Hemostatic and Absorbent PolyHIPE–Kaolin Composites for 3D Printable Wound Dressing Materials

A novel hemostatic and absorbent wound dressing material compatible with 3D printing is developed to address deficiencies in current wound dressing protocol. The design involves an open celled, microporous hydrogel foam via a high internal phase emulsion (HIPE) template with biocompatible components and tunable hemostatic character by kaolin loading, the viscosity and cure kinetics of which are tailored for 3D printing applications. The use of nontoxic mineral oil organic phase results in cytocompatability with human dermal fibroblasts. Kaolin distribution is shown by X‐ray diffraction and elemental dispersive spectroscopy to be exfoliated and dispersed in the hydrogel dressing. In addition to demonstrating high fluid absorption and noncytotoxicity of relevant cell lines, the high internal phase emulsion polymers (polyHIPEs) also match the hemostatic performance of commercial wound dressing materials. Furthermore, the polyHIPEs display the requisite rheological properties for 3D printing that result in the fabrication of a prototype dressing with hierarchical porosity and a large number of controllable form factors.     

Generation of Silicone Poly‐HIPEs with Controlled Pore Sizes via Reactive Emulsion Stabilization

Macrocellular silicone polymers are obtained after solidification of the continuous phase of a poly(dimethylsiloxane) emulsion, which contains poly(ethylene glycol) drops of sub‐millimetric dimensions. Coalescence of the liquid template emulsion is prohibited by a reactive blending approach. The relationship is investigated in detail between the interfacial properties and the emulsion stability, and micro‐ and millifluidic techniques are used to generate macrocellular polymers with controlled structural properties over a wider range of cell sizes (0.2–2 mm) and volume fractions of the continuous phase (0.1%–40%). This approach could easily be transferred to a wide range of polymeric systems.

     

Effect of pH and Pea Protein: Xanthan Gum Ratio on Emulsions with High Oil Content and High Internal Phase Emulsion Formation

Electrostatic interaction between protein and polysaccharides could influence structured liquid oil stability when emulsification is used for this purpose. The objective of this work was to structure sunflower oil forming emulsions and High Internal Phase Emulsions (HIPEs) using pea protein (PP) and xanthan gum (XG) as a stabilizer, promoting or not their electrostatic attraction. The 60/40 oil-in-water emulsions were made varying the pH (3, 5, and 7) and PP:XG ratio (4:1, 8:1, and 12:1). To form HIPEs, samples were oven-dried and homogenized. The higher the pH, the smaller the droplet size (Emulsions: 15.60–43.96 µm and HIPEs: 8.74–20.38 µm) and the oil release after 9 weeks of storage at 5 °C and 25 °C (oil loss < 8%). All systems had weak gel-like behavior, however, the values of viscoelastic properties (G′ and G″) increased with the increment of PP:XG ratio. Stable emulsions were obtained at pHs 5 and 7 in all PP:XG ratios, and at pH 3 in the ratio 4:1. Stable HIPEs were obtained at pH 7 in the ratios PP:XG 4:1, 8:1, and 12:1, and at pH 5 at PP:XG ratio 4:1. All these systems presented different characteristics that could be exploited for their application as fat substitutes.     

Pure Protein Scaffolds from Pickering High Internal Phase Emulsion Template

The formation of hierarchical porous protein scaffolds from oil‐in‐water (o/w) high internal phase emulsions (HIPEs) stabilized by bovine serum albumin (BSA) protein nanoparticles (Pickering HIPE) is reported. The route consists of three principal steps. First, a stable o/w HIPE stabilized by BSA protein nanoparticles is formulated. Next, crosslinking the dispersed protein nanoparticles gives rise to a gel in the continuous water phase to freeze the emulsion's microstructure. Finally, removal of the oil components and water directly leads to a three dimensional, bimodal meso‐macroporous protein scaffold, which is suitable for a wide range of biomedical applications.     

Porous multifunctional fluoropolymer composite foams prepared via humic acid modified Fe3O4 nanoparticles stabilized Pickering high internal phase emulsion using cationic fluorosurfactant as co-stabilizer

Fluoropolymers are very important owing to their excellent application performances, especially in extreme conditions. On the other hand, the preparation of porous fluoropolymers is a difficult task due to unavailability of suitable surfactants as well as tedious synthesis steps. Here we prepared multifunctional porous fluoropolymer composite foams with a simple process of “high internal phase emulsion (HIPE)” by using humic acid modified iron oxide nanoparticles (HA-Fe₃O₄ NPs) and cationic fluorosurfactant (CFS) (PDMAEMA-b-PHFBA) as co-stabilizer. The inclusion of HA-Fe₃O₄ NPs in the system made fluoro-HIPE more stable than the emulsion prepared using only CFS or other conventional stabilizers. Morphology of the prepared polyHIPE was easily controlled by altering the concentration of HA-Fe₃O₄ and/or CFS in the original formulation. Adjustment of the porous structure with open/close cells was performed and the average diameter of the pores tuned between 4.9 and 23 μm. With the increase in specific surface area by using nanoparticles (NPs) and CFS as co-surfactants, Pickering HIPE monoliths adsorbed double amount of oil compared to foams based solely on HIPE template. Multiple functional groups were bound onto Fe₃O₄ NPs through HA modification that made the fluoro-monolith capable of adsorbing dye, i.e. methylene blue, from water. A simple centrifugation enabled regeneration of the oil soaked foams and adsorption capacity was not decreased after 10 adsorption/regeneration cycles.     

