Internal Phase Volume Research Articles

Interconnected Macroporous Polymers Synthesized from Silica Particle Stabilized High Internal Phase Emulsions

n-Octadecyltrimethoxysilane (ODS)-modified silica particles were used as sole Pickering stabilizer to prepare water-in-oil Pickering high internal phase emulsions (HIPEs) with an internal phase volume of 80%. After polymerization of the continuous phase of HIPEs, interconnected macroporous polymers were obtained when modified silica was initially dispersed in water to form a micelle-like structure. However, silica particles in oil phase resulted in closed-cell pores. The pore size, the pore wall morphology, and the interconnectivity of polymer foams could be adjusted finely by the grafted amounts of ODS, modified silica concentrations, and the initial location of Pickering stabilizer. The gas permeation of interconnected porous polymers increased dramatically with the increase of the hydrophobicity of silica particles from 3 to 153 mL/min.

Facile fabrication of poly(L-lactic acid)-grafted hydroxyapatite/poly(lactic-co-glycolic acid) scaffolds by Pickering high internal phase emulsion templates.

Porous scaffolds consisting of bioactive inorganic nanoparticles and biodegradable polymers have gained much interest in bone tissue engineering. We report here a facile approach to fabricating poly(l-lactic acid)-grafted hydroxyapatite (g-HAp)/poly(lactide-co-glycolide) (PLGA) nanocomposite (NC) porous scaffolds by solvent evaporation of Pickering high internal phase emulsion (HIPE) templates, where g-HAp nanoparticles act as particulate stabilizers. The resultant porous scaffolds exhibit an open and rough pore structure. The pore structure and mechanical properties of the scaffolds can be tuned readily by varying the g-HAp nanoparticle concentration and internal phase volume fraction of the emulsion templates. With increasing the g-HAp concentration or decreasing the internal phase volume fraction, the pore size and the porosity decrease, while the Young's modulus and the compressive stress enhance. Moreover, the in vitro mineralization tests show that the bioactivity of the scaffolds increases with increasing the g-HAp concentration. Furthermore, the anti-inflammatory drug ibuprofen (IBU) is loaded into the scaffolds, and the drug release studies indicate that the loaded-IBU exhibits a sustained release profile. Finally, in vitro cell culture assays prove that the scaffolds are biocompatible because of supporting adhesion, spreading, and proliferation of mouse bone mesenchymal stem cells. All the results indicate that the solvent evaporation based on Pickering HIPE templates is a promising alternative method to fabricate NC porous scaffolds for potential bone tissue engineering applications.

Investigation of ethyl cellulose microsponge gel for topical delivery of eberconazole nitrate for fungal therapy.

The aim of the study was to investigate ethyl cellulose microsponges as topical carriers for the controlled release and cutaneous drug deposition of eberconazole nitrate (EB). EB microsponges were prepared using the quasiemulsion solvent diffusion method. The effect of formulation variables (drug:polymer ratio, internal phase volume and amount of emulsifier) and process variables (stirring time and stirring speed) on the physical characteristics of microsponges were investigated. The optimized microsponges were dispersed into a hydrogel and evaluated. Spherical and porous EB microsponge particles were obtained. The optimized microsponges possessed particle size, drug content and entrapment efficiency of 24.5 µm, 43.31% and 91.44%, respectively. Microsponge-loaded gels demonstrated controlled release, nonirritancy to rat skin and antifungal activity. An in vivo skin deposition study demonstrated fourfold higher retention in the stratum corneum layer as compared with commercial cream. Developed ethyl cellulose microsponges could be potential pharmaceutical topical carriers of EB in antifungal therapy.

