by large geometrical transformations of dual light/heat stimuli-responsive molecular motor amphiphiles. Detailed insight into the reversible photoisomerization and thermal helix inversion at the molecular level, supramolecular assembly transformations at the microscopic level, and the stimuli-responsive foam properties at the macroscopic level, as determined by UV-vis absorption and NMR spectroscopies, electron microscopy, and foamability and in situ surface tension measurements, is presented. By selective use of external stimuli, e.g., light or heat, multiple states and properties of macroscopic foams can be controlled with very dilute aqueous solutions of the motor amphiphiles (0.2 weight%), demonstrating the potential of multiple stimuli-responsive supramolecular systems based on an identical molecular amphiphile and providing opportunities for future soft materials.

Food-Grade Emulsions and Emulsion Gels Prepared by Soy Protein-Pectin Complex Nanoparticles and Glycyrrhizic Acid Nanofibrils

Glycyrrhizic acid (GA) and GA nanofibrils (GN) have been shown to be efficient natural emulsifiers for formation and stabilization of food emulsions. In this work, the emulsion properties of GN in the presence of soy protein isolate-pectin complex nanoparticles (SPNPs) were studied to understand the impact of the nanofibril-nanoparticle interactions on emulsion stabilization. In the presence of low GN concentrations (0.1-0.5 wt %), the synergy in reducing the interfacial tension was observed due to SPNPs-GN complexation in the bulk and at the interface by hydrogen bonding, endowing the prepared emulsions with an overall smaller droplet size. However, obvious flocculation and clustering of oil droplets occurred in these emulsions (especially at 0.25 and 0.5 wt % GN), which are probably induced by a depletion mechanism. At high GN concentrations (1-2 wt %), due to the preferential adsorption, the GN mainly dominated the interface and the subsequent formation and properties of emulsions. Accordingly, the self-standing emulsion gels were obtained, showing a small droplet size with d₃₂ of about 1.0-1.5 μm, homogeneous appearance and microstructure, and encouraging rheological properties including high gel strength, shear sensitivity, and good thixotropic recovery. This is mainly attributed to the formation of a fibrillar hydrogel network in the continuous phase as well as around the droplet surfaces.

Tough, Stretchable, Compressive Double Network Hydrogel Using Natural Glycyrrhizic Acid Tailored Low-Molecular-Weight Gelator Strategy: In Situ Spontaneous Formation of Au Nanoparticles To Generate a Continuous Flow Reactor

Traditional solid supports of metal nanoparticles (MNPs) often suffer from the poor mechanical performance, the low recycling efficiency, and the mass loss in the regeneration process. To overcome this limit, in this work, we reported a natural triterpenoid-tailored low-molecular-weight gelator (LMWG) strategy to fabricate double network (DN) hydrogels with excellent mechanical properties for supporting MNPs. In this strategy, the supramolecular fibrillar structure of glycyrrhizic acid (GL) and the cross-linked polyacrylamide (PAAm) were used as the first physical network and the second chemical network, respectively. The resulting GL/PAAm DN gels possessed tough, stretchable, and compressive properties, as well as high fatigue resistance. In addition, the ice-templating technique has been used to recast the DN gel through the anisotropical growth of ice crystals for increasing the porosity and surface area. On account of the reductibility of the diglucuronic moiety of GL, gold nanoparticles (AuNPs) were in situ spontaneously reduced from Au(III) ions without external reducing reagents and anchored on the pore surface of Recast-GL/PAAm DN gel. This AuNP-anchored Recast-GL/PAAm DN gel can be used as a continuous flow reactor to catalyze the reduction of 4-nitrophenol to 4-aminophenol with high catalytic activity, good recyclability, and long-term stability. Our work provided an effective strategy to generate promising supports of MNPs with highly mechanical properties and excellent catalytic efficiencies.

Interfacial rheological behaviors of amphiphilic sodium cholesteryl glycylglycine

The present study was conducted to investigate the effects of the strong van der Waals interaction and sterol skeleton of surfactants on their interfacial rheological behaviors by comparing the interfacial properties of sodium cholesteryl glycylglycine (Chol-GG-Na) and sodium lauryl glycylglycine (C12-GG-Na) at the oil-aqueous interface. The interfacial dilational rheological experiment results indicate a significant increase in the interfacial activity and intermolecular interaction with the introduction of the cholesteryl group. Therefore, a compact interfacial layer with a remarkably high dilational modulus was obtained with the adsorption of Chol-GG-Na. The cholesteryl group also has a significant impact on the dynamic processes such as it slows down the motion of the molecules due to which the diffusion exchange between the bulk and the interface decreases. Besides, the rigid skeleton makes rearrangement and conformation adjustment difficult. These impacts become more pronounced when the adsorption layer approaches a close and ordered arrangement, which has been confirmed by the relaxation measurements. The reported results provide a theoretical foundation for the potential applications of cholesteryl-based surfactants in the food, pharmaceutical, cosmetic and petroleum industries.