Porous biodegradable polyesters. I. Preparation of porous poly(L‐lactide) films by extraction of poly(ethylene oxide) from their blends

Porous poly(L ‐lactide) (PLLA) films were prepared by water extraction of poly(ethylene oxide) (PEO) from solution‐cast PLLA and PEO blend films. The dependence of blend ratio and molecular weight of PEO on the porosity and pore size of films was investigated by gravimetry and scanning electron microscopy. The film porosity and extracted weight ratio were in good agreement with the expected for porous films prepared using PEO of low molecular weight (M_w = 1 × 10³), but shifted to lower values than expected when high molecular weight PEO (M_w = 1 × 10⁵) was utilized. The maximum pore size was larger for porous films prepared from PEO having higher molecular weight, when compared at the same blending ratio of PLLA and PEO before water extraction. Differential scanning calorimetry of as‐cast PLLA and PEO blend films revealed that PLLA and PEO were phase‐separated at least after solvent evaporation. On the other hand, comparison of blend films before and after extraction suggested that a small amount of PEO was trapped in the amorphous region between PLLA crystallites even after water extraction and hindered PLLA crystallization during solvent evaporation. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 629–637, 2000     

Kinetic studies of thermally induced phase separation in polymer–diluent system

Thermally induced phase separation was studied by the light scattering in polypropylene/methyl salicylate system. Data could be well fitted with the linear Cahn theory for spinodal decomposition (SD) in the early stage of phase separation. Characteristic properties of the early stage of SD, such as an apparent diffusion coefficient and an interphase periodic distance, were obtained. The periodic distance ranged from 3 μm to 4 μm. The growth of the phase‐separated structure obeyed power‐law scaling in the later stage, and the structure factor could be scaled into a universal time‐independent form. Domain sizes obtained from the light‐scattering measurements were consistent with the optical microscope measurements. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1028–1036, 2000     

Polydopamine-coated poly(vinylidene fluoride) membranes with high ultraviolet resistance and antifouling properties for a photocatalytic membrane reactor

We modified poly(vinylidene fluoride) (PVDF) membranes with a polydopamine (PDA) coating for photocatalytic membrane reactor application with appropriate UV resistance and studied the effects of the PDA coating conditions (i.e., coating time and dopamine concentration) and UV irradiation time on the modified PVDF membrane properties. The PVDF membrane that was surface-coated with the appropriate dopamine solution concentration and coating time played a key role in controlling the membrane properties and in protecting the modified membrane against UV radiation. The optimization of the coating condition not only completely protected the modified membrane from free-radical attack initiated through UV irradiation but also improved the membrane hydrophilicity, antifouling properties, filtration performance, and mechanical strength of the membrane. UV irradiation of the membrane that was surface-coated with a high-concentration dopamine solution for a long coating time resulted in a higher mechanical strength than that of the membrane without the application of UV irradiation. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47312.     

Physiological and psychological evaluations in low- and high-frequency noise using near-infrared spectroscopy

This study aims to evaluate physiological and psychological states using near infrared spectroscopy in noise environments with low or high frequencies. Our system assumes that noise affects brain activity in the frontal lobe. In order to evaluate the subject’s states in a noise environment, we constructed an experimental system that measures the subject’s states. The experimental method adopted here was borrowed from our previous studies. In the present study, we collected experimental data about the subject’s unpleasant or pleasant experiences by producing a noise environment with low and high frequencies. We conclude that noises with low or high frequencies affect our psychological states as well as brain activity in the frontal lobe.     

Non-destructive monitoring of creaming of oil-in-water emulsion-based formulations using magnetic resonance imaging

A non-destructive method for monitoring creaming of emulsion-based formulations is in great demand because it allows us to understand fully their instability mechanisms. This study was aimed at demonstrating the usefulness of magnetic resonance (MR) techniques, including MR imaging (MRI) and MR spectroscopy (MRS), for evaluating the physicochemical stability of emulsion-based formulations. Emulsions that are applicable as the base of practical skin creams were used as test samples. Substantial creaming was developed by centrifugation, which was then monitored by MRI. The creaming oil droplet layer and aqueous phase were clearly distinguished by quantitative MRI by measuring T₁ and the apparent diffusion coefficient. Components in a selected volume in the emulsions could be analyzed using MRS. Then, model emulsions having different hydrophilic–lipophilic balance (HLB) values were tested, and the optimal HLB value for a stable dispersion was determined. In addition, the MRI examination enables the detection of creaming occurring in a polyethylene tube, which is commonly used for commercial products, without losing any image quality. These findings strongly indicate that MR techniques are powerful tools to evaluate the physicochemical stability of emulsion-based formulations. This study will make a great contribution to the development and quality control of emulsion-based formulations.     

