Combined emulsifying capacity of polysaccharide particles of different size and shape

Characteristics and stabilization of Pickering emulsions constructed using myosin from bighead carp (Aristichthys nobilis)

Myosin from bighead carp (Aristichthys nobilis) as a main type of fish protein possesses a good emulsifying ability. However, whether bighead carp myosin (BCM) could construct stable Pickering emulsions is still unclear. Therefore, myosin particles and Pickering emulsions stabilized by bighead carp myosin (BCMPEs) were analyzed. The surface structure of BCM particles at 0.6 mol/L NaCl treatment was uniform and compact with a contact angle of 86.4 ± 2.7°, exhibiting the potential ability to construct O/W Pickering emulsions. The size and flocculation index (FI) of BCMPEs decreased with the increase in BCM concentrations of 1%-4% (w/v). Reversely, the size of BCMPEs increased with the increase in oil-water ratios. BCM particles could uniformly distribute at the oil-water interface to stabilize BCMPEs at a BCM concentration of 4% (w/v) and an oil-water ratio of 6:4 (v/v). This study could help explore fish proteins to construct Pickering emulsions for the deep processing of fish products.

Multiple Pickering emulsions stabilized by food-grade particles as innovative delivery systems for bioactive compounds

The most common carrier for encapsulation of bioactive components is still simple emulsion. Recently, bio-based novel emulsion systems such as multiple emulsions (MEs) and Pickering emulsions (PEs) have been introduced as innovative colloidal delivery systems for encapsulation and controlled release of bioactive compounds. Multiple PEs (MPEs), which carries both benefit of MEs and PEs could be fabricated by relatively scalable and simple operations. In comparison with costly synthetic surfactants and inorganic particles which are widely used for stabilization of both MEs and PEs, MPEs stabilized by food-grade particles, while having health-promoting aspects, are able to host the "clean label" and "green label" attributes. Nevertheless, in achieving qualified techno-functional attributes and encapsulation properties, the selection of suitable materials is a crucial step in the construction of such complex systems. Current review takes a cue from both MEs and PEs emulsification techniques to grant a robust background for designing various MPEs. Herein, various fabrication methods of MEs and PEs are described comprehensively in a physical viewpoint in order to find key conception of successful formulation of MPEs. This review also highlights the link between the underlying aspects and exemplified specimens of evidence which grant insights into the rational design of MPEs through food-based ingredients to introduces MPEs as novel colloidal/functional materials. Their utilization for encapsulation of bioactive compounds is discussed as well. In the last part, instability behavior of MPEs under various conditions will be discussed. In sum, this review aims to gain researchers who work with food-based components, basics of innovative design of MPEs.

Pickering emulsions stabilized with differently charged particles

For addressing health issues and ecological concerns, the cosmetic and pharmaceutical industries are facing the challenge of designing emulsions without the use of surfactants. Emulsions stabilized by colloidal particles, known as Pickering emulsions, are promising in this matter. In this article, three different types of particles (neutral, anionic and cationic) are used alone or in binary mixtures as stabilizers of Pickering emulsions. The influence of the particles' charge on the emulsions' properties and the synergies between the different types of particles are studied. It is demonstrated that the kinetics of adsorption of the particles at the water/oil interface control the coverage and their organization at the droplet surface, rather than their interactions after adsorption. Binary mixtures of differently charged particles are a powerful way to control the droplet coverage and the particle loading in the emulsions. In particular, the combination of anionic and cationic particles led to smaller droplets and higher particle coverage of emulsion droplets.

Starch physical treatment, emulsion formation, stability, and their applications

Pickering emulsions are increasingly preferred over typical surfactant-based emulsions due to several advantages, such as lower emulsifier usage, simplicity, biocompatibility, and safety. These types of emulsions are stabilized using solid particles, which produce a thick layer at the oil-water interface preventing droplets from aggregating. Starch nano-particles (SNPs) have received considerable attention as natural alternatives to synthetic stabilizers due to their unique properties. Physical formulation processes are currently preferred for SNP production since they are environmentally friendly procedures that do not require the use of chemical reagents. This review provides a thorough overview in a critical perspective of the physical processes to produce starch nano-particles used as Pickering emulsion stabilizers, fabricated by a 2-step process. Specifically, the reviewed physical approaches for nano-starch preparation include high hydrostatic pressure, high pressure homogenization, ultrasonication, milling and antisolvent precipitation. All the essential parameters used to evaluate the effectiveness of particles in stabilizing these systems are also presented in detail, including the hydrophobicity, size, and content of starch particles. Finally, this review provides the basis for future research focusing on physical nano-starch production, to ensure the widespread use of these natural stabilizers in the ever-evolving field of food technology.

