Structural Properties of Span 80/Tween 80 Reverse Micelles by Molecular Dynamics Simulations

Self-stabilising water-in-oil droplets through controlled spontaneous emulsification

HYPOTHESIS

The application of emulsion droplets as vessels for confined reactions, encapsulation, and material assembly is limited by the difficulty in achieving strong stabilisation against coalescence, particularly for water-in-oil (W/O) emulsions. Here, we investigate the time-dependent influence of spontaneous emulsification on macroemulsion stability, which remains poorly understood. We hypothesise that this non-equilibrium process can be harnessed as a practical stability-enhancing strategy and characterise the factors influencing this process in a variety of systems.

EXPERIMENTS

Daughter droplet behaviour in W/O macroemulsions predominantly containing the non-ionic surfactant Span 80 was studied through time-resolved optical microscopy, dynamic light scattering, and rheology. The effects of surfactant composition and viscosity on spontaneous emulsification behaviour and stability were investigated in mixed oil phases of isoparaffin and either oleic acid or mineral oil.

FINDINGS

Our study provides mechanistic insights and design guidelines for formulating emulsions which self-stabilise through daughter droplets assembling into elastic interfacial structures. This strategy does not require expensive components and is not specific to emulsion composition. Importantly, we also show that spontaneous emulsification does not always enhance stability. Effective stabilisation requires robust interfacial films between daughter and parent droplets and controlled continuous phase viscosity: if the viscosity is low, interfacial structures do not assemble, whereas a very high viscosity leads to buckling and deformation.

Interfacial Rheology as a Tool to Characterize the Dynamics of Spontaneous Emulsification

Water-in-oil emulsions are critical in various fields, including food, agriculture, personal care, and pharmaceuticals. In some situations, spontaneous emulsification occurs in emulsions with high concentrations of oil-soluble surfactants, in which the parent water drops fragment into finer droplets, forming a network near the interface, which exhibits interfacial elasticity. This study investigates this phenomenon using a water/Span 80-paraffin oil system. We measured interfacial shear elasticity and used microscopy to capture the dynamics. The time of onset of the network depends on the contact time between the two liquid phases and the Span 80 concentration, scaling inversely with the square of the bulk concentration of Span 80. Beyond the time of onset of network formation, different trends are observed, depending on the concentration of Span 80. At higher concentrations, the interfacial elasticity shows a maximum, followed by a minimum. This oscillatory trend in the interfacial elasticity is an outcome of the formation of multiple layers of water droplets at the interface. The existence of multiple layers is also observed through an optical microscope. In a more viscous paraffin oil, both the emulsification rate and the elasticity peak are reduced. No spontaneous emulsification is observed when the paraffin oil is replaced with silicone oil. Moreover, spontaneous emulsification is suppressed by the addition of a salt. On the contrary, the addition of Tween 80 in water increases the rate of spontaneous emulsion, resulting in larger droplets and a denser emulsion layer. However, the drops form a very weak network, as indicated by a negligibly small interfacial elasticity.

Optimized nanostructured lipid carriers from aceh traditional coconut (Pliek) oil: a promising topical formulations for atopic dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin condition characterized by dry skin, severe itching, redness, and inflammation. Its complex etiology, involving genetic, immunological, and environmental factors, necessitates innovative therapeutic approaches. This study investigates nanostructured lipid carriers (NLCs) formulated with traditional fermented coconut (Cocos nucifera L.) oil from Aceh (pliek oil). The NLC was optimized using Box-Behnken Design and prepared through high shear homogenization and ultrasonication. The optimized formula consisted of 8% w/w lipid phase, 2 min sonication time, and 6% Tween 80, resulting in a particle size of 207.1 ± 0.93 nm, a polydispersity index of 0.275 ± 0.005, and a zeta potential of - 30.2 ± 0.78 mV. A 1:1 ratio of Tween 80 and Span 20 ensured stable NLC. The NLC of Pliek oil (NLC-PL) gel met EuroGuiDerm standards for AD treatment, with a pH of 5.62 ± 0.06, indicating skin compatibility. Histological analysis demonstrated that the NLC-PL gel (2.5% w/w pliek oil) significantly reduced MC903-induced ear thickness and inflammation compared to the negative control (p < 0.05), and suppressed mast cell numbers, comparable to the positive control (p > 0.05). Enzyme-Linked Immunosorbent Assay (ELISA) confirmed its role as a c-jun N-terminal kinase 1 (JNK1) inhibitor, supporting its potential as targeted topical therapy for AD. This study aligns with the study's objective to develop innovative treatments for AD.

