Nanoparticle Stabilized Pickering Emulsion Research Articles

Preparation of Cinnamon Oil‐Loaded Antibacterial Composite Microcapsules by In Situ Polymerization of Pickering Emulsion Templates

AbstractIn this study, the cinnamon oil (CMO)‐loaded antibacterial composite microcapsules with silicon dioxide (SiO2)/poly(melamine formaldehyde) (PMF) hybrid shells are effectively and facilely constructed by in situ polymerization of SiO2 nanoparticle–stabilized Pickering emulsion templates. The morphological structure, composition, and thermal performance of the microcapsules are determined by scanning electronic microscopy, Fourier transform infrared spectroscopy, and thermal gravimetric analysis. In addition, in vitro CMO release and antimicrobial investigations of the microcapsules are also performed, respectively. The results demonstrate that the microcapsules own an approximately spherical shape with a core–shell structure. Moreover, the micro‐encapsulation of CMO clearly increases its thermal stability, and meanwhile results in obtaining microcapsules with the controlled CMO release and visibly long‐term antimicrobial effects. All the results show that in situ polymerization based on templating Pickering emulsions is an attractive method to construct antibacterial essential oil–loaded microcapsules, which can be served as promising antibacterial materials.

Modulation of interfacial phenolic antioxidant distribution in Pickering emulsions via interactions between zein nanoparticles and gallic acid

The impacts of protein nanoparticles on the interfacial distribution of antioxidants and the oxidative stability in Pickering emulsions are attracting increasing research interests. In the present work, the distribution of gallic acid (GA) in zein nanoparticles-stabilized Pickering emulsions (ZPE) was determined by employing a pseudophase kinetic model. The interfacial distribution of GA was found to be favored in ZPEs with higher zein nanoparticle concentration (Czein). Upon increasing Czein, the interfacial loading of nanoparticles (Γ) dominated the modulation of %GAI via hydrogen bonding between zein nanoparticles and GA. The interfacial percentage of GA (%GAI) increased from 28% to 39% as Γ increased from 0.48 to 1.12 mg/m2. In the presence of GA, a direct correlation between Czein or Γ and oxidation stability was recognized, whereas the oxidative stability showed a non-linear dependence on either Czein or Γ in the absence of GA. By excluding antioxidant effects of zein nanoparticles, we found that the %GAI, which was regulated by Γ, took the leading role over the physical barrier effect on the oxidative stability of emulsions. The present work extends our current knowledge on how protein based nanoparticles manipulate the interfacial distribution of antioxidant and then affect the oxidative stability of emulsions.

Zein nanoparticle stabilized Pickering emulsion enriched with cinnamon oil and its effects on pound cakes

Pickering emulsion enriched with cinnamon essential oil (EO) was applied to partially replace butter in pound cakes and to inhibit mold growth. Pickering emulsions stabilized by zein nanoparticles were dominated by elasticity (G' > Gʺ), indicating the formation of gel-like network microstructure. The aldehyde groups of cinnamaldehyde may interact with amino groups on zein nanoparticles at oil-water interface to enhance the viscoelastic properties of Pickering emulsions, which explained the increased storage modulus as the amount of EO increased. Pickering emulsion of 20 g zein nanoparticle solution (ZNS) +20 g sunflower oil significantly increased the hardness of pound cakes, while Pickering emulsion with 5 g EO addition maintained the texture and colour compared with control group. EO also exerted antimicrobial effect to pound cakes, as the yeasts and molds of 5 g and 10 g EO emulsion added cakes were 1.55 and 1.42 log CFU/g after 12-day room-temperature storage compared with 2.96 log CFU/g of control group. To conclude, Pickering emulsion of 20 g ZNS+15 g oil+5 g EO showed the best effect to replace 20% butter in pound cakes to lower the calorie intake and extend the shelf-life without altering the texture and colour.

