Nano-emulsions: Formation by low-energy methods

Nanoemulsions for synthesis of biomedical nanocarriers

Nanoemulsions are kinetically stabilized emulsions with droplet sizes in the nanometer scale. These nanodroplets are able to confine spaces in which reactions of polymerization or precipitation can take place, leading to the formation of particles and capsules that can act as nanocarriers for biomedical applications. This review discusses the different possibilities of using nanoemulsions for preparing biomedical nanocarriers. According to the chemical nature, nanocarriers prepared in nanoemulsions are classified in polymeric, inorganic, or hybrid. The main synthetic strategies for each type are revised, including miniemulsion polymerization, nanoemulsion-solvent evaporation, spontaneous emulsification, sol-gel processes, and combination of different techniques to form multicomponent materials.

Biochemical effects of deferasirox and deferasirox-loaded nanomicellesin iron-intoxicated rats

Deferasirox (DFX) was formulated into oil-in-water microemulsions in the presence of pluronicto improve its oral bioavailability. The size of the DFX-loadedmicroemulsions system measured by dynamic light scattering (DLS) was about 9 nm. The anti-proliferative and anti-lipid peroxidation effects of DFX and DFX-loaded microemulsions were assessed on Human umbilical vein endothelial (HUVEC) cells. Our in vitro results showed that HUVEC cells are more susceptible to free DFX as compared to DFX-loaded microemulsions. Although both free and encapsulated DFX attenuated FeCl₃-induced lipid peroxidation, after 6 and 12 h treatment, DFX-loaded microemulsions did not appear a better ameliorator than DFX. To compare the in vivo efficacy of free DFX and DFX-loaded microemulsions in iron- intoxicated rats, the animals were orally administered with 25 mg/kg DFX, or 25 mg/kg DFX microemulsions, respectively. In vivo gavage handling of free DFX significantly increased serum biochemical parameters. There was also a significant increase in lipid peroxidation in rats who received free DFX compared to those in the control rats. Treatment with DFX-loaded microemulsions restored the elevated levels of serum AST, ALT, and creatinine levels and also reduced liver MDA content. Histopathological analysis of renal and hepatic tissues was in line with the biochemical results. In conclusion, DFX-loaded microemulsions induce less toxicity than free DFX and appear a more desirable and safer drug carrier in combating the iron-overload complications. Theoretical simulations are performed to get better insight regarding interactions between DFX and surfactant F127.

Polyglycerol Ester-Based Low Energy Nanoemulsions with Red Raspberry Seed Oil and Fruit Extracts: Formulation Development toward Effective In Vitro/In Vivo Bioperformance

This study focuses on the development of biocompatible oil-in-water (O/W) nanoemulsions based on polyglycerol esters, as promising carriers for natural actives: red raspberry seed oil—RO and hydro-glycolic fruit extracts from red raspberry—RE and French oak—FE. Nanoemulsions were obtained via phase inversion composition (PIC) method at room temperature by dilution of microemulsion phase, confirmed by visual appearance, percentage of transmittance, microscopic, rheological and differential scanning calorimetry (DSC) investigations. The results have shown that the basic RO-loaded formulation could be further enriched with hydro-glycolic fruit extracts from red raspberry or French oak, while keeping a semi-transparent appearance due to the fine droplet size (Z-ave: 50 to 70 nm, PDI value ≤ 0.1). The highest antioxidant activity (~92% inhibition of the DPPH radical) was achieved in the formulation containing both lipophilic (RO) and hydrophilic antioxidants (FE), due to their synergistic effect. The nanoemulsion carrier significantly increased the selective cytotoxic effect of RO towards malignant melanoma (Fem-X) cells, compared to normal human keratinocytes (HaCaT). In vivo study on human volunteers showed satisfactory safety profiles and significant improvement in skin hydration during 2 h after application for all nanoemulsions. Therefore, polyglycerol ester-based nanoemulsions can be promoted as effective carriers for red raspberry seed oil and/or hydro-glycolic fruit extracts in topical formulations intended for skin protection and hydration.

Nutraceutical delivery through nano-emulsions: General aspects, recent applications and patented inventions

Nanostructured emulsions have a significant potential for encasing, transport and delivery of hydrophilic and lipophilic nutraceuticals and other bioactive compounds by providing enhanced stability and functionality in food and pharmaceutical applications. As highlighted in recent researches, essential fatty acids (EFA) and oils (EO), antioxidants, vitamins, minerals, pro and prebiotics, and co-enzymes, are common bioactives encapsulated in nanoscale delivery systems in order to protect them from degradation during processing and storage, and to improve bioavailability after their consumption. Nanoemulsions (NEs) as delivery systems for nutraceuticals comprise either oil-in-water (O/W) or water-in-oil (W/O) biphasic dispersion with nano-sized droplets, which are stabilized through an active surfactant. Both high- and low- energy methods are used to produce well-structured and stable NEs with advanced structural and rheological features. The in vitro and in vivo studies are focused to assess the nutraceutical releasing profile, gastrointestinal transportation and cytotoxicity of nutraceutical loaded NE. Within the last three decades, a number of NE systems have been developed for certain purposes and submitted for patent approval. Currently, there are many issued patents published as well as and applications under process. This review focus on the current status of food-grade NEs in terms of formation, characterization, relevant applications of nutraceutical delivery, and the recent developments including patented systems.

