Freeze–thaw stability of lecithin and modified starch-based nanoemulsions

Interfacial crystallized oleogel emulsion with improved freeze-thaw stability and tribological properties: Influence of cooling rate

In this study, the influence of cooling rate on the freeze-thaw stability, rheological and tribological properties of interfacial crystalized oleogel emulsion was investigated. Results showed that slower cooling rate could promote formation of larger crystals and stronger network in oleogels. Additionally, oleogel emulsions showed higher freeze-thaw stability than those stabilized solely by emulsifiers. The slower cooling rate resulted in larger crystals adsorbed at the droplet surface. This led to greater steric hindrance that prevented the migration of oil droplets with higher resistance to disruption by ice crystals. The rheological and tribological measurements suggested that with appropriate amount of crystals, the tribological properties were better maintained for emulsions prepared at slow cooling rate after freeze-thaw treatment. This strategy greatly enriched oleogel emulsion formulations and provided important clues for potential applications in food products involved with freeze-thaw treatment.

Freeze-thaw stability of Pickering emulsion stabilized by modified soy protein particles and its application in plant-based ice cream

Pickering emulsions are of great interest to the food industry and their freeze-thaw stability important when used in frozen foods. Particles of soybean isolate (SPI) were heat treated and then crosslinked with transglutaminase (TG) enzyme to produce Pickering emulsions. The protein particles produced using unheated and uncrosslinked SPI (NSPI) was used as the benchmark. The mean particle size, absolute zeta potential, and surface hydrophobicity of protein particles produced using heat treatment and TG crosslinking (at 40 U/g) SPI (HSPI-TG-40) were the highest and substantially higher than those produced using NSPI. The thermal treatment of protein particles followed by crosslinking with TG enzyme improved the freeze-thaw stability of Pickering emulsions stabilized by them. The Pickering emulsions produced using HSPI-TG-40 had the lowest temperature for ice crystal formation and they had better freeze-thaw stability. The plant-based ice cream prepared by HSPI-TG-40 particle-stabilized Pickering emulsions had suitable texture and freeze-thaw stability compared to the ice cream produced using NSPI. The Pickering particles produced using heat treatment of SPI followed by crosslinking with TG (at 40 U/g) produced the most freeze-thaw stable Pickering emulsions. These Pickering particles and Pickering emulsions could be used in frozen foods such as ice cream.

A Reversibly Thermoresponsive, Theranostic Nanoemulgel for Tacrolimus Delivery to Activated Macrophages: Formulation and In Vitro Validation

Despite long-term immunosuppression, organ transplant recipients face the risk of immune rejection and graft loss. Tacrolimus (TAC, FK506, Prograf®) is an FDA-approved keystone immunosuppressant for preventing transplant rejection. However, it undergoes extensive first-pass metabolism and has a narrow therapeutic window, which leads to erratic bioavailability and toxicity. Local delivery of TAC directly into the graft, instead of systemic delivery, can improve safety, efficacy, and tolerability. Macrophages have emerged as promising therapeutic targets as their increased levels correlate with an increased risk of organ rejection and a poor prognosis post-transplantation. Here, we present a locally injectable drug delivery platform for macrophages, where TAC is incorporated into a colloidally stable nanoemulsion and then formulated as a reversibly thermoresponsive, pluronic-based nanoemulgel (NEG). This novel formulation is designed to undergo a sol-to-gel transition at physiological temperature to sustain TAC release in situ at the site of local application. We also show that TAC-NEG mitigates the release of proinflammatory cytokines and nitric oxide from lipopolysaccharide (LPS)-activated macrophages. To the best of our knowledge, this is the first TAC-loaded nanoemulgel with demonstrated anti-inflammatory effects on macrophages in vitro.