Effect of molecular weight and pH on the self-assembly microstructural and emulsification of amphiphilic sodium alginate colloid particles

Biopolymer-based Pickering emulsions have attracted increasing interest in research areas including food, pharmaceutics and drug delivery. However, understanding of self-assembly behavior from the dedicate structure of stabilizers has not been well explored yet. In this work, we proposed to investigate how molecular weight affect the self-assembly behavior and to explore the potential of biopolymer colloidal particle-stabilized Pickering emulsion for controlling release of hydrophobic drugs. Amphiphilic sodium alginate derivatives (Ugi-Alg) with three molecular weights (685 kDa, 307 kDa and 48 kDa) were successfully incorporated with a hydrophobic group. Based on the characterizations of morphology and rheology behavior, the high-molecular-weight derivatives (H-Ugi-Alg) can form a compact micelle structure in aqueous solution. Emulsions stabilized by H-Ugi-Alg exhibited a higher stability and stronger viscoelasticity than those using Ugi-Alg with a lower molecular weight. In addition to the entangled polymer chains caused by higher molecular weight and hydrophobic association, the partially protonated carboxyl groups reduced electrostatic repulsion at pH = 4.2 also facilitate the formation of compact micelle structure. Approximately 78.6% of the encapsulated curcumin released from the emulsion stabilized by H-Ugi-Alg, which exhibits a similar release efficiency compared with the nanoparticle-stabilized Pickering emulsions.

Dual-Functional Coatings with Self-Lubricating and Self-Healing Properties by Combining Poly(urea–formaldehyde)/SiO2 Hybrid Microcapsules Containing Linseed Oil

Poly(urea–formaldehyde)/SiO2 hybrid microcapsules containing linseed oil are successfully fabricated in a SiO2 nanoparticles stabilized Pickering emulsion system by use of in situ polymerization. T...

Modeling of Sedimentation and Creaming in Suspensions and Pickering Emulsions

Suspensions and emulsions are prone to kinetic instabilities of sedimentation and creaming, wherein the suspended particles and droplets fall or rise through a matrix fluid. It is important to understand and quantify sedimentation and creaming in such dispersed systems as they affect the shelf-life of products manufactured in the form of suspensions and emulsions. In this article, the unhindered and hindered settling/creaming behaviors of conventional emulsions and suspensions are first reviewed briefly. The available experimental data on settling/creaming of concentrated emulsions and suspensions are interpreted in terms of the drift flux theory. Modeling and simulation of nanoparticle-stabilized Pickering emulsions are carried out next. The presence of nanoparticles at the oil/water interface has a strong influence on the creaming/sedimentation behaviors of single droplets and swarm of droplets. Simulation results clearly demonstrate the strong influence of three-phase contact angle of nanoparticles present at the oil/water interface. This is the first definitive study dealing with modeling and simulation of unhindered and hindered creaming and sedimentation behaviors of nanoparticle-stabilized Pickering emulsions.

The impact of lipases on the rheological behavior of colloidal silica nanoparticle stabilized Pickering emulsions for biocatalytical applications

The use of Pickering emulsions for biocatalytical applications has recently received increased attention in cases where hydrophobic reactants are involved. For process applications, knowledge of the emulsion’s rheology is crucial for the fluid dynamical design of equipment and selection of operating conditions. Colloidal silica nanoparticle stabilized Pickering emulsions usually exhibit shear-thinning behavior caused by a complex particle-particle network. While this has been observed by many authors, no publication has yet dealt with the rheology of silica nanoparticle stabilized Pickering emulsions containing enzymes. Thus, the aim of this study was to investigate the impact of the commonly used biocatalyst lipase (type and concentration), the dispersed phase volume fraction and the silica particle concentration on the rheological behavior of water-in-oil Pickering emulsions. For this purpose, the impact of the named parameters on the viscosity curves were measured. Lipases reduced the viscosities and transferred the rheological behavior from shear-thinning to Newtonian, which might be due to interactions of the lipase molecules via the formation of intermolecular disulfide bonds, which disturb the hydrogen-bond based silica particle-particle network. However, by increasing the dispersed phase volume fraction or the silica particle concentration the rheological behavior of emulsions became again shear-thinning. This work will help to produce bioactive Pickering emulsions with tailor-made characteristics.

Carbon Nanoparticle-Stabilized Pickering Emulsion as a Sustainable and High-Performance Interfacial Catalysis Platform for Enzymatic Esterification/Transesterification

A sustainable and efficient reaction system for enzymatic oil modification is imperative for the food industry. Given the interfacial activation effect of lipase, the sufficient oil–water interface...