Spontaneous Formation of Double Emulsions at Particle-Laden Interfaces

HYPOTHESIS

Traditionally, double emulsions are produced in the presence of both oil-soluble and water-soluble surfactants in sequential droplet formation settings or unique fluidic designs. Micelles, assemblies of surfactants in liquid mediums, can generate single emulsion droplets without requiring input energy. We hypothesize that the synergy between nanoparticles in one phase, and micelles in the other phase can spontaneously generate double emulsions. Nanoparticles can become surface-activated by adsorbing surfactants and form the second type of emulsions from the initially emulsified phase by micelles.

EXPERIMENTS

We design a thermodynamically-driven emulsification platform where double emulsions are spontaneously formed as soon an aqueous nanoparticle dispersion is placed in contact with an oleic micellar solution. Confocal and cryogenic-scanning electron microscopies are utilized to characterize structure and intensity of emulsions at various concentrations of silica nanoparticle and Span micelles. The rate of particle surface activation and emulsification and the amount of water intake are quantified using dynamic light scattering, dynamic interfacial tension, and density measurements.

FINDINGS

Nanoscale water droplets nucleate in the oil in form of swollen micelles. Over time, nanoparticles form a water-shell encapsulating the swollen-micelle rich oil phase. The gradual surfaceactivation of nanoparticles is key in self-double emulsification and controlling the emulsion intensity. We build on this new discovery and design a novel system for double emulsification. Incorporating nanoparticles into spontaneous emulsification systems opens novel routes for designing emulsion-based materials.

Design and characterization of oil-in-water nanoemulsion for enhanced oil recovery stabilized by amphiphilic copolymer, nonionic surfactant, and LAPONITE® RD

The application of nanotechnology in the oil and gas industry has attracted widespread attention in recent years. This study aims to develop a nanoemulsion (NE) for use in enhanced oil recovery (EOR). The NE stabilized by anion amphiphilic copolymer, nonionic surfactant (Brij30) and modified LAPONITE® RD was prepared by the phase inversion composition (PIC) method. The appearance of the emulsion is translucent and the average particle size is less than 60 nm. The micromorphology and interfacial tension (IFT) are examined using transmission electron microscopy (TEM) and a spinning drop IFT meter, respectively. The NE possesses good stability evaluated by conductivity and particle size tests. The absolute value of the zeta potential of NE increases when modified LAPONITE® RD is added. In a core flooding experiment with an artificial sandstone core, the NE flooding increased oil recovery by 23.53% compared to water flooding.

Nanoemulsions: A Better Approach for Antidiabetic Drug Delivery

Conventional delivery of antidiabetic drugs faces many problems like poor absorption, low bioavailability, and drug degradation. Nanoemulsion is a unique drug technology, which is very suitable for the delivery of antidiabetic drugs. In recent years, the flaws of delivering anti-hypoglycaemic drugs have been overcome by choosing nanoemulsion drug technology. They are thermodynamically stable and also provide the therapeutic agent for a longer duration. Generally, nanoemulsions are made up of either oil-in-water or water-in-oil and the size of the droplets is from fifty to thousand nanometer. Surfactants are critical substances that are added in the manufacturing of nanoemulsions. Only the surfactants which are approved for human use can be utilized in the manufacturing of nanoemulsions. Generally, the preparation of emulsions includes mixing of the aqueous phase and organic phase and using surfactant with proper agitation. Nanoemulsions are used for antimicrobial drugs, and they are also used in the prophylaxis of cancer. Reduction in the droplet size may cause variation in the elastic and optical behaviour of nanoemulsions.

Fabrication of nanoparticles for bone regeneration: new insight into applications of nanoemulsion technology

Introducing synthetic bone substitutes into the clinic was a major breakthrough in the regenerative medicine of bone. Despite many advantages of currently available bone implant materials such as biocompatiblity and osteoconductivity, they still suffer from relatively poor bioactivity, osteoinductivity and osteointegration. These properties can be effectively enhanced by functionalization of implant materials with nanoparticles such as osteoinductive hydroxyapatite nanocrystals, resembling inorganic part of the bone, or bioactive polymer nanoparticles providing sustained delivery of pro-osteogenic agents directly at implantation site. One of the most widespread techniques for fabrication of nanoparticles for bone regeneration applications is nanoemulsification. It allows manufacturing of nanoscale particles (<100 nm) that are injectable, 3D-printable, offer high surface-area-to-volume-ratio and minimal mass transport limitations. Nanoparticles obtained by this technique are of particular interest for biomedical engineering due to fabrication procedures requiring low surfactant concentrations, which translates into reduced risk of surfactant-related in vivo adverse effects and improved biocompatibility of the product. This review discusses nanoemulsion technology and its current uses in manufacturing of nanoparticles for bone regeneration applications. In the first section, we introduce basic concepts of nanoemulsification including nanoemulsion formation, properties and preparation methods. In the next sections, we focus on applications of nanoemulsions in fabrication of nanoparticles used for delivery of drugs/biomolecules facilitating osteogenesis and functionalization of bone implants with special emphasis on biomimetic hydroxyapatite nanoparticles, synthetic polymer nanoparticles loaded with bioactive compounds and bone-targeting nanoparticles. We also highlight key challenges in formulation of nanoparticles via nanoemulsification and outline potential further improvements in this field.

