Phase transitions in O/W lauryl acrylate emulsions during phase inversion, studied by light microscopy and cryo-TEM

Food-Grade Nanoemulsions: Preparation, Stability and Application in Encapsulation of Bioactive Compounds

Nanoemulsions have attracted significant attention in food fields and can increase the functionality of the bioactive compounds contained within them. In this paper, the preparation methods, including low-energy and high-energy methods, were first reviewed. Second, the physical and chemical destabilization mechanisms of nanoemulsions, such as gravitational separation (creaming or sedimentation), flocculation, coalescence, Ostwald ripening, lipid oxidation and so on, were reviewed. Then, the impact of different stabilizers, including emulsifiers, weighting agents, texture modifiers (thickening agents and gelling agents), ripening inhibitors, antioxidants and chelating agents, on the physicochemical stability of nanoemulsions were discussed. Finally, the applications of nanoemulsions for the delivery of functional ingredients, including bioactive lipids, essential oil, flavor compounds, vitamins, phenolic compounds and carotenoids, were summarized. This review can provide some reference for the selection of preparation methods and stabilizers that will improve performance in nanoemulsion-based products and expand their usage.

Preparation of photochromic liquid core nanocapsules based on theoretical design

Photochromic materials have attracted considerable attention for their practical applications in optoelectronic devices. In this study, we developed the photochromic liquid core nanocapsules by polymerization of oil-in-water (O/W) nanoemulsion monomer droplets on the basis of Hansen solubility parameters. The thermoresponsive amphiphilic block copolymers (POEGMA_m-b-PSt_n and POEGMA_m-b-PMMA_n) were synthesized by sequential reversible addition fragmentation chain transfer (RAFT) polymerization of hydrophilic oligo(ethylene glycol) methyl ether methacrylate and hydrophobic styrene or MMA. The O/W nanoemulsion methyl methacrylate (MMA) droplets, dissolving dipropylene glycol methyl-n-propyl ether (DPMNP) and (E)-3-(adamantan-2-ylidene)-4-[1-(2,5-dimethyl-3-furyl) ethylidene]dihydro-2,5furandione (Aberchrome 670) as a core liquid and a photochromic dye, respectively, were obtained through the phase inversion temperature emulsification technique using POEGMA_m-b-PSt_n as a surfactant. As theoretically predicted in terms of the spreading coefficients, the DPMNP solution of Aberchrome 670 was successfully encapsulated by coacervation of the crosslinked PMMA condensed phase. Aberchrome 670 dissolved in a liquid core was found to photoisomerize twice as fast as that dispersed in the solid polymer matrices.

Electrolytes as a tuning parameter to control nano-emulsion and nanoparticle size

Schematic representation of the effect of the electrolytes addition in the aqueous phase of the NE on NE droplet size.

Novel lipid-free nanoformulation for improving oral bioavailability of coenzyme Q10

To improve the bioavailability of orally administered lipophilic coenzyme Q10 (CoQ10), we formulated a novel lipid-free nano-CoQ10 system stabilized by various surfactants. Nano-CoQ10s, composed of 2.5% (w/w) CoQ10, 1.67% (w/w) surfactant, and 41.67% (w/w) glycerol, were prepared by hot high-pressure homogenization. The resulting formulations were characterized by particle size, zeta potential, differential scanning calorimetry, and cryogenic transmission electron microscopy. We found that the mean particle size of all nano-CoQ10s ranged from 66.3 ± 1.5 nm to 92.7 ± 1.5 nm and the zeta potential ranged from −12.8 ± 1.4 mV to −41.6 ± 1.4 mV. The CoQ10 in nano-CoQ10s likely existed in a supercooled state, and nano-CoQ10s stored in a brown sealed bottle were stable for 180 days at 25°C. The bioavailability of CoQ10 was evaluated following oral administration of CoQ10 formulations in Sprague-Dawley rats. Compared to the values observed following administration of CoQ10-Suspension, nano-CoQ10 modified with various surfactants significantly increased the maximum plasma concentration and the area under the plasma concentration-time curve. Thus, the lipid-free system of a nano-CoQ10 stabilized with a surfactant may be an effective vehicle for improving oral bioavailability of CoQ10.

Chemical and physical characterization of remotely loaded bupivacaine liposomes: comparison between large multivesicular vesicles and small unilamellar vesicles

Large multivesicular liposomes (LMVV) remotely loaded with bupivacaine (Bupisome) were previously demonstrated to be a stable, long-acting local anesthetic. We demonstrate that this is not the case for small unilamellar vesicles (SUV) of the same lipid composition also remotely loaded with bupivacaine. We show that the trapped volume in LMVV is 21-fold higher and the drug-to-lipid mole ratio is 10-fold higher than in SUV. Cryo-transmission electron micrographs and differential interference contrast microscopy show that there are no bupivacaine crystals inside LMVV and SUV. The thermotropic characterization studied by DSC demonstrates that the drug interacts with the liposome membrane, which, together with the above results on the drug-to-lipid ratio, explains the small in vitro drug release from the SUV and large (but <100%) release from the LMVV after 24 h at 37 °C. The absence of analgesia in mice treated locally with SUV loaded with bupivacaine compared with prolonged analgesia from LMVV correlates well with the in vitro results. The study indicates that in LMVV and SUV, part of the bupivacaine is associated with the liposomal membrane, which is poorly available for analgesia. The membrane fraction is very high in SUV and much smaller in LMVV. The much larger trapped volume of the LMVV explains the higher drug availability and better analgesia of LMVV.