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.

Influence of Cellulose Nanofibers on the Behavior of Pickering Emulsions. Part 1. Microscopy and Startup Flow Test

The dispersibility of flexible polymer chains present at the emulsion's interface between the dispersed and continuous phase has obvious effects on rheology and dielectric properties of the whole emulsion. Cellulose nanofiber (CNF)-based Pickering emulsions are good systems to research these properties with respect to their microscopic phase structure, dielectric, and rheological properties by using CNF as a water-dispersible Pickering emulsifier, liquid paraffin as an oil phase, and didodecyldimethylammonium bromide (DDAB) as a cationic auxiliary surfactant. The CNF and DDAB contents were systematically varied while the water-to-paraffin oil ratio was kept constant to discern the influence of the Pickering emulsifiers. Polarized optical microscopic images reveal that the droplets tend to shrink at higher CNF content but grow bigger when increasing the DDAB content, which is proved by fluorescence analysis of the CNF dispersibility with varying DDAB content. The dielectric damping exhibits a minimum, whose value decreases with increasing DDAB and CNF content. Increasing the DDAB content promotes the solubilization of CNF in the aqueous phase, which will increase the overall viscosity and yield points. Similarly, a higher CNF content leads to a higher viscosity and yield point, but at high DDAB contents, the viscosity function exhibits an S-shape at intermediate CNF contents. To evaluate the results further, they were compared with CNF dispersions (without oil phase), which showed a surfactant effect slightly on maximum stress but strongly on yield stress τy, indicating that DDAB can promote the formation of a CNF network rather than the viscosity of the whole system. This paper provides information on how a systematical variation of the composition influences morphology and physico-chemical interactions as detected by broadband dielectric spectroscopy and rheological behavior.

Compositionally Anisotropic Colloidal Surfactant Decorated with Dual Metallic Nanoparticles as a Pickering Emulsion Stabilizer and Their Application in Catalysis

We aim to introduce compositionally anisotropic Janus particles, hemispheres of which was modified by hydrophilic poly(2-dimethyl amino ethyl methacrylate) [poly(DMAEMA)] brushes to display amphiphilic surfactant-type characteristics. Acquired by the electrohydrodynamic co-jetting technique, these colloidal surfactants were employed to stabilize octanol/water-based Pickering emulsion, which shows prolonged stability for more than 4 months. To explore their potential as the interfacial catalyst, iron(0) nanoparticles were incorporated in one hemisphere during electrojetting, whereas gold nanoparticles (GNPs) were patched onto the surface of the other hemisphere, which was previously modified by the poly(DMAEMA) brush. Ultimately, simultaneous rapid reduction (100% conversion in 1 min) of p-nitrophenol or methyl orange (MO) by GNPs in the aqueous phase and dechlorination of trichloroethylene (a hazardous chlorinated solvent waste) present in the octanol phase were accomplished at the organic-water interface stabilized by the Janus particles decorated by dual metallic nanoparticles. In addition, facile recovery and recyclability of the catalyst were also achieved. The novel colloidal surfactant demonstrated in this study may open up a new avenue to accomplish catalysis of several organic reactions occurring at the water-oil interface.

Effect of hydrocolloids on physicochemical properties, stability, and digestibility of Pickering emulsions stabilized by nanofibrillated cellulose