Preparation of a stabilized aqueous polystyrene suspension via phase inversion

Polymer suspensions have found various applications in novel technologies. In this research, an aqueous suspension of polystyrene was prepared via the phase inversion method using sodium lauryl sulfate (SLS) as an anionic surfactant and two co-surfactants. The effects of co-surfactant ratio and salt concentration were investigated and the stability and characteristics of the prepared samples were identified. All samples possessed a zeta potential lower than −50 mV which reveals an electrostatic stability. The sample PS-1, containing the lower salt concentration of 1 × 10⁻³ M, was the most stable sample, while its stability decreases with increasing salt concentration. The sample PS-5 during the electrical conductivity measurement exhibited partial instability via agglomeration of polymer on the probe. Rheology measurements revealed that the suspension behavior varies between Newtonian and non-Newtonian. Eventually, PS-1 containing 4.00 g polystyrene, 1.70 g SLS and a co-surfactant ratio of 0.66, suspended within 150 mL of 0.003 M aqueous NaCl solution, exhibited proper stability.

The phase inversion emulsification method was used to prepare polystyrene aqueous suspensions. Final suspensions were characterized to determine the most stable suspension.

Nanoemulsion: A Novel Drug Delivery Approach for Enhancement of Bioavailability

BACKGROUND

Poor bioavailability and solubility of drugs in aqueous phase are the most important problems of newly developed chemical entities that can be improved by nanoemulsion.

OBJECTIVES

BCS class II and IV which are poorly soluble in water demonstrate various problems in conventional dosage forms. For the improvement of solubility, bioavailability and getting the best therapeutic effect of poorly soluble drugs nanoemulsion is the best solution.

METHODS

Nanoemulsion are thermodynamically unstable isotropic system with droplet size 1-100 nm in which two immiscible fluids are combined together to form one phase by using an emulsifying agent. Nanoemulsion can be designed to promote the bioavailability of API by trapping them inside.

RESULTS

Nanoemulsion can be developed in many dosage forms such as oral, parenteral, topical, ophthalmic dosage form in large scale using common operation at a very low cost. Large range of lipophilic drugs can be easily incorporated in nanoemulsion.

CONCLUSION

In this review, attention is focused on the type of nanoemulsions, their advantages over other dosage form, method for their preparation, characterization, applications and patents in various fields.

Studies on the Effect of Oil and Surfactant on the Formation of Alginate-Based O/W Lidocaine Nanocarriers Using Nanoemulsion Template

The application of various nanocarrier systems was widely explored in the field of pharmaceuticals to achieve better drug encapsulation and delivery. The aim of this study was to encapsulate lidocaine in alginate-based o/w nanocarriers based on the type of oil (i.e., solid or liquid), using a nanoemulsion template prepared by ultrasound-assisted phase inversion temperature (PIT) approach. The nanoemulsion template was initially prepared by dissolving lidocaine in the oil phase and surfactant and alginate in the aqueous phase, and keeping the PIT at around 85 °C, accompanied by gradual water dilution at 25 °C, to initiate the formation of nanoparticles (o/w) with the aid of low frequency ultrasound. The composition and concentration of the oil phase had a major impact on the particle size and led to an increase in the size of the droplet. The lipids that showed a higher drug solubility also showed higher particle size. On the other hand, increasing the concentration of surfactant decreases the size of the droplet before the concentration of the surfactant exceeds the limit, after which the size of the particle increases due to the aggregates that could be produced from the excess surfactant. The method used produced nanoemulsions that maintained nano-sized droplets < 50 nm, over long-term storage. Our findings are important for the design of nanocarrier systems for the encapsulation of lipophilic molecules.

Preparation, characterization, and evaluation of antioxidant activity and bioavailability of a self-nanoemulsifying drug delivery system (SNEDDS) for buckwheat flavonoids

The self-nanoemulsifying drug delivery system has shown many advantages in drug delivery. In this study, a self-nanoemulsifying drug delivery system of buckwheat flavonoids was prepared for enhancing its antioxidant activity and oral bioavailability. A nanoemulsion of buckwheat flavonoids was developed and characterized, and its antioxidant, in vitro release, and in vivo bioavailability were determined. The nanoemulsion was optimized by the central composite design response surface experiment, and its particle size, polymer dispersity index (PDI), zeta potential, morphology, encapsulation efficiency, and stability were evaluated. The antioxidant activity was tested by measuring its 2,2-diphenyl-1-picrylhydrazyl scavenging activity, hydroxyl radical scavenging activity, and superoxide anion scavenging ability. In vitro release of buckwheat flavonoids nanoemulsion showed a higher cumulative release than the suspension, and the release fitting model followed the Ritger–Peppas and Weibull models. The effective concentration of the nanoemulsion was evaluated in vivo using a Wistar rat model, and the area under the plasma concentration-time curve of the buckwheat flavonoids nanoemulsion was 2.2-fold higher than that of the buckwheat flavonoid suspension. The C_max of the nanoemulsion was 2.6-fold greater than that of the suspension. These results indicate that the nanoemulsion is a promising oral drug delivery system that can improve the oral bioavailability to satisfy the clinical requirements.

