Fabrication of soft,stimulus-responsive structures with sub-micron resolution via two-photon polymerization of poly(ionic liquid)s

Soft, stimulus-responsive 3D structures created from crosslinked poly(ionic liquid)s (PILs) have been fabricated at unprecedented sub-micron resolution by direct laser writing (DLW). These structures absorb considerable quantities of solvent (e.g., water, alcohol, and acetone) to produce PIL hydrogels that exhibit stimulus-responsive behavior. Due to their flexibility and soft, responsive nature, these structures are much more akin to biological systems than the conventional, highly crosslinked, rigid structures typically produced using 2-photon polymerization (2-PP). These PIL gels expand/contract due to solvent uptake/release, and, by exploiting inherited properties of the ionic liquid monomer (ILM), thermo-responsive gels that exhibit reversible area change (30?±?3%, n?=?40) when the temperature is raised from 20?°C to 70?°C can be created. The effect is very rapid, with the response indistinguishable from the microcontroller heating rate of 7.4?°C?s^?1. The presence of an endoskeleton-like framework within these structures influences movement arising from expansion/contraction and assists the retention of structural integrity during actuation cycling.     

The effect of cisapride on dysmotility-like functional dyspepsia: reduction of the fasting and postprandial area, but not of the postprandial antral expansion

OBJECTIVE: To test the effect of cisapride on symptom score and on fasting and postprandial antral area in patients with dysmotility-like functional dyspepsia compared with controls. METHODS: Nineteen consecutive patients with dysmotility-like functional dyspepsia (13 females, six males, aged 18-79 y) and 12 control subjects (six females, six males, aged 19-68 y) were investigated. A symptom score including six upper digestive symptoms rated from 0 to 3 was applied. The patients received in a randomized order cisapride 10 mg t.i.d. (n = 10), or placebo (n = 9) for 3 days. The controls also received cisapride (n = 6) or placebo (n = 6) in the same way. The antral area in fasting condition and immediately after a semiliquid test meal (250 ml, 342 kcal) was assessed by real-time ultrasonography in front of the aorta and mesenteric vein. The measurements were carried out before starting and after finishing the trials with cisapride and placebo. RESULTS: The symptom score (mean +/- SD) was 7.1 +/- 2.4 in dysmotility-like functional dyspepsia vs 0.5 +/- 0.2 in controls (P < 0.0001). The fasting antral area was 4.5 +/- 0.9 cm2 in dysmotility-like functional dyspepsia vs 2.2 +/- 0.2 cm2 in controls (P < 0.0001). Postprandial antral area was also larger in dysmotility-like dyspepsia than in controls (6.2 +/- 1.0 vs 3.0 +/- 0.3 cm2, Pb= 0.0001). Symptom score correlated with fasting antral area in dysmotility-like functional dyspepsia (rb= 0.38, Pb= 0.05). Cisapride decreased the symptom score to 4.5 +/- 2.5 (P = 0.0009) and placebo to 5.3 +/- 2.4 (P = 0.02). Cisapride significantly reduced the fasting antral area and the postprandial antral area in the dyspeptic group, but not in the control group. Postprandial antral expansion was not influenced by cisapride. Placebo did not change the sonographic parameters in both groups. CONCLUSIONS: In dysmotility-like functional dyspepsia, fasting and postprandial antral areas are wider than in controls. Despite a good placebo response, cisapride is effective in improving the symptoms in dysmotility-like functional dyspepsia, associated with the reduction of fasting and postprandial antral areas.     

Synthesis, characterization, and application of fluorescence sensing lipobeads for intracellular pH measurements

This paper describes the synthesis and characterization of micrometric phospholipid-coated polystyrene particles, named lipobeads, with pH-sensing capability and their application for intracellular pH measurements in murine macrophages. The phospholipids used to coat the particles are labeled with fluorescein (a pH-sensitive dye) and tetramethylrhodamine (a pH-insensitive dye), which serves as a referencing fluorophore for increased accuracy of the pH measurements. The synthesis of the pH-sensing lipobeads is realized by the covalent attachment of the fluorescent phospholipids to the surface of carboxylated polystyrene particles. The pH dynamic range of the sensing particles is between 5.5 and 7.0 with a sensitivity of 0.1 pH unit. The excitation light intensity is reduced to minimize photobleaching of the fluorescein-phospholipid conjugates. The fluorescent lipobeads are used to measure the pH in single macrophages. The lipobeads are ingested by the macrophages and directed to lysosomes, which are the cellular organelles involved in the phagocytosis process. Despite the high lysosomal levels of digestive enzymes and acidity, the absorbed particles remain stable for over 6 h in the cells when they are stored in a phosphate-buffered saline solution at pH 7.4.     

The influence of coatings on subsurface mechanical properties of laser peened 2011-T3 aluminum

High power Q-switched laser systems are currently being developed for use in a process known as laser shock processing or laser peening which results in significantly improved fatigue properties in aluminum components. An ablative, sacrificial coating such as paint or metal foil is used to protect the aluminum component from surface melting by the laser pulse, which adversely affects fatigue life. This paper, using nano-indentation, analyzes the effect of the paint and foil coatings on the shock wave propagation into the aluminum specimen and the resulting change in mechanical properties versus depth. Near the surface, hardness was found to be increased by the laser peening, however this process decreased the measured elastic modulus. The laser pulse energy density and properties of the foil including its adhesion to the aluminum alloy were found to influence the change in surface mechanical properties.     

