Effect of cosurfactant addition on phase behavior and microstructure of a water dilutable microemulsion

Performance of ethanol transformable microemulsions and remediation of salinized oil - contaminated soils

The effective and efficient separation of oil pollutants solubilized in microemulsions (MEs) represents a significant challenge in the remediation of oil-contaminated soils (OS). In this study, phase-transformable W/O microemulsions (W/O-MEs) were configured for efficient elution of salinized OS. Meanwhile, the phase transformation mechanism was demonstrated by investigating of the effect of ethanol concentration on microemulsions phase behavior. Firstly, W/O-MEs with an oil removal efficiency (Re) of 90.2 wt% were formulated through an analysis of the phase distribution and elution effect. Furthermore, the impact of ethanol concentration on microemulsion phase behavior was investigated in depth using dynamic light scattering (DLS), interfacial tension (IFT), and UV-visible spectroscopy. The findings substantiated that ethanol can facilitate the transformation of W/O-MEs (Winsor II) to O/W-MEs (Winsor I), thereby enhancing oil Re and separation capability. Moreover, a microemulsion elution route for salinized OS was devised on the basis of the principles of continuity and recycling in industrial cleaning processes. The results demonstrated that the ethanol and water facilitated the desorption of residues, including residual oils, surfactants, salts and alkalis, achieving an oil Re of 97.2 wt%. In particular, the recovered ethanol and water can be recycled for microemulsion preparation. Finally, the efficiency and feasibility of the microemulsion elution process is evaluated using scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), fluorescence imaging, and contact angle (CA) analysis. This study provides theoretical guidance for the application of microemulsion elution in the remediation of industrial OS.

Microemulsions Improve the Cutaneous Co-Localization of Lipoic Acid and Quercetin and Antioxidant Effects in Cutaneous Cells and Tissue

Quercetin and α-lipoic acid are antioxidants with potential applications in the treatment of various skin conditions, such as wounds and chemoprevention of skin cancer. To enable their effective topical co-delivery and co-localization in the tissue, we developed microemulsions (ME). The selected ME (ME-50) formed a stable system with a mean droplet size of 134.4 ± 17.9 nm, increasing to 224.9 ± 19.9 nm upon antioxidants co-incorporation. The ME preserved the antioxidant capacities of the molecules, with DPPH (2,2-diphenyl-1-picrylhydrazyl) scavenging assay showing an IC50 of 6.2 ± 0.1 µg/mL, similar to the solution. Skin penetration studies revealed a 2.4-fold increase in quercetin (Q) accumulation in the stratum corneum and a 3.5-fold increase in the delivery to viable epidermis and dermis (ED) after a 12 h-treatment with the ME compared to control solutions; α-lipoic acid (LA) penetration improved up to 1.9-fold in ED upon ME incorporation. Treatment with Q + LA co-loaded ME enhanced the antioxidant activity in the stratum corneum and ED by 1.3-fold and 2.0-fold, respectively, compared to solutions. Treatment with the ME for 24 h also reduced oxidative species levels by 55% in H2O2-exposed keratinocytes compared to the control (untreated) cells. Taken together, these results suggest that ME-50 is a promising delivery system for enhancing the cutaneous co-delivery of quercetin and α-lipoic acid and the antioxidant effects in the tissue, offering a potential topical treatment for oxidative stress-related skin conditions.

Understanding Microemulsions and Nanoemulsions in (Trans)Dermal Delivery

Continuously explored in pharmaceuticals, microemulsions and nanoemulsions offer drug delivery opportunities that are too significant to ignore, namely safe delivery of clinically relevant drug doses across biological membranes. Their effectiveness as drug vehicles in mucosal and (trans)dermal delivery is evident from the volume of published literature. Commonly, their ability to enhance skin permeation is attributed to dispersion size, a characteristic closely related to solubilization capacity. However, the literature falls short on distinctions between microemulsions and nanoemulsions for definitions, behavior, or specific differences in their mechanisms of action in (trans)dermal delivery. The focus is typically on surfactant/cosurfactant ratio and droplet size but the role of mesostructures or the effect of cosolvent (Csol), oil (O) or water (W) on permeation profile remain poorly explained. Towards a deeper understanding of these vehicles in (trans)dermal drug delivery, this review begins with their conceptual and practical distinctions before delving into the published works for less obvious but potentially important underlying mechanisms; notably composition and the competitive positioning of system constituents in the resulting microstructures and subsequent effect(s) these may have on skin structures and drug permeability. For practical purposes, this review focuses on formulation systems based on ternary diagrams with commonly accepted non-ionic surfactants, cosurfactants, cosolvents, and oils used in pharmaceutical applications.