The Impact of Surfactant Structures and High-Speed Mixing Dynamics in Achieving Nano-Sized Emulsions with Simple High-Speed Homogenization

Purpose

This study investigates the impact of various mixing parameters and surfactant combinations on the physical characteristics of nanoemulsions produced using high-speed homogenization. Nanoemulsions are explored for their capacity to enhance transdermal drug delivery in pharmaceutical and cosmetic contexts.

Methods

Employing a standard high-speed homogenizer typical in the cosmetic industry, we tested different combinations of Polysorbate (Tween®) and Sorbitan ester (Span®) surfactants under single and intermittent process configurations. Key parameters assessed included particle size, size distribution, Oswald ripening, and creaming index.

Results

Nanoemulsions synthesized had particle sizes below 200 nm and appeared as white liquids with slight creaming. Extended mixing times were associated with smaller droplet sizes and reduced creaming. Both processing methods yielded similar nanoemulsion properties, indicating minimal impact from the type of process used. The nanoemulsions exhibited polydispersity indices ranging from 0.3 to 0.5, suggesting a uniform size distribution, and showed negligible Oswald ripening, which indicates stable droplet sizes over time.

Conclusion

The study confirms that precise control of mixing parameters and the selection of appropriate surfactant pairs are more critical than the choice of process in producing stable nanoemulsions. With efficient use of standard high-speed homogenizers, stable nanoemulsions suitable for large-scale production can be achieved, providing a cost-effective method for pharmaceutical and cosmetic industries.

Development and Analysis of Bilayer Foamed Oleogels Stabilized with Ecogel™: Exploring the Role of Tween 80 in Modifying Physicochemical Properties

Oleogels are structured materials formed by immobilizing oil within a polymer network. This study aimed to synthesize bilayer foamed oleogels using Ecogel™ as an emulsifier-a natural gelling and emulsifying agent commonly used to stabilize emulsions. Ecogel™ is multifunctional, particularly in cosmetic formulations, where it aids in creating lightweight cream gels with a cooling effect. However, the specific goal of this study was to investigate the physicochemical properties of oleogels formed with Ecogel™, Tween 80, gelatin, and glycerin. The combination of these ingredients has not been studied before, particularly in the context of bilayer foamed oleogels. The biphasic nature of the resulting materials was explored, consisting of a uniform lower phase and a foamed upper layer. Several analytical techniques were employed, including FT-IR spectrophotometric analysis, moisture content evaluation, surface wettability measurements, microscopic imaging, and rheological studies, in addition to surface energy determination. The results demonstrated that the addition of Tween 80 significantly improved the stability and rigidity of the oleogels. Furthermore, storage at reduced temperatures after synthesis enhanced the material's stabilizing properties. These materials also showed an affinity for interacting with non-polar compounds, indicating potential applications in skincare, especially for interaction with skin lipids.

