Lipid nanoemulsions (NEs), owing to their controllable size (20 to 500 nm), stability and biocompatibility, are now frequently used in various fields, such as food, cosmetics, pharmaceuticals, drug ...delivery, and even as nanoreactors for chemical synthesis. Moreover, being composed of components generally recognized as safe (GRAS), they can be considered as "green" nanoparticles that mimic closely lipoproteins and intracellular lipid droplets. Therefore, they attracted attention as carriers of drugs and fluorescent dyes for both bioimaging and studying the fate of nanoemulsions in cells and small animals. In this review, the composition of dye-loaded NEs, methods for their preparation, and emerging biological applications are described. The design of bright fluorescent NEs with high dye loading and minimal aggregation-caused quenching (ACQ) is focused on. Common issues including dye leakage and NEs stability are discussed, highlighting advanced techniques for their characterization, such as Förster resonance energy transfer (FRET) and fluorescence correlation spectroscopy (FCS). Attempts to functionalize NEs surface are also discussed. Thereafter, biological applications for bioimaging and single-particle tracking in cells and small animals as well as biomedical applications for photodynamic therapy are described. Finally, challenges and future perspectives of fluorescent NEs are discussed.
High‐speed two‐photon microscopy can be used to analyze vascular dynamics in living animals and is essential for the understanding of brain diseases. Recent advances in fluorescent probes/optical ...systems have allowed successful imaging of the hippocampal vasculature in the deep brain of mice (1 mm from the brain surface) under low‐speed conditions (1–2 fps); however, using high‐speed techniques (>30 fps), observation of the deep‐brain vasculature is still challenging. Here, a new nanoemulsion that encapsulates thousands of red‐emissive pyrene dye molecules while maintaining their high two‐photon brightness 1.5 × 102 GM (GM = 10−50 cm4·s·photon−1·molecule−1) at 960 nm excitation and delivers a large amount of such pyrene dyes (65 nmol) into the blood vessels of mice is developed. Remarkably, the nanoprobe is found to exploit the inherent performance of a commonly used Ti:sapphire excitation laser and a sensitive gallium arsenide phosphide nondescanned fluorescence detector to the limit, enabling visualization of the brain vasculature under the cortex region of mice (up to 1.5 mm) under very low‐speed conditions. As a highlight, such a nanoprobe is successfully used to directly observe the blood flow in the hippocampal CA1 region (1.1 mm) through high‐speed resonant scanning (120 fps).
A novel dye‐loaded nanoemulsion is developed for high‐speed two‐photon microscopic imaging of the deep‐brain vasculature in mice. The nanoprobe delivers numerous bright pyrene dyes into the blood vessels of mice, fully exploiting the performance of a Ti:sapphire laser and a gallium arsenide phosphide detector. This approach allows the visualization of hippocampal blood flow in mice at above the video rate.
Background
Aspergillus niger is one of the most common fungal contaminants of food products, leading to several economic losses on fruit, vegetables and other food products during storage. Over the ...years, several new techniques have been developed to control fungal growth, including photodynamic inactivation, in which excitation of a photosensitizer in the right wavelength leads to ROS production and microbial death.
Results
On this paper, curcumin was used as a natural photosentitizer against A. niger spores. Nanoemulsions were used in order to encapsulated curcumin and increase its water solubility. Results showed that spores inhibition could reach up to 80% after 3 min of irradiation while values for un‐encapsulated curcumin were around 30%.
Conclusion
Results presented show that nanoemulsions could be use to enhance the photoinactivation properties of curcumin, against fungal spores from A. niger. This type of process can be use for food decontamination and preservation.
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•Stable crude oil/water nanoemulsions stabilized by biosurfactant are formulated.•The formulated nanoemulsions possess favorable characteristics for EOR applications.•At low shear ...rates, the emulsions showed shearing-thinning behavior.•At high shear rates, the emulsions showed shearing-thickening behavior,•Crude oil is completely recovered from the emulsion in < 1 h upon HCl addition.
The successful utilization of nanoemulsions in several applications would require the formulation of emulsions with excellent characteristics. Ideally, the nanoemulsions should be stabilized using bioemulsifiers, which do not negatively impact the environment throughout their cradle-to-grave lifetime. Thus, crude oil-in-water (O/W) nanoemulsions with exceptional properties were prepared in this study using rhamnolipid biosurfactant as a bioemulsifier. The obtained results reveal that rhamnolipid can produce O/W nanoemulsions with an average droplet size as low as 35.0 ± 6.6 nm. The nanoemulsions also have highly negative zeta potential, low interfacial tension, and long-term kinetic stability. Interestingly, almost all the formulated O/W nanoemulsions using different rhamnolipid dosages and oil/water ratios showed three different flow behaviors (i.e., shear-thinning, Newtonian, and shear-thickening at low, medium, and high shear rates, respectively). Additionally, the nanoemulsion formulated using 50/50 crude oil/water volumetric ratio displayed higher apparent viscosity than the crude oil at elevated temperatures (greater than 63 ⁰C). Furthermore, despite that all the formulated nanoemulsions were extremely stable, they can be easily, completely, and quickly (within ≤ 1 h) switched-off if needed via pH-switching. The results presented herein demonstrate the potential of biosurfactants for enhanced oil recovery (EOR) and other oilfield applications.