In this study, the effect of hydrocolloids with different electrostatic characteristics, namely negatively charged xanthan gum (XG), positively charged chitosan (CH), and non-ionic guar gum (GG), on the physicochemical properties, stability, and lipid digestibility of 10% (w/w) soybean oil-in-water Pickering emulsions stabilized by nanofibrillated cellulose (NFC) was investigated. Addition of XG and CH to the NFC-stabilized emulsions significantly increased the oil droplet sizes and apparent viscosity at high shear rates as compared with the addition of GG. The XG added emulsion showed the lowest rate and extent of creaming, whereas the CH added emulsion gave the highest extent of creaming. The addition of XG and CH led to a more pronounced effect on in vitro lipid digestion, i.e. changes in droplet sizes, surface charges, microstructure, and free fatty acid (FFA) release, than the addition of GG. The XG added emulsion showed the lowest rate and extent of lipid digestion possibly due to the high viscosity of the aqueous phase, large oil droplet sizes, and interaction of XG and calcium, resulting in the reduction of lipase activity. The CH added emulsion exhibited the highest extent of lipid digestion possibly due to binding between CH and FFAs and move away from the droplet surfaces, thereby facilitating the lipase activity. In summary, it can be concluded that ionic hydrocolloids exerted more influence on NFC-stabilized Pickering emulsions than non-ionic ones. These results may facilitate the design of highly stable emulsion-based functional food products with added hydrocolloids to promote health and wellness.

Emulsifying capacity of peanut polysaccharide: Improving interfacial property through the co-dissolution of protein during extraction

The co-dissolution of residual protein from byproduct (PPSI) was employed to improve the interfacial property of peanut polysaccharide (PPS). Protein content in the PPSI and PPS were 16.89% and 2.58%, respectively. The convent bonding and intermolecular interaction maintained the complex structure in PPSI. More protein promoted the shift from linear chain conformation to spherical particle, weakened surface charge, induced stronger intermolecular attraction and wettability, which facilitated interfacial adsorption of PPSI. Concomitantly, the linear chain after adsorbing the O/W interface was observed in PPSI-polystyrene, promoting the cross-linking between adsorption layers and thereby forming the elastic interfacial film. Consequently, the emulsion borne smaller size. Subsequently, the particles in continuous phase moved to the adsorption layer via intermolecular interaction and then formed a gel, enhancing stability against oil coalescence, the thermal and refrigerated treatments. Additionally, the acidified (pH 3.0) PPSI further strengthened the emulsion structure and improved its creaming and freeze-thaw stability.

Spray dried nanoemulsions loaded with curcumin, resveratrol, and borage seed oil: The role of two different modified starches as encapsulating materials

Recently, food industries are directing on the promotion of innovative food matrices fortified with bioactive compounds in order to enhance the consumer's health. Octenyl succinic anhydride modified starches (OSA-MS) such as Hi-cap100 (HCP) and purity gum 2000 (PUG) were used to fabricate emulsions co-entrapped with borage seed oil (BSO), resveratrol (RES) and curcumin (CUR), which were further spray dried to obtain powders. The fabricated microcapsules loaded with BSO, RES, and CUR displayed excellent dissolution performance, high encapsulation efficiency (≈93.05%) as well as semi-spherical shape, revealed via scanning electron microscopy (SEM). We also evaluated the impact of storage time (4 weeks) and temperature (40 °C) on the physicochemical characterization of OSA-MS coated microcapsules. Microcapsules coated with HCP exhibited greater oxidative stability, lower water activity and moisture contents rather than PUG coated microcapsules during storage because of its good film-forming properties. Addition of CUR enhanced the oxidative stability and retention of bioactive compounds. HCP microcapsules loaded with BSO + RES + CUR presented supreme retention of RES (70.32%), CUR 81.6% and γ-linolenic acid (≈ 96%). Our findings showed that CUR acted as an antioxidant agent; also, lower molecular weight OSA-MS as wall material could be used for the entrapment of bioactive compounds and promotion of innovative food products.

Nanocellulose in Emulsions and Heterogeneous Water-Based Polymer Systems: A Review

Nanocelluloses (i.e., bacterial nanocellulose, cellulose nanocrystals, and cellulose nanofibrils) are cellulose-based materials with at least one dimension in the nanoscale. These materials have unique and useful properties and have been shown to assemble at oil-water interfaces and impart new functionality to emulsion and latex systems. Herein, the use of nanocellulose in both emulsions and heterogeneous water-based polymers is reviewed, including dispersion, suspension, and emulsion polymerization. Comprehensive tables describe past work employing nanocellulose as stabilizers or additives and the properties that can be tailored through the use of nanocellulose are highlighted. Even at low loadings, nanocellulose offers an unprecedented level of control as a property modifier for a range of emulsion and polymer applications, influencing, for example, emulsion type, stability, and stimuli-responsive behavior. Nanocellulose can tune polymer particle properties such as size, surface charge, and morphology, or be used to produce capsules and polymer nanocomposites with enhanced mechanical, thermal, and adhesive properties. The role of nanocellulose is discussed, and a perspective for future direction is presented.