A nonionic microemulsion co-loaded with atorvastatin and quercetin: Simultaneous spectroscopic analysis and payload release kinetics

In this study, we have co-loadedatorvastatin (ATR) and quercetin (QCT) in a nonionic microemulsion. After developing a derivative ratio spectrophotometric technique for simultaneous analysis of ATR and QCT, pseudoternary phase diagram was constructed utilizing1:4 d-α-tocopherol polyethylene glycol 1000 succinate (TPGS) and ethanol as surfactant and cosurfactant, respectively. Oleic acid was used as oil phase. Structural characterization of the formulation was carried out along a water dilution line created in monophasic region. Characterizations at these dilution points were performed using dynamic light scattering and polarized light microscopy. The average hydrodynamic size of the optimized formulation was found to be 18.9 nm and it did not change upon loading of ATR and QCT. In vitro release was assessed for the formulations loaded with different ratios of ATR and QCT, and the data were fitted to different mathematical models. Interestingly, we noticed differences in release kinetics during changes in dose ratios, particularly for QCT. Higuchi kinetics, observed at equal dose, shifted to Korsmeyer-Peppas model at higher QCT-ATR ratio (2:1 and 4:1). This difference is attributable to the ability of QCT molecules of overwhelming the interface at higher concentrations. Altogether, our observations highlight that the ratio of payloads should be selected carefully in order to avoid unpredictable release patterns.

A study on the preparation conditions of lidocaine microemulsion based on multi-objective genetic algorithm

Background: Topical lidocaine microemulsion preparations with low toxicity, low irritation, strong transdermal capability and convenient administration are urgently needed. Methods: Box-Behnken design was performed for three preparation conditions of 5% lidocaine microemulsions: mass ratio of the mass ratio of surfactant/(oil phase + surfactant) (X1), the mass ratio of olive oil/(α-linolenic acid + linoleic acid) (X2) and the water content W% (X3). Then, five multi-objective genetic algorithms were used to optimize the three evaluation indices to optimize the effects of lidocaine microemulsion preparations. Finally, the ideal optimization scheme was experimentally verified. Results: Non-dominated Sorting Genetic Algorithm-II was used for 30 random searches. Among these, Scheme 2: X1 = 0.75, X2 = 0.35, X3 = 75%, which resulted in Y1 = 0.17 μg/(cm2·s) and Y2 = 0.74 mg/cm2; and the Scheme 19: X1 = 0.68, X2 = 1.42, X3 = 75% which resulted in Y1 = 0.14 μg/(cm2·s) and Y2 = 0.80 mg/cm2, provided the best matches for the objective function requirements. The maximum and average fitness of the method have reached stability after 3 generations of evolution. Experimental verification of the above two schemes showed that there were no statistically significant differences between the measured values of Y1 and Y2 and the predicted values obtained by optimization (p > 0.05) and are close to the target value. Conclusion: Two lidocaine microemulsion preparation protocols were proposed in this study. These preparations resulted in good transdermal performance or long anesthesia duration, respectively.