Oral delivery of fish oil in oil-in-water nanoemulsion: development, colloidal stability and modulatory effect on in vivo inflammatory induction in mice

To improve the oral absorption of fish oil and test its anti-inflammatory effect, a fish oil nanoemulsion was developed using cis-4,7,10,13,16,19-docosahexaenoic fatty acid as a biomarker for oral administration. The colloidal stability tests of the fish oil nanoemulsion showed an average size of 155.44 nm ± 6.46 (4 °C); 163.04 nm ± 9.97 (25 °C) and polydispersity index 0.22 ± 0.02 (4 °C), 0.21 ± 0.02 (25 °C), indicating systems with low polydispersity and stable droplets. The fish oil nanoemulsion did not alter the cell viability of the RAW 264.7 macrophages and, at a concentration of 0.024 mg/mL, was kinetically incorporated into the cells after 18 h of contact. The nanoemulsion was maintained in the gastrointestinal region for a significantly shorter period of time (p ≤ 0.05) compared to the intake of fish oil in free form. Inflammatory tests demonstrated that nanoemulsion and fish oil showed less (p ≤ 0.05) neutrophil infiltration after 24h of sepsis induction and there was a significant reduction (p ≤ 0.05) in the volume of paw edema in female adult Balb/c mice who received the nanoemulsion diet compared to the other experimental groups (control, formalin, fish oil and sunflower oil). These results indicate that the fish oil nanoemulsion was significantly effective in the dietary conditions tested here, presenting satisfactory responses in the modulation of inflammatory disorders, demonstrating interesting and beneficial nutraceutical effects.

Development of nanoparticles coated with cassava bagasse pectin (Manihot esculenta Crantz) containing β-carotene for mucoadhesive applications

Pectin (PC) extracted from a solid residue from cassava roots (Manihot esculenta Crantz) was used to coat nanoparticles (NP) containing β-carotene (BC) aiming at the gastrointestinal administration of this lipophilic nutraceutical. The NP were prepared by spontaneous emulsification method using food grade components. Pectin-coated NP have been successfully prepared as confirmed by the increased particle size and negative surface charges due to the pectin's anionic nature. NP showed spherical shape and monodisperse distribution, with a mean size of 21.3 nm (polydispersity index (PDI) 0.29) for BC PC T80-NP (nanoparticle with β-carotene, pectin and Tween 80) and 261.4 nm (PDI 0.1) for BC PC T20-NP (nanoparticle with β-carotene, pectin and Tween 20). BC was encapsulated at amounts of 530 and 324 µg/ml for BC PC T80-NP and BC PC T20-NP, respectively, with high encapsulation efficiency (> 95%), increasing its antioxidant capacity in vitro, besides no cytotoxic effect. However, only BC PC T20-NP was stable over a 90 days storage period (4°C) and revealed a strong interaction between pectin and mucin. These results suggest that pectin-coated BC PC T20-NP is a promising strategy to improve the bioavailability and permeation of BC for administration through mucosal surfaces.

Therapeutic Nanoemulsion: Concept to Delivery

Nanoemulsions (NEs) or nanometric-scaled emulsions are transparent or translucent, optically isotropic and kinetically stable heterogeneous system of two different immiscible liquids namely, water and oil stabilized with an amphiphilic surfactant having droplet size ranges up to 100 nm. They offer a variety of potential interests for certain applications: improved deep-rooted stability; excellent optical clarity; and, enhanced bioavailability due to its nanoscale of particles. Though there is still comparatively narrow insight apropos design, development, and optimization of NEs, which mainly stems from the fact that conventional characteristics of emulsion development and stabilization only partly apply to NEs. The contemporary article focuses on the nanoemulsion dosage form journey from concept to key application in drug delivery. In addition, industrial scalability of the nanoemulsion, as well as its presence in commercial and clinical practice, are also addressed.

Physicochemical Characteristics of Four Limonene-Based Nanoemulsions and Their Larvicidal Properties against Two Mosquito Species, Aedes albopictus and Culex pipiens molestus

Negative impacts on the environment from the continuous use of synthetic insecticides against mosquitoes has driven research towards more ecofriendly products. Phytochemicals, classified as low-risk substances, have been recognized as potential larvicides of mosquitoes; however, problems related to water solubility and stability are limiting factors for their use in mosquito control programs in the field. In this context, many researchers have focused on formulating essential oils in nanoemulsions, exploiting innovative nanotechnology. In the current study, we prepared 4 (R)-(+)-limonene oil-in-water nanoemulsions using low and high energy methods, and we evaluated their physicochemical characteristics (e.g., viscosity, stability, mean droplet diameter, polydispersity index) and their bioactivity against larvae of two mosquito species of great medical importance, namely, Cx. pipiens molestus and Ae. albopictus. According to the dose-response bioassays with the limonene-based nanoemulsions and pure limonene (dissolved in organic solvent), the tested nanoformulations improved the activity of limonene against Ae. albopictus larvae, while the performance of limonene was either the same or better than limonene against Cx. pipiens molestus, depending on the applied system. Overall, we achieved the production of limonene-based delivery nanosystems, with sufficient lethal properties against mosquito larvae to consider them promising larvicidal formulations applicable to mosquito breeding sites.

Therapeutic nanoemulsions in ophthalmic drug administration: Concept in formulations and characterization techniques for ocular drug delivery

The eye is the specialized part of the body and is comprised of numerous physiological ocular barriers that limit the drug absorption at the action site. Regardless of various efforts, efficient topical ophthalmic drug delivery remains unsolved, and thus, it is extremely necessary to advance the contemporary treatments of ocular disorders affecting the anterior and posterior cavities. Nowadays, the advent of nanotechnology-based multicomponent nanoemulsions for ophthalmic drug delivery has gained popularity due to the enhancement of ocular penetrability, improve bioavailability, increase solubility, and stability of lipophilic drugs. Nanoemulsions offer the sustained/controlled drug release and increase residence time which depend on viscosity, compositions, and stabilization process, etc.; hence, decrease the instillation frequency and improve patient compliance. Further, due to the nanosized of nanoemulsions, the sterilization process is easy as conventional solutions and cause no blur vision. The review aims to summarizes the various ocular barriers, manufacturing techniques, possible mechanisms to the retention and deep penetration into the eye, and appropriate excipients with their under-lying selection principles to prevent destabilization of nanoemulsions. This review also discusses the characterization parameters of ocular drug delivery to spike the interest of those contemplating a foray in this field. Here, in short, nanoemulsions are abridged with concepts to design clinically advantageous ocular drug delivery.