Improving the bioaccessibility and in vitro absorption of 5-demethylnobiletin from chenpi by se-enriched peanut protein nanoparticles-stabilized pickering emulsion

Abstract 5-demethylnobiletin (5DN) in aged citrus peel (chenpi) is a unique polymethoxyflavone that has been shown to exhibit superior anti-cancer effects, but its low water-solubility and poor oral bioavailability may limit its application as a potent nutraceutical. In this study, Se-enriched peanut protein nanoparticles-stabilized Pickering emulsions (PPEs) were used to encapsulate 5DN to enhance its bioaccessibility, cellular uptake and transport rate. The preparation of PPEs, and their digestion profiles in gastrointestinal tract, cell uptake and transport were investigated. Results showed that the bioaccessibility of 5DN was significantly higher within PPEs (18.3%) than in bulk oil (9.2%). Besides, PPEs-encapsulated 5DN has a greater apical-to-basolateral (AP-BL) transport rate (26.9 × 10−6 cm s−1) than 5DN (21.7 × 10−6 cm s−1). It was proved PPEs may promote the bioavailability of 5DN, and this type of delivery system may be useful for the application of 5DN and other crystalline nutraceuticals in functional foods and beverages.

Ultralow Tribological Properties of Polymer Composites Containing [BMIm]PF6‐Loaded Multilayer Wall Microcapsule

AbstractMultilayer wall microcapsules efficiently loaded with a lubricant (ionic liquid [BMIm]PF6) are successfully synthesized via a combination of interfacial and in situ polymerization reactions based on lignin nanoparticle–stabilized Pickering emulsion templates. The resulting microcapsules are spherical in shape, with an ideal structure of a rough outer surface and a smooth inner surface. The mean diameter and wall thickness of the resultant microcapsules are 52 ± 18 µm and 3–6 µm. The core fraction is ≈71.29 wt%. Compared with the pure epoxy resin, the friction coefficient of self‐lubricating composites decreases by 83.6% (from 0.55 to 0.09) and the wear rate decreases by 218 times (from 76.8 × 10−14 to 0.352 × 10−14 m3 N−1 m−1) by incorporating 20 wt% of the resultant microcapsules into the epoxy resin. It is demonstrated that [BMIm]PF6, a more efficient lubricant, release from the microcapsules during the friction process produced a boundary lubricating film. The bipolar property of [BMIm]PF6 makes the lubricating film firmer, which can efficiently prevent direct contact between the resin matrix and counterface. Furthermore, the rough poly(urea‐formaldehyde) outer surface of multilayer microcapsules brings in an improved interface property between the microcapsules and resin matrix.

Zein/gum Arabic nanoparticle-stabilized Pickering emulsion with thymol as an antibacterial delivery system

Zein/gum Arabic (GA) nanoparticles (ZGPs) were fabricated to stabilize the oil-water interface of a Pickering emulsion. The Pickering emulsion was successfully fabricated at an oil fraction of 0.3 with 6.25% concentration of ZGPs. The droplet size and creaming index of the Pickering emulsions were influenced significantly by the concentrations of the ZGPs and oil fractions. Morphological observations showed that droplet aggregation occurred when the concentrations of ZGPs decreased or the oil fraction increased. The interfacial tension and rheological properties of the Pickering emulsions indicated that the ZGPs formed a stable oil-water interfacial layer and limited agglomeration and Ostwald ripening. Thymol loaded ZGP-stabilized Pickering emulsion was able to significantly inhibit the growth of E. coli. In addition, the ZGP-stabilized Pickering emulsion with thymol exhibited a controlled-release effect of thymol and antibacterial activity due to the protective effect of the stable interfacial layer of the ZPGs.

Physical stabilities of taro starch nanoparticles stabilized Pickering emulsions and the potential application of encapsulated tea polyphenols

In this research, Pickering emulsion stabilized by taro starch nanoparticles was successfully prepared, and the potential application of encapsulating tea polyphenols was investigated. The nanoparticle size (about 460 nm) and contact angle (81.5°) of taro starch indicate that it is suitable for adsorbing on the oil-water interface and forming a dense interfacial layer. Emulsion stability at different particle concentrations, oil-water ratios, and sodium chloride concentrations has been systematically studied. By considering the particle size, zeta potential, and stability index of Pickering emulsion, it is considered that the emulsion has the best stability when the particle concentration is 7% and the oil fraction is 0.5. Low concentration of salt ions (0.04 mM NaCl) will cause a slight flocculation to improve the stability, but adding high concentration of salt will make emulsion break. In addition, we found that this Pickering emulsion could encapsulate the tea polyphenols greatly with a retention rate of up to 67%. The findings may have great significance for the design and fabrication of native starch particle stabilized emulsion.

Fabrication and Characterization of Quinoa Protein Nanoparticle-Stabilized Food-Grade Pickering Emulsions with Ultrasound Treatment: Effect of Ionic Strength on the Freeze-Thaw Stability.