High Internal Phase Emulsion Templating with Self-Emulsifying and Thermoresponsive Chitosan-graft-PNIPAM-graft-Oligoproline

High internal phase emulsion (HIPE)-templating is an attractive method of producing high porosity polymer foams with tailored pore structure, pore size and porosity. However, this method typically requires the use of large amounts of surfactants to stabilize the immiscible liquid phases, and polymerizable monomers/cross-linker in the continuous minority phase to solidify the HIPE, which may not be desirable in many applications. We show that polyHIPEs with a porosity of 73% can be formed solely using a copolymer of chitosan-graft-PNIPAM-graft-oligoproline (CSN-PRO), which acts simultaneously as emulsifier and thermoresponsive gelator, and forms upon removal of the liquid templating phases, the bulk structure of the resulting polyHIPE. With only a small amount of surfactant (1%v/v in the aqueous phase), and varying the polymer concentration and internal phase volume ratio, different polyHIPEs with porosities of up to 99%, surface areas in excess of 300 m(2)/g and controlled pore interconnectivity can be formed. The poly(CSN-PRO)HIPEs are also shown to be thermoresponsive and remained intact when immersed into water above 34 °C but dissolve below their LCST, which is useful for applications such as drug delivery and tissue engineering scaffolds.

Impact of surfactant selection on the formulation and characterization of microparticles for pulmonary drug delivery

The effect of suspension stabilizers, internal aqueous phase volume and polymer amount were investigated for the production of protein loaded poly(d,l lactide-co-glycolide) (PLGA) microparticles suitable for pulmonary drug delivery. PLGA microparticles were produced adopting water-in-oil-in-water (W/O/W) solvent evaporation technique and were investigated for surface morphology, particle size, encapsulation efficiency (EE%) and in-vitro release profile. Porous surface morphologies with a narrow size distribution were observed when employing 0.5 ml internal aqueous phase; 23.04 µm (±0.98), 15.05 µm (±0.27) and 22.89 µm (±0.41) for PVA, Tween 80 and oleic acid. Porous microparticles exhibited increased size and reduction in EE% with increasing internal aqueous phase, with non-porous microparticles produced when adopting 2.0 ml internal aqueous phase. The selection of stabilizer influences the size of the pores formed thus offers potential for the aerodynamic properties of the microparticles to be manipulated to achieve suitable aerosolization characteristics for pulmonary delivery of proteins.

English

Advancement in drug delivery could come from innovating improvement to the existing drug delivery system. Lornoxicam (Lxm) loaded ethyl cellulose microspheres were prepared by emulsion solvent evaporation technique and also to investigate the effect of variations in drug concentration, polymer concentration, internal phase volume, continuous phase volume and emulsifier concentration on the particle size, shape, % yield, percent entrapment efficiency and in vitro drug release behavior. The scanning electron microscopy (SEM) revealed that microspheres had good spherical geometry with smooth surface. The result showed that the maximum yield of the microspheres was found to be 64.23 ± 0.25%, with particle size in the range of 64.24 ± 1.82 to 81.83 ± 3.43 μm and encapsulation efficiency was found to be in a range of 60.34 ± 1.63 to 71.61 ± 1.20%. The average particle size and entrapment efficiency of microspheres were enhanced with increasing polymer concentration but reduced with increasing internal phase volume, external phase volume and emulsifier concentration. In vitro release profile of microspheres was in the range of 75.65 ± 2.3 to 87.78 ± 2.3% at the end of 12 h. It was concluded that Lxm loaded ethyl cellulose microspheres formulation showed sustained effect over a period of 12 h. Key words: Ethyl cellulose, lornoxicam, microspheres, solvent evaporation, sustained release.

Macroporous materials from water-in-oil high internal phase emulsion stabilized solely by water-dispersible copolymer particles

Water-in-oil (W/O) high internal phase emulsions (HIPEs) were prepared by utilizing water-dispersible copolymer particle stabilizer, whose concentration in the internal phase could reach as high as 12.0 wt% (equivalent to 52 wt% relative to the continuous phase). Accordingly, the macroporous materials with high content of skeleton substance would be obtained by the dissolving of these copolymer particles into the continuous phase and without any chemical reaction. And the morphology, the density and the mechanical property of the macroporous materials could be easily tailored through varying the standing time after emulsification, particle concentration in the aqueous phase and the internal phase volume ratio.

