Phase behavior, microstructural transition, antimicrobial and antioxidant activities of a water-dilutable thymol microemulsion

Natural Amphiphilic Shellac Nanoparticle-Stabilized Novel Pickering Emulsions with Droplets and Bi-continuous Structures

Shellac is a natural amphiphilic substance, and its nanoparticles can be used to stabilize Pickering emulsions with droplets and bi-continuous structures. In this study, shellac nanoparticles (SNPs) were produced through the anti-solvent method, and these SNPs were used to produce a series of Pickering emulsions. Fourier transform infrared results showed that SNPs were generated through hydrogen bonding and hydrophobic effects. The contact angle of SNPs was 122.3°, indicating that hydrophobicity was their dominant characteristic. According to the results of confocal laser scanning microscopy, the Pickering emulsions stabilized by SNPs showed oil-in-water, bi-continuous structure, and water-in-oil characteristics, which were dependent on the oil-phase content. The resistance value of the emulsified part of these Pickering emulsion systems significantly increased at an oil-phase ratio of 80-90% (more than 10⁵ MΩ), as compared with the 10-70% oil-phase content (around 1 MΩ). The viscosity of SNP-stabilized Pickering emulsions with bi-continuous structures was highest at 40% oil-phase content. The porous material prepared by using Pickering emulsions with bi-continuous structures as a template had an interconnected structure and was able to absorb both water and oil. This study indicated that these amphiphilic SNPs readily form bi-continuous structures and effectively stabilize Pickering emulsions with droplets. These SNPs are expected to have increased application in food and pharmaceutical industries.

Formation of sacha inchi oil microemulsion systems: effects of non-ionic surfactants, short-chain alcohols, straight-chain esters and essential oils

BACKGROUND

This study reports the formation of sacha inchi oil (SIO) microemulsions for food and cosmetic applications. Effects of non-ionic surfactants, short-chain alcohols, essential oil and straight-chain esters on the phase behavior and formulation of U-type microemulsion were investigated. Pseudo ternary phase diagrams were constructed to assess the influence of these factors using water titration method. Structural transitions were measured along several water dilution lines using conductivity and viscosity tools.

RESULTS

Among four different surfactants, Tween 80 solubilized the maximum oil and induced the formation of a U-type microemulsion system. Oil solubilization was decreased in the presence of short-chain alcohols. In addition, the system containing straight-chain esters as the cosolvent showed a higher expansion effect in the U-type areas than that containing essential oils. Finally, upon water dilution of three systems with SIO/ethyl acetate of 1:1, 1:2 and 1:3, microstructural transition from W/O to bicontinuous occurred at 200 g kg^-1 (w/w) water content, and then to O/W structure at 650 g kg^-1 (w/w) water content.

CONCLUSION

Straight-chain esters as cosolvent is a potential strategy to extend the dilutability of SIO microemulsions. © 2021 Society of Chemical Industry.

Targeting foodborne pathogens via surface-functionalized nano-antimicrobials

The incorporation of antibiotics and bioactive compounds into non-toxic nanoparticles has been popularly used to produce effective antimicrobial nanocarriers against foodborne pathogens. These systems can protect antimicrobials against harsh environments, control their release, and increase their antimicrobial activities; however, their functions can be decreased by some major barriers. Intracellular localization of bacteria protects them from the host immune system and antimicrobial agents. Also, bacteria can cause constant infection by nestling in professional phagocytic cells. In the last years, surface functionalization of nanocarriers by passive and active modification methods has been applied for their protection against clearance from the blood, increasing both circulation time and uptake by target cells. For achieving this objective, different functional agents such as specifically targeted peptides internalize ligands, saccharide ligands, or even therapeutic molecules (e.g., antibodies or enzymes) are used. In this review, techniques for functionalizing the surface of antimicrobial-loaded nanocarriers have been described. This article offers a comprehensive review of the potential of functional nanoparticles to increase the performance of antimicrobials against foodborne pathogens through targeting delivery.

Preparation of Eprinomectin Nanoemulsions and Determination of Their Pharmacokinetics and Pharmacodynamics in Dairy Cows

This study aimed to develop an anthelmintic that leaves no residues and is safe and efficient for use in cows. We constructed classical pseudoternary phase diagrams using experimental animal data to optimize and characterize the eprinomectin nanoemulsion formulas. The emulsion samples prepared with ethyl acetate, polysorbate 80, and 1-propanediol as the main components were transparent and uniform when observed under a Hitachi transmission electron microscope (TEM) system. A Mastersizer 3000 laser particle size analyzer was used to determine the particle sizes of the prepared nanoemulsions. The nanoemulsions were homogeneously dispersed, with an average particle size of 12.61 nm and a polydispersity index of (PDI) 0.297. High-performance liquid chromatography confirmed no statistically significant changes in the samples after 24 months at 4 °C, 25 °C, and 37 °C; the samples exhibited long-term stability. The PK/PD studies confirmed that the injection of eprinomectin nanoemulsions at a dose of 0.2 mg/kg body weight was effective, with a withdrawal period of 0 days for dairy cows. The total extermination rate of the nanoemulsions against adult nematodes was 98.40±1.52%. The AUC_milk/plasma ratio was 0.67±0.03. The optimal dose was found to be 0.2 mg/kg body weight.