Synthesis of bio-inspired cellulose nanocrystals-soy protein isolate nanoconjugate for stabilization of oil-in-water Pickering emulsions

The development of hybrid polysaccharide-protein complexes as Pickering emulsion stabilizers has attracted increasing research interest in recent years. This work presents an eco-friendly surface modification strategy to functionalize hydrophilic cellulose nanocrystals (CNC) using hydrophobic soy protein isolate (SPI) via mussel adhesive-inspired poly (l-dopa) (PLD) to develop improved nanoconjugates as stabilizers for oil-in-water Pickering emulsion. The physicochemical properties of the CNC-PLD-SPI nanoconjugate were evaluated by solid-state 13C NMR, FT-IR, TGA, XRD, contact angle analysis, and TEM. The modified CNC (conjugation content of 38.22 ± 1.21%) had lowered crystallinity index, higher thermal stability, and more hydrophobic than unmodified CNC, with an average particle size of 309.9 ± 8.0 nm. Use of amphiphilic CNC-PLD-SPI nanoconjugate with greater conformational flexibility as Pickering stabilizer produced oil-in-water emulsions with greater physical stability.

Controlling the microstructure of emulsions by exploiting particle-polyelectrolyte association

HYPOTHESIS

Albeit solid stabilized emulsions are studied for several decades, the surface of the emulsion drops most often are coated with densely packed and jammed monolayer of particles. However, a control over the area that the particles occupy on the drop surface is necessary, especially in applications involving controlled release of active compounds from emulsions. We hypothesize that it is possible to achieve precise control over the concentration of particles on the surface of emulsions by tailoring the adsorption of different species in a multi-component dispersion used for emulsification.

EXPERIMENTS

To this end, we carry out emulsification of oil and aqueous dispersions consisting of a combination of oppositely charged colloidal particles and polyelectrolyte. The droplet size distribution and storage stability of the oil-in-water emulsions, the microstructure, the percentage area of the drop surface occupied by the particles and the adsorption behavior of particle-polyelectrolyte binary dispersions are investigated.

FINDINGS

Our results demonstrate that the association between oppositely charged colloidal particles and polyelectrolyte can be exploited to obtain surface active species that aid in the formation of emulsions. Moreover, we found that the concentration of particle-polyelectrolyte complexes and polyelectrolyte in the dispersions used in emulsification greatly influence the mean diameter of the emulsions and their microstructure. Our findings provide a strategy to achieve control over surface coverage of particles on the emulsion droplets across a wide range - from a theoretically possible maximum, ≈90%, to as low as ≈5%. Interestingly, the emulsions formulated are found to possess excellent storage stability irrespective of the particle coverage on the drop surface.

Resveratrol loaded Pickering emulsions stabilized by OSA modified rice starch granules

Resveratrol is a photosensitive, bioactive molecule which has received increasing research interest during the past decade for its antioxidant properties. However, it has low solubility in water or common triglyceride oils. Resveratrol solubilization in oil can only be achieved in essential oils, such as flavour oils, but the stability of emulsions produced with this type of oils is low as they are prone to creaming phenomena and Oswald ripening. In this study, resveratrol was first dissolved in orange oil which was mixed into a medium-chain triglyceride (Miglyol) at different ratios and used as the internal phase of oil-in-water emulsions (O/W). The emulsions were stabilized by octenyl succinic anhydride (OSA) modified rice starch granules using two different ratios of starch particle:oil to study the influence of interfacial coverage on the final emulsion droplet size and emulsion stability. The results of this study indicated that stable Pickering emulsions could be prepared using OSA-modified rice starch granules even at partial coverage conditions. Emulsions prepared at an oil fraction of 0.5 using 30% v/v mixture of orange oil in Miglyol as the dispersed phase seemed to be an appropriate resveratrol carrier system, obtaining encapsulation efficiency values close to 90% which results in emulsions with a resveratrol concentration of 8.45 mg/L. Hence, the emulsions prepared are suitable for food fortification applications.