Synergistic stabilization and tunable structures of Pickering high internal phase emulsions by nanoparticles and surfactants

The preparation of Pickering emulsions with an internal phase volume fraction of exceeding 95% is still a challenge to date. In this work, Pickering high internal phase emulsions (HIPEs) with an ultrahigh internal phase fraction of 98.5% were prepared using hydrophobic silica nanoparticles (H30) and nonionic surfactant of Span 85 as a dual emulsifier system. Water-in-hexane (W/O) HIPEs stabilized by a mixture of H30 and Span 85 were investigated. Increasing Span 85 concentration in mixture would result in the appearance of smaller droplets of several to tens of micrometers in the HIPEs while a population of large droplets of hundreds of micrometers would appear with increasing H30 concentration. Furthermore, the influences of Span 85 and H30 on the formation of HIPEs were investigated from the polymerized HIPEs (polyHIPEs) synthesized through these HIPEs templates using styrene as the oil phase. The synergism between particles and surfactant exists and plays a crucial role in the stability of HIPEs. This research opens up a new insight into the fabrication of Pickering HIPEs with an ultrahigh internal phase fraction.

Liquid Screen: A Novel Method To Produce an In-Situ Gravel Pack

Summary Gravel packs are conventionally used as a permeable solid layer in the annulus between a production screen and the walls of the wellbore in weakly consolidated subterranean formations. Gravel packing is a well-known technique for sand control, whereby unconsolidated fines produced from the soft formation are filtered away from the production fluids. However, gravel packs can be problematic. The bridging of sand particles within the gravel pack can create voids that can result in mechanical failures or significantly reduce the effectiveness of gravel packs to restrain fines from flowing along with the hydrocarbons produced. As an alternative, we present a pioneering method to prepare void-free and mechanically sound permeable barriers in subterranean formations as an alternative to gravel packing. The method of preparation involves the curing of Pickering water-in-oil medium-internal-phase emulsions (MIPEs) or high-internal-phase emulsions (HIPEs) containing monomers in the annular space between a rock formation and pipe. The emulsions were prepared simply by adding low amounts of nonionic surfactant and dispersant to premade Pickering emulsions that were stabilized by oleic-acid (OA) -modified silica particles. The resulting macroporous solid materials, known as “poly(merised)Pickering-M/HIPEs,” have a gas permeability of up to 2.6 darcys and are highly interconnected and permeable to hydrocarbons. This paper shows that it is possible to tailor the gas permeability and mechanical performance of the permeable barrier by altering the emulsion internal-phase volume, the volume of surfactant added to the premade Pickering emulsion, and the composition and constituents of the continuous monomer phase; styrene, divinylbenzene (DVB), and poly(ethylene glycol) dimethacrylate were used in the monomer phase.

Influence of process variables on essential oil microcapsule properties by carbohydrate polymer–protein blends

Carbohydrate polymer–protein blends Zanthoxylum limonella oil (ZLO) loaded microcapsules were prepared by multiple emulsion solvent evaporation technology and the influence of various processing variables on the properties of ZLO loaded microcapsules were examined systematically. It was found that the internal aqueous alginate phase volume, external aqueous gelatin phase volume and concentration of surfactant in external aqueous gelatin phase have a significant influence on microcapsules properties. The essential oil-loaded microcapsules were smooth and spherical in shape as revealed by scanning electron micrograph. Results of Fourier transform infrared (FTIR) spectroscopy indicated stable character and showed the absence of chemical interaction between the microencapsulated oil and carbohydrate polymer–protein blends. Differential scanning calorimetry (DSC) study revealed the antioxidant nature of ZLO in the microcapsules. The release rate of ZLO loaded microcapsules was analyzed by UV–vis spectrophotometer. 83.80% of oil encapsulation efficiency was obtained depending upon the processing variables. Thus, proper control of the processing variables involved in this technology could allow effective incorporation of essential oil into the core of the carbohydrate polymer–protein blends matrix.