Self-Assembled Cationic-Covered Nanoemulsion as A Novel Biocompatible Immunoadjuvant for Antiserum Production Against Tityus serrulatus Scorpion Venom

This study assesses the efficacy of different nanoemulsion formulations as new and innovative adjuvants for improving the in vivo immunization against the Tityus serrulatus scorpion venom. Nanoemulsions were designed testing key-variables such as surfactants, co-solvents, and the influence of the temperature, which would be able to induce the phase transition from a liquid crystal to a stable nanoemulsion, assessed for four months. Additionally, cationic-covered nanoemulsion with hyper-branched poly(ethyleneimine) was prepared and its performance was compared to the non-cationic ones. The physicochemical properties of the selected nanoemulsions and the interactions among their involved formulation compounds were carefully monitored. The cytotoxicity studies in murine macrophages (RAW 264.7) and red blood cells were used to compare different formulations. Moreover, the performance of the nanoemulsion systems as biocompatible adjuvants was evaluated using mice immunization protocol. The FTIR shifts and the zeta potential changes (from -18.3 ± 1.0 to + 8.4 ± 1.4) corroborated with the expected supramolecular anchoring of venom proteins on the surface of the nanoemulsion droplets. Cell culture assays demonstrated the non-toxicity of the formulations at concentrations less than 1.0 mg/mL, which were able to inhibit the hemolytic effect of the scorpion venom. The cationic-covered nanoemulsion has shown superior adjuvant activity, revealing the highest IgG titer in the immunized animals compared to both the non-cationic counterpart and the traditional aluminum adjuvant. In this approach, we demonstrate the incredible potential application of nanoemulsions as adjuvants, using a nanotechnology platform for antigen delivery system on immune cells. Additionally, the functionalization with hyper-branched poly(ethyleneimine) enhances this recognition and improves its action in immunization.

Nano-emulsification of Aeollanthus suaveolens Mart. Ex Spreng essential oil modifies its neuroeffects?

Oil in water nano-emulsions are drug delivery systems constituted by liquid lipophilic nano-droplets dispersed through the external aqueous phase, often reaching the kinetic stability with surfactant as stabilizers. Essential oils can be the oily phase or the source of bioactive compounds. In this study, the essential oil of Aeollanthus suaveolens-a plant used in folk medicine due to its psychopharmacological effects-was used for preparation of fine nano-emulsions by a low-energy titrating method. Monodisperse small nano-droplets (ca. 70 nm; PdI 0.200) were assembled by using blends of non-ionic surfactants, indicating modulation on surfactant system lead to altering the physical property. In a separate set of experiments, we investigated the role of this modulation on biological properties of the optimal nano-emulsion. The zebrafish embryos were more susceptible to the nano-emulsion than the bulk essential oil, showing the improved bioactivity due to nano-sizing. Therefore, adult zebrafish was treated, and paralysis was observed in the groups treated with the nano-emulsion, being this finding in accordance with hypnosis. At the same essential oil dose, another behavior was observed, suggesting that expected dose-dependent effects associated to sedative-hypnotics can be achieved by nano-sizing of psychoactive essential oils. This paper contributes to the state-of-art drug delivery systems by opening perspectives for novel sedative-hypnotics nano-emulsified essentials oils that can reach hypnotic effects at considerably lower dose, when compared with bulk materials, being useful for further completed dose-response studies.Graphical abstract.

New Low-Energy Method for Nanoemulsion Formation: pH Regulation Based on Fatty Acid/Amine Complexes

Phase inversion composition methods and phase inversion temperature methods are the common methods for nanoemulsion formation. The mechanisms governing both PIC and PIT are the same: composition or temperature can trigger a change in the surfactant spontaneous curvature during the emulsification process. It is anticipated that pH may also induce a change in the spontaneous curvature of pH-responsive surfactants to prepare nanoemulsions. Therefore, fatty acid/amine complexes were synthesized through electrostatic interactions. Based on these complexes, nanoemulsions were successfully prepared by pH regulation. Electrical conductivity and pH measurements were employed to determine the phase inversion process. Dynamic light scattering, digital fluorescence microscopy, and transmission electron microscopy were employed to characterize the droplet size and morphology of the nanoemulsion. The effects of complex concentration, NaCl concentration, and pH of the system were investigated. The developed method, phase inversion pH (PIpH) method, is a moderate and easy-control method. Using this method, the size distributions of nanoemulsion are monomodal and narrow. Nanoemulsion prepared by PIpH has a unique pH-responsive behavior that can be controllably regulated among nanoemulsions, emulsions, and phase separation systems.