Summary
The increasing consumer's demand regarding the healthy diet has promoted the research towards novel approaches for preserving minimally processed fruits and vegetables without the necessity ...of using preservatives. Emulsion‐based edible coatings technology is considered a valuable alternative to improve fresh‐cut fruit and vegetable quality. This review discusses some recent advances for the preservation of the quality and safety of fresh‐cut fruits and vegetables with respect to the use of nanoemulsion‐based edible coatings as carrier of functional compounds such as antimicrobial agents, antioxidants and texture enhancers. It focuses especially on the use of natural functional compounds in food preservation as an alternative to synthetic additives. Moreover, the preparation and characterisation of nanoemulsion are also reviewed.
Schematic of fresh‐cut apple coated by nanoemulsion.
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D-limonene is an important constituent of citrus fruits, such as oranges and lemons, and can be extracted as a natural essential oil for controlling the agricultural pests because of ...its antifungal and insecticidal activities. However, the hydrophobicity of D-limonene hinders its full potential and excellent performance. In this research, the effect of emulsifier type, dosage, and emulsification method on the formation and stability of D-limonene-loaded nanoemulsions was investigated by sample appearance, microstructural observations, droplet size measurement, and multiple light scattering analysis. Nanoemulsions prepared with emulsifier (EL-40) exhibited the highest stability, with an appropriate HLB (Hydrophilic Lipophilic Balance) value of 13.5. The stability of nanoemulsions increased at higher emulsifier dosage from 2% to 6%. Also, nanoemulsions fabricated by dropwise addition of aqueous phase (deionized water) into D-limonene as the oil phase premixed with emulsifier were the most stable samples. The optimized formulation of D-limonene-loaded nanoemulsions was determined as: 10 % D-limonene, 6% EL-40, and 84 % deionized water. The quality indicators of this formulation were acceptable in terms of FAO standards. Finally, D-limonene-loaded nanoemulsions could inhibit the growth of various fungal pathogens, including Pyricularia oryzae (rice blast), Rhizoctonia solani (rice sheath blight), Colletortrichum gloeosporiodes (pepper anthracnose), and Phomopsis amygdali (peach shoot blight). This research provides a practical solution for the formulation of stable and effective nanoemulsions containing D-limonene for the control of agricultural crop diseases.
The recent focus in the development of novel nanosystems for biomedical applications lays firmly on their interactions with biomolecules. Thermodynamic parameters driving the interaction between ...nanoparticles and proteins provide insights into complex processes at bio/nanointerface. The present work aims to investigate the binding mechanisms and the dominant contributions that determine the adsorption processes during the interactions of a model protein, that is, bovine serum albumin, with a new type of drug delivery systems, Vitamin E/sphingomyelin nanoemulsions, plain and coated with polyethylene glycol, and d‐ɑ‐tocopheryl polyethylene glycol succinate. The binding parameters (binding constant, binding stoichiometry, enthalpy, Gibbs energy, and entropy changes of binding) are evaluated by the isothermal titration calorimetry with a MicroCaliTC200 equipment. The effect of nanoemulsions on the protein stability is examined by measuring the thermodynamic parameters for the protein's unfolding (heat capacity; enthalpy, entropy, and free energy changes) with a NanoDSC (TA Instrument) apparatus. The thermodynamic profile shows for all compositions an entropy‐driven interaction dominated by hydrophobic forces due to the rearrangements/displacement of the surrounding water molecules, while maintaining the native conformation of the protein. All the information acquired by thermodynamic approach may significantly enhance the knowledge with special focus on PEGylated nanoemulsions used for biomedical applications.
Thermodynamic parameters at bio/nano interface emerge as key descriptors for the dominant contributions determining the adsorption processes
Nanoemulsions are the transparent or translucent type of emulsion having droplet sizes ranging from 20 to 500 nm. The stability and application of nanoemulsions depend on the droplet and ...physicochemical characteristics. The droplet characteristics are studied through the droplet size, droplet composition, droplet concentration, zeta potential, polydispersity, and interfacial tension. The physicochemical properties are studied by their optical property, rheological property, gravitational separation, droplet aggregation, Ostwald ripening, and chemical stability. The emulsifiers and surfactants aid in the emulsification process and are selected according to the requirements of emulsification methods and expected nanoemulsion quality. The methods used for nanoemulsion preparation can be broadly classified into high-energy and low-energy methods. The high-energy methods include high-pressure valve homogenization, high-pressure microfluidic homogenization, ultrasonic homogenization, and rotor-stator homogenization. Similarly, the low energy methods are phase inversion temperature, phase inversion composition, spontaneous emulsification, membrane emulsion, and solvent displacement/solvent evaporation method. The high-energy methods are rapid in comparison to low-energy methods and can handle a large volume of liquid. The low energy methods provide better control over droplet size. Nanoemulsions have broad applications in the food industry such as in the quality enhancement and shelf-life improvement of bakery products, dairy products, meat products, fruit and vegetable products, and also in probiotics and nutraceuticals.
•High energy and low energy methods are the two methods that are employed for the development of nanoemulsions.•Both natural and synthetic emulsifiers can be used for the preparation of nanoemulsions.•Nanoemulsion coatings improve the sensorial properties and the storage stability of the foods.•Nanoemulsion coatings enhance the storage stability of the probiotics and aid in their controlled release.
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