Folate-conjugated near-infrared fluorescent perfluorocarbon nanoemulsions as theranostics for activated macrophage COX-2 inhibition

Activated macrophages play a critical role in the orchestration of inflammation and inflammatory pain in several chronic diseases. We present here the first perfluorocarbon nanoemulsion (PFC NE) that is designed to preferentially target activated macrophages and can deliver up to three payloads (two fluorescent dyes and a COX-2 inhibitor). Folate receptors are overexpressed on activated macrophages. Therefore, we introduced a folate-PEG-cholesterol conjugate into the formulation. The incorporation of folate conjugate did not require changes in processing parameters and did not change the droplet size or fluorescent properties of the PFC NE. The uptake of folate-conjugated PFC NE was higher in activated macrophages than in resting macrophages. Flow cytometry showed that the uptake of folate-conjugated PFC NE occurred by both phagocytosis and receptor-mediated endocytosis. Furthermore, folate-conjugated PFC NE inhibited the release of proinflammatory cytokines (TNF-α and IL-6) more effectively than nonmodified PFC NE, while drug loading and COX-2 inhibition were comparable. The PFC NEs reported here were successfully produced on multiple scales, from 25 to 200 mL, and by using two distinct processors (microfluidizers: M110S and LM20). Therefore, folate-conjugated PFC NEs are viable anti-inflammatory theranostic nanosystems for macrophage drug delivery and imaging.

Influence of the Emulsifier Sodium Caseinate-Xanthan Gum Complex on Emulsions: Stability and Digestive Properties

In this study, virgin coconut oil (VCO) nanoemulsions were prepared by ultrasonication using a sodium caseinate (SC) and xanthan gum (XG) complex as an emulsifier. The stability and digestion characteristics of SC/XG-VCO emulsions formed by co-adsorption and SC-VCO-XG emulsions formed by layer adsorption were compared. The stability of the two emulsions was studied under different pH, ionic strength, heat treatment, freeze-thaw cycles, and storage conditions, and the droplet size and zeta potential were used as indicators to assess the stability. In addition, the stability of oxidation and the digestive properties of both emulsions were studied. It was found that the SC-VCO-XG emulsions had better environmental stability, oxidative stability, storage stability, and digestibility compared to SC/XG-VCO emulsions. This study has shown that the formation method of protein-polysaccharide stabilized emulsions has an impact on the stability and digestibility properties of the emulsions, and that the emulsion carriers constructed by layer adsorption are more suitable for subsequent industrial production and development.

Effect of high γ-irradiation dosage on physico-chemical, functional and emulsion properties of almond gum powder

Almond gum is a natural biopolymer produced by Almond tree that is non-toxic, biodegradable, and biocompatible. These features make it suitable for applications in the food, cosmetic, biomedical, and packaging industries. To ensure its wide application in these fields, green modification process is necessary. Gamma irradiation is often used as a sterilisation and modification technique, due to its high penetration power. Thus, evaluating its effects on the physicochemical and functional properties of gum after exposure is important. To date, limited studies have reported the use of high dose of γ-irradiation on the biopolymer. Therefore, the present study demonstrated the effect of a high dose of γ-irradiation (0, 24, 48, and 72 kGy) on the functional and phytochemical properties of almond gum powder. The irradiated powder was studied for its color, packing, functional, and bioactive properties. The results revealed a significant increase in water absorption capacity, oil absorption capacity, and solubility index. However, a decreasing trend was observed in the foaming index, L value, pH, and emulsion stability with the radiation dose. Besides, sizable effects were observed in the IR spectra of irradiated gum. Phytochemical properties were significantly improved with an increase in dose. The emulsion was prepared from irradiated gum powder, where the highest creaming index was observed at 72 kGy and a decreasing trend in zeta potential. These results suggested that γ-irradiation treatment is a successful method to generate desirable cavity, pore sizes, functional properties, and bioactive compounds. This emerging approach could modify the natural additive with distinct internal structure for specific uses in wide range of food, pharmaceutical and other industrial applications.

