Stearic Acid as Polymerization Medium, Dopant and Hydrophobizer: Chemical Oxidative Polymerization of Pyrrole.

In recent years, fatty acids have garnered significant attention as a natural phase-change material and a hydrophobizer due to their biocompatibility and biodegradability. In this study, the utilization of fatty acid is proposed as a polymerization medium for the first time. As a specific reaction, chemical oxidative polymerizations of pyrrole is conducted using ferric chloride as an oxidant in a stearic acid medium. The polymerizations resulted in the production of micrometer-sized polypyrrole (PPy) grains, which are aggregates of atypical primary particles with submicrometer size. The PPy grains are doped with stearic acid, suggesting that the stearic acid functioned as a dopant and a hydrophobizing agent as well as a polymerization medium. The dried PPy grains can adsorb at the air-water interface and function as a liquid marble stabilizer with light-to-heat photothermal properties. The liquid marble can move on a planar air-water interface by Marangoni flow induced by NIR laser light irradiation.

Polyhedral Vinyl Polymer Particles Synthesized Via Solvent-Free Radical Polymerization.

Liquid marbles (LMs) with a cubic shape are created by using various vinyl monomers as an inner liquid and polymer plates with mm size as a stabilizer. The relationship between the surface tension of the vinyl monomers and formability of the LMs is investigated. LMs can be fabricated using vinyl monomers with surface tensions of 42.7-40.3 mN m-1. The cubic polymer particles are successively synthesized via free-radical polymerizations by irradiation of the cubic LMs with UV light in a solvent-free manner. In addition, controlling the number of polymer plates per one LM, the shape of the plate or the coalescence of the LMs can lead to production of polymer particles with desired forms (e.g., Platonic and rectangular solids) that correspond to the shapes of the original LMs.

Non-Aqueous Polyhedral Liquid Marbles Stabilized with Polymer Plates Having Surface Roughness.

Hydrophobic polymer plates with smooth and rough surfaces are used as a stabilizer for cubic liquid marbles (LMs) to study the effect of surface roughness on their formation. The smooth and rough polymer plates can stabilize LMs using liquids with surface tensions of 72.8-26.6 and 72.8-22.9 mN m-1, respectively. It is clarified that the higher the surface roughness, the lower the surface tension of the liquids are stabilized to form the LMs. These results indicated that the introduction of surface roughness improves the hydrophobicity of the polymer plates and the rough polymer plates can stabilize LMs using liquids with a wider surface tension range. Electron microscopy studies and numerical analyses confirmed that the LMs can be formed, when the Cassie-Baxter wetting state, where θY>90° (θY: the contact angle on smooth surfaces) and θR>90° (θR: the contact angle on rough surfaces), and the metastable Cassie-Baxter wetting state, where θY<90° and θR>90°, are realized. Finally, the synthesis of cubic polymer particles are succeeded by free radical polymerization of the cubic LMs containing a hydrophobic vinyl monomer (dodecyl acrylate) in a solvent-free manner.

Stimulus-Responsive Gas Marbles as an Amphibious Carrier for Gaseous Materials.

Gas marbles are a new family of particle-stabilized soft dispersed system with a soap bubble-like air-in-water-in-air structure. Herein, stimulus-responsive character is successfully introduced to a gas marble system for the first time using polymer particles carrying a poly(tertiary amine methacrylate) (pKa ≈7) steric stabilizer on their surfaces as a particulate stabilizer. The gas marbles exhibited long-term stability when transferred onto the planar surface of liquid water, provided that the solution pH of the subphase is basic and neutral. In contrast, the use of acidic solutions led to immediate disintegration of the gas marbles, resulting in release of the inner gas. The critical minimum solution pH required for long-term gas marble stability correlates closely with the known pKa value for the poly(tertiary amine methacrylate) stabilizer. It also demonstrates amphibious motions of the gas marbles.

pH- and Photoresponsive Liquid Plasticine.