Polymerised high internal phase ionic liquid-in-oil emulsions as potential separators for lithium ion batteries

In situ ionic liquid (IL) filled poly(merized) high internal phase emulsion monoliths and films were produced by polymerizing surfactant stabilized IL/monomer emulsion templates. The resulting in situ ionic liquid filled macroporous polymers have almost the ionic conductivity of the neat ionic liquid electrolyte. The effect of surfactant and lithium salt concentration, monomer to crosslinker ratio as well as internal phase volume ratio on the morphology and ionic conductivity were studied. It was found that the morphology of the resulting polyHIPEs affects significantly their ionic conductivity. PolyHIPEs with bigger pore throats have a higher ionic conductivity.

Microstructural Response During Isothermal and Isobaric Loading of a Precipitation-Strengthened Ni-29.7Ti-20Hf High-Temperature Shape Memory Alloy

A stable Ni-rich Ni-29.7Ti-20Hf (at. pct) shape memory alloy, with relatively high transformation temperatures, was shown to exhibit promising properties at lower raw material cost when compared to typical NiTi-X (X = Pt, Pd, Au) high-temperature shape memory alloys (HTSMAs). The excellent dimensional stability and high work output for this alloy were attributed to a coherent, nanometer size precipitate phase observed using transmission electron microscopy. To establish an understanding of the role of these precipitates on the microstructure and ensuing stability of the NiTiHf alloy, a detailed study of the micromechanical and microstructural behaviors was performed. In-situ neutron diffraction at stress and temperature was used to obtain quantitative information on phase-specific internal strain, texture, and phase volume fractions during both isothermal and isobaric testing of the alloy. During isothermal testing, the alloy exhibited low isothermal strains due to limited detwinning, consistent with direct measurements of the bulk texture through neutron diffraction. This limited detwinning was attributed to the pinning of twin and variant boundaries by the dispersion of fine precipitates. During isobaric thermal cycling at 400 MPa, the high work output and near-perfect dimensional stability was attributed to the presence of the precipitates that act as homogeneous sources for the nucleation of martensite throughout the material, while providing resistance to irrecoverable processes such as plastic deformation.

Synergistic Stabilization of High Internal Phase Pickering Emulsions by a Mixture of Nanoparticle and Polymer

In this paper, we have prepared high internal phase Pickering emulsions (Pickering HIPEs) with internal phase volume fraction 90% which are stabilized by a mixture of silica nanoparticles (H30) and poly(L-lactide-co-glycolide) (PLGA). HIPEs with an internal phase volume not more than 75% could be prepared solely by H30 nanoparticles. Using PLGA as stabilizer, phase separation takes place and stable emulsions are not formed. Synergistic interaction between H30 particles and PLGA molecules plays an im- portant part in preparation of HIPEs. Using inorganic particles and polymer as co-stabilizer will be a new and effective method to prepare HIPEs.

Vinyl Ester Oligomer Crosslinked Porous Polymers Prepared via Surfactant‐Free High Internal Phase Emulsions

Using vinyl ester resin (VER) containing styrene (or methyl methacrylate) and vinyl ester oligomer (VEO) as external phase, Pickering high internal phase emulsions (Pickering HIPEs) having internal phase volume fraction of up to 95 vol% were prepared with copolymer particles as sole stabilizer. Polymerizing the external phase of these Pickering HIPEs led to porous polymers (poly‐Pickering‐HIPEs). Compared to the polystyrene‐ (PS‐) based poly‐Pickering‐HIPEs which were prepared with mixture of styrene and divinylbenzene (DVB) as crosslinker, the poly‐Pickering‐HIPEs herein showed much higher elastic modulus and toughness. The elastic modulus of these poly‐Pickering‐HIPEs increased with increasing the VEO concentration in the external phase, while it decreased with increasing internal phase volume fraction. Increasing VEO concentration in the external phase also resulted in a decrease in the average void diameter as well as a narrow void diameter distribution of the resulting poly‐Pickering‐HIPEs. In addition, there were many small pores in the voids surface caused by the volume contraction of VER during the polymerization, which suggests a new method to fabricate porous polymers having a well‐defined hierarchical pore structure.