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.

PLGA-Based Nano-Encapsulation of Trachyspermum Ammi Seed Essential Oil (TSEO-PNP) as a Safe, Natural, Efficient, Anticancer Compound in Human HT-29 Colon Cancer Cell Line

Colorectal cancer is a lethal and commonly diagnosed cancer worldwide. To halt its burden more efficient targeted strategies are needed. Trachyspermum ammi seed essential oil (TSEO) contains several anticancer phytochemicals that maybe more effective via PLGA-based nano-encapsulation. TSEO-PNP nanoparticles were synthesized utilizing evaporation and ultra-sonication-based emulsification methods. Their size, morphology, and stability were defined by DLS, SEM, and surface zeta-potential data, respectively. The TSEO-PNP antioxidant apoptotic, cytotoxic, and antiangiogenic impacts on both cell lines (HT-29 and HUVEC) were studied by FRAP/ABTS, Q-PCR, MTT, and CAM assays, respectively. Moreover, further confirmatory measurements such as AO/EB fluorescent staining and flow cytometry analysis were performed to verify apoptosis. Stable (-32.42 mV) 206.21-nm TSEO-PNP induced apoptosis in the HT-29 cells. Apoptosis was confirmed by significant overexpression of apoptotic genes (Cas-9 and BAX), down-regulation of the anti-apoptotic (BCL-2) gene, fluorescent AO/EB staining, and flow cytometry data following increased TSEO-PNP treatment doses. TSEO-PNP exhibited a meaningful dose- and time-dependent cancer-specific cytotoxic impact on HT-29 cells. The TSEO-PNP has three main anticancer activities on HT-29 colon cancer cells including oxidant reduction, apoptosis induction, and angiogenesis suppression.

Influence of polysorbates (Tweens) on structural and antimicrobial properties for microemulsions

Polysorbates (Tweens) are one of the most used excipients for essential oils encapsulation. In this work, the polysorbate based microemulsions (PMEs) for R-(+)-limonene (LMN) encapsulation were investigated for the structural and antimicrobial properties. PMEs were constructed using the pseudoternary phase diagrams, and then characterized for electrical conductivity, rheology, size distribution and particle geometry. Conductivity and rheological measurement results showed that Tween 80 and Tween 60 based microemulsions have identical phase transitions. Dynamic light scattering demonstrated that hydrodynamic diameters of oil-in-water microemulsions decreased from 30 nm to 25 nm during the dilution, while small-angle X-ray scattering indicated that their spherical geometries were maintained. PMEs exhibited enhanced antimicrobial efficiencies in vitro against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. Interestingly, when Tween 80 was replaced by Tween 60, PME was observed more effective against S. aureus. The two PMEs structural analogues exhibited different antimicrobial efficiencies corresponding to the bioactivity of polysorbates. In conclusion, PMEs can be considered as a desirable system for LMN encapsulation to enhance its solubility and antimicrobial efficiency. Furthermore, the difference in the antimicrobial efficiency suggested that the choice of emulsifiers should be concerned to improve further applications.

Preservation of traditional Chinese pork balls supplemented with essential oil microemulsion in a phase-change material package

BACKGROUND

In this study, we evaluated the combined effect of cinnamon essential oil (CEO) microemulsions, and a temperature buffering package using phase-change material (PCM) microcapsules on the physicochemical property, lipid oxidation, and bacterial load of traditional Chinese pork balls (shi zi tou) during temperature fluctuation storage for 9 days.

RESULTS

Transmission electron microscope characterization revealed that n-tetradecane microcapsules possessed a core-shell spherical shape with a size ranging from 300 to 600 nm. The use of n-tetradecane microcapsule packaging was found to maintain cold storage temperature efficiently. After 9 days of storage, the combination of CEO microemulsions with n-tetradecane microcapsules did not lead to changes in the color parameters of pork balls. At day 9, n-tetradecane microcapsules, used alone or in combination with CEO microemulsions, showed lower thiobarbituric acid reactive substances (TBARS) values than the control group, while their combination exhibited the lowest pH and 1,1-diphenyl-2-picrylhydrazyl (DPPH) values. Furthermore, the combination treatment retarded the growth of total plate count, lactic acid bacteria, Enterobacteriaceae, and Staphylococcus spp. after 4 and 9 days.