Liquid marbles (LMs) can be prepared by adsorption of hydrophobic particles at the air-liquid interface of a water droplet. LMs have been studied for their application as microreaction vessels. However, their opaqueness poses challenges for internal observation. Liquid plasticines (LPs), akin to LMs, can be prepared by the adsorption of hydrophobic particles with a diameter of 50 nm or less, at the air-liquid interface of a water droplet. Unlike LMs, LPs are transparent, allowing for internal observation, thus presenting promising applications as reactors and culture vessels on a microliter scale. In this study, the surface of silica particles, approximately 20 nm in diameter, was rendered hydrophobic to prepare hydrophobic silica particles (SD0). A small amount of poly(2-(diisopropylamino)ethyl methacrylate) (PDPA) was then grafted onto the surface of SD0, yielding SD1. SD0 particles exhibited consistent hydrophobicity irrespective of the environmental pH atmosphere. Under acidic conditions, SD1 became hydrophilic due to the protonation of pendant tertiary amines in the grafted PDPA chains. However, SD1 alone was unsuitable for LP preparation due to its high surface wettability regardless of atmospheric pH, attributable to the presence of PDPA-grafted chains. Therefore, to prepare pH-responsive LP, SD1 and SD0 were mixed (SD1/SD0 = 3/7). Upon exposure to HCl gas, these LPs ruptured, with the leaked water from the LPs being absorbed by adjacent paper. Moreover, clear LPs, prepared using an aqueous solution containing a water-soluble photoacid generator (PAG), disintegrated upon exposure to light as PAG generated acid, leading to LP breakdown. In summary, pH-responsive LPs, capable of disintegration under acidic conditions and upon light irradiation, were successfully prepared in this study.

Chiral Transfer of Linear Polysiloxane with Preferred-Handed Helical Conformation.

We report the preparation of chiral silica using a linear polysiloxane main chain with a preferred-handed helical structure as the template. Poly(methylvinyl siloxane) (PMVS) with a cysteine derivative side chain designated as PMVS-Cys was prepared using anionic polymerization and an ene-thiol reaction. PMVS-Cys forms a helical conformation in both solution and film via hydrogen bonding between amide groups at side chains. The helical structure remains during the calcination process, resulting in silica with helical structure. The silica with a helical structure shows optical activity.

Nitrogen-Containing Carbon Tubes Fabricated by Light Irradiation.

Cotton-core/polypyrrole (PPy)-sheath fibers (cotton/PPy fibers) were synthesized by aqueous chemical oxidative seeded polymerization and were utilized as precursors for nitrogen-containing carbon (NCC) tubes. Irradiation of the cotton/PPy fibers with a near-infrared (NIR) laser heated them to approximately 300 °C due to light-to-heat photothermal conversion by the PPy, and the cotton core was thermally decomposed and vaporized. Scanning electron microscopy studies revealed the formation of tubes with monodispersed diameters, and elemental microanalysis, Fourier transform infrared spectroscopy, and Raman spectroscopy confirmed that the PPy sheath was converted into NCC. Furthermore, sunlight also worked as the light source in fabricating the NCC tubes. The thicknesses of the tubes were controlled between 410 nm and 2.30 µm by tuning the PPy sheath thickness. The method developed in this study can be extended to other polymeric fibers, including acrylic and wool fibers. The shapes of the cross sections and surface nanomorphologies of the NCC tubes can be reflected in those of the polymer/PPy fibers.

Modulation of prostaglandin transport activity of SLCO2A1 by annexin A2 and S100A10.

