Nanoparticle-stabilized Emulsions Research Articles

Multifunctional gelatin nanoparticle stabilized-Pickering emulsion hydrogel based on dextran and amikacin with controlled drug release and enhanced antibacterial capability for promoting infected wound healing

Plant essential oils possess broad-spectral antimicrobial property, but the applications are impeded by their insolubility in water, extreme volatility, and strong irritation. Nanoparticle-stabilized emulsion (Pickering emulsion) gels are colloidal systems with ability to accommodate two immiscible phases in one system. The thick adsorption nanoparticle layers and the cross-linked networks in continuous phase could provide protective barriers for antibacterial oil and achieve on-demand controlled release. An emulsion hydrogel templated from gelatin nanoparticle-stabilized emulsion is one-pot constructed by conducting a tunable cross-linking process between oxidized dextran (Odex) and amikacin in the continuous phase and concomitantly trapping tea tree essential oil (TO) droplets in the three-dimensional network. The resulted emulsion hydrogel presents tunable gelation time, adequate mechanical strength, fascinating injectability, and self-healing capability. It is pH-responsiveness and presents controlled release of amikacin and TO, exhibiting a long-term bacteriostasis of 144 h. The emulsion hydrogel facilitates the outstanding wound healing efficiency in 14 days (95.2 ± 0.8 % of wound closure), accompanied with enhanced collagen deposition and angiogenic activities. The incorporation of TO into emulsion hydrogel system reduced its irritation and improved its biosafety, showing potential application in bacteria inhibition even as implants in vivo.

Breakup dynamics of nanofluid droplets in T-typed microchannels

The breakup behavior and dynamics of nanofluid droplets in the T-shaped microchannel were investigated, focusing on the effect of nanoparticles on droplets breakup. It was found that the solid particle layer formed by the adsorption of nanoparticles at the droplet interface would greatly limit the droplet deformation. Three breakup flow patterns were observed: non-breakup, breakup with partial obstruction, and breakup with permanent obstruction. The droplet breakup could be divided into three stages. In the squeezing stage, the nanoparticles made the droplet breakup slow down, resulting in decrease of power-law exponent α. In the transition stage, the adsorption of nanoparticles changed the surface properties of droplets, reducing the slope k. In the rapid pinching stage, the decrease of nanoparticle concentration or the increase of the dispersed phase capillary number Cad contributed to a growth in power-law exponent β. This study provides crucial data and technical support for applications of nanoparticle-stabilized emulsions.

Hydroxypropyl methyl cellulose/soybean protein isolate nanoparticles incorporated broccoli leaf polyphenol to effectively improve the stability of Pickering emulsions

This study prepared SPI-Pol-HPMC (SPH) nanoparticles from soybean protein isolate (SPI), hydroxypropyl methyl cellulose (HPMC), and broccoli leaf polyphenol (Pol) and used them as a stabilizer for the Pickering emulsion. The SPH (2:1) nanoparticles have the best ability to encapsulate broccoli leaf polyphenols, with uniform particle size distribution, and a more dense and stable structure. The chemical and hydrogen bonding forces between the SPH nanoparticle components were enhanced. Additionally, the 1.5 % SPH nanoparticle-stabilized emulsions exhibited good physical stability, manifesting as small particle droplets with good rheological properties and uniform dispersion. The volume fraction of the emulsified phase of the 1.5 % SPH nanoparticle-stabilized emulsions was the greatest after 21 days of storage. Interestingly, SPH nanoparticles also improved the oxidative stability of the emulsions, as evidenced through their lower peroxide values and thiobarbituric acid active substances. The aforementioned results suggest that SPH nanoparticles may be used as food-grade emulsifiers that stabilize emulsions and inhibit their lipid oxidation.

Curcumin-encapsulated hydrophilic gelatin nanoparticle to stabilize fish oil-loaded Pickering emulsion

Herein, pH-cycle method was explored to prepare curcumin-encapsulated hydrophilic bovine bone gelatin (BBG/Cur) nanoparticle and then the obtained nanoparticle was applied to stabilize fish oil-loaded Pickering emulsion. The nanoparticle had a high encapsulation efficiency (93.9 ± 0.5 %) and loading capacity (9.4 ± 0.1 %) for curcumin. The nanoparticle-stabilized emulsion had higher emulsifying activity index (25.1 ± 0.9 m2/g) and lower emulsifying stability index (161.5 ± 18.8 min) than BBG-stabilized emulsion. The pH affected the initial droplet sizes and creaming index values of the Pickering emulsions: pH 11.0 < pH 5.0 ≈ pH 7.0 ≈ pH 9.0 < pH 3.0. Curcumin provided obvious antioxidant effect for the emulsions, which was also dependent on pH. The work suggested pH-cycle method could be used to prepare hydrophobic antioxidant-encapsulated hydrophilic protein nanoparticle. It also provided basic information on the development of protein nanoparticles for Pickering emulsion stabilization.