CONCLUSIONS

The combinations of CEO microemulsions and PCM microcapsules could extend the shelf-life of cooked pork products, suggesting a feasible strategy for meat preservation. © 2020 Society of Chemical Industry.

A review on antifungal activity and mode of action of essential oils and their delivery as nano-sized oil droplets in food system

An escalated demand of minimally processed food and increased negative perception for synthetic preservative has led to a lookout for a natural preservative. Essential oils (EOs) are volatile and aromatic secondary metabolites of plants that have been tapped mainly for its flavour and fragrances and various biological properties such as antimicrobial and antioxidant. The constituents and antifungal potential of EOs have been reported widely in the present scientific literature. Moreover, the current scientific research dealing with the mode of action of EOs on fungal spores and mycelial cells are very scarce, unlike bacteria. The antimicrobial efficacy of EO in real food system may alter due to interaction with food matrix components. Besides, minimum alteration in sensory qualities while retaining its maximum activity is the most sought-after criteria for food preservation with EOs. If the oil is applied in excess to have better antimicrobial activity, it may end up having an unacceptable organoleptic impact on the food. Appropriate edible delivery systems of EOs as an emulsion is a probable approach to retain the maximum efficacy of EOs in the food system. Nano-emulsification of EO could increase its bioactivity due to increased bioavailability in the food matrix. The basis of this review is to provide an overview of current knowledge about the antifungal properties and antifungal mode of action of EOs, and to recognize the application of EO as nano-sized oil droplets in the food system.

Fourth-Generation Antibiotic Gatifloxacin Encapsulated by Microemulsions: Structural and Probing Dynamics

To overcome the increased disease rate, utilization of the versatile broad spectrum antibiotic drugs in controlled drug-delivery systems has been a challenging and complex consignment. However, with the development of microemulsion (μE)-based formulations, drugs can be effectively encapsulated and transferred to the target source. Herein, two biocompatible oil-in-water (o/w) μE formulations comprising clove oil/Tween 20/ethylene glycol/water (formulation A) and clove oil/Tween 20/1-butanol/water (formulation B) were developed for encapsulating the gatifloxacin (GTF), a fourth-generation antibiotic. The pseudoternary phase diagrams were mapped at a constant surfactant/co-surfactant (1:1) ratio to bound the existence of a monophasic isotropic region for as-formulated μEs. Multiple complementary characterization techniques, namely, conductivity (σ), viscosity (η), and optical microscopy analyses, were used to study the gradual changes that occurred in the microstructure of the as-formulated μEs, indicating the presence of a percolation transformation to a bicontinuous permeate flow. GTF showed good solubility, 3.2 wt % at pH 6.2 and 4.0 wt % at pH 6.8, in optimum μE of formulation A and formulation B, respectively. Each loaded μE formulation showed long-term stability over 8 months of storage. Moreover, no observable aggregation of GTF was found, as revealed by scanning transmission electron microscopy and peak-to-peak correlation of IR analysis, indicating the stability of GTF inside the formulation. The average particle size of each μE, measured by dynamic light scattering, increased upon loading GTF, intending the accretion of drug in the interfacial layers of microdomains. Likewise, fluorescence probing sense an interfacial hydrophobic environment to GTF molecules in any of the examined formulations, which may be of significant interest for understanding the kinetics of drug release.

Observation of a structural gradient in Winsor-III microemulsion systems

We demonstrate here for the first time via small-angle neutron scattering (SANS) that the middle, bicontinuous microemulsion (BμE) phase of Winsor-III systems undergoes a gradual change of structure and composition in the vertical direction, contrary to the commonly held belief of uniform structure and composition. A vertical stage was deployed to enable precise alignment of a custom-designed rectangular cell containing the WIII system with respect to the neutron beam, allowing for several different vertical positions to be analyzed. For the water/AOT/CK-2,13 (two-tailed alkyl ethoxylate containing a 1,3-dioxolane linkage)/heptane Winsor-III system, the quasi-periodic repeat distance (d) and correlation length (ξ), obtained from the Teubner-Strey model applied to the SANS data, decreased and the surface area per volume of the surfactant monolayer (via Porod analysis) increased in the downward direction, trends that reflect an increase of surfactant concentration, consistent with the ultralow interfacial tension that often occurs for the lower liquid-liquid interface of many WIII systems. The water/sodium dodecyl sulfate (SDS)/1-pentanol/dodecane system shared the same trend with regard to d as observed for AOT/CK-2,13. In contrast, for SDS/pentanol, ξ increased and the amphiphilicity factor (fa) decreased in the downward direction, trends consistent with a decrease of cosurfactant (pentanol) concentration in the downward direction. Non-uniformity in the vertical direction has implications in the transport of solutes between WIII phases during the extractive purification of proteins or the removal of heavy metals and pollutants from wastewater, or the deposition of BμEs onto hydrophilic vs. hydrophobic surfaces as thin coatings.