Design of Nanocrystalline Suspension of Dutasteride for Intramuscular Prolonged Delivery

The aim of the study is to formulate an injectable nanocrystalline suspension (NS) of dutasteride (DTS), a hydrophobic 5α-reductase inhibitor used to treat benign prostatic hyperplasia and scalp hair loss, for parenteral long-acting delivery. A DTS-loaded NS (DTS-NS, 40 mg/mL DTS) was prepared using a lab-scale bead-milling technique. The optimized DTS-NS prepared using Tween 80 (0.5% w/v) as a nano-suspending agent, was characterized as follows: rod/rectangular shape; particle size of 324 nm; zeta potential of -11 mV; and decreased drug crystallinity compared with intact drug powder. The DTS-NS exhibited a markedly protracted drug concentration-time profile following intramuscular injection, reaching a maximum concentration after 8.40 days, with an elimination half-life of 9.94 days in rats. Histopathological observations revealed a granulomatous inflammatory response at the injection site 7 days after intramuscular administration, which significantly subsided by day 14 and showed minimal inflammation by day 28. These findings suggest that the nanosuspension system is a promising approach for the sustained release parenteral DTS delivery, with a protracted pharmacokinetic profile and tolerable local inflammation.

Rosuvastatin Flexible Chitosomes: Development, In Vitro Evaluation and Enhancement of Anticancer Efficacy Against HepG2 and MCF7 Cell Lines

Rosuvastatin (ROS), a statin drug with promising anticancer properties has a low bioavailability of approximately 20% due to lipophilicity and first-pass metabolism. This study aimed to enhance ROS anticancer efficacy through loading into flexible chitosomes. The chitosomes were prepared starting from negatively charged liposomes through electrostatic interactions with chitosan. The conversion of zeta potential from negative to positive confirmed the successful formation of chitosomes. The chitosan coating increased the particle size and zeta potential, which ranged from 202.0 ± 1.7 nm to 504.7 ± 25.0 nm and from - 44.9 ± 3.0 mV to 50.1 ± 2.6 mV, respectively. Chitosan and drug concentrations had an important influence on the chitosome properties. The optimum chitosome formulation was used to prepare ROS-loaded flexible chitosomes using different concentrations of four edge activators. The type and concentration of edge activator influenced the particle size, drug entrapment efficiency, and drug release rate of the flexible chitosomes. Flexible chitosomes significantly increased drug permeation through rat abdominal skin compared to control transferosomes and drug solution. The optimal ROS flexible chitosomes containing sodium deoxycholate as an edge activator had a 2.23-fold increase in ROS cytotoxic efficacy against MCF7 cells and a 1.84-fold increase against HepG2 cells. These results underscore the potential of flexible chitosomes for enhancing ROS anticancer efficacy.

Kinetic description of water transport during spontaneous emulsification induced by Span 80

Spontaneous emulsification is a phenomenon that forms nanometer-sized droplets (nanodroplets) without the application of any external force, and the mechanism has been actively studied for application to various technologies. In this study, we analyzed the kinetics of spontaneous emulsification induced by Span 80. The measurement of water concentration in Span 80 hexadecane solution indicated that the chemical potential of water in the nanodroplets decreased as the amount of water in the nanodroplets decreased. Based on this result, water transport between the aqueous phase and nanodroplets in which the chemical potential of water was controlled was quantitatively investigated by using a microfluidic device. The results demonstrate that the kinetics of water transport during spontaneous emulsification induced by Span 80 was described by a model of osmotic transport through an organic liquid film between the aqueous phase and nanodroplets.

A microfluidic double emulsion platform for spatiotemporal control of pH and particle synthesis

The temporal control of pH in microreactors such as emulsion droplets plays a vital role in applications including biomineralisation and microparticle synthesis. Typically, pH changes are achieved either by passive diffusion of species into a droplet or by acid/base producing reactions. Here, we exploit an enzyme reaction combined with the properties of a water-oil-water (W/O/W) double emulsion to control the pH-time profile in the droplets. A microfluidic platform was used for production of ∼100-200 μm urease-encapsulated double emulsions with a tuneable mineral oil shell thickness of 10-40 μm. The reaction was initiated on-demand by addition of urea and a pulse in base (ammonia) up to pH 8 was observed in the droplets after a time lag of the order of minutes. The pH-time profile can be manipulated by the diffusion timescale of urea and ammonia through the oil layer, resulting in a steady state pH not observed in bulk reactive solutions. This approach may be used to regulate the formation of pH sensitive materials under mild conditions and, as a proof of concept, the reaction was coupled to calcium phosphate precipitation in the droplets. The oil shell thickness was varied to select for either brushite microplatelets or hydroxyapatite particles, compared to the mixture of different precipitates obtained in bulk.

