Process optimization and stability of d-limonene nanoemulsions prepared by catastrophic phase inversion method

The aim of this study was to optimize the process and stability of d-limonene nanoemulsions. The nanoemulsions were prepared by catastrophic phase inversion method using Tween 80 as surfactant. According to the results, the SOR value would considerably affect the turbidity and the mean particle diameter of emulsions. At a high concentration of surfactant (S/O = 1.5), d-limonene nanoemulsions could be obtained. In addition, the formation of nanoemulsions may be primarily related to the viscosity of oil phase. When the oil phase contained less than 15% (w/w) olive oil, the nanoemulsions could be prepared. The turbidities and the mean particle diameters of d-limonene nanoemulsions with adding the same concentration of different plant oils were similar. Furthermore, it can be found that adding olive oil could enhance the stability of d-limonene nanoemulsion system and decrease Ostwald ripening rate, and the Ostwald ripening rate of d-limonene nanoemulsion at 4 °C was higher than that at 28 °C.     

Synthesis,microstructure, and magnetic properties of monosized Mn x Zn y Fe3 ? x ? y O4 ferrite nanocrystals

We report the synthesis and characterization of ferrite nanocrystals which exhibit high crystallinity and narrow size distributions. The three types of samples including Zn ferrite, Mn ferrite, and Mn-Zn ferrite were prepared via a non-aqueous nanoemulsion method. The structural, chemical, and magnetic properties of the nanocrystals are analyzed by transmission electron microscopy, X-ray diffraction, X-ray fluorescence, and physical property measurement system. The characterization indicates that the three types of ferrite nanocrystals were successfully produced, which show well-behaved magnetic properties, ferrimagnetism at 5 K and superparamagnetism at 300 K, respectively. In addition, the magnetization value of the ferrites increases with the increasing concentration of Mn.     

Effect of mixing protocol on formation of fine emulsions

Emulsions are usually stabilised with a mixture of surfactants with different hydrophilicity. The initial partitioning of surfactants between the dispersed phase and continuous phase, and how these phases are brought into contact, can significantly affect the emulsification processes. Dynamic-phase behaviour maps were prepared to allow for a systematic investigation of the effects of emulsification routes on emulsion properties. Six semibatch modes of additions with constant surfactant concentration across the routes were selected. For a target cyclohexane-in-water emulsion using a pair of polyoxyethylene nonylphenyl ether surfactants with a specified HLB and water volume fraction, fine droplets could form only if water dissolving the water-soluble surfactant was added to the oil dissolving the oil-soluble surfactant. This route allowed the transitional inversion to occur and as a result fine droplets were formed due to an ultra-low interfacial tension. The addition of water dissolving the water-soluble surfactant to oil dissolving the oil-soluble surfactant, direct emulsification method, produced by far large droplets because of a rather high interfacial tension. In a series of experiment, the semibatch direct and phase-inversion emulsification method, were assimilated in situ. The impeller location was used as a variable that controls which phase is added as the dispersed phase. The location of impeller in relation to the interface did not affect the emulsion drop size at a high agitation rate, but it did at a low agitation rate. Under low agitation speed and when the impeller was placed in the oil phase, the oil layer progressively, but slowly, dragged the water phase and eventually inverted to an oil-in-water emulsion, indicating that transitional-phase inversion has locally occurred in the oil layer. At a high agitation speed the mechanical energy provided by the impeller homogenised the emulsion instantaneously and did not allow the optimum formulation and the associated ultra-low interfacial tension to be reached regardless of location of the impeller. A high impeller speed increased drop size by transforming the transition inversion mechanism to a catastrophic mechanism under which the size of drops is mainly determined by the mechanical energy provided. This paper aims to show how some of the complexities involved in emulsification processes can be explained by consulting with dynamic-phase maps.     

Formation and stability of emulsions using a natural small molecule surfactant: Quillaja saponin (Q-Naturale)

Q-Naturale^® is a natural food-grade surfactant isolated from the bark of the Quillaja saponaria Molina tree. The major surface active components of Q-Naturale^® are believed to be saponin-based amphiphilic molecules. In this study, we compared the effectiveness of this natural surfactant for forming and stabilizing emulsions with a synthetic surfactant (Tween 80) that is widely used in the food industry. We examined the influence of homogenization pressure, number of passes, and emulsifier concentration on the particle size produced. Q-Naturale^® was capable of forming relatively small droplets (d < 200 nm) at low surfactant-to-oil ratios (SOR < 0.1) using high pressure homogenization (microfluidization), but the droplets were not as small as those produced using Tween 80 under similar conditions (d < 150 nm). Q-Naturale^®-coated droplets were stable to droplet coalescence over a range of pH values (2–8), salt concentrations (0–500 mM NaCl) and temperatures (20–90 °C). However, some droplet flocculation was observed under highly acidic (pH 2) and high ionic strength (≥400 mM NaCl) conditions, which was attributed to screening of electrostatic repulsion. Indeed, Q-Naturale^®-coated droplets had a relatively high negative charged at neutral pH that decreased in magnitude with decreasing pH. These results indicate that Q-Naturale^® is an effective natural surfactant that may be able to replace synthetic surfactants in food and beverage products.     