Mechanisms of lipid oxidation in water-in-oil emulsions and oxidomics-guided discovery of targeted protective approaches

Lipid oxidation is an inevitable event during the processing, storage, and even consumption of lipid-containing food, which may cause adverse effects on both food quality and human health. Water-in-oil (W/O) food emulsions contain a high content of lipids and small water droplets, which renders them vulnerable to lipid oxidation. The present review provides comprehensive insights into the lipid oxidation of W/O food emulsions. The key influential factors of lipid oxidation in W/O food emulsions are presented systematically. To better interpret the specific mechanisms of lipid oxidation in W/O food emulsions, a comprehensive detection method, oxidative lipidomics (oxidomics), is proposed to identify novel markers, which not only tracks the chemical molecules but also considers the changes in supramolecular properties, sensory properties, and nutritional value. The microstructure of emulsions, components from both phases, emulsifiers, pH, temperature, and light should be taken into account to identify specific oxidation markers. A correlation of these novel oxidation markers with the shelf life, the organoleptic properties, and the nutritional value of W/O food emulsions should be applied to develop targeted protective approaches for limiting lipid oxidation. Accordingly, the processing parameters, the application of antioxidants and emulsifiers, as well as packing and storage conditions can be optimized to develop W/O emulsions with improved oxidative stability. This review may help in emphasizing the future research priorities of investigating the mechanisms of lipid oxidation in W/O emulsion by oxidomics, leading to practical solutions for the food industry to prevent oxidative rancidity in W/O food emulsions.

Resveratrol-Loaded Chia Seed Oil-Based Nanogel as an Anti-Inflammatory in Adjuvant-Induced Arthritis

Natural anti-inflammatory nutraceuticals may be useful in preventing rheumatoid arthritis from worsening. Resveratrol (RV) and chia seed oil, having antioxidant potential, can assist in avoiding oxidative stress-related disorders. This investigation developed and evaluated resveratrol-loaded chia seed oil-based nanoemulsion (NE) gel formulations through in vitro and in vivo studies. The physical stability and in vitro drug permeability of the chosen formulations (NE1 to NE10) were studied. The optimized RV-loaded nanoemulsion (NE2) had droplets with an average size of 37.48 nm that were homogeneous in shape and had a zeta potential of -18 mV. RV-NE2, with a permeability of 98.21 ± 4.32 µg/cm²/h, was gelled with 1% carbopol-940P. A 28-day anti-arthritic assessment (body weight, paw edema, and levels of pro-inflammatory mediators including TNF-α, IL-6, IL-1β, and COX-2) following topical administration of RV-NE2 gel showed significant reversal of arthritic symptoms in arthritic Wistar rats induced by Freund's complete adjuvant injection. Therefore, RV-NE2 gel demonstrated the potential to achieve local therapeutic benefits in inflammatory arthritic conditions due to its increased topical bioavailability and balancing of pro-inflammatory mediators.

Synergistic effect of doxorubicin lauroyl hydrazone derivative delivered by α-tocopherol succinate micelles for the treatment of glioblastoma

We hypothesized that tocopherol succinate (TOS) and D-α-tocopherol polyethylene2000 succinate (TPGS₂₀₀₀) micelles could work as a drug delivery system while enhancing the anti-cancer efficacy of doxorubicin lauryl hydrazone derivative (DOXC₁₂) for the treatment of glioblastoma. The DOXC₁₂-TOS-TPGS₂₀₀₀ micelles were formulated with synthesized DOXC₁₂ and TPGS₂₀₀₀. They showed a high drug loading of hydrophobic DOXC₁₂ (29%), a size of <100 nm and a pH sensitive drug release behaviour. In vitro, fast uptake of DOXC₁₂-TOS-TPGS₂₀₀₀ micelles by GL261 cells was observed. For cytotoxicity, DOXC₁₂-TOS-TPGS₂₀₀₀ micelles were evaluated on two glioblastoma cell lines and showed synergism between DOXC₁₂ and TOS-TPGS_2000. The higher cytotoxicity of DOXC₁₂-TOS-TPGS₂₀₀₀ micelles was mainly caused by necrosis. The DOXC₁₂-TOS-TPGS₂₀₀₀ micelles seem to be a promising delivery system for enhancing the anticancer efficacy of doxorubicin in glioblastoma (GBM).