Stirred cell membrane emulsification for multiple emulsions containing unrefined pumpkin seed oil with uniform droplet size

Stirred cell membrane emulsification was used to create double water-in-oil-in-water emulsions at the dispersed phase flux of up to 3200 L m −2 h −1. The oil phase was unrefined pumpkin seed oil or sunflower oil containing 30% by volume of internal water phase and the external water phase was 2% Tween 20 (polyoxyethylene sorbitan monolaurate) or 2% Pluronic F-68 (polyoxyethylene-polyoxypropylen copolymer). Using microengineered nickel membranes with pore sizes between 15 and 40 μm, median drop sizes of double emulsion droplets were in the range between 100 and 430 μm, depending mainly on the shear at the membrane surface and dispersed phase injection rate. In most cases the drops were very uniform, with span (i.e. 90% drop size minus 10% drop size divided by median size) values of around 0.5. This data is similar to what was obtained previously for simple O/W emulsions of the same materials. Hence, the internal water phase, and internal surfactant, 5% PGPR (polyglycerol polyricinoleate), did not adversely influence the emulsification process. A marker material, copper sulfate, was added to the internal water phase and the release of copper was monitored with respect to time. For both lipid systems, at the larger droplet size, there was a significant period of no copper release, followed by almost linear release with time. This initial period was absent when the drop size was close to 100 μm. The initial entrapment efficiency of the copper, in all experiments, was higher than 94%.

Macroporous Polymers Obtained in Highly Concentrated Emulsions Stabilized Solely with Magnetic Nanoparticles

Magnetic macroporous polymers have been successfully prepared using Pickering high internal phase ratio emulsions (HIPEs) as templates. To stabilize the HIPEs, two types of oleic acid-modified iron oxide nanoparticles (NPs) were used as emulsifiers. The results revealed that partially hydrophobic NPs could stabilize W/O HIPEs with an internal phase above 90%. Depending upon the oleic acid content, the nanoparticles showed either an arrangement at the oil-water interface or a partial dispersion into the oil phase. Such different abilities to migrate to the interface had significant effects on the maximum internal phase fraction achievable and the droplet size distribution of the emulsions. Highly macroporous composite polymers were obtained by polymerization in the external phase of these emulsions. The density, porosity, pore morphology and magnetic properties were characterized as a function of the oleic acid content, concentration of NPs, and internal phase volume of the initial HIPEs. SEM imaging indicated that a close-cell structure was obtained. Furthermore, the composite materials showed superparamagnetic behavior and a relatively high magnetic moment.

Development of enteric submicron particles formulation of α-amylase for oral delivery

Enteric submicron particles (SPs) formulations of α-amylase were prepared by w/o/w emulsion solvent evaporation using hydroxypropyl methylcellulose phthalate (HPMCP) and Eudragit L 100, to avoid gastric inactivation of α-amylase. Smaller internal and external aqueous phase volume provided maximum encapsulation efficiency (71.92–73.40%), least particle size (546.4–595.4 nm) and 23–26% loss of enzyme activity. Release studies in 0.1 N HCl confirmed the gastro-resistance of formulations. The anionic SPs aggregated in 0.1 N HCl (i.e. gastric pH 1.2), due to protonation of carboxylic groups of enteric polymer. The aggregates being < 500 µm size would not impede gastric emptying. However, at pH >5.0 (duodenal pH), SPs showed de-aggregation due to restoration of surface charge. HPMCP and Eudragit L 100 SPs facilitated almost complete release of α-amylase within 30 min at pH 6.0 and 6.8, respectively, following Higuchi kinetics. PXRD and DSC indicated amorphous character and scanning electron microscope showed spherical shape of SPs. In simulated gastro-intestinal pH condition, HPMCP and Eudragit L 100 SPs showed good digestion of cooked rice and could serve as potential carrier for oral enzyme delivery. Stability studies indicated the formulations as quite stable to ensure 2 years shelf life at room temperature.