Transitional phase inversion of emulsions monitored by in situ near-infrared spectroscopy

Water-heptane/toluene model emulsions were prepared to study emulsion transitional phase inversion by in situ near-infrared spectroscopy (NIR). The first emulsion contained a small amount of ionic surfactant (0.27 wt % of sodium dodecyl sulfate) and n-pentanol as a cosurfactant. In this emulsion, the study was guided by an inversion coordinate route based on a phase behavior study previously performed. The morphology changes were induced by rising aqueous phase salinity in a "steady-state" inversion protocol. The second emulsion contained a nonionic surfactant (ethoxylated nonylphenol) at a concentration of 3 wt %. A continuous temperature change induced two distinct transitional phase inversions: one occurred during the heating of the system and another during the cooling. NIR spectroscopy was able to detect phase inversion in these emulsions due to differences between light scattered/absorbed by water in oil (W/O) and oil in water (O/W) morphologies. It was observed that the two model emulsions exhibit different inversion mechanisms closely related to different quantities of the middle phases formed during the three-phase behavior of Winsor type III.

Aromatic organic contaminant removal from an aqueous environment by p(4-VP)-based materials

p(4-vinylpyridine) (p(4-VP)) hydrogels were prepared in bulk (macro, 5 × 6 mm) and in nanosizes (370 nm) dimensions. The prepared hydrogels were used to remove organic aromatic contaminates such as 4-nitrophenol (4-NP), 2-nitrophenol (2-NP), phenol (Ph) and nitrobenzene (NB) from an aqueous environment. Important parameters affecting the absorption phenomena, such as the initial concentration of the organic species and the absorbent, absorption rate, absorption capacity, pH and the temperature of the medium, were evaluated for both hydrogel sizes. The absorption capacity of bulk and microgels were found to be 4-NP>2-NP>Ph>NB. Furthermore, p(4-VP) microgels were embedded in poly(acrylamide) (p(AAm)) bulk hydrogel as a microgel-hydrogel interpenetrating polymer network and proved to be very practical in overcoming the difficulty of using the microgels in real applications. Moreover, it was demonstrated that separately prepared magnetic ferrite particles inserted inside p(4-VP) microgels during synthesis allowed for trouble-free removal of p(4-VP)-magnetic composite microgels from the aqueous environment by an externally applied magnetic field upon completion of their task.

Novel and Improved Nanomaterials, Chemistries and Apparatus for Nanobiotechnology: the NACBO Project

This article outlines the nature and activities of the recently completed EU Framework Programme 6 Integrated Project, Novel and Improved Nanomaterials, Chemistries and Apparatus for Nanobiotechnology (NACBO). This project was designed to yield new nanomaterials, surface activation and synthetic nucleic acid chemistries, procedures and hardware for applications in forensics and diagnostics. It provides details on the project’s structure and partnership along with its principal objectives and successes in terms of publications and commercial exploitation.

Reversible Addition–Fragmentation Chain Transfer (RAFT) Polymerization in Miniemulsion Based on In Situ Surfactant Generation

Reversible addition–fragmentation chain transfer (RAFT) polymerization of styrene has been implemented in aqueous miniemulsion based on the in situ surfactant generation approach using oleic acid and potassium hydroxide in the absence of high energy mixing. The best results were obtained using the RAFT agent 3-benzylsulfanyl thiocarbonyl sufanylpropionic acid (BSPAC), most likely as a result of the presence of a carboxylic acid functionality in the RAFT agent that renders it surface active and thus imparts increased colloidal stability. Stable final miniemulsions were obtained with no coagulum with particle diameters less than 200 nm. The results demonstrate that the RAFT miniemulsion polymerization of styrene employing the low energy in situ surfactant method is challenging, but that a system that proceeds predominantly by a miniemulsion mechanism can be achieved under carefully selected conditions.

Characterisation and Skin Distribution of Lecithin-Based Coenzyme Q10-Loaded Lipid Nanocapsules

The purpose of this study was to investigate the influence of the inner lipid ratio on the physicochemical properties and skin targeting of surfactant-free lecithin-based coenzyme Q10-loaded lipid nanocapsules (CoQ10-LNCs). The smaller particle size of CoQ10-LNCs was achieved by high pressure and a lower ratio of CoQ10/GTCC (Caprylic/capric triglyceride); however, the zeta potential of CoQ10-LNCs was above /- 60 mV/ with no distinct difference among them at different ratios of CoQ10/GTCC. Both the crystallisation point and the index decreased with the decreasing ratio of CoQ10/GTCC and smaller particle size; interestingly, the supercooled state of CoQ10-LNCs was observed at particle size below about 200 nm, as verified by differential scanning calorimetry (DSC) in one heating-cooling cycle. The lecithin monolayer sphere structure of CoQ10-LNCs was investigated by cryogenic transmission electron microscopy (Cryo-TEM). The skin penetration results revealed that the distribution of Nile red-loaded CoQ10-LNCs depended on the ratio of inner CoQ10/GTCC; moreover, epidermal targeting and superficial dermal targeting were achieved by the CoQ10-LNCs application. The highest fluorescence response was observed at a ratio of inner CoQ10/GTCC of 1:1. These observations suggest that lecithin-based LNCs could be used as a promising topical delivery vehicle for lipophilic compounds.