Development of Nanoemulsions for Topical Application of Mupirocin

Mupirocin (MUP) is a topical antibacterial agent used to treat superficial skin infections but has limited application due to in vivo inactivation and plasma protein binding. A nanoemulsion formulation has the potential to enhance the delivery of mupirocin into the skin. MUP-loaded nanoemulsions were prepared using eucalyptus oil (EO) or eucalyptol (EU), Tween^® 80 (T80) and Span^® 80 (S80) as oil phase (O), surfactant (S) and cosurfactant (CoS). The nanoemulsions were characterised and their potential to enhance delivery was assessed using an in vitro skin model. Optimised nanoemulsion formulations were prepared based on EO (MUP-NE EO) and EU (MUP-NE EU) separately. MUP-NE EO had a smaller size with mean droplet diameter of 35.89 ± 0.68 nm and narrower particle size index (PDI) 0.10 ± 0.02 nm compared to MUP-NE EU. Both nanoemulsion formulations were stable at 25 °C for three months with the ability to enhance the transdermal permeation of MUP as compared to the control, Bactroban^® cream. Inclusion of EU led to a two-fold increase in permeation of MUP compared to the control, while EO increased the percentage by 48% compared to the control. Additionally, more MUP was detected in the skin after 8 h following MUP-NE EU application, although MUP deposition from MUP-NE EO was higher after 24 h. It may be possible, through choice of essential oil to design nanoformulations for both acute and prophylactic management of topical infections.

Effect of pectin on the properties of nanoemulsions stabilized by sodium caseinate at neutral pH

The effect of different concentrations of low methoxyl pectin (LMP) on lipid oxidation and physical stability of sodium caseinate (CAS) stabilized nanoemulsions under neutral pH was investigated. The addition of pectin at low concentration (≤ 0.10 wt%) had no significant effect on the average size of nanoemulsions, but a slight size increase and phase separation were observed at higher concentrations of pectin (≥ 0.25 wt%). This result suggests that LMP can not adsorb at the oil/water interfacial CAS membrane at neutral pH. However, in the presence of LMP, the physical stability of nanoemulsions against high salt concentrations and freeze-thaw cycles was significantly enhanced. Moreover, nanoemulsions containing pectin have a better ability to inhibit lipid and protein oxidation than nanoemulsions without pectin after 3 weeks, and the lowest lipid hydroperoxide content was observed for nanoemulsions containing 0.25 wt% pectin.

Characterization of a Novel High Internal Phase Pickering Emulsions Stabilized by Soy Protein Self-Assembled Gel Particles

In this paper, a novel high-internal-phase Pickering emulsion (HIPPE) prepared by acid-induced self-assembly SPI gel (A/S-SPIG) was investigated. The steady-state shear test results showed that all HIPPEs were typical shear thinning emulsion, which could form stable emulsion (0.2–1.2% SPI concentration). The network structure of HIPPE stabilized by A/S-SPIG particles (0.2–1.2% SPI concentration) was continuously enhanced with increasing SPI concentration. The high concentration of SPI particles increased the crystallization temperature of the stabilized HIPPE. Meanwhile, at a concentration of 1.2%, HIPPE has the best cohesive property and stability against delamination due to weakened mobility. In conclusion, A/S-SPIG was proved excellent HIPPE stabilized particle.

Development and Evaluations of Transdermally Delivered Luteolin Loaded Cationic Nanoemulsion: In Vitro and Ex Vivo Evaluations

Introduction: Luteolin (LUT) is natural flavonoid with multiple therapeutic potentials and is explored for transdermal delivery using a nanocarrier system. LUT loaded cationic nanoemulsions (CNE1–CNE9) using bergamot oil (BO) were developed, optimized, and characterized in terms of in vitro and ex vivo parameters for improved permeation. Materials and methods: The solubility study of LUT was carried out in selected excipients, namely BO, cremophor EL (CEL as surfactant), labrasol (LAB), and oleylamine (OA as cationic charge inducer). Formulations were characterized with globular size, polydispersity index (PDI), zeta potential, pH, and thermodynamic stability studies. The optimized formulation (CNE4) was selected for comparative investigations (% transmittance as %T, morphology, chemical compatibility, drug content, in vitro % drug release, ex vivo skin permeation, and drug deposition, DD) against ANE4 (anionic nanoemulsion for comparison) and drug suspension (DS). Results: Formulations such as CNE1–CNE9 and ANE4 (except CNE6 and CNE8) were found to be stable. The optimized CNE4 based on the lowest value of globular size (112 nm), minimum PDI (0.15), and optimum zeta potential (+26 mV) was selected for comparative assessment against ANE4 and DS. The %T values of CNE1–CNE9 were found to be ˃95% and CEL content slightly improved the %T value. The spherical CNE4 was compatible with excipients and showed % total drug content in the range of 97.9–99.7%. In vitro drug release values from CNE4 and ANE4 were significantly higher than DS. Moreover, permeation flux (138.82 ± 8.4 µg/cm²·h), enhancement ratio (8.23), and DD (10.98%) were remarkably higher than DS. Thus, ex vivo parameters were relatively high as compared to DS which may be attributed to nanonization, surfactant-mediated reversible changes in skin lipid matrix, and electrostatic interaction of nanoglobules with the cellular surface. Conclusion: Transdermal delivery of LUT can be a suitable alternative to oral drug delivery for augmented skin permeation and drug deposition.