Advances on nanoformulation approaches for delivering plant-derived antioxidants: A case of quercetin

Oxidative stress has been implicated in tumorigenic, cardiovascular, neuro-, and age-related degenerative changes. Antioxidants minimize the oxidative damage through neutralization of reactive oxygen species (ROS) and other causative agents. Ever since the emergence of COVID-19, plant-derived antioxidants have received enormous attention, particularly in the Indian subcontinent. Quercetin (QCT), a bio-flavonoid, exists in the glycosylated form in fruits, berries and vegetables. The antioxidant potential of QCT analogs relates to the number of free hydroxyl groups in their structure. Despite presence of these groups, QCT exhibits substantial hydrophobicity. Formulation scientists have tested nanotechnology-based approaches for its improved solubilization and delivery to the intended site of action. By the virtue of its hydrophobicity, QCT gets encapsulated in nanocarriers carrying hydrophobic domains. Apart from passive accumulation, active uptake of such formulations into the target cells can be facilitated through well-studied functionalization strategies. In this review, we have discussed the approaches of improving solubilization and bioavailability of QCT with the use of nanoformulations.

Design, Characterization, and Evaluation of Diosmetin-Loaded Solid Self-microemulsifying Drug Delivery System Prepared by Electrospray for Improved Bioavailability

Diosmetin (DIOS) is a functional compound with poor water solubility, bad permeability, and crystal form. Self-microemulsifying drug delivery system (SMEDDS) was an effective formulation to overcome these shortcomings. In this study, liquid SMEDDS was prepared using Capmul® MCM C8 EP/NF, Cremophor EL, and PEG 400 (2:5.6:2.4, w/w/w) as excipients. Then, the novel technology of electrospray solidified liquid SMEDDS and prepared solid SMEDDS for inhibiting crystallization. Polyvinyl pyrrolidone (PVP) was used as carrier to construct DIOS-loaded solid SMEDDS, with polyethylene oxide (PEO) contributing to the formation of regular sphere in the process of spinning. The particle size of solid SMEDDS (194 ± 5 nm) was much bigger than of liquid SMEDDS (25 ± 1 nm), while DIOS-loaded solid SMEDDS showed greater dissolution rates in pH 1.2 and pH 6.8 media through in vitro drug release study. The solid nanoparticles were smooth and uniform from the graph of a scanning electron microscope (SEM). The graph of a transmission electron microscope (TEM) showed that small droplets were loaded in the matrix. Furthermore, DIOS was encapsulated by matrix in amorphous state via differential scanning calorimetry (DSC) and attenuated total reflection Fourier transform infrared (ATR-FTIR). The crystalline of DIOS was not formed in solid SMEDDS due to the characteristic peaks of DIOS disappeared in X-ray diffraction (XRD) pattern. Therefore, the oral bioavailability of DIOS improved significantly compared with liquid SMEDDS (4.27-fold). Hence, solid SMEDDS could improve the solubility and bioavailability of DIOS, through transfer of the state of crystalline to amorphous by electrospray technology.

Microemulsion Delivery System Improves Cellular Uptake of Genipin and Its Protective Effect against Aβ1-42-Induced PC12 Cell Cytotoxicity

Genipin has attracted much attention for its hepatoprotective, anti-inflammatory, and neuroprotection activities. However, poor water solubility and active chemical properties limit its application in food and pharmaceutical industries. This article aimed to develop a lipid-based microemulsion delivery system to improve the stability and bioavailability of genipin. The excipients for a genipin microemulsion (GME) preparation were screened and a pseudo-ternary phase diagram was established. The droplet size (DS), zeta potential (ZP), polydispersity index (PDI), physical and simulated gastrointestinal digestion stability, and in vitro drug release properties were characterized. Finally, the effect of the microemulsion on its cellular uptake by Caco-2 cells and the protective effect on PC12 cells were investigated. The prepared GME had a transparent appearance with a DS of 16.17 ± 0.27 nm, ZP of −8.11 ± 0.77 mV, and PDI of 0.183 ± 0.013. It exhibited good temperature, pH, ionic strength, and simulated gastrointestinal digestion stability. The in vitro release and cellular uptake data showed that the GME had a lower release rate and better bioavailability compared with that of free genipin. Interestingly, the GME showed a significantly better protective effect against amyloid-β (Aβ1-42)-induced PC12 cell cytotoxicity than that of the unencapsulated genipin. These findings suggest that the lipid-based microemulsion delivery system could serve as a promising approach to improve the application of genipin.