Polysaccharide nanoparticles: from fabrication to applications

The present review highlights the developments in polysaccharide nanoparticles with a particular focus on applications in biomedicine, cosmetics and food.

Starch granule stabilized Pickering emulsions: an 8-year stability study

BACKGROUND

Pickering emulsions are known to have advantages over conventional emulsions, in particular, improved and long-term stability against coalescence. This research is an eight-year stability investigation of oil-in-water Pickering emulsions stabilized by quinoa starch granules modified by octenyl succinic anhydride (OSA). Two different concentrations of starch (i.e. 200 and 600 mg mL^-1 based on oil) were used at oil fraction (ϕ) of 0.1. The emulsions were prepared using a high-pressure homogenizer. The emulsions were stored in a refrigerator (at 6 °C) and evaluated using particle size analyzer over the storage period and light microscopy at the end of the storage period.

RESULTS

Starch granule stabilized Pickering emulsions produced by a high-pressure homogenizer displayed remarkable storage stability over the eight years with no indication of coalescence. In addition, the results showed that increasing the concentration of starch granules resulted in a decrease in droplet sizes. The sizes measured by the particle size analyzer showed a decline over the storage period which was due to dissociation of some networks of aggregated droplets that, in addition to representing smaller droplet sizes, resulted in the release of free and unbound starch entrapped in these networks.

CONCLUSIONS

This study showed that Pickering emulsions produced by OSA modified starch granules from quinoa can be used in practical applications for the development of highly stable formulations when prolonged storage is required. © 2020 Society of Chemical Industry.

Recent advances of characterization techniques for the formation, physical properties and stability of Pickering emulsion

Recently, there have been increasing demand for the application of Pickering emulsions in various industries due to its combined advantage in terms of cost, quality and sustainability. This review aims to provide a complete overview of the available methodology for the physical characterization of emulsions that are stabilized by solid particles (known as Pickering emulsion). Current approaches and techniques for the analysis of the formation and properties of the Pickering emulsion were outlined along with the expected results of these methods on the emulsions. Besides, the application of modelling techniques has also been elaborated for the effective characterization of Pickering emulsions. Additionally, approaches to assess the stability of Pickering emulsions against physical deformation such as coalescence and gravitational separation were reviewed. Potential future developments of these characterization techniques were also briefly discussed. This review can act as a guide to researchers to better understand the standard procedures of Pickering emulsion assessment and the advanced methods available to date to study these emulsions, down to the minute details.

Structure and Immunomodulatory Activity of Microparticulate Mushroom Sclerotial β-Glucan Prepared from Polyporus rhinocerus

In this study, an immunologically active novel microparticulate mushroom β-glucan (PRA-1p) was prepared using an alkali-soluble glucan PRA-1 by an emulsification and cross-linking method. PRA-1 was a hyperbranched (1→3),(1→6)-β-d-glucan with a degree of branching of 0.89, isolated from the sclerotia of Polyporus rhinocerus. PRA-1 had a rod-like conformation, while PRA-1p exhibited a monodisperse and homogeneous spherical conformation with a diameter ranging from 0.3 to 2.0 μm in water. PRA-1p significantly induced nitric oxide and reactive oxygen species production as well as morphological changes of murine macrophages (RAW 264.7 cells) and upregulated their phagocytic activity. Furthermore, PRA-1p treatment markedly enhanced the secretion of cytokines, including cutaneous T cell-attracting chemokine 27, granulocyte-colony-stimulating factor, monocyte chemoattractant protein 1, macrophage inflammatory protein 1α, macrophage inflammatory protein 2, regulated on activation, normal T cell expressed and secreted, soluble tumor necrosis factor receptor 1, and tissue inhibitors of metalloproteinases. Activation of RAW 264.7 cells triggered by PRA-1p was associated with activation of inducible nitric oxide synthase, nuclear factor κB, extracellular signal-regulated kinase, and protein kinase B. This work suggests that novel PRA-1p derived from the mushroom sclerotia of P. rhinocerus has potential application as an immunostimulatory agent.