Development of Liposomal and Liquid Crystalline Lipidic Nanoparticles with Non-Ionic Surfactants for Quercetin Incorporation

The aim of the present study is the development, physicochemical characterization, and in vitro cytotoxicity evaluation of both empty and quercetin-loaded HSPC (hydrogenated soy phosphatidylcholine) liposomes, GMO (glyceryl monooleate) liquid crystalline nanoparticles, and PHYT (phytantriol) liquid crystalline nanoparticles. Specifically, HSPC phospholipids were mixed with different non-ionic surfactant molecules (Tween 80 and/or Span 80) for liposomal formulations, whereas both GMO and PHYT lipids were mixed with Span 80 and Tween 80 as alternative stabilizers, as well as with Poloxamer P407 in different ratios for liquid crystalline formulations. Subsequently, their physicochemical properties, such as size, size distribution, and ζ-potential were assessed by the dynamic and electrophoretic light scattering (DLS/ELS) techniques in both aqueous and biological medium with serum proteins. The in vitro biological evaluation of the empty nanosystems was performed by using the MTT cell viability and proliferation assay. Finally, the entrapment efficiency of quercetin was calculated and the differences between the two different categories of lipidic nanoparticles were highlighted. According to the results, the incorporation of the non-ionic surfactants yields a successful stabilization and physicochemical stability of both liposomal and liquid crystalline nanoparticles. Moreover, in combination with an appropriate biosafety in vitro profile, increased encapsulation efficiency of quercetin was achieved. Overall, the addition of surfactants improved the nanosystem's stealth properties. In conclusion, the results indicate that the physicochemical properties were strictly affected by the formulation parameters, such as the type of surfactant.

Unravelling the mechanisms of drugs partitioning phenomena in micellar systems via NMR spectroscopy

Despite extensive use of micelles in materials and colloidal science, their supramolecular organization as well as host-guest interactions within these dynamic assemblies are poorly understood. Small guest molecules in the presence of micelles undergo constant exchange between a micellar aggregate and the surrounding solution, posing a considerable challenge for their molecular level characterisation. In this work we reveal the interaction maps between small guest molecules and surfactants forming micelles via novel applications of NMR techniques supported with state-of-the-art analytical methods used in colloidal science. Model micelles composed of structurally distinct surfactants (block non-ionic polymer Pluronic® F-127, non-ionic surfactant Tween 20 or Tween 80, and ionic surfactant sodium lauryl sulphate, SLS) were selected and loaded with model small molecules of biological relevance (i.e. the drugs fluconazole, FLU or indomethacin, IMC) known to have different partition coefficients. Molecular level organization of FLU or IMC within hydrophilic and hydrophobic domains of micellar aggregates was established using the combination of NMR methods (1D ¹H NMR, 1D ¹⁹F NMR, 2D ¹H-¹H NOESY and 2D ¹H-¹⁹F HOESY, and the multifrequency-STD NMR) and corroborated with molecular dynamics (MD) simulations. This is the first application of multifrequency-STD NMR to colloidal systems, enabling us to elucidate intricately detailed patterns of drug/micelle interactions in a single NMR experiment within minutes. Importantly, our results indicate that flexible surfactants, such as block copolymers and polysorbates, form micellar aggregates with a surface composed of both hydrophilic and hydrophobic domains and do not follow the classical core-shell model of the micelle. We propose that the magnitude of changes in ¹H chemical shifts corroborated with interaction maps obtained from DEEP-STD NMR and 2D NMR experiments can be used as an indicator of the strength of the guest-surfactant interactions. This NMR toolbox can be adopted for the analysis of broad range of colloidal host-guest systems from soft materials to biological systems.