The uses of resveratrol for neurological diseases treatment and insights for nanotechnology based-drug delivery systems

Neurological disorders have been growing in recent years and are highly prevalent globally. Resveratrol (RES) is a natural product from plant sources such as grape skins. This compound has shown biological activity in many diseases, in particular, those that act on the central nervous system. The mechanism of action and the key points in neurological disorders were described and show the targeted mechanism of action. Due to the insolubility of this compound; the use of nanotechnology-based systems has been proposed for the incorporation of RES and RES-loaded nanocarriers have been designed for intranasal administration, oral or parenteral routes to deliver it to the brain. In general, these nanosystems have shown to be effective in many studies, pharmacological and pharmacokinetic assays, as well as some cell studies. The outcomes show that RES has been reported in human clinical trials for some neurological diseases, although no studies were performed in humans using nanocarriers, animal and/or cellular models have been reported to show good results regarding therapeutics on neurological diseases. Thus, the use of this nutraceutical has shown true for neurological diseases and its loading into nanocarriers displaying good results on the stability, delivery and targeting to the brain.

Curcumin and Quercetin-Loaded Nanoemulsions: Physicochemical Compatibility Study and Validation of a Simultaneous Quantification Method

Biphasic oil/water nanoemulsions have been proposed as delivery systems for the intranasal administration of curcumin (CUR) and quercetin (QU), due to their high drug entrapment efficiency, the possibility of simultaneous drug administration and protection of the encapsulated compounds from degradation. To better understand the physicochemical and biological performance of the selected formulation simultaneously co-encapsulating CUR and QU, a stability test of the compound mixture was firstly carried out using X-ray powder diffraction and thermal analyses, such as differential scanning calorimetry (DSC) and thermogravimetric analyses (TGA). The determination and quantification of the encapsulated active compounds were then carried out being an essential parameter for the development of innovative nanomedicines. Thus, a new HPLC-UV/Vis method for the simultaneous determination of CUR and QU in the nanoemulsions was developed and validated. The X-ray diffraction analyses demonstrated that no interaction between the mixture of active ingredients, if any, is strong enough to take place in the solid state. Moreover, the thermal analysis demonstrated that the CUR and QU are stable in the nanoemulsion production temperature range. The proposed analytical method for the simultaneous quantification of the two actives was selective and linear for both compounds in the range of 0.5-12.5 µg/mL (R² > 0.9997), precise (RSD below 3%), robust and accurate (recovery 100 ± 5 %). The method was validated in accordance with ICH Q2 R1 "Validation of Analytical Procedures" and CDER-FDA "Validation of chromatographic methods" guideline. Furthermore, the low limit of detection (LOD 0.005 µg/mL for CUR and 0.14 µg/mL for QU) and the low limit of quantification (LOQ 0.017 µg/mL for CUR and 0.48 µg/mL for QU) of the method were suitable for the application to drug release and permeation studies planned for the development of the nanoemulsions. The method was then applied for the determination of nanoemulsions CUR and QU encapsulation efficiencies (> 99%), as well as for the stability studies of the two compounds in simulated biological fluids over time. The proposed method represents, to our knowledge, the only method for the simultaneous quantification of CUR and QU in nanoemulsions.

Synthesis and Technology of Nanoemulsion-Based Pesticide Formulation

Declines in crop yield due to pests and diseases require the development of safe, green and eco-friendly pesticide formulations. A major problem faced by the agricultural industry is the use of conventional agrochemicals that contribute broad-spectrum effects towards the environment and organisms. As a result of this issue, researchers are currently developing various pesticide formulations using different nanotechnology approaches. The progress and opportunities in developing nanoemulsions as carriers for plant protection or nanodelivery systems for agrochemicals in agricultural practice have been the subject of intense research. New unique chemical and biologic properties have resulted in a promising pesticide nanoformulations for crop protection. These innovations-particularly the nanoemulsion-based agrochemicals-are capable of enhancing the solubility of active ingredients, improving agrochemical bioavailability, and improving stability and wettability properties during the application, thus resulting in better efficacy for pest control and treatment. All of these-together with various preparation methods towards a greener and environmentally friendly agrochemicals-are also discussed and summarized in this review.

Low-Temperature Miniemulsion-Based Routes for Synthesis of Metal Oxides

The use of miniemulsions containing chemical precursors in the disperse phase is a versatile method to produce nanoparticles and nanostructures of different chemical nature, including not only polymers, but also a variety of inorganic materials. This Minireview focuses on materials in which nanostructures of metal oxides are synthesized in processes that involve the miniemulsion technique in any of the steps. This includes in the first place those approaches in which the spaces provided by nanodroplets are directly used to confine precipitation reactions that lead eventually to oxides. On the other hand, miniemulsions can also be used to form functionalized polymer nanoparticles that can serve either as supports or as controlling agents for the synthesis of metal oxides. Herein, the description of essential aspects of the methods is combined with the most representative examples reported in the last years for each strategy.

Nanosystems of plant-based pigments and its relationship with oxidative stress

Plant-based pigments are widely present in nature, they are classified depending on their chemical structure as tetrapyrroles, carotenoids, polyphenolic compounds, and alkaloids and are extensively used in medicine, food industry, clothes, and others. Recently they have been investigated due to their role in the areas of food processing, food safety and quality, packaging, and nutrition. Many studies indicate a relationship between bioactive pigments and Non-Communicable Diseases derived from oxidative stress. Their biological applications can help in preventing oxidative injuries in the cell caused by oxygen and nitrogen reactive species. Those pigments are easily degraded by light, oxygen, temperature, pH conditions, among others. Nanotechnology offers the possibility to protect bioactive ingredients and increase its bioavailability after oral administration. Safety to humans (mainly evaluated from toxicity data) is the first concern for these products. In the present work, we present a comprehensive outlook of the most important plant-based pigments used as food colorants, the principal nanotechnology systems prepared with them, and the relationship of these compounds with the oxidative stress and related Non-Communicable Disease.