A comparison of emulsion stability for different OSA-modified waxy maize emulsifiers: Granules, dissolved starch, and non-solvent precipitates

This work investigates the stability of emulsions prepared by using octenyl succinic anhydride (OSA)-modified waxy maize starch in the form of granules, dissolved starch, and non-solvent precipitated starch as Pickering emulsion stabilisers. The aim of this study was to investigate the effects of different forms of starches on the stability of emulsion using light microscopy, light scattering, and static multiple light scattering. All starch samples were hydrophobically modified with 3% (w/w) n-octenyl succinyl anhydride (OSA). Starch polymer solutions were prepared by dissolving OSA- modified starch in water in an autoclave at 140°C. Non-solvent precipitates were obtained through ethanol precipitation of dissolved waxy maize. The stability of the oil/water emulsions were different for the three forms of starches used. The granule-based emulsions were unstable, with only a small proportion of the granules adsorbed onto oil droplets, as viewed under a light microscope. The emulsions were observed to cream after 2 hours. The dissolved starch and non-solvent precipitate-based emulsions were stable towards creaming for months, and they had almost 100% emulsifying index (EI = 1) by visual observation and EI ~ 0.9 by multiple light scattering measurements. The results from light microscopy and multiple light scattering measurements indicated the occurrence of coalescence for all three types of emulsions. The coalescence was fastest within days for the granule stabilised system while it was slower both for the dissolved starch and non-solvent precipitate-based emulsions. The latter demonstrated the least degree of coalescence over time. Thus, it was concluded that differences in starch particle size and molecular structure influenced the emulsion droplet size and stability. A decreased particle size correlates to a decrease in droplet size, thus increasing stabilisation against creaming. However, stability towards coalescence was low for the large granules but was best for the non-solvent precipitate starch indicating that there is a window of optimal particle size for stability. Thus, best emulsifying properties were obtained with the non-solvent precipitates (~ 120 nm particle size) where the emulsions remained stable after one year of storage. In conclusion, this study illustrated the potentiality of non-solvent precipitated starch as emulsion stabilizers.

Methods for producing microstructured hydrogels for targeted applications in biology

Hydrogels have been broadly studied for applications in clinically motivated fields such as tissue regeneration, drug delivery, and wound healing, as well as in a wide variety of consumer and industry uses. While the control of mechanical properties and network structures are important in all of these applications, for regenerative medicine applications in particular, matching the chemical, topographical and mechanical properties for the target use/tissue is critical. There have been multiple alternatives developed for fabricating materials with microstructures with goals of controlling the spatial location, phenotypic evolution, and signaling of cells. The commonly employed polymers such as poly(ethylene glycol) (PEG), polypeptides, and polysaccharides (as well as others) can be processed by various methods in order to control material heterogeneity and microscale structures. We review here the more commonly used polymers, chemistries, and methods for generating microstructures in biomaterials, highlighting the range of possible morphologies that can be produced, and the limitations of each method. With a focus in liquid-liquid phase separation, methods and chemistries well suited for stabilizing the interface and arresting the phase separation are covered. As the microstructures can affect cell behavior, examples of such effects are reviewed as well. STATEMENT OF SIGNIFICANCE: Heterogeneous hydrogels with enhanced matrix complexity have been studied for a variety of biomimetic materials. A range of materials based on poly(ethylene glycol), polypeptides, proteins, and/or polysaccharides, have been employed in the studies of materials that by virtue of their microstructure, can control the behaviors of cells. Methods including microfluidics, photolithography, gelation in the presence of porogens, and liquid-liquid phase separation, are presented as possible strategies for producing materials, and their relative advantages and disadvantages are discussed. We also describe in more detail the various processes involved in LLPS, and how they can be manipulated to alter the kinetics of phase separation and to yield different microstructured materials.