Crotamiton-loaded tea tree oil containing phospholipid-based microemulsion hydrogel for scabies treatment: in vitro, in vivo evaluation, and dermatokinetic studies

Crotamiton (CRT) is a commonly approved drug prescribed for the scabies treatment in many countries across the globe. However, poor aqueous solubility and low bioavailability, and side effects restrict its use. To avoid such issues, an appropriate carrier system is necessary which can address the aforementioned challenges for attaining enhanced biopharmaceutical attributes. The current study intends to provide a detailed account on the development and evaluation of CRT-loaded microemulsion (ME) hydrogel formulation containing tea tree oil (TTO) for improved drug delivery for scabies treatment in a safe and effective manner. Pseudo-ternary phase diagrams were constructed with TTO as the oily phase, and Cremophor^®EL was used as the surfactant in a mass ratio 2:1 with co-surfactants (mixture of phospholipid 90G and Transcutol^®P), and aqueous solution as the external phase. The optimized drug-loaded ME formulation was evaluated for skin penetration, retention, compliance, and dermatokinetics. The nonirritant behavior of the formulation was revealed by skin histopathology, which showed no changes in normal skin histology. In comparison to the conventional product, dermatokinetic experiments revealed that CRT has greater penetration and distribution in the epidermis of the mice skin. The findings imply that the proposed lipid-based ME hydrogel can aid in the resolution of CRT issues by providing a better and safer delivery option to epidermis and deeper epidermis in substantial quantities.

Emulsions Incorporated in Polysaccharide-Based Active Coatings for Fresh and Minimally Processed Vegetables

The consumption of minimally processed fresh vegetables has increased by the consumer's demand of natural products without synthetic preservatives and colorants. These new consumption behaviors have prompted research on the combination of emulsion techniques and coatings that have traditionally been used by the food industries. This combination brings great potential for improving the quality of fresh-cut fruits and vegetables by allowing the incorporation of natural and multifunctional additives directly into food formulations. These antioxidant, antibacterial, and/or antifungal additives are usually encapsulated at the nano- or micro-scale for their stabilization and protection to make them available by food through the coating. These nano- or micro-emulsions are responsible for the release of the active agents to bring them into direct contact with food to protect it from possible organoleptic degradation. Keeping in mind the widespread applications of micro and nanoemulsions for preserving the quality and safety of fresh vegetables, this review reports the latest works based on emulsion techniques and polysaccharide-based coatings as carriers of active compounds. The technical challenges of micro and nanoemulsion techniques, the potential benefits and drawbacks of their use, the development of polysaccharide-based coatings with natural active additives are considered, since these systems can be used as alternatives to conventional coatings in food formulations.

Foray into Concepts of Design and Evaluation of Microemulsions as a Modern Approach for Topical Applications in Acne Pathology

With a fascinating complexity, governed by multiple physiological processes, the skin is considered a mantle with protective functions which during lifetime are frequently impaired, triggering dermatologic disorders. As one of the most prevalent dermatologic conditions worldwide, characterized by a complex pathogenesis and a high recurrence, acne can affect the patient's quality of life. Smart topical vehicles represent a good option in the treatment of a versatile skin condition. By surpassing the stratum corneum known for diffusional resistance, a superior topical bioavailability can be obtained at the affected place. In this direction, the literature study presents microemulsions as a part of a condensed group of modern formulations. Microemulsions are appreciated for their superior profile in matters of drug delivery, especially for challenging substances with hydrophilic or lipophilic structures. Formulated as transparent and thermodynamically stable systems, using simplified methods of preparation, microemulsions have a simple and clear appearance. Their unique structures can be explained as a function of the formulation parameters which were found to be the mainstay of a targeted therapy.