Coalescence dynamics of nanofluid droplets in T-junction microchannel

The effect of nanoparticles on droplet coalescence in microchannel was investigated experimentally. The interaction between acid-functionalized nanoparticles and polymers with complementary terminal functional groups facilitates the adsorption of particles at the oil–water interface. Three flow patterns were observed: squeezing coalescence, decompression coalescence and non-coalescence. The presence of nanoparticles significantly reduces the droplet coalescence percentage, and stable droplets could be obtained when the particles concentration increased to 1%. Furthermore, it was found that the film drainage time of squeezing coalescence was independent of the nanoparticles concentration. However, the film drainage time of decompression coalescence increases with nanoparticles concentration. Taking the influence of nanoparticles on the film drainage time into consideration, a new prediction model was proposed. Coupling the droplet contact time with the film drainage time, the critical capillary number for droplet coalescence was obtained. This work could provide important data and technical support for the application of nanoparticle-stabilized emulsions.

Nanoparticle‐Stabilized Emulsion Bioink for Digital Light Processing Based 3D Bioprinting of Porous Tissue Constructs (Adv. Healthcare Mater. 12/2022)

Emulsion Bioinks In article number 2102810 by Rui Liu and co-workers, a nanoparticle-stabilized emulsion bioink via integration of two immiscible aqueous phases is developed to directly bioprint macroporous hydrogel constructs. The bioprinted macroporous hydrogel constructs do excellent service to the proliferation, spreading, and maturation of encapsulated cells in vitro and in vivo.

Nanoparticle stabilized emulsion with surface solidification for profile control in porous media

Profile control is utilized to redirect the injection water to low permeability region where a large amount of crude oil lies. Performed gel particles are the commonly used agent for redistributing water by blocking the pores in high permeability region. But the capability of deep penetration of performed gel particles is poor. Here, we formulate nanoparticle stabilized emulsion (NSE). The stability and the effect of NSE on the fluid redirection in a three-dimensional porous medium were investigated. By using μ-PIV (particle image velocimetry), it was found that the velocity gradient of continuous fluid close to the nanoparticle stabilized droplets is much higher than that close to surfactant stabilized droplets. NSE behaves as solid particle in preferential seepage channels, which will decrease effectively the permeability, thereby redirecting the subsequent injection water. Furthermore, NSE shows high stability compared with emulsion stabilized by surfactant in static and dynamic tests. In addition, water flooding tests also confirm that the NSE can significantly reduce the permeability of porous media and redirect the fluid flow. Our results demonstrate NSE owns high potential to act as profile control agent in deep formation.

Nanoparticle-Stabilized Emulsion Bioink for Digital Light Processing Based 3D Bioprinting of Porous Tissue Constructs.

A challenge for bioprinting tissue constructs is enabling the viability and functionality of encapsulated cells. Rationally designed bioink that can create appropriate biophysical cues shows great promise for overcoming such challenges. Here, a nanoparticle-stabilized emulsion bioink for direct fabrication of porous tissue constructs by digital light processing based 3D bioprinting technology is introduced. The emulsion bioink is integrated by the mixture of aqueous dextran microdroplets and gelatin methacryloyl solution and is further rendered stable by β-lactoglobulin nanoparticles. After bioprinting, the printed tissue constructs create the macroporous structure via removal of dextran, thereby providing favorable biophysical cues to promote the viability, proliferation, and spreading of the encapsulated cells. Moreover, a trachea-shaped construct containing chondrocytes is bioprinted and implanted in vivo. The results demonstrate that the generated macroporous construct is of benefit to cartilage tissue rebuilding. This work offers an advanced bioink for the fabrication of living tissue constructs by activating the cell behaviors and functions in situ and can lead to the development of 3D bioprinting.