Resveratrol-Loaded Nanoemulsions: In Vitro Activity on Human T24 Bladder Cancer Cells

The chemopreventive potential of Resveratrol (RV) against bladder cancer and its mechanism of action have been widely demonstrated. The physicochemical properties of RV, particularly its high reactivity and low solubility in aqueous phase, have been limiting factors for its bioavailability and in vivo efficacy. In order to overcome these limitations, its inclusion in drug delivery systems needs to be taken into account. In particular, oil-in-water (O/W) nanoemulsions (NEs) have been considered ideal candidates for RV encapsulation. Since surfactant and oil composition can strongly influence NE features and their application field, a ternary phase diagram was constructed and evaluated to select a suitable surfactant/oil/water ratio. The selected sample was deeply characterized in terms of physical chemical features, stability, release capability and cytotoxic activity. Results showed a significant decrease in cell viability after the incubation of bladder T24 cancer cells with RV-loaded NEs, compared to free RV. The selected NE formulation was able to preserve and improve RV cytotoxic activity by a more rapid drug uptake into the cells. O/W NEs represent an effective approach to improve RV bioavailability.

Food-Grade Nanoemulsions for the Effective Delivery of β-Carotene

Utilization of β-carotene in functional food products is limited due to chemical instability, lower water-solubility, and higher melting point. The present research was designed to formulate a nanoemulsion system for the effective delivery of β-carotene. β-Carotene was successfully incorporated into nanoemulsions using the ultrasonication method. During 60 days of storage, the droplet size of β-carotene-containing nanoemulsions varied from 112.36 to 133.9 nm at 4 °C and from 112.36 to 147.1 nm at 25 °C. The oxidation stability of olive oil was remarkably increased when incorporated into nanoemulsions. β-Carotene nanoemulsions remained stable under varying ionic strengths (50-400 mM), pH values (2-8), and freeze-thaw cycles (four). The values of turbidity and total color difference increased over time and at a higher temperature. Degradation of β-carotene was substantially slower in nanoemulsions, and the addition of antioxidants significantly increased the retention of β-carotene in nanoemulsions. These findings suggest that the ultrasonic homogenization method has potential for the preparation of β-carotene nanoemulsions with desirable properties. These nanoemulsions can be effectively used for the incorporation of β-carotene in the food and beverage industry.

Effects of Emulsifier Type and Post-Treatment on Stability, Curcumin Protection, and Sterilization Ability of Nanoemulsions

Curcumin has a high inhibitory effect on many potential diseases caused by bacteria and fungi. However, its degradability and low water solubility limit its application. Loading curcumin with an emulsion delivery system can overcome these problems. Five different types of emulsifiers were used to prepare the curcumin-loaded nanoemulsions, namely, Tween 80 (T80), Span 80 (S80), sodium dodecyl sulfate (SDS), soybean protein isolate (SPI), and lecithin (LEC). The effects of emulsifier types and post-treatment methods on emulsion stability and curcumin-load efficiency were studied. In addition, photodynamic inactivation was used to test the antibacterial effect of nanoemulsions on Escherichia coli under blue light excitation. The five types of emulsifiers could form uniform emulsions with good storage stability and with antibacterial capacity on Escherichia coli. Among them, the T80 and LEC emulsions had good stability, coating effect, and sterilization performance under heating or room temperature. Both curcumin-loaded bactericidal emulsions had the potential for large-scale applications. A nanoemulsions delivery system could effectively improve the dispersion and chemical stability of curcumin in water. An emulsion loaded with antibacterial photosensitizer represents a new idea for the storage and preservation of food commodities.