Recent advances in encapsulation of curcumin in nanoemulsions: A review of encapsulation technologies, bioaccessibility and applications

Curcumin is widely acknowledged for its beneficial activities. However, its application has remained challenging due to its low aqueous solubility, biochemical/structural degradation and poor bioavailability. For these reasons, many researches are aimed at overcoming these limitations using lipid-based nanosystems to encapsulate curcumin, especially nanoemulsions. This review highlights the theoretical aspects and recent advances of preparation technologies (phase inversion temperature, phase inversion composition, ultrasonication, high pressure homogenization and microfluidization) for encapsulation of curcumin in nanoemulsions. Additionally, the specific factors in designing nanoemulsions systems that affect the chemical stability and in vitro bioaccessibility of the encapsulated curcumin are discussed. Also, the importance of nanoemulsions in improving antioxidant, anti-inflammatory and anticancer activities of curcumin is underlined. Curcumin-loaded nanoemulsions preparation technologies have been proposed to provide efficient, systematic, and practical protocols for improved applications of curcumin. Additionally, key factors that influence curcumin delivery include the nature of emulsifier, the type and the amount of carrier oil and emulsifier-curcumin interactions. The pharmacological activities of curcumin including antioxidant, anti-inflammatory and anticancer activities can be improved by nanoemulsions.

Green synthesis of garlic oil nanoemulsion using ultrasonication technique and its mechanism of antifungal action against Penicillium italicum

Penicillium italicum (P. italicum) can cause significant economic loss of fruits and vegetables. Although garlic oil (GO) is an effective antimicrobial agent, the unstability and hydrophobicity limit its use as an environmentally friendly alternative to the conventional antibiotics against P. italicum. In this study, we focused on the fabrication and characterization of a functional GO nanoemulsion (NE) using ultrasonic technique and revealed the antifungal mechanism of the GO NE on P. italicum based on morphological, structural and molecular analyses. The optimal hydrophilic lipophilic balance (HLB) value determined for GO was 14 through the combination of Tween 80 and Span 80. Then the Box-Benhnken Design (BBD) was applied to produce the GO NE and the effects of different fabrication parameters on the particle size were evaluated. The optimal GO NE was selected with the GO concentration of 5.5%, the Smix concentration of 10%, the ultrasonic time of 5 min and the power of 50%. This GO NE had the smallest particle size of 52.27 nm, the best antifungal effect and the most stability. Furthermore, the antifungal mechanism of the GO NE on P. italicum was evaluated by extracellular conductivity, micro-Raman spectra, fluorescence imaging and scanning electron microscopy (SEM) imaging. The results presented that the GO NE retained the antifungal active ingredients. The fungal cell structure and morphology were malformed after treated with the GO NE and the lipids, nucleic acids and protein of P. italicum were destructed. Finally, the optimal GO NE was applied in vivo and P. italicum in citrus was successfully inhibited. It indicated that the optimal GO NE had the better antifungal activity against P. italicum than the pure GO. Besides, the minimum inhibitory concentration (MIC) of GO after preparing into the NE was changed from 3.7% to 0.01265% with about 300 times improvement of bioavailability. Therefore, the synthetic GO NE which promoted the bioavailability of GO was recommended as a promising alternative to inhibit P. italicum in vegetables and fruits.

Nanoemulsion as a feasible and biocompatible carrier for ocular delivery of travoprost: Improved pharmacokinetic/pharmacodynamic properties

Travoprost is a synthetic prostaglandin F2α analogue used in treatment of glaucoma. Due to its water insolubility and oily nature, novel delivery systems need to be developed to enhance its bioavailability, and sustain its release. In the current work, travoprost nanoemulsion was explored as a novel carrier prepared using low energy technique. Results showed that travoprost nanoemulsions exhibited suitable nanodroplet size, zeta potential, pH, refractive index, controlled release, as well as sufficient stability under accelerated conditions. In vivo studies delineated the enhanced absorption of travoprost nanoemulsion compared to the marketed eye drops Travatan®, as proven by the higher C_max and AUC of the former, and its prolonged intraocular pressure reduction time. Moreover, the nanoemulsion formulation was proven safe and non-irritant to ocular surfaces. Therefore, it can be suggested that travoprost nanoemulsion is a promising ocular delivery system for glaucoma treatment.

Nano-emulsification Enhances the Larvicidal Potential of the Essential Oil of Siparuna guianensis (Laurales: Siparunaceae) Against Aedes (Stegomyia) aegypti (Diptera: Culicidae)

Siparuna guianensis (Laurales: Siparunaceae) has a terpene-rich essential oil with great potential for larvicides. The poor water miscibility of their compounds makes nano-emulsions of great interest for novel bioactive systems, including for control of Aedes aegypti (Diptera: Culicidae). This species is adapted to urban environments with important role in the epidemiology of some arboviruses such as dengue, chikungunya fever, zika, and urban yellow fever. The aim of the present study was to evaluate the feasibility of nano-emulsification to affect Ae. aegypti larvae. An optimal system was achieved by using a nonionic single surfactant, highlighted by its satisfactory size distribution profile. Moreover, improved larvicidal activity in comparison to bulk essential oil can be observed for the nano-emulsions. The estimated LC50 and LC90 values after 24 h of treatment of larvae with the essential oil were, respectively, 86.5232 and 134.814 µg/ml, while the estimated LC50 and LC90 value after treatment with the nano-emulsion were 24.7572 and 75.2452 µg/ml, respectively. The utilization of a simple technique to produce a fine nano-emulsion opens perspective for further integrative practices of mosquito control and giving value to this Amazon plant species may encourage its sustainable use and contribute to conservation policies.