Microstructure, hydrophobicity and thermal stability of wood treated by silica/montmorillonite nanoparticle-stabilized Pickering emulsion (I)

Microstructure, hydrophobicity and thermal stability of wood treated by silica/montmorillonite nanoparticle-stabilized Pickering emulsion (I)

Magnetic Polyurethane Microcarriers from Nanoparticle-Stabilized Emulsions for Thermal Energy Storage

Hydrated inorganic salts are phase change materials (PCMs) with promising thermal energy storage capacity. However, their application is commonly restricted because of problems of phase segregation...

Structural and functional properties of perilla protein isolate extracted from oilseed residues and its utilization in Pickering emulsions

The objective of this study was to investigate the effects of defatting methods (hot-pressing, cold-pressing and solvent-extraction) on the functional and structural properties of perilla protein isolate (PPI) extracted from oilseed residues. Cold-pressing residues isolated protein (CRIP) exhibited the highest foaming ability (90.67%), emulsification capacity (3390.09 m2/g) and water holding capacity (2.17 g/g), which were attributed to its high surface hydrophobicity (119.29) and solubility (78.71%) and small particle size (318 nm). However, the oil holding capacity of CRIP (2.31 g/g) was slightly lower than that of hot-pressing residues isolated protein (HRIP). Furthermore, the water/oil holding capacity, foaming capacity and emulsifying stability of CRIP and HRIP were significantly higher than that of solvent-extraction residues isolated protein (SRIP). Interestingly, there were no significant differences in the secondary structure and ternary conformation among CRIP, HRIP and SRIP. At the oil-water ratio of 5:5 and PPI nanoparticles concentration of 2.0%, the creaming index of CRIP, HRIP and SRIP nanoparticle-stabilized Pickering emulsions after 7 d of storage were 26.01%, 29.42% and 31.45%, respectively. The emulsifying stability of CRIP nanoparticle-stabilized emulsions was better than that of HRIP and SRIP nanoparticle-stabilized emulsions, which was ascribed to the small droplet size (27.55 μm) and high ζ-potential (−52.74 mV) of CRIP nanoparticle-stabilized emulsion. These results indicated that PPI extracted from cold-pressing residues demonstrated excellent functional properties and could be used as a potential food-grade emulsifier for Pickering emulsions fabrication.

Elucidating the effect of enzymatic polymerized polysaccharide particle morphology on emulsion properties

Exploiting the shape of Pickering stabilizers offers the ability to unlock the full potential of nanoparticle-stabilized emulsions for applications in enhanced oil recovery, pharmaceuticals, cosmetics, and coatings. In this work, we utilize engineered polysaccharide particles derived from the enzymatic polymerization of glucose from sucrose with controlled shape for the stabilization of dodecane-in-water emulsions. Altering the particle shape (spherical aggregates, fibrids, or platelets), while maintaining a neutral surface charge allows for a systematic examination of the role of particle shape in the stabilization of emulsions. We find that platelet-shaped particles reduce the interfacial tension and result in the smallest droplet size, while emulsions stabilized by aggregates and fibrids are governed by a network of particles in the continuous phase. Exploiting the synergy between these particles allowed for the tuning of their microstructure and rheological signature which allows us to map and tailor these emulsions for a wider variety of applications.

Polymer-functionalized silica nanoparticles for improving water flood sweep efficiency in Berea sandstones

Extraction of oil trapped after primary and secondary oil production stages still poses many challenges in the oil industry. Therefore, innovative enhanced oil recovery (EOR) technologies are required to run the production more economically. Recent advances suggest renewed application of surface-functionalized nanoparticles (NPs) for oil recovery due to improved stability and solubility, stabilization of emulsions, and low retention on porous media. The improved surface properties make the NPs more appropriate to improve microscopic sweep efficiency of water flood compared to bare nanoparticles, especially in challenging reservoirs. However, the EOR mechanisms of NPs are not well understood. This work evaluates the effect of four types of polymer-functionalized silica NPs as additives to the injection water for EOR. The NPs were examined as tertiary recovery agents in water-wet Berea sandstone rocks at 60 °C. The NPs were diluted to 0.1 wt. % in seawater before injection. Crude oil was obtained from North Sea field. The transport of NPs though porous media, as well as nanoparticles interactions with the rock system, were investigated to reveal possible EOR mechanisms. The experimental results showed that functionalized-silica NPs can effectively increase oil recovery in water-flooded reservoirs. The incremental oil recovery was up to 14% of original oil in place (OOIP). Displacement studies suggested that oil recovery was affected by both interfacial tension reduction and wettability modification, however, the microscopic flow diversion due to pore plugging (log-jamming) and the formation of nanoparticle-stabilized emulsions were likely the relevant explanations for the mobilization of residual oil.