Preparation and quality evaluation of a volatile oil microemulsion from Flos magnoliae and Centipeda minima

In order to improve the water solubility of the volatile oils extracted from Flos magnoliae (FM) and Centipeda minima (CM), they were prepared as a microemulsion (ME), which were then used in the development of an FM and CM volatile oil ME for the treatment of allergic rhinitis (AR). ME was prepared by phase inversion emulsification, and the prescription factors such as emulsifier, co‑emulsifier, oil phase, Km, which represents the ratio of the mass of emulsifier to that of the co‑emulsifier, and preparation factors such as temperature affecting the formation of the ME were selected according to the formation area of ME in a pseudo‑ternary phase diagram. The quality of the ME was evaluated based on its appearance, particle size, Zeta potential and stability. The content of eucalyptol in ME was determined by gas chromatography‑mass spectrometry (GC‑MS). The cumulative permeability of the ME within 24 h was measured with a transdermal diffusion tester. The results revealed that the best formula for preparation of the ME was as follows: Castor oil polyoxyethylene ether (EL‑40) was the emulsifier; the co‑emulsifier was anhydrous ethanol; the Km was 2:1; the mixed phase of volatile oil and isopropyl myristate with mass ratio of 1:1 was used as oil phase; and the preparation temperature was 25˚C. The content of eucalyptol in the ME was 2.57 mg/g, and the cumulative permeability of the ME in 24 h was significantly increased compared with that of the reference oil solution. The appearance of the ME was uniform, and the solution was transparent. In conclusion, compared with traditional preparations, FM and CM volatile oil ME is a novel, improved and more effective preparation for the treatment of AR.

Stability, deformation and rupture of Janus oligomer enabled self-emulsifying water-in-oil microemulsion droplets

Microemulsions exist widely in nature, daily life and industrial manufacturing processes, including petroleum production, food processing, drug delivery, new material fabrication, sewage treatment, etc. The mechanical properties of microemulsion droplets and a correlation to their molecular structures are of vital importance to those applications. Despite studies on their physicochemical determinants, there are lots of challenges of exploring the mechanical properties of microemulsions by experimental studies. Herein, atomistic modelling was utilized to study the stability, deformation, and rupture of Janus oligomer enabled water-in-oil microemulsion droplets, aiming at revealing their intrinsic relationship with Janus oligomer based surfactants and oil structures. The self-emulsifying process from a water, oil and surfactant mixture to a single microemulsion droplet was modulated by the amphiphilicity and structure of the surfactants. Four microemulsion systems with an interfacial thickness in the range of 7.4-17.3 Å were self-assembled to explore the effect of the surfactant on the droplet morphology. By applying counter forces on the water core and the surfactant shell, the mechanical stability of the microemulsion droplets was probed at different ambient temperatures. A strengthening response and a softening regime before and after a temperature-dependent peak force were identified followed by the final rupture. This work demonstrates a practical strategy to precisely tune the mechanical properties of a single microemulsion droplet, which can be applied in the formation, de-emulsification, and design of microemulsions in oil recovery and production, drug delivery and many other applications.

Synthesis, Colloidal Characterization and Targetability of Phenylboronic Acid Functionalized α-Tocopheryl Polyethylene Glycol Succinate in Cancer Cells

This study reports targetable micelles developed after covalent functionalization of α-tocopheryl polyethylene glycol succinate (TPGS) with amino phenylboronic acid (APBA). Nuclear magnetic resonance (NMR) and infrared (IR) spectroscopic results showed successful attachment of APBA to the hydrophilic segment of TPGS. Dynamic light scattering and small-angle neutron scattering studies revealed that the conjugate self-assembled in water to produce spherical core-shell micelles (14–20 nm) which remained stable against temperature (ca. 25–45 °C) and pH changes. The micelles could solubilize a high payload of paclitaxel (PLX) without exhibiting changes in the average size. However, at the saturation solubility, drug molecules migrated from the core to the shell region and engaged with APBA groups via π–π stacking interaction. Confocal microscopy and cell sorting analyses verified the effective translocation ability of TPGS-APBA micelles in sialic acid (SA) expressing MDA-MB-453 cells. At equivalent PLX dose, TPGS-APBA micelles showed about a twofold improvement in apoptotic death among the cells exposed for 2 h. Our findings indicate that the attachment of APBA can be a potential strategy for improving the intra-cellular localization of carriers among cancer cells expressing SA residues.