Porous,bicontinuous, and cationic polyelectrolyte obtained by high internal phase emulsion polymerization

In this work, a cationic polyelectrolyte was synthesized through oil‐in‐water high internal phase emulsion polymerization. The porous polymer was obtained using the monomer (4‐vinyl benzyl)trimethylammonium chloride and cross‐linked with N,N‐methylene‐bis‐acrylamide; additionally, ethylene glycol dimethacrylate (EGDMA) was used as the second cross‐linker, which was solubilized in the discontinuous phase leading to a bicontinuous‐like HIPE system because of the characteristics of this cross‐linker and the phase, where polymerized several effects on the polyHIPE were expected. In this way, the effect of the emulsifier and EGDMA content on the pore size, swelling, and rheological properties was assessed. It was observed that an increased concentration of the emulsifier in the polymerization decreased the pore size, narrowed its size distribution, and diminished the swelling capacity of the polymer. Additionally, the poly (HIPE) displayed a close‐cell structure explained by the locus of initiation starting from the droplets of the emulsion. After the addition of EGDMA, the polymer exhibited a major decrease in pore size and a significant decrease in swelling attributed to the polymerized skin layer on the droplet and hydrophobicity provided by the polyEGDMA, respectively. Rheological assays revealed an increase in the complex modulus and shear stress as the pore size decreased, but the addition of EGDMA did not produce an increase in the modulus, as expected. Finally, the sorption capabilities of the cationic porous polymers were evaluated through kinetic and isotherm sorption experiments using the anionic dye Acid Black 24.     

Emulsion Inks for 3D Printing of High Porosity Materials

Photocurable emulsion inks for use with solid freeform fabrication (SFF) to generate constructs with hierarchical porosity are presented. A high internal phase emulsion (HIPE) templating technique was utilized to prepare water‐in‐oil emulsions from a hydrophobic photopolymer, surfactant, and water. These HIPEs displayed strong shear thinning behavior that permitted layer‐by‐layer deposition into complex shapes and adequately high viscosity at low shear for shape retention after extrusion. Each layer was actively polymerized with an ultraviolet cure‐on‐dispense (CoD) technique and compositions with sufficient viscosity were able to produce tall, complex scaffolds with an internal lattice structure and microscale porosity. Evaluation of the rheological and cure properties indicated that the viscosity and cure rate both played an important role in print fidelity. These 3D printed polyHIPE constructs benefit from the tunable pore structure of emulsion templated material and the designed architecture of 3D printing. As such, these emulsion inks can be used to create ultra high porosity constructs with complex geometries and internal lattice structures not possible with traditional manufacturing techniques.

     

Pickering emulsions stabilized by biocompatible particles: A review of preparation,bioapplication, and perspective

The phenomenon of adsorption of solid particles at fluid interfaces to stabilize emulsions or foams have been known for more than a century. Today, particle-stabilized emulsions, often referred to as Pickering emulsions, are receiving growing attention as they are encountered in oil recovery and have long been used in personal care products and food industry. Over the past 10 years the focus of the Pickering emulsion has also increasingly shifted to biomedical applications with thanks to novel syntheses of a wide range of biocompatible particle stabilizers. Here, a brief overview of the development of biocompatible particles is given for Pickering emulsion stabilization, including alginate, poly(lactic-co-glycolic acid) (PLGA), and protein-based particles. The materials prepared by templating from emulsion stabilized with biocompatible particles include colloidal capsules and hierarchically porous materials. It is hoped that the understanding gained from the recent intense activity in the field will enable more researchers to modify existing materials and design new formulations, which would be beneficial for exploring more biological applications.     

On the effect of gold nanoparticles loading within carbonaceous macro-mesocellular foams toward lithium-sulfur battery performances

Novel carbonaceous monolith foams loaded with gold nanoparticles have been synthesized and thoroughly characterized over several length scale. Their Li-S battery electrode capabilities have been assessed and compared while varying the gold loading and subsequently the specific surface area. Their capacities expressed in either mass (mA h g⁻¹) or volume (mA h cm⁻³) dimensions have shown that specific surface area and nanoparticles loading are acting in a strong partitioning mode, rather than a cooperative mode, which does not favor the use of gold nanoparticles loading as efficient incremental path toward optimizing porous carbonaceous-based Li-S battery electrodes.     

Leveraging Actinide Hydrolysis Chemistry for Targeted Th and U Separations using Amidoxime-Functionalized Poly(HIPE)s

P olymerized h igh i nternal p hase e mulsions (poly(HIPE)s) are porous polymer monoliths whose synthesis can easily be tailored to allow incorporation of functional units. In this work, nitrile containing poly(HIPE)s have been prepared with either acrylonitrile (AN) or 4-cyanostyrene (4CS) comonomers. Post-synthetic modification of these nitrile-containing poly(HIPE)s yields their corresponding amidoximated analogues, which were studied for actinide uptake. These amidoxime-functionalized, porous polymers were shown to adsorb 95 % Th⁴⁺ species from aqueous solution within 30 minutes. In contrast to other amidoxime containing polymers the uptake of UO₂²⁺ in these poly(HIPE)s is lower under similar conditions. A critical analysis of actinide separations and high-energy X-ray scattering data provides insight into the polymers’ selectivity, enabled by the uptake of multinuclear Th clusters.