Nanoemulsions for health, food, and cosmetics: a review

Nanoemulsions are gaining importance in healthcare and cosmetics sectors as a result of the unique properties of nanosized droplets, such as high surface area. Here we review nanotechnology and nanoemulsions with focus on emulsifiers and nanoemulsifiers, and applications for drugs and vaccines delivery, cancer therapy, inflammation treatment, cosmetics, perfumes, polymers, and food. We discuss nanoemulsion safety and properties, e.g., stability, emulsification, solubility, molecular number and arrangements, ionic strength, pH and temperature.

Bergamot essential oil nanoemulsions: antimicrobial and cytotoxic activity

Bergamot essential oil (BEO) is well-known for its food preservation activity, as well as anticancer efficacy. However, the poor BEO water solubility and deriving low bioaccessibility have limited its wider applications. The incorporation in nanoemulsions of BEO and its refined fractions was investigated to enhance its dispersibility in water to promote its antimicrobial activity, tested against Escherichia coli, Lactobacillus delbrueckii, and Saccharomyces cerevisiae, and its cytotoxicity already at low concentrations. Different nanoemulsion formulations were tested based on food-grade ingredients, which were characterized in terms of hydrodynamic diameter and polydispersity index, and physical stability. The antimicrobial activity against all the tested micro-organisms was observed to be higher for BEO in its initial composition, than the light fraction, richer in d-limonene, ß-pinene, and γ-terpinene, or the heavy fraction, richer in linalyl acetate and linalool. Remarkably, the use of BEO nanoemulsions notably enhanced the antimicrobial activity for all the tested oils. BEO exhibited also a measurable cytotoxic activity against Caco-2 cells, which was also enhanced by the use of the different nanoemulsions tested, in comparison with free oil, which discourages the direct use of BEO nanoemulsions as a food preservative. Conversely, BEO nanoemulsions might find use in therapeutic applications as anticarcinogenic agents.

Fabrication and Characterization of Quinoa Protein Nanoparticle-Stabilized Food-Grade Pickering Emulsions with Ultrasound Treatment: Effect of Ionic Strength on the Freeze-Thaw Stability

The development of multilayered interfacial engineering on the emulsion freeze-thaw properties has recently attracted widespread attention, because of the essential freeze-thaw storage process in some emulsion-matrix food products. In this research, we studied the role of salt concentration on the freeze-thaw properties of quinoa protein (QPI) nanoparticles-stabilized Pickering emulsions. The QPI nanoparticles (particle concentration c = 2%, w/v) with increasing particle size and surface hydrophobicity ( H₀) were fabricated by ultrasound treatment at 100 W for 20 min, by varying the NaCl addition (salt concentrations, 0-500 mM). The sonicated QPI nanoparticles with increasing salt concentrations showed higher β-sheet structure contents and stronger hydrophobic interactions, which were attributed to the decreasing charged groups and particle aggregation by electrostatic interactions. As compared to the sonicated QPI nanoparticles-stabilized Pickering emulsions ( c = 2%, oil fraction φ = 0.5) without salt accretion, the emulsions with salt accretion exhibited better freeze-thaw properties after three freeze-thaw circulations, which might be mainly caused by the generation of gel-like three-dimensional structure and multilayered network at the droplets' interface with smaller droplet sizes. Increasing the salt concentration progressively enhanced the freeze-thaw properties of sonicated QPI nanoparticles-stabilized Pickering emulsions probably due to the inhibit formation of ice crystal by the "salting-out" effects. The results of this study would provide great significance to investigate the role of salt concentration in the freeze-thaw properties of protein-stabilized Pickering emulsions.

Importance of crystallinity of anchoring block of semi-solid amphiphilic triblock copolymers in stabilization of silicone nanoemulsions

Polymer emulsifiers solidified at the interface between oil and water can provide exceptional dispersion stability to emulsions due to the formation of unique semi-solid interphase. Our recent works showed that the structural stability of paraffin-in-water emulsions highly depends on the oil wettability of hydrophobic block of methoxy poly(ethylene glycol)-block-poly(ε-caprolactone) (mPEG-b-PCL). Here we investigate the effects of the crystallinity of hydrophobic block of triblock copolymer-based emulsifiers, PCLL-b-PEG-b-PCLL, on the colloidal properties of silicone oil-in-water nanoemulsions. The increased ratio of l-lactide to ε-caprolactone decreases the crystallinity of the hydrophobic block, which in turn reduces the droplet size of silicone oil nanoemulsions due to the increased chain mobility at the interface. All of the prepared nanoemulsions are very stable for a month at 37°C. However, the exposure to repeated freeze-thaw cycles quickly destabilizes the nanoemulsions prepared using the polymer with the reduced crystallinity. This work demonstrates that the anchoring chain crystallization in the semi-solid interphase is critically important for the structural robustness of nanoemulsions under harsh physical stresses.