On the dynamics of population inversion for 3 μm Er3+lasers

A generalized model for 3-μm (⁴I_11/2 →⁴I_13/2)Er lasers is proposed. The essential energy transfer processes present in the single-doped Er ³⁺ systems (up-conversion from ⁴I_13/2, up-conversion from ⁴ I_11/2, cross-relaxation from ⁴S _3/2), as well as those present in Cr³⁺ codoped Er ³⁺ systems, are taken into account. In the frame of this model, the main features of 3 μm Er³⁺ lasers, such as long pulse or CW operation, the change of emission wavelength as a function of pumping conditions, and the effects of codoping with Ho³⁺ or Tm³⁺ ions, are explained     

Ultrastructural evaluation of mesenchymal stem cells from inflamed periodontium in different in vitro conditions

This research aimed to observe the behavior of mesenchymal stem cells (MSCs) isolated from periodontal granulation tissue (gt) when manipulated ex vivo to induce three‐dimensional (3D) spheroid (aggregates) formation as well as when seeded on two bone scaffolds of animal origin. Periodontal gt was chosen as a MSC source because of its availability, considering that it is eliminated as a waste material during conventional surgical therapies. 3D aggregates of cells were generated; they were grown for 3 and 7 days, respectively, and then prepared for transmission electron microscopic analysis. The two biomaterials were seeded for 72 h with gtMSCs and prepared for scanning electronic microscopic observation. The ultrastructural analysis of 3D spheroids remarked some differences between the inner and the outer cell layers, with a certain commitment observed at the inner cells. Both scaffolds showed a relatively smooth surface at low magnification. Macro‐ and micropores having a scarce distribution were observed on both bone substitutes. gtMSCs grew with relative difficulty on the biomaterials. After 72 h of proliferation, gtMSCs scarcely covered the surface of bovine bone scaffolds, demonstrating fibroblast‐like or star‐like shapes with elongated filiform extensions. Our results add other data on the possible usefulness of gtMSC and could question the current paradigm regarding the complete removal of chronically inflamed gts from the defects during periodontal surgeries. Until optimal protocols for ex vivo manipulation of MSCs are available for clinical settings, it is advisable to use biocompatible bone substitutes that allow the development of progenitor cells. Microsc. Res. Tech. 78:792–800, 2015. © 2015 Wiley Periodicals, Inc.     

Synthesis and characterization of glycerol-adipic acid hyperbranched polyesters

The structure and molecular weight of the hyperbranched polyesterification of adipic acid and glycerol were characterized by ¹³C NMR spectroscopy and size-exclusion chromatography as a function of reaction time and reaction stoichiometry. The glycerol substitution patterns and the extent of reaction of both glycerol and adipic acid were determined by NMR. The glycerol species concentrations determined by NMR were used with a Macosko–Miller conditional probability model to predict the hyperbranched polyester weight-average molecular weight. The model accommodated the difference in primary and secondary –OH reactivity and any substituent effects to glycerol –OH reactivity. In all cases, the predicted weight-average molecular weights were in excellent agreement with the absolute molecular weights determined by size-exclusion chromatography with light scattering detection.     

Effect of LaCoO3 perovskite deposition on ceria-based supports on total oxidation of VOC

Supported LaCoO₃ perovskites with 10 wt.% loading were prepared by impregnation of different supports containing ceria with a solution of La and Co nitrates and citric acid. All precursors were calcined at 700 °C for 5 h. XRD investigations indicated the perovskite formation via “citrate” precursor only on ceria support. All catalysts were tested for toluene total oxidation in the temperature range 100–600 °C. In spite of a large surface area, alumina-supported perovskites showed a lower global activity. It appears then the necessity of the presence of a perovskite phase for good oxidative activity. In terms of reaction rates higher reaction rates per perovskite weight were observed for all supported catalysts when compared to bulk LaCoO₃.     

Analytical electron tomography mapping of the SiC pore oxidation at the nanoscale

Silicon carbide is a ceramic material that has been widely studied because of its potential applications, ranging from electronics to heterogeneous catalysis. Recently, a new type of SiC materials with a medium specific surface area and thermal conductivity, called β-SiC, has attracted overgrowing interest as a new class of catalyst support in several catalytic reactions. A primary electron tomography study, performed in usual mode, has revealed a dual surface structure defined by two types of porosities made of networks of connected channels with sizes larger than 50 nm and ink-bottled pores with sizes spanning from 4 to 50 nm. Depending on the solvent nature, metal nanoparticles could be selectively deposited inside one of the two porosities, a fact that illustrates a selective wetting titration of the two types of surfaces by different liquids. The explaining hypothesis that has been put forward was that this selectivity against solvents is related to the pore surface oxidation degree of the two types of pores. A new technique of analytical electron tomography, where the series of projections used to reconstruct the volume of an object is recorded in energy filtered mode (EFTEM), has been implemented to map the pore oxidation state and to correlate it with the morphology and the accessibility of the porous network. Applied, for the first time, at a nanoscale resolution, this technique allowed us to obtain 3D elemental maps of different elements present in the analysed porous grains, in particular oxygen; we found thus that the interconnected channel pores are more rapidly oxidized than the ink-bottled ones. Alternatively, our study highlights the great interest of this method that opens the way for obtaining precise information on the chemical composition of a 3D surface at a nanometer scale.