Preparation of highly functionalized thermoresponsive composites containing TiO2/Fe3O4 nanoparticles

Highly functionalized thermoresponsive composites in which two kinds of functional inorganic particles and thermoresponsive polymer work concertedly were prepared. In this study, poly(N‐isopropylacrylamide) and calcium alginate were used as the thermoresponsive polymer and structure support polymer, respectively. TiO₂ and Fe₃O₄ were used as functional inorganic nanoparticles. The thermoresponsive functional composites were prepared using a single‐tube nozzle by modifying the simple process to prepare microcapsules reported in our previous study. The experimental results showed that the TiO₂/Fe₃O₄‐embedded thermoresponsive composites were successfully obtained. The resulting composites exhibited thermoresponsive volume change and photocatalytic activity. Localized heating of the thermoresponsive bead containing Fe₃O₄ was also achieved by applying an alternating current (AC) magnetic field on the bead. Because of the localized heating property, repeated shrinking‐swelling movement (i.e., pumping movement) of the composite was achieved by applying an AC magnetic field intermittently. Finally, based on the experimental results, the effect of the promoted mass transfer of the substrate and product due to thermoresponsive pumping on the enhancement of the apparent photocatalytic activity was simulated. The results showed the effectiveness of thermoresponsive pumping in improving the apparent photocatalytic activity of TiO₂ nanoparticles embedded in the composite gel. POLYM. COMPOS., 37:2293–2300, 2016. © 2015 Society of Plastics Engineers     

Amorphous nanosilica induce endocytosis-dependent ROS generation and DNA damage in human keratinocytes

Background

The alveolar macrophage (AM) - first line of innate immune defence against pathogens and environmental irritants - constitutively expresses peroxisome-proliferator activated receptor γ (PPARγ). PPARγ ligand-induced activation keeps the AM quiescent, and thereby contributes to combat invaders and resolve inflammation by augmenting the phagocytosis of apoptotic neutrophils and inhibiting an excessive expression of inflammatory genes. Because of these presumed anti-inflammatory functions of PPARγ we tested the hypothesis, whether reduced functional receptor availability in mutant mice resulted in increased cellular and molecular inflammatory response during acute inflammation and/or in an impairment of its resolution.

Methods

To address this hypothesis we examined the effects of a carbon-nanoparticle (CNP) lung challenge, as surrogate for non-infectious environmental irritants, in a murine model carrying a dominant-negative point mutation in the ligand-binding domain of PPARγ (P465L/wt). Animals were instilled intratracheally with Printex 90 CNPs and bronchoalveolar lavage (BAL) was gained 24 h or 72 h after instillation to investigate its cellular and protein composition.

Results

Higher BAL cell numbers - due to higher macrophage counts - were found in mutants irrespective of treatment. Neutrophil numbers in contrast were slightly lower in mutants. Intratracheal CNP instillation resulted in a profound recruitment of inflammatory neutrophils into the alveolus, but genotype related differences at acute inflammation (24 h) and resolution (72 h) were not observed. There were no signs for increased alveolar-capillary membrane damage or necrotic cell death in mutants as determined by BAL protein and lactate-dehydrogenase content. Pro-inflammatory macrophage-derived cytokine osteopontin was higher, but galectin-3 lower in female mutants. CXCL5 and lipocalin-2 markers, attributed to epithelial cell stimulation did not differ.

Conclusions

Despite general genotype-related differences, we had to reject our hypothesis of an increased CNP induced lung inflammation and an impairment of its resolution in PPARγ defective mice. Although earlier studies showed ligand-induced activation of nuclear receptor PPARγ to promote resolution of lung inflammation, its reduced activity did not provide signs of resolution impairment in the settings investigated here.     

Highly Enhanced Nucleating Effect of Melt‐Recrystallized Stereocomplex Crystallites on Poly(L‐lactic acid) Crystallization

In the general processing temperature range of poly(L ‐lactic acid) (PLLA) articles (210–240 °C), PLLA/poly(D ‐lactic acid) (PDLA) stereocomplex (SC) crystallites melted just above the endset temperature of SC melting (228–238 °C) and recrystallized during cooling were found to act as the most effective nucleating agents for enhancing the crystallization of PLLA compared to partially melted SC crystallites (211–227 °C) or those melted far above the endset temperature of SC melting (240 and 250 °C) and recrystallized during cooling. The high nucleating effect of the SC crystallites melted in the temperature range of 228–238 °C was found to be caused by their smaller sizes or the larger number of SC crystallites per unit mass. The incorporation of such SC crystallites facilitates the processing of PLLA articles having high crystallinity and, therefore, high heat‐resistance in a shorter period to reduce the production cost.