Multifunctional Liquid Marble Compound Lenses.

Mosquito compound eyes are elaborate multifunctional hierarchical structures. The presence of ordered curved features spanning length scales of nanometers to millimeters provides the mosquito eye with a wide field of view, an infinite depth of field, and antifogging properties. Developing bio-inspired compound lenses is challenging because of the need to mimic all characteristic curvatures along with their functionalities. Herein, we show how the curvature inherent to nanoparticles, emulsion droplets, and liquid marbles can be employed to mimic the hierarchical structure and functionality of mosquito compound eyes. At the nanometer to micrometer length scale we employ nanoparticle-stabilized emulsion droplets of photocurable oil to form microlenses with nanoscale surface features. After polymerization, the microlenses form a monolayer on an oil droplet to create an optically clear, millimeter scale, liquid marble that functions as a compound lens. We characterize the optical and surface properties of the compound lenses and find that they reproduce the functionality of the mosquito eye. Additionally, we exploit the mobility and reconfigurability of liquid marbles to create arrays (centimeter scale) of compound lenses and other types of functional lenses such as the Janus lens that magnifies the image acquired by the compound lens. Simple and scalable methods to create compound lenses could aid in the development of miniaturized advanced vision systems.

Functionalized Nanoparticles for the Dispersion of Gas Hydrates in Slurry Flow.

Gas hydrates are crystals that can form in oil and gas production. Their agglomeration in flowlines may disrupt the normal production. One current strategy of hydrate management is to inject an anti-agglomerant, a type of low-dosage hydrate inhibitor that prevents hydrate agglomeration. Concerns in the use of these chemicals include their toxicity, cost, and environmental impacts. In this study, we exploited functionalized nanoparticles in place of anti-agglomerants to produce hydrate slurry, with the potential benefit of nanoparticles to be more environmentally friendly and conveniently recyclable. We coated 256 nm spherical silica nanoparticles with different hydrophobicity and evaluated their performance for the hydrate dispersion at atmospheric and high pressure. Nanoparticles with moderate hydrophobicity stabilized oil-in-water (O/W) or water-in-oil (W/O) emulsions. Direct visualization of the cyclopentane hydrate formation from the nanoparticle-stabilized emulsions revealed different morphologies of hydrate particles depending on whether the nanoparticles prevented agglomeration. We also measured the apparent viscosity of a hydrate–nanoparticle mixture using a high-pressure rheometer. Nanoparticles with moderate hydrophobicity during hydrate formation slowed the viscosification, reduced the maximum viscosity, increased the water conversion, and ultimately helped to maintain a low steady-state viscosity. Increasing nanoparticle or salt concentrations also improved the gas hydrate dispersion. Our study demonstrated the great potential of using nanoparticles in preventing agglomeration of gas hydrates under realistic pipeline flow conditions.

Oil emulsions in naturally fractured Porous Media

Abstract Most of the studies regarding the formation and stability of emulsions focus on the conditioning and management of crude oil on surface facilities. Since a great deal of the crude oil produced is in the form of stable emulsions, it is often claimed that these emulsions are formed through chokes and other flow constrictions in oil field equipment. However, emulsions are produced in wells, which not only lack these constrictions but also are produced at low flow rates, demonstrating the fact that emulsions can be formed within the well itself. The present work reviews the literature regarding the formation and properties of heavy and extra-heavy oil emulsions in naturally fractured porous media due to the current relevance that these types of crude oil exploitation take, satisfying the hydrocarbon energy demand. Moreover, emulsions have received more attention recently since they can be formed in-situ and improve oil recovery. To understand the flow mechanics of emulsions in porous media, different models to describe their transportation are presented. Finally, the formation of emulsions in the reservoir for enhanced oil recovery purposes, including the use of nanoparticle-stabilized emulsions is discussed.