Solute carrier organic anion transporter family member 2A1 (SLCO2A1) is a prostaglandin (PG) transporter and serves as the osmosensitive ATP-permeable maxi-anion channel (Maxi-Cl). Since a heterotetrameric complex of annexin A2 (ANXA2) and S100A10 is obligatory for the channel activity, the present study aimed to determine if they regulate SLCO2A1-mediated PG transport. This study examined PGE2 uptake and ATP release in Anxa2 and/or S100a10 knockout (KO) murine breast C127 cells. Deletion of Slco2a1 decreased PGE2-d4 uptake by wild-type (WT) cells in an isotonic medium (290 mosmol/kgH2O). Decreased osmolarity (135 mosmol/kgH2O) stimulated ATP release but did not affect PGE2 uptake kinetics, showing Km (1,280 nM) and Vmax (10.38 pmol/15 s/mg protein) similar to those in isotonic medium (1,227 nM and 10.65 pmol/15 s/mg protein), respectively, in WT cells. Deletion of Anxa2 associated with loss of S100a10 diminished SLCO2A1-mediated ATP release and uncompetitively inhibited PGE2 uptake with lowered Km (376 nM) and Vmax (2.59 pmol/15 s/mg protein). Moreover, the immunoprecipitation assay confirmed the physical interaction of ANXA2 with SLCO2A1 in WT cells. Enforcement of ANXA2 expression to Anxa2 KO cells partially restored PGE2 uptake and increased Km (744.3 nM) and Vmax (9.07 pmol/15 s/mg protein), whereas the uptake clearance (Vmax/Km) did not change much regardless of ANXA2 expression. These results suggest that an ANXA2/S100A10 complex modulates PG transport activity but osmolality has little effect on it; therefore, the bound form of SLCO2A1, which functions as a PG transporter and Maxi-Cl, may exist regardless of changes in the cell volume.NEW & NOTEWORTHY A previous study indicated that the ANXA2/S100A10 complex represents the regulatory component of SLCO2A1-mediated Maxi-Cl channel activity. The present study showed that apparent PGE2 uptake by C127 cells was osmoinsensitive and uncompetitively inhibited by loss of ANXA2 expression, demonstrating that ANXA2 is a regulatory factor of SLCO2A1-mediated PG transport activity.

Colloidally Stable Polypyrrole Nanoparticles Synthesized by Surfactant-Free Coupling Polymerization.

Surfactant-free polypyrrole (PPy) nanoparticles, which were colloidally stable in aqueous medium, were successfully synthesized by coupling polymerization of pyrrole using Fe(NO3)3 solids in the absence of any colloidal stabilizer. The pyrrole monomers were gradually supplied from the vapor phase, and the coupling reaction of the monomers could proceed to generate PPy in a water medium. The resulting PPy nanoparticles were extensively characterized in terms of diameter, bulk chemical composition, surface chemistry, and colloidal stability by dynamic light scattering, electron microscopy, elemental microanalysis, Fourier transform infrared spectroscopy, Raman spectroscopy, electrophoresis, and X-ray photoelectron spectroscopy. The characterization results indicated that the PPy nanoparticles can be colloidally stable based on the electrostatic stabilization mechanism due to cationic charges generated on the PPy molecules by doping during the polymerization. General chemical oxidative polymerization in aqueous medium using the Fe(NO3)3 oxidant without a colloidal stabilizer as a control experiment resulted in generation of atypical PPy aggregates with over a micrometer size, indicating that the polymerization at low ionic strength is essential for colloidal particle formation. Finally, it was demonstrated that the PPy nanoparticles worked as a surfactant-free black-colored particulate emulsifier by adsorption at the oil-water interface to stabilize Pickering-type oil-in-water emulsions.

Controlling Circularly Polarized Luminescence Using Helically Structured Chiral Silica as a Nanosized Fused Quartz Cell.

Circularly polarized luminescence (CPL) is typically achieved with a chiral luminophore. However, using a helical nanosized fused quartz cell consisting of chiral silica, we could control the wavelength and helical sense of the CPL of an achiral luminophore. Chiral silica with a helical nanostructure was prepared by calcining a mixture of polyhedral oligomeric silsesquioxane (POSS)-functionalized isotactic poly(methacrylate) (it-PMAPOSS) and a small amount of chiral dopant. The chiral silica encapsulated functional molecules, including luminophores, along the helical nanocavity, leading to induced circular dichroism (ICD) and induced circularly polarized luminescence (iCPL). Because chiral silica can act as a helical nanosized fused quartz cell, it can encapsulate not only the luminophore but also solvent molecules. By changing the solvent in the luminophore-containing nanosized fused quartz cell, the wavelength of the CPL was controlled. This method provides an effective strategy for designing novel CPL-active materials.

An implication of the mitochondrial carrier SLC25A3 as an oxidative stress modulator in NAFLD.