Stability of surfactant-free high internal phase emulsions and its tailoring morphology of porous polymers based on the emulsions

Stable water-in-oil (w/o) high internal phase emulsions (HIPEs) having an internal phase of up to 95 vol% were prepared. The poly(styrene-methyl methacrylate-acrylic acid) (P(St-MMA-AA)) copolymer particles were used as stabilizer. The HIPEs prepared with addition of copolymer particles to the aqueous phase were stabilized by copolymer particles initially, followed by the mixture of copolymer particles and copolymer as the particles eventually dissolves in the organic phase, and finally by only copolymer. Stable w/o HIPEs having an internal phase of up to 92 vol% were also formed with P(St-MMA-AA) copolymer dissolved in the organic phase as the sole stabilizer. Porous polymers (polyHIPEs) were prepared based on these two types of surfactant-free HIPEs. The morphology of the polyHIPEs, such as the surface roughness of the voids and average void diameter, were tailored by tuning the internal phase volume fraction, NaCl, copolymer, and crosslinker concentrations.

이트라코나졸 마이크로스폰지의 약물 전달 시스템: 제조, 특성 및 방출 연구

Itraconazole is a triazole antifungal agent to inhibit most fungal pathogens. To improve the oral absorption and dissolution of poorly water-soluble itraconazole, microsponge system composed of Eudragit ® E100 and polyvinyl alcohol (PVA) formulated by quasi-emulsion solvent diffusion method, and its physicochemical properties and pharmacokinetic parameters of itraconazole were studied. The microsponge of itraconazole were discrete free flowing microsized particles with perforated orange peel like morphology as visualized by scanning electron microscope (SEM). Results showed that the drug loading efficiency, production yield, and particle size of itraconazole microsponge were affected by drug to polymer ratio, the volume of internal phase containing methylene chloride, stirring rate and the concentration of PVA used. Also, the results showed that the dissolution rate of itraconazole from the microsponges was affected by drug to polymer ratio. In other words, the release rate of itraconazole from micropsonges was increased from at least 27.43% to 64.72% after 2 h. The kinetics of dissolution mechanism showed that the dissolution data followed Korsmeyer-Peppas model. Therefore, these results suggest that microsponge system can be useful for the oral delivery of itraconazole by manipulating the release profile.

In vitro release characteristics and cellular uptake of poly(D,L-lactic-co-glycolic acid) nanoparticles for topical delivery of antisense oligodeoxynucleotides

The efficacy of antisense oligodeoxynucleotides (AsODNs) is compromised by their poor stability in biological fluids and the inefficient cellular uptake due to their size and negative charge. Since chemical modifications of these molecules have resulted in a number of non-antisense activities, incorporation into particulate delivery systems has offered a promising alternative. The aim of this study was to evaluate various poly(D,L-lactic-co-glycolic acid) (PLGA) nanoparticles for AsODN entrapment and delivery. PLGA nanoparticles were prepared using the double emulsion solvent evaporation method. The influence of formulation parameters such as PLGA concentration and volume ratio of internal aqueous phase volume (Va1) to organic phase volume (Vo) to external aqueous phase volume (Va2) on particle size, polydispersity index (PDI) and zeta potential (ZP) was investigated using a full factorial study. The particle size increased with increasing PLGA concentrations and volume ratios, with an interaction detectable between the two factors. AsODN entrapment efficiencies ranged between 49.97% and 54.95% with no significant difference between various formulations. By fitting the in vitro release profiles to a dual first order release model it was shown that the AsODN release occurred via two processes: a diffusion controlled process in the early phase (25 to 32% within one day) and a PLGA degradation process in the latter (39 to 70% after 14 days). Cellular uptake studies using primary corneal epithelial cells suggested active transport of nanoparticles via endocytosis. PLGA nanoparticles therefore show potential to successfully entrap AsODNs, transport them into cells and release them over time due to polymer erosion.