Investigating the Fluid-Solid Interaction of Acid Nonionic Nanoemulsion with Carbonate Porous Media

The subject of rock–fluid interaction is important in cases where flow through porous media is occurring. One special case is when the fluid reacts with the porous matrix. In this case, the mass transfer and reaction rate control the dissolution pattern. This article aimed to study the interaction between an acid nanoemulsion system and a carbonate porous media. Nanoemulsions were developed to retard the rock’s dissolution and to promote the formation of conductivity channels. Nanoemulsions were prepared using ALK100 (alkyl alcohol ethoxylate) and RNX110 (alkylphenol ethoxylate) (nonionic surfactants), sec-butanol (co-surfactant), xylene isomers (oil phase), and a solution of HCl (aqueous phase). The obtained systems were characterized in terms of surface tension, droplet diameter, and reactivity. X-ray fluorescence/diffraction (XRF/XRD) and X-ray microtomography (microCT) were performed on carbonate porous media samples treated with the acid systems in order to observe the effects of the fluid–rock interaction. The results showed that the acid nanoemulsion, presenting a low oil content formulation, showed the low surface tension and droplet size characteristic of nanoemulsions. It was experimentally verified that the reactivity in the nanoemulsion media was mass-transfer-retarded, and that the wormhole pattern was verified under the studied conditions.

Biomedical perfluorohexane-loaded nanocapsules prepared by low-energy emulsification and selective solvent diffusion

Perfluorohexane-loaded nanocapsules are interesting materials for many biomedical applications such as oxygen delivery systems or contrast agents. However, their formulation into stable colloidal systems is challenging because of their hydro- and lipophobicity, high density and high vapour pressure. In this study, perfluorohexane-loaded polymeric nanocapsules are prepared for the first time by low-energy emulsification and selective solvent diffusion. The colloidal stability of the perfluorohexane nano-emulsion templates has been improved by the incorporation of an apolar low-density oil (isopropyl myristate) in the dispersed phase, thus addressing droplet coarsening and migration phenomena. The perfluorohexane-loaded nanocapsules prepared from the nano-emulsions show sizes smaller than the corresponding emulsion templates (below 150 nm by dynamic light scattering) and exhibit good stability under storage conditions. Hyperspectral enhanced dark field microscopy revealed a layered core/shell structure and allowed also to confirm the encapsulation of perfluorohexane which was quantified by elemental microanalysis. Although isopropyl myristate has an unfavourable biocompatibility profile, cell viability is enhanced when perfluorohexane is present in the nanocapsules, which is attributed to its high oxygen transport capacity.

Advances in controlled release pesticide formulations: Prospects to safer integrated pest management and sustainable agriculture

As the world is striving hard towards sustainable agricultural practices for a better tomorrow, one of the primary focuses is on effective pest management for enhanced crop productivity. Despite newer and potent chemicals as pesticides, there are still substantial crop losses, and if by any means this loss can be tackled; it will alleviate unwanted excessive use of chemical pesticides. Scientific surveys have already established that pesticides are not being utilized by the crops completely rather a significant amount remains unused due to various limiting factors such as leaching and bioconversion, etc., resulting in an adverse effect on human health and ecosystems. Concerted efforts from scientific diaspora toward newer and innovative strategies are already showing promise, and one such viable approach is controlled release systems (CRS) of pesticides. Moreover, to bring these smart formulations within the domain of current pesticide regulatory framework is still under debate. It is thus, paramount to discuss the pros and cons of this new technology vis-à-vis the conventional agrarian methods. This review deliberates on the developmental updates in this innovative field from the past decades and also appraises the challenges encumbered. Additionally, critical information and the foreseeable research gaps in this emerging area are highlighted.

Development, larvicide activity, and toxicity in nontarget species of the Croton linearis Jacq essential oil nanoemulsion

In this study, the essential oil (EO) from leaves of Croton linearis Jacq was extracted and characterized by GC/MS. The EO hydrophilic-lipophilic balance required (rHLB) for nanoemulsion (NE) development was determined by the Griffin' method. For evaluating the larvicidal effect against Aedes aegypti, the preparation process of NE was optimized, using a central composite design. It was also evaluated the possible toxic effect of NE in nontarget species. The leaves of C. linearis contain 1.50% of EO, enclosing 61 volatile compounds, mainly eucalyptol (26.66%). The best surfactant, oil:water ratio (4.5-5.0-91.5; % w:w:w), allows to achieve the optimal NE, using a stirring speed of 800 rpm, the addition rate of 0.5 ml/min, and a stirring time of 30 min. NE (with particle size = 163 nm) showed a larvicide effect (LC₅₀ = 17.86 μg/mL) more potent than the whole EO (LC₅₀ = 64.24 μg/mL). NE showed neither hemolytic effect nor cytotoxicity, and it was classified as a nontoxic product, according to the OECD class toxicity test (IC₅₀ > 2000 mg/kg). This product arises in a new green bio-larvicide that could be used for mosquito control.