Nonalcoholic fatty liver disease (NAFLD) is a type of steatosis not associated with excessive alcohol intake and includes nonalcoholic steatohepatitis (NASH), which can progress to advanced fibrosis and hepatocellular carcinoma. Mitochondrial dysfunction causes oxidative stress, triggering hepatocyte death and inflammation; therefore, the present study aimed to explore relationship between mitochondrial carriers and oxidative stress. Firstly, we established a high fat diet (HFD)-fed ICR mouse NAFLD model characterized by obesity with insulin resistance and found transcriptional upregulation of Slc25a17 and downregulation of Slc25a3 (isoform B) and Slc25a13 in their fatty liver. A mitochondrial phosphate and Cu carrier, SLC25A3, was further studied in wild-type (wt) and SLC25A3-defective HepG2 cells (C1 and C3). SLC25A3 deficiency had insignificant effect on mitochondrial membrane potential (MtMP) and oxygen consumption rate (OCR) in untreated cells but suppressed them when cells were exposed to oleic acid. C1 and C3 cells were prone to produce reactive oxygen species (ROS), and increased ROS was associated with reduced mRNA expression of glutathione peroxidase (GPX) 1 and glutathione disulfide reductase (GSX) in these cell lines. Interestingly, cytoplasmic and mitochondrial Cu accumulation significantly reduced in C1 cells, demonstrating a predominant contribution of SLC25A3 to Cu transport into mitochondrial matrix. Cytotoxicity of free fatty acids was unchanged between wt and SLC25A3-deficient cells. These results indicate that reduced expression of SLC25A3 in fatty liver contributes to electron leak from mitochondria by limiting Cu availability, rendering hepatocytes more susceptible to oxidative stress. This study provides evidence that SLC25A3 is a novel risk factor for developing NASH.

Nonspherical Epoxy Resin Polymer Particles Synthesized via Solvent-Free Polyaddition Reactions.

Cubic liquid marbles (LMs) were fabricated by using various epoxy monomers as internal liquids and millimeter-sized polymer plates as stabilizers. Successively, cubic polymer particles were synthesized via solvent-free polyaddition reactions by exposing the cubic LMs to NH3 vapor used as a curing agent. The effect of the solubility parameters (SPs) for the epoxy monomers on the formation of the cubic polymer particles was investigated. As a result, we succeeded in fabricating cubic polymer particles reflecting the shapes of the original LMs by using epoxy monomers with SP values of 23.70-21.66 (MPa)1/2. Furthermore, the shapes of the LMs could be controlled on demand (e.g., pentahedral and rectangular) by control of the number of polymer plates per LM and/or coalescence of the LMs, resulting in fabrication of polymer particles with shapes reflecting those of the LMs.

Aqueous Bubbles Stabilized with Millimeter-Sized Polymer Plates.

(Sub)millimeter-sized hexagonal polymer plates that were monodisperse in shape and size were utilized as stabilizers for aqueous bubbles, and the effects of the hydrophilic-hydrophobic property, size, and solid concentration of the plates on the formability, stability, and shape and structure of aqueous bubbles were investigated. The formability and stability of the bubbles were improved by increasing the hydrophobicity of the plate surface, decreasing the plate size, and increasing the solid concentration of the plates. For plates with suitable water wettability, three-dimensional bubbles with nearly spherical and polyhedral shapes were formed by the adsorption of plates to the bare air bubbles introduced into the continuous water phase by air-water mixing. On the contrary, two-dimensional bubbles with accordion-type structures consisting of alternating layers of plates and entrapped air bubbles were formed by the transfer of multiple plates with poor wettability from the air phase to the water phase by air-water mixing. Furthermore, a correlation was found between the bubble/stabilizer size ratio and bubble shape for plates with the suitable wettability: bubbles with nearly spherical shapes were formed when the bubble/plate size ratios were >2, bubbles with hexahedral, pentahedral, and tetrahedral shapes were formed when the size ratios were approximately 1, and bubbles with triangular and sandwich shapes were formed when the size ratios were <0.8. Additionally, bubbles with similar shapes were formed when the bubble/plate size ratios were close, even when the sizes of the plates and bubbles were different.