The development of multilayered interfacial engineering on the emulsion freeze-thaw properties has recently attracted widespread attention, because of the essential freeze-thaw storage process in some emulsion-matrix food products. In this research, we studied the role of salt concentration on the freeze-thaw properties of quinoa protein (QPI) nanoparticles-stabilized Pickering emulsions. The QPI nanoparticles (particle concentration c = 2%, w/v) with increasing particle size and surface hydrophobicity ( H0) were fabricated by ultrasound treatment at 100 W for 20 min, by varying the NaCl addition (salt concentrations, 0-500 mM). The sonicated QPI nanoparticles with increasing salt concentrations showed higher β-sheet structure contents and stronger hydrophobic interactions, which were attributed to the decreasing charged groups and particle aggregation by electrostatic interactions. As compared to the sonicated QPI nanoparticles-stabilized Pickering emulsions ( c = 2%, oil fraction φ = 0.5) without salt accretion, the emulsions with salt accretion exhibited better freeze-thaw properties after three freeze-thaw circulations, which might be mainly caused by the generation of gel-like three-dimensional structure and multilayered network at the droplets' interface with smaller droplet sizes. Increasing the salt concentration progressively enhanced the freeze-thaw properties of sonicated QPI nanoparticles-stabilized Pickering emulsions probably due to the inhibit formation of ice crystal by the "salting-out" effects. The results of this study would provide great significance to investigate the role of salt concentration in the freeze-thaw properties of protein-stabilized Pickering emulsions.

Production and characterization of chitin nanocrystals from prawn shell and their application for stabilization of Pickering emulsions

In this study chitin nanocrystals were produced from prawn shells and used for production of Pickering emulsions. Chitin was obtained by deproteination, demineralization and discoloration of prawn and applied for development of nanocrystal by acid hydrolysis. Chitin and nanocrystals had production yields of 22 and 20%, and crystallinity indexes of 76 and 88%, respectively. Nanocrystals showed spherical morphology and their alpha structure did not change with acid hydrolysis. Thermal analysis indicated higher order of nanocrystals in comparison to chitin. Finally, the ability of developed nanoparticles for producing Pickering emulsions was compared with a conventional surfactant stabilized emulsion. The results showed that mean diameter of oil droplet of nanoparticle stabilized Pickering emulsion was lower than lecithin containing emulsion with the same concentration (4.5 versus 10.9 μm). Pickering emulsions showed high stability during four weeks of storage. Finally, the data approved the high potential of chitin nanocrystals for obtaining long term and thermally stable emulsions.

Facile synthesis of starch-based nanoparticle stabilized Pickering emulsion: its pH-responsive behavior and application for recyclable catalysis

Starch-based nanoparticles participate in the stimulus-responsive Pickering emulsion for recyclable catalysis.

Nanocolloidosomes with Selective Drug Release for Active Tumor-Targeted Imaging-Guided Photothermal/Chemo Combination Therapy.

Selective drug release is highly desirable for photothermal/chemo combination therapy when two or even more theranostic agents are encapsulated together within the same nanocarrier. A conventional nanocarrier can hardly achieve this goal. Herein, doxorubicin and indocyanine green (DOX/ICG)-loaded nanocolloidosomes (NCs), with selective drug release, were fabricated as a novel multifunctional theranostic nanoplatform for photothermal/chemo combination therapy. Templating from galactose-functionalized hydroxyethyl starch-polycaprolactone (Gal-HES-PCL) nanoparticles-stabilized Pickering emulsions, the resultant DOX/ICG@Gal-HES-PCL NCs had a diameter of around 140 nm and showed an outstanding tumor-targeting ability, preferable tumor penetration capability, and promotion of photothermal effect. Moreover, these NCs can be used for NIR fluorescence imaging and thus render real-time imaging of solid tumors with high contrast. Collectively, such NCs achieved the best in vivo antitumor efficacy combined with laser irradiation compared with DOX/ICG@HES-PCL NCs and DOX/ICG mixture. These NCs are valuable for active tumor-targeted imaging-guided combination therapy against liver cancer and potentially other diseases.