Protein extraction into the bicontinuous microemulsion phase of a Water/SDS/pentanol/dodecane winsor-III system: Effect on nanostructure and protein conformation

Bicontinuous microemulsions (BμEs), consisting of water and oil nanodomains separated by surfactant monolayers of near-zero curvature, are potentially valuable systems for purification and delivery of biomolecules, for hosting multiphasic biochemical reactions, and as templating media for preparing nanomaterials. We formed Winsor-III systems by mixing aqueous protein and sodium dodecyl sulfate (SDS) solutions with dodecane and 1-pentanol (cosurfactant) to efficiently extract proteins into the middle (BμE) phase. Bovine serum albumin (BSA) and cytochrome c partitioned to the BμE phase at 64% and 81% efficiency, respectively, producing highly concentrated protein solutions (32 and 44gL^-1, respectively), through release of water and oil from the BμEs. Circular dichroism spectroscopic analysis demonstrated that BSA underwent minor secondary structural changes upon incorporation into BμEs, while the secondary structure of cytochrome c and pepsin underwent major changes. Small-angle x-ray scattering (SAXS) results show that proteins promoted an increase of the interfacial fluidity and surface area per volume for the BμE surfactant monolayers, and that each protein uniquely altered self-assembly in the Winsor-III systems. Cytochrome c partitioned via electrostatic attractions between SDS and the protein's positively-charged groups, residing near the surfactant head groups of BμE monolayers, where it decreased surfactant packing efficiency. BSA partitioned through formation of SDS-BSA complexes via hydrophobic and electrostatic attractive interactions. As the BSA-SDS ratio increased, complexes' partitioning favored BμEs over the oil excess phase due to the increased hydrophilicity of the complexes. This study demonstrates the potential utility of BμEs to purify proteins and prepare nanostructured fluids possessing high protein concentration.

Encapsulation of Antibiotic Levofloxacin in Biocompatible Microemulsion Formulation: Insights from Microstructure Analysis

Microemulsions (μEs) are unique systems that offer exciting perspectives in biophysical research for mimicing biomembranes at the molecular level. In the present study, biocompatible μE formulation of a new oil-in-water (o/w) system comprising clove oil/Tween 20/2-propanol/water was accomplished for encapsulating an antibiotic, levofloxacin (LVF). The pseudoternary phase diagram was delineated at a constant cosurfactant/surfactant (2:1) ratio to meet the economic feasibility. The gradual changes occurring in the microstructure of the as-formulated four-component μEs were explored via multiple complementary characterization techniques. The results of electrical conductivity (σ), viscosity (η), and optical microscopic measurements suggested the existence of a percolation transition to a bicontinuous structure in the microregions of the as-formulated μE. LVF displayed a high solubility (5.0 wt %) at the pH of 6.9 in an optimum μE formulation comprising 2-propanol (36.4%), Tween 20 (18.2%), clove oil (20.7%), and water (24.7%). The LVF-loaded μE composition showed long-term stability for over 6 months of storage. Fourier transform IR analysis showed that LVF was stable inside the μE formulation, indicating the absence of any possible aggregation of LVF. Dynamic light scattering revealed that the average particle size of drug-free μE (64.5 ± 3.4 nm) increases to 129.7 ± 5.8 nm upon loading of LVF, suggesting the accumulation of LVF in the interfacial layers of the micelles. Moreover, fluorescence measurements indicated that LVF might be localized in the interfacial film of μE system, which may result in a controlled release of drug.

Physical characterization and antioxidant activity of thymol solubilized Tween 80 micelles

Attempts were made to solubilize thymol in Tween 80 micelle to study the solubilization mechanism of thymol and the effect of solubilization on its antioxidant activity. The maximum solubilized concentration of thymol in a 2.0% (w/v) Tween 80 micelle solution is 0.2 wt%. There was no significant difference in Z-average diameter between the empty micelles and thymol solubilized micelles. ¹H NMR spectra indicated that 3-H and 4-H on the benzene ring of thymol interacted with the ester group between the hydrophilic head group and the hydrophobic tail group of Tween 80 by Van der Waals’ force. Ferric reducing antioxidant potential (FRAP) and cupric ion reducing antioxidant capacity (CUPRAC) assays showed that the reducing antioxidant activity of free thymol did not change after solubilized in Tween 80 micelles. Compared to free thymol, the solubilized thymol showed higher activities to scavenge DPPH (2,2-diphenyl-1-picrylhydrazyl) and hydroxyl radicals. The present study suggested a possible preparation of thymol-carrying micelles with enhanced antioxidant activities that could be applied in food beverages.