N-glycosylation modifies prostaglandin E2 uptake by reducing cell surface expression of SLCO2A1.

SLCO2A1 functions as a prostaglandin (PG) influx transporter to facilitate intracellular oxidation of PGs and its defect causes dysregulation of PG signaling and metabolism. This study aimed to clarify effects of N-glycosylation on functional SLCO2A1 expression. Putative N-glycosylation site(s) (N134, N478, and/or N491) of human SLCO2A1 were mutated to Q and wild-type (WT) and mutant forms were expressed in HEK293 and human epithelial cells. Molecular weight of WT decreased to nearly 55 kDa by PNGase F treatment and was identical to that of triple mutant (TM, i.e., N134Q/N478Q/N491Q). Transport affinity of TM for PGE2 (Km of 392.7 nM) was comparable to that of WT (Km of 328.5 nM); however, immunoassays showed that TM cell surface expression remained at 24% of WT in HEK293 cells, resulting in a reduced cellular PGE2 uptake. These results suggest N-glycosylation modifies cellular PGE2 uptake by decreasing SLCO2A1 localization to the plasma membrane.

Photo- and Thermoresponsive Liquid Marbles Based on Fatty Acid as Phase Change Material Coated by Polypyrrole: From Design to Applications.

Responsive liquid marbles (LMs), which can change their shape, stability, and motion by the application of stimuli, attract a growing interest due to their wide range of applications. Our approach to design photo- and thermoresponsive LMs is based on the use of micrometer-sized fatty acid (FA) particles as phase change material covered with polypyrrole (PPy) overlayers with photothermal property. The core-shell particles were synthesized by aqueous chemical oxidative seeded dispersion polymerization. First, we investigated the effect of the alkyl chain length of FA on the resulting FA/PPy core-shell particles by characterizing their size and its distribution, shape, morphology, chemical composition, and photothermal behavior. Then LMs were fabricated by rolling water droplets on the dried FA/PPy particle powder bed and their light and temperature dual stimuli-responsive nature was studied as a function of the FA alkyl chain length. For all FAs studied, LMs disrupted in a domino manner by light irradiation as the first trigger: the temperature of the FA/PPy particles on the LM surface increased by light irradiation, followed by phase change of FA core of the particles from solid to liquid, resulting in disruption of the LM and release of the encapsulated water. The disruption time was closely correlated to the melting point of FA linked to the alkyl chain length and light irradiation power, and it could be controlled and tuned easily between quasi instantaneous and approximately 10 s. Finally, we showed potential applications of the LMs as a carrier for controlled delivery and release of substances and a sensor.

Characteristics of organic removal for supermarket wastewater treatment with an anaerobic baffled reactor and efficacy evaluation of changing HRT.

An anaerobic baffled reactor (ABR) is one of the useful wastewater treatment technologies, but the knowledge about its treatment performance for actual wastewater with load fluctuation is limited. The organic removal performance of an ABR for treating supermarket wastewater was evaluated. The ABR, which consisted of eight columns, was examined under four hydraulic retention time (HRT) conditions of 19.4, 12.9, 8.0, and 4.4 h. As a result, the unfiltered chemical oxygen demand (COD) removal efficiency was 80 (±8) % at an HRT of 19.4 h. When the HRT was shortened to 12.9 h, the average unfiltered COD removal efficiency decreased to 58 (±15) %. However, it showed buffering effect against high load inflow in the first column, indicating that it is useful as a pretreatment system under this condition. At an HRT of 4.4 h, the unfiltered COD removal efficiency decreased to 9%, indicating the system failed. The results of the microbial community structure analysis showed that the detection frequency of acidogenic bacteria decreased in proportion to the extension of residence time in the reactor. These results indicate that the ABR is useful for the treatment of supermarket wastewater with load fluctuations as a main treatment system at a HRT of 19.4 h and as a pretreatment system at a HRT of 12.9 h.

Photo/Thermo Dual Stimulus-Responsive Liquid Marbles Stabilized with Polypyrrole-Coated Stearic Acid Particles.