Gas Pickering Emulsion Templated Hollow Carbon for High Rate Performance Lithium Sulfur Batteries

A CO2 in water nanoparticle stabilized Pickering emulsion is used to template micrometer sized hollow porous nitrogen doped carbon particles for high rate performance lithium sulfur battery. For the first time, nanoparticles serve the dual role of an emulsion stabilizer and a pore template for the shell, directly utilizing in situ generated CO2 bubbles as template for the core. The minimalistic nature of this method does not require expensive surfactants or additional core templates. Upon polymerization of melamine formaldehyde onto CO2, a robust polymer/silica composite shell is formed and transformed into a porous shell upon washing. The micrometer‐sized hollow morphology in combination with its nitrogen rich porous shell demonstrates impressive rate capabilities of 670 and 500 mAh g−1 even at a high rate of 7C and 9C, respectively. This material also possesses excellent cycle durability, exhibiting a low capacity decay of 0.088%/cycle over 300 cycles. Measurement of the shuttle current and impedance provides interesting insight into the polysulfide mass transfer mechanism of hollow structured sulfur hosts.

Factors influencing the stability and type of hydroxyapatite stabilized Pickering emulsion

Hydroxyapatite (HAp) nanoparticle stabilized Pickering emulsion was fabricated with poly(l-lactic acid) dissolved in dichloromethane (CH2Cl2) solution as oil phase and HAp aqueous dispersion as aqueous phase. Pickering emulsion was cured via in situ solvent evaporation method. Effect of PLLA concentrations, pH value, HAp concentrations, oil-water ratio, emulsification rates and times were studied on emulsion stability and emulsion type, etc. The results indicated emulsion stability increased with the increase of HAp concentration, emulsification rate and time; it is very stable when pH value of aqueous phase was adjusted to 10. Stable W/O and O/W emulsions were fabricated successfully using as-received HAp particles as stabilizer by adjusting the fabricating parameters. The interaction between HAp and PLLA played an important role to stabilize Pickering emulsions. SEM results indicated that both microsphere and porous materials were fabricated using emulsion stabilized by unmodified HAp nanoparticles, implying that both W/O and O/W emulsion type were obtained.

TiO2–SA–Arg nanoparticles stabilized Pickering emulsion for photocatalytic degradation of nitrobenzene in a rotating annular reactor

Pickering emulsions stabilized by salicylic acid and arginine modified titanium dioxide (TiO2–SA–Arg) nanoparticles were prepared in this study for photocatalytic degradation of nitrobenzene in a rotating annular reactor, and the effects of various design parameters of the rotating annular reactor, initial nitrobenzene concentration, catalyst amount, and solution pH on the degradation rate of nitrobenzene were investigated. Meanwhile, the degradation mechanism of nitrobenzene was proposed. The results show that increasing the aeration rate, the rotational speed, and light intensity results in a higher photocatalytic degradation rate of nitrobenzene owing to the effective clearance of electrons and a high quantity of oxidative free radicals. The degradation of nitrobenzene in the rotating annular reactor follows the pseudo first-order kinetics, but it is not well described by the Langmuir–Hinshelwood equation. Aeration has a significant effect on the photocatalytic degradation pathway of nitrobenzene. Because nitrobenzene can undergo reduction reaction as electron acceptors and oxidative degradation initiated by hydroxyl free radicals, the photocatalytic degradation of nitrobenzene follows the reduction mechanism under no aeration, but the oxidation mechanism under aeration.

Double emulsion derived from kafirin nanoparticles stabilized Pickering emulsion: Fabrication, microstructure, stability and in vitro digestion profile

Edible colloidal particles stabilized Pickering emulsions have gained renewed research interest during the past ten years. The concept of stabilizing at least one interface of a double emulsion with a layer of colloidal particles, or Pickering double emulsion, has been realized only in very few cases. Unique properties of Pickering double emulsions, such as interfacial structure, instability mechanism and digestion profile after oral intake have scarcely been investigated. In this work, a water-in-oil-in-water (W/O/W) Pickering double emulsion utilizing kafirin nanoparticles as outer layer stabilizer (KDE) was formulated. The effects of formulation parameters, including lipophilic emulsifier content, volume ratio of inner water phase (W1) to oil phase (O), volume ratio of W1/O to external water phase (W2) and kafirin particle concentration, on the formation of KDE were systematically investigated. The cross-section structure and the attachment of protein particles at the external interface were revealed via cryo-scanning electron microscopy (cryo-SEM). Its structural instability during storage was then studied by monitoring the leakage of encapsulated dye and structural evolution via confocal laser scanning microscopy. Finally, the digestion profiles in simulated gastric and intestinal fluids were assessed by microscopic analysis and in vitro lipolysis. Results suggest that osmotic pressure gradients-driven swelling is the major challenge for long-term stability of KDE during storage and processing. Under simulated gastric digestion process, KDE underwent structural collapse and its lipid digestion profile in simulated intestinal fluids followed similar trend as the kafirin particles-stabilized single Pickering emulsion.