Neuropharmacokinetic evaluation of lactoferrin-treated indinavir-loaded nanoemulsions: remarkable brain delivery enhancement

Objective: Indinavir (IDV), an antiretroviral protease inhibitor used in treatment of HIV infection, has limited entry into brain due to efflux by the P-glycoprotein presented in blood–brain barrier. The aim of present study was to develop lactoferrin-treated nanoemulsion containing indinavir (Lf-IDV-NEs) for delivery to brain.

Methods: Indinavir-loaded nanoemulsions (IDV-NEs) were prepared by high-speed homogenization method, and then lactoferrin was coupled to IDV-NEs by water soluble EDC method.

Results: The hydrodynamic diameters, polydispersity index, and zeta potential of IDV-NEs were 112?±?3.5?nm, 0.20?±?0.02, and ?33.2?±?2.6?mV, respectively. From in vivo studies in animal model of rats, the AUC_0–4?h of brain concentration–time profile of IDV-NEs and Lf-IDV-NEs were 1.6 and 4.1 times higher than free drug, respectively. The brain uptake clearance of IDV-NEs and Lf-IDV-NEs were, interestingly, 393- and 420-times higher than the free drug.

Conclusions: It can be concluded that applying both lactoferrin-treated and non-treated nanoemulsions clearly leads to significant brain penetration enhancement of indinavir, an effect which is more pronounced in the case of Lf-IDV-NEs with the higher drug residence time in brain.     

Grape berry coatings of lemongrass oil-incorporating nanoemulsion

Grape berries are highly perishable and vulnerable to contamination with foodborne pathogens. Nanoemulsions of lemongrass oil (LO) were developed for coating of grape berries (Vitis labruscana Bailey) to improve the shelf life and microbiological safety. Vortex mixing, high-shear probe mixing, and dynamic high pressure (DHP) processing were tested as methods of incorporating LO into a carnauba-based solution (0.5–4.0 g/100 g LO). The coating solutions produced by DHP demonstrated the highest emulsion stability and resulted in uniform and continuous coatings on grape berries. The coating on the berries with 3.0 g/100 g LO initially inhibited Salmonella typhimurium and Escherichia coli O157:H7 inoculated on the berries by more than 3.2 and 2.6 log CFU/g, respectively. The coatings did not significantly alter the flavor of the berries and improved their glossiness. Antimicrobial effects against S. typhimurium and E. coli O157:H7 were exhibited during storage at 4 and 25 °C for 28 days. The coatings were also effective on reducing losses of weight, firmness, phenolic compounds, and antioxidant activity and delaying increases in total anthocyanin concentration in the berries. The LO-nanoemulsion coatings have demonstrated the potential to inhibit foodborne pathogen contamination of grape berries, and prolong their shelf life.     

Oxidation of Methyl Linoleate in Oil-in-Water Micro- and Nanoemulsion Systems

Oxidation of methyl linoleate in O/W emulsions having droplets of median diameters ranging from 17 nm to 8.0 μm was carried out at 40°C. The oxidation process was analyzed on the basis of a kinetic equation of the autocatalytic type. The induction period was found to be shorter and the oxidation rate constant lower for emulsions with smaller oil droplets. The stoichiometry between methyl linoleate and oxygen was observed to be independent of both the size of oil droplet and the type of the surfactant and was found to be unity during the early stage of the oxidation. However, more oxgen was consumed in the oxidation of the methyl linoleate in the later half of the oxidation process.     

流感疫苗纳米乳佐剂的研究进展

纳米乳是一种新型的载药系统,作为佐剂应用于流感疫苗的研究。本文主要介绍了纳米乳佐剂的结构特点,将其应用于流感疫苗研究的诸多优势,以及纳米乳佐剂的组成成分、主要制备方法和工艺等。在此基础上,对目前国际上和国内将纳米乳佐剂应用于流感疫苗的研究进展状况作一综述。     

Rheological Properties of Nanoemulsions Stabilized by Polysorbate 80

The rheological properties of nanoemulsions based on three types of oil phases, namely, Crodamol GTCC, Crodamol PC, and oleic acid, were analyzed and determined. The emulsions were stabilized by Polysorbate 80. Geranic acid was selected as a model active substance. The obtained results confirm that the studied nanoemulsions are pseudoplastic non‐Newtonian fluids. The Herschel‐Bulkley model accurately describes the rheological properties of the developed systems. The phase inversion point for the Crodamol GTCC/Polysorbate 80/water system was observed at 50 wt % dispersed‐phase concentration. The rheological results served as the basis for calculation of a theoretical diffusion coefficient of the active ingredient in the studied nanoemulsions.     

Improving the antimicrobial activity of d-limonene using a novel organogel-based nanoemulsion

The purpose of this research was to develop a novel antimicrobial delivery system by encapsulating d-limonene into an organogel-based nanoemulsion and investigating its antimicrobial activity. The d-limonene organogel-based nanoemulsion was prepared by high pressure homogenization method. The surfactant concentration had a major impact on the droplets' formation and distribution. At the optimal condition (10% w/w Tween 80, 100 Mpa, and 10 Cycles) the smallest droplet size (d ≈ 36 nm) could be obtained, which has shown a narrow structure and good stability. Results from the antimicrobial activity have shown the encapsulation of d-limonene (4% w/w) into the organogel-based nanoemulsion contributed to the increase of its antimicrobial activity. In addition, the mechanism of d-limonene organogel-based nanoemulsion against the tested microorganisms was studied by the electronic microscope observation and the cell constituent release. This research would have an important implication for the design of more efficient antimicrobial systems for food preservation and production.