In this study, we report on the fabrication of photo/thermo dual stimulus-responsive liquid marbles (LMs) that can be disrupted by light irradiation and/or heating. To stabilize the LMs, we synthesized micrometer-sized stearic acid (SA) particles coated with overlayers of polypyrrole (PPy) by aqueous chemical oxidative seeded dispersion polymerization. The SA/PPy core-shell particles could adsorb at the air-water interface to stabilize LMs by rolling water droplets on the particle powder bed. The presence of SA, known as a phase-change material, which undergoes a transition from solid to liquid by heating, and PPy, which can transduce light to heat, gives rise to the photo and thermo dual stimulus-responsive characters of the LMs. The disruption of the LMs could be induced in a cascade manner: light irradiation on the LM induced a temperature increase, followed by melting of the SA component on the LM surface, leading to its disruption and release of the inner water. The disruption time is linked to the PPy loading and light irradiation power, and it can be tuned from quasi-instantaneous to a few tens of seconds. The melting of SA due to a light-induced phase change from the solid to liquid state is a new mechanism to trigger the disruption of LMs. We finally demonstrated two applications of the LMs as a light-responsive microreactor and a sensor.

"Foam Marble" Stabilized with One Type of Polymer Particle.

There has been increasing interest in colloidal particles adsorbed at the air-water interface, which lead to stabilization of aqueous foams and liquid marbles. The wettability of the particles at the interface is known to play an important role in determining the type of air/water dispersed system. Foams are preferably formed using relatively hydrophilic particles, and liquid marbles tend to be formed using relatively hydrophobic particles. In this study, submicrometer-sized polystyrene particles carrying poly(N,N-diethylaminoethyl methacrylate) hairs (PDEA-PS particles), which are synthesized by dispersion polymerization, are demonstrated to work as a particulate stabilizer for both aqueous foams and liquid marbles. A key point for the hydrophilic PDEA-PS particles to stabilize both aqueous foams and liquid marbles, which have been generally stabilized with hydrophilic and hydrophobic particles, respectively, is the wetting mode of the particles with respect to water. The flocculates of PDEA-PS particles adsorb to the air-water interface from the aqueous phase to stabilize foam in a Wenzel mode, and the dried PDEA-PS particles adsorb to the interface as aggregates from the air phase to stabilize liquid marbles in a metastable Cassie-Baxter mode. On the basis of the difference in the wetting mode, stabilization of an air-in-water-in-air multiple gas-liquid dispersed system, named "foam marble", is realized. After the evaporation of water from the foam marble, a porous sphere is successfully obtained with pore sizes of a few tens of micrometers (reflecting the bubble sizes) and a few tens of nanometers (reflecting the gap sizes among the PDEA-PS particles).

Synthesis of Polypyrrole and Its Derivatives as a Liquid Marble Stabilizer via a Solvent-Free Chemical Oxidative Polymerization Protocol.

Solvent-free chemical oxidative polymerizations of pyrrole and its derivatives, namely N-methylpyrrole and N-ethylpyrrole, were conducted by mechanical mixing of monomer and solid FeCl3 oxidant under nitrogen atmosphere. Polymerizations occurred at the surface of the oxidant, and optical and scanning electron microscopy studies confirmed production of atypical grains with diameters of a few tens of micrometers. Fourier transform infrared spectroscopy studies indicated the presence of hydroxy and carbonyl groups which were introduced during the polymerization due to overoxidation. The polymer grains were doped with chloride ions, and the chloride ion dopant could be removed by dedoping using an aqueous solution of sodium hydroxide, which was confirmed by elemental microanalysis and X-ray photoelectron spectroscopy studies. Water contact angle measurements confirmed that the larger the alkyl group on the nitrogen of pyrrole ring the higher the hydrophobicity and that the contact angles increased after dedoping in all cases. The grains before and after dedoping exhibited photothermal properties: the near-infrared laser irradiation induced a rapid temperature increase to greater than 430 °C. Furthermore, dedoped poly(N-ethylpyrrole) grains adsorbed to the air-water interface and could work as an effective liquid marble stabilizer. The resulting liquid marble could move on a planar water surface due to near-infrared laser-induced Marangoni flow and could disintegrate by exposure to acid vapor via redoping of the poly(N-ethylpyrrole) grains.