Storage and Temperature Stability of Emulsified Biodiesel-Diesel Blends

The scarcity of fossil fuel has led to the recent worldwide commercialization of biodiesel-blended diesel. The benefits associated with emulsion fuels have encouraged researchers to study the blended emulsified fuels in diesel engines. Recent results show the effectiveness of blended emulsified fuels in terms of better fuel economy and less harmful emissions. Investigation on the stability of these blended emulsified fuels during storage in the fuel tank is equally crucial for commercialization and practical application. A systematic study on the storage stability of water in biodiesel/diesel blend nanoemulsions (nEs) is presented in this work. A mixture of two biodegradable surfactants, Span 80 and Tween 80, is used to stabilize the nEs. The nEs are formulated by subjecting a mixture of 5 vol % of each surfactant, 5 vol % of water, and 85 vol % of pure or blended diesel to high shear homogenization at 5000 rpm for 2 min. Storage stability of the emulsified fuels is studied for 65 days at 25 °C with the help of dynamic light scattering and viscosity measurements. The mean droplet size increases, and the stability decreases with an increase in the biodiesel concentration. The smallest mean droplet size is 32 nm for emulsified fuel using pure diesel, and these emulsions remain stable for 65 days. No macroscopic phase separation is observed for any sample aged for 24 days. A moderate increment in droplet sizes is observed during this period. The droplet size increases significantly when more than 15 vol % biodiesel is used in the fuel blend. Those samples show stratification after 65 storage days. An increment in the zero-shear viscosity of the samples over aging helps hinder the rapid coalescence of the droplets, thus preventing phase separation. Furthermore, the thermal stability of the samples is also investigated at elevated temperatures up to 50 °C. The nEs are found to be highly stable within this temperature range and showed a moderate change in mean droplets size, especially when the concentration of biodiesel in the emulsified fuel blend is less than 15 vol %.

Cyclosporine and Pentoxifylline laden Tailored Niosomes for the effective management of Psoriasis: In-vitro Optimization, Ex-vivo and Animal Study

Psoriasis is a chronic skin inflammatory auto-immune disorder. Cyclosporine is the drug of choice in severe cases of psoriasis for systemic administration. But its systemic administration leads to some serious side effects like nephrotoxicity and cardiovascular disorders. Pentoxifylline is reported to reduce such side effects of cyclosporine and also it is found useful in the management of psoriasis. In this study, Box-Behnken design was used to prepare and optimize Cyclosporine and Pentoxifylline loaded niosomes. The optimized niosomes were prepared using cholesterol and surfactant (7:3), a total of 500µmol. Ratio of Tween 80 to span 80 for the preparation of optimized niosome was 0.503 (tween80:span80), and hydration and sonication time were kept at 60 minutes and 10 minutes, respectively. Size, Poly Dispersity Index, zeta potential, and % entrapment efficiency of Pentoxifylline and cyclosporine, for optimized niosomes were found to be 179nm, 0.285, -37.5mV, 84.6%, and 75.3%, respectively. The optimized niosomes were further studied for in-vitro skin permeation and skin deposition. Though niosomes significantly influenced the permeation of both drugs, only a small amount of drug (both cyclosporine and Pentoxifylline) was permeated through the skin. In comparison with the permeation, the quantity of drug retained in the stratum corneum and viable epidermis (SC and VED) was very high. In the in-vivo studies conducted on mice induced with psoriasis using imiquimod, both the histopathology and psoriasis area severity index has shown marked improvement in the skin condition of mice treated with niosomes loaded with Pentoxifylline and cyclosporine, in comparison with the solution/suspension of individual drugs. The study shows that niosomes could be effectively used for the simultaneous delivery of cyclosporine and Pentoxifylline for the better management of psoriasis.