Synergistic performance of lecithin and glycerol monostearate in oil/water emulsions

The effects of the combination of two low-molecular weight emulsifiers (lecithin and glycerol-monostearate (GMS)) on the stability, the dynamic interfacial properties and rheology of emulsions have been studied. Different lecithin/GMS ratios were tested in order to assess their impact in the formation and stabilization of oil in water emulsions. The combination of the two surfactants showed a synergistic behaviour, mainly when combined at the same ratio. The dynamic film properties and ζ-potential showed that lecithin dominated the surface of oil droplets, providing stability to the emulsions against flocculation and coalescence, while allowing the formation of small oil droplets. At long times of adsorption, all of the mixtures showed similar interfacial activity. However, higher values of interfacial pressure at the initial times were reached when lecithin and GMS were at the same ratio. Interfacial viscoelasticity and viscosity of mixed films were also similar to that of lecithin alone. On the other hand, emulsions viscosity was dominated by GMS. The synergistic performance of lecithin-GMS blends as stabilizers of oil/water emulsions is attributed to their interaction both in the bulk and at the interface.

Formation and Stability of Vitamin E Enriched Nanoemulsions Stabilized by Octenyl Succinic Anhydride Modified Starch

Vitamin E (VE) is highly susceptible to autoxidation; therefore, it requires systems to encapsulate and protect it from autoxidation. In this study, we developed VE delivery systems, which were stabilized by Capsul® (MS), a starch modified with octenyl succinic anhydride. Influences of interfacial tension, VE viscosity, molecular weight distribution, and surfactant type (MS versus Tween 80) on stability and droplet size obtained by high-pressure homogenization were investigated. Both surfactants reduced interfacial tension and small droplet diameters (<350 nm) were produced at high VE content (80% oil phase, w/w) and low emulsifier (2.5%, w/w), which was attributed to their molecular distribution and interfacial characteristics and the magnitude of disruptive forces generated within homogenizer. MS nanoemulsions were stable to droplet coalescence at high temperature–short time exposure (30, 55, 80°C; 30 min). Results indicated that MS can be used successfully to stabilize VE nanoemulsions at ambient temperatures. Such nanoemulsions may be incorporated in many food products.

Bioavailability of encapsulated resveratrol into nanoemulsion-based delivery systems

Different O/W nanoemulsion-based delivery systems were developed in order to optimize the bioavailability of encapsulated resveratrol for potential oral administration. Blank formulations without resveratrol had no negative effect on cell viability or the cytoskeleton structure of Caco-2 cells (XTT viability assay and confocal microscopy). All nanoemulsions were then evaluated based on permeability tests on Caco-2 cells. As a result, the most efficient formulations were lecithin-based nanoemulsions which were able to transport resveratrol through cell monolayers in characteristically shorter times (1-6h) than those required for their metabolization (3-12h), allowing for better preservation of the integrity of the emulsion droplets, thus better protecting the resveratrol molecule. Fluorescence spectroscopy studies confirmed that resveratrol was encapsulated in the inner core of the nanoemulsions, which provides protection against chemical degradation. Furthermore, the developed systems also demonstrated the capability of nanoemulsions in sustained release of resveratrol from dialysis bags compared to the unencapsulated compound.

Phospholipids at the interface: current trends and challenges

Phospholipids are one of the major structural elements of biological membranes. Due to their amphiphilic character, they can adopt various molecular assemblies when dispersed in water, such as bilayer vesicles or micelles, which give them unique interfacial properties and render them very attractive in terms of foam or emulsion stabilization. This article aims at reviewing the properties of phospholipids at the air/water and oil/water interfaces, as well as the recent advances in using these natural components as stabilizers, alone or in combination with other compounds such as proteins. A discussion regarding the challenges and opportunities offered by phospholipids-stabilized structure concludes the review.