Emulsion Stabilization with Functionalized Cellulose Nanoparticles Fabricated Using Deep Eutectic Solvents

In this experiment, the influence of the morphology and surface characteristics of cellulosic nanoparticles (i.e., cellulose nanocrystals [CNCs] and cellulose nanofibers [CNFs]) on oil-in-water (o/w) emulsion stabilization was studied using non-modified or functionalized nanoparticles obtained following deep eutectic solvent (DES) pre-treatments. The effect of the oil-to-water ratio (5, 10, and 20 wt.-% (weight percent) of oil), the type of nanoparticle, and the concentration of the particles (0.05–0.2 wt.-%) on the oil-droplet size (using laser diffractometry), o/w emulsion stability (via analytical centrifugation), and stabilization mechanisms (using field emission scanning electron microscopy with the model compound—i.e., polymerized styrene in water emulsions) were examined. All the cellulosic nanoparticles studied decreased the oil droplet size in emulsion (sizes varied from 22.5 µm to 8.9 µm, depending on the nanoparticle used). Efficient o/w emulsion stabilization against coalescence and an oil droplet-stabilizing web-like structure were obtained only, however, with surface-functionalized CNFs, which had a moderate hydrophilicity level. CNFs without surface functionalization did not prevent either the coalescence or the creaming of emulsions, probably due to the natural hydrophobicity of the nanoparticles and their instability in water. Moderately hydrophilic CNCs, on the other hand, distributed evenly and displayed good interaction with both dispersion phases. The rigid structure of CNCs meant, however, that voluminous web structures were not formed on the surface of oil droplets; they formed in flat, uniform layers instead. Consequently, emulsion stability was lower with CNCs, when compared with surface-functionalized CNFs. Tunable cellulose nanoparticles can be used in several applications such as in enhanced marine oil response.

Formulation and optimization of pH sensitive drug releasing O/W emulsions using Albizia lebbeck L. seed polysaccharide

Smart polymers, one of the class of polymers with extensive growth in the last few decades due to their wide applications in drug targeting and controlled delivery systems. With this in mind, the aim of the present study is to design and formulate smart releasing o/w emulsion by using Albizia lebbeck L. seed polysaccharide (ALPS). For this purpose, the physicochemical and drug release characteristics like emulsion capacity (EC), emulsion stability (ES), viscosity, microscopy, zeta potential, polydispersity index (PDI) and in-vitro drug release were performed. The EC and ES values were found to increase with an increased concentration of ALPS. The emulsion formulations were statistically designed by using 3² full factorial design. All the emulsions showed a shear-thinning behavior. The zeta potential and polydispersity index were found to be in the range of -35.83 mV to -19.00 mV and 0.232-1.000 respectively. Further, the percent cumulative drug release of the emulsions at 8 h was found to be in the range of 30.19-82.65%. The drug release profile exhibited zero order release kinetics. In conclusion, the ALPS can be used as a natural emulsifier and smart polymer for the preparation of pH sensitive emulsions in drug delivery systems.

Doubly pH Responsive Emulsions by Exploiting Aggregation of Oppositely Charged Nanoparticles and Polyelectrolytes

We present a simple and modular approach to realize highly stable pH responsive Pickering emulsion from mixtures of commercially available oppositely charged nanoparticle and polyelectrolyte. While highly charged nanoparticles and polyelectrolytes when used solely do not stabilize emulsions, we show that the electrostatic attraction between oppositely charged nanoparticles and polyelectrolytes can be exploited to formulate emulsions with long-term stability of up to 8 months. The Ludox CL nanoparticles and poly(4-styrenesulfonate) sodium salt (PSS) when dispersed in aqueous solution at pH 2-11 form particle polyelectrolyte complexes (PPCs) due to heteroaggregation. These complexes are effective in stabilizing oil-in-water Pickering emulsions. We demonstrate that this is due to the formation of weakly charged complexes that are surface active and hence readily adsorbed to the oil-water interface created during emulsification. We show that the composition of nanoparticles and polyelectrolytes in the mixture as well as the pH can be tuned to control the average diameter of the emulsions droplets. Immediate destabilization and doubled responsiveness of the emulsions stabilized by particle polyelectrolyte complexes are illustrated by changing the pH of the stable emulsions formed at intermediate pH to either 1 or 13. The aggregation behavior of nanoparticle-polyelectrolyte mixtures and the effect of various parameters such as mixing fraction, pH, and energy input on the formation of Pickering emulsions is discussed. Furthermore, we show that the formation of near charge neutral aggregates that exhibit optimal wetting conditions is a requirement to accomplish emulsion formation. The visualization of particle polyelectrolyte complexes around the emulsion droplets, their morphology prior to emulsification, and their wetting properties are also investigated to elucidate the mechanism of emulsification.