Scrutinizing the Feasibility of Nonionic Surfactants to Form Isotropic Bicelles of Curcumin: a Potential Antiviral Candidate Against COVID-19

Investigating bicelles as an oral drug delivery system and exploiting their structural benefits can pave the way to formulate hydrophobic drugs and potentiate their activity. Herein, the ability of non-ionic surfactants (labrasol®, tween 80, cremophore EL and pluronic F127) to form curcumin loaded bicelles with phosphatidylcholine, utilizing a simple method, was investigated. Molecular docking was used to understand the mechanism of bicelles formation. The % transmittance and TEM exhibited bicelles formation with labrasol® and tween 80, while cremophor EL and pluronic F127 tended to form mixed micelles. The surfactant-based nanostructures significantly improved curcumin dissolution (99.2 ± 2.6% within 10 min in case of tween 80-based bicelles) compared to liposomes and curcumin suspension in non-sink conditions. The prepared formulations improved curcumin ex vivo permeation over liposomes and drug suspension. Further, the therapeutic antiviral activity of the formulated curcumin against SARS-CoV-2 was potentiated over drug suspension. Although both Labrasol® and tween 80 bicelles could form bicelles and enhance the oral delivery of curcumin when compared to liposomes and drug suspension, the mixed micelles formulations depicted superiority than bicelles formulations. Our findings provide promising formulations that can be utilized for further preclinical and clinical studies of curcumin as an antiviral therapy for COVID-19 patients. Graphical Abstract.

Exploration of bromelain laden nanostructured lipid carriers: An oral platform for bromelain delivery in rheumatoid arthritis management

Bromelain, a cysteine protease exhibits promising potential in amelioration of wide variety of inflammatory disorders. Its denaturation or aggregation in gastric milieu depletes its therapeutic potential along with unpredictable prophylactic hypersensitivity reactions. Hence, efficient carrier system to improve bromelain's stability and avoid related side effects is of utmost importance. Therefore, present investigation was undertaken to prepare bromelain loaded nanostructured lipid carriers (Br-NCs) with high drug loading, stability and efficacy in rheumatoid arthritis management. Br-NCs fabricated via double emulsion solvent evaporation method were characterized for physical properties, morphology and stability. Optimized batch exhibited spherical shape, nanometric size (298.23 nm) and entrapment efficiency ~77% with sustained release behavior and improved gastric stability. Br-NCs exhibited 4.63-folds improvement in shelf-life compared to bromelain at room temperature. The protective potential of orally administered Br-NCs in rheumatoid arthritis was evaluated via assessing arthritis severity in wistar rats along with biochemical, hematological and immunological parameters. Br-NCs remarkably (p < 0.05) diminished paw edema, joint stiffness, mechanical allodynia and tissue damage along with alleviation of oxidative stress and immunological markers. Radiological joint alterations were also notably preserved with Br-NCs. Thus, preclinical studies distinctly manifested that Br-NCs formulation opens new avenue for development of novel effective therapeutic modality for rheumatoid arthritis management.

Charge and Electrical Double Layer Formation in a Nonpolar Solvent Using a Nonionic Surfactant

In this work, we study the charge formation and the characteristics of the electrical double layer in a nonpolar medium using electrical impedance spectroscopy. To stabilize the free ionic species, a nonionic surfactant is added to the system. The conductivity and permittivity of the medium are obtained from high- to medium-frequency impedance data. Based on the correlation between (viscosity-adjusted) conductivity and surfactant concentration, we conclude that charge formation occurs due to a disproportionation mechanism. We accordingly estimate the concentration of the charge carriers in the sample and the Debye length of the diffuse double layer. The capacitance of the electrical double layer can be extracted from the low-frequency impedance data. We use this data to calculate the electrode distance of an equivalent parallel-plate capacitor. It is found that this distance is on the order of magnitude of Angstroms, indicating that the measured electrical double-layer capacitance is in fact the Stern layer capacitance.