Improving freeze-thaw stability of soy nanoparticle-stabilized emulsions through increasing particle size and surface hydrophobicity

There is increasing interest in improving the freeze-thaw stability of emulsions by interfacial engineering in the food colloid field. The present work reported that for Pickering emulsions stabilized by heat-induced soy protein isolate (SPI) nanoparticles, their freeze-thaw stability could be well modulated by modifying the characteristics of the nanoparticles. The SPI nanoparticles with different characteristics (e.g., particle size, surface hydrophobicity) were obtained by heating the SPI solutions at initial concentrations (ci) of 0.25–6.0 wt% at 95 °C for 15 min. All the initial Pickering emulsions were formed at an oil fraction of 0.4 and protein concentration of 0.25 wt% in the aqueous phase, in the presence of 300 mM NaCl. In general, increasing the ci resulted in a progressive enhancement in freeze-thaw stability of the emulsions against creaming and coalescence, but accelerated the flocculation. The higher creaming stability at higher ci values seemed to be closely associated with the enhanced coalescence stability, as well as the strengthened gel-like network of these initial emulsions. There were close interplays between the freeze-thaw stability and the properties of the initial emulsions, or characteristics (e.g. particle size or surface hydrophobicity) of heat-induced SPI nanoparticles. The results confirmed that the SPI nanoparticles with larger sizes, higher surface hydrophobicity and more efficient packing at interface exhibit a greater potential to produce Pickering emulsions with higher freeze-thaw stability. The findings would be of relevance for understanding the freeze-thaw stability of Pickering emulsions stabilized by protein-based particles, as well as for the development of protein-stabilized emulsion formulations with a high freeze-thaw stability.

Synthesizing Pickering Nanoemulsions by Vapor Condensation.

Nanoparticle-stabilized (Pickering) emulsions are widely used in applications such as cosmetics, drug delivery, membranes, and material synthesis. However, formulating Pickering nanoemulsions remains a significant challenge. Herein, we show that Pickering nanoemulsions can be obtained in a single step even at very low nanoparticle loadings (0.2 wt %) by condensing water vapor on a nanoparticle-infused subcooled oil that spreads on water. Droplet nuclei spontaneously submerge within the oil after nucleating at the oil-air interface, resulting in the suppression of droplet growth by diffusion, and subsequently coalesce to larger sizes until their growth is curtailed by nanoparticle adsorption. The average nanoemulsion size is governed by the competition between nanoparticle adsorption kinetics and droplet growth dynamics, which are in turn a function of nanoparticle size, concentration, and condensation time. Controlling such factors can lead to the formation of highly monodisperse nanoemulsions. Emulsion formation via condensation is a fast, scalable, energy-efficient process that can be adapted for a wide variety of emulsion-based applications in biology, chemistry, and materials science.

Nanoparticle-stabilized Emulsions for Improved Mobility Control for Adverse-mobility Waterflooding

Nanoparticle-stabilized Emulsions for Improved Mobility Control for Adverse-mobility Waterflooding

Experimental measurement and modeling of nanoparticle-stabilized emulsion rheological behavior

Emulsions have wide applications in various fields, especially in the petroleum industry. The rheological behavior of water-oil emulsions plays an important role in oil production, transportation and enhanced oil recovery methods Rheology of emulsions is affected by various factors such as dispersed phase fraction, droplet size distribution, a concentration of emulsifying agents, solid concentration, etc. Emulsion stabilization by solids, especially nanoparticles increased the stability, improved the rheological properties and consequently, incrementing the oil recovery from a subterranean formation. It can be pointed out that in very limited cases, the effects of nanoparticles on droplet size distribution of emulsion were investigated and models for prediction of the rheological behavior of solid-stabilized water-in-oil emulsions were not presented. The experiments were carried out using crude oil (petroleum) and fumed silica particle (namely Aerosil R972). In this communication, the effects of different parameters, including water volume fraction, nanoparticle concentration, shear rate, and angular frequency were investigated on the rheological behavior of water-in-oil emulsion. According to the results of rheological experiments, it can be pointed out that the influence of the nanoparticles on the viscosity of water-in-oil emulsions is mainly affected by the water/oil ratio, a number of nanoparticles, shear rate and angular frequency. Nanoparticle decreased water droplet diameter and increased the stability, elasticity and viscosity of the emulsion. In addition, for a better understanding of the effect of these parameters on the viscosity of the water-in-oil emulsions, apparent viscosity models were used. Based on the experimental data, a new equation was developed to estimate the relative viscosity of solid-free and solid-stabilized emulsions. The obtained results demonstrated that the proposed model has increased accuracy than previously published correlations.