Self‐Assembly of ATRP‐Synthesized PCH‐b‐PtBA‐b‐PCH Triblock Copolymers Observed by Time‐Resolved SAXS

The phase behavior of PCH‐b‐PtBA‐b‐PCH triblock copolymers has been studied. Measurements in the wide‐angle region probed the existence of microphase segregation through variation of block mobility and thermal expansion coefficients. SAXS experiments pointed out that most copolymers present ordered nanostructures, mostly hexagonally packed cylinders, the morphology being confirmed by AFM. An unusual disorder‐to‐order transition is observed in one copolymer synthesized from a macroinitiator with intermediate length and the highest outer‐block molecular weight, whereas none of the copolymers shows an order‐to‐disorder transition upon heating over the temperature range analyzed.

     

Fluorene‐Based Single‐Chain Copolymers for Color‐Stable White Light‐Emitting Diodes

Fluorene‐based single‐chain copolymers with a white light emitter consisting of a blue and an orange chromophore have been synthesized and their photophysical and electroluminescent properties are investigated. The experimental results suggest that only a relatively small fraction of the orange‐emitting units incorporated into the fluorene is needed to achieve efficient white light emission by controlled incomplete energy transfer. A device from a copolymer with 0.02% DDQ content showed the highest external quantum efficiency of 2.64% with a luminance efficiency of 4.06 cd · A^?1 with CIE coordinates (0.28, 0.24). The EL emissions are extremely stable over a wide range of current densities.

     

Synthesis and Properties of pH‐ and Temperature‐Sensitive Poly[(N‐isopropylacrylamide)‐co‐(2‐methylenebutane‐1,4‐dioic acid)] Hydrogels

Summary: Hydrogels of NIPA and MBDA were synthesized by free‐radical crosslinking copolymerization with different monomer ratios and with two concentrations of the crosslinking agent. The aim of this work was to study the swelling behavior of these gels that are both temperature and pH sensitive. PNIPA hydrogels are typical examples of thermo‐shrinking hydrogels with a LCST, T_C, around 31–34 °C. MBDA is a weakly ionizable monomer which imparts a pH sensitiveness to the copolymer hydrogels. The pH influence on the swelling behavior of the studied hydrogels was analyzed using deionized water and aqueous HCl and NaOH as swelling media. According to the results found in deionized water, the swelling processes of P(NIPA‐MBDA) hydrogels follow second‐order kinetics at 22 and 37 °C. The equilibrium water content, W_∞, and the rate constant, K, increased at greater concentrations of MBDA and decreased as the crosslinking agent concentration increased. As the MBDA content in the hydrogel increased, the collapsing of the hydrogels at higher temperatures than the LCST became of less importance. The degree of swelling of pure PNIPA hydrogels was not influenced by the pH of the swelling medium. However, this influence increased as the MBDA content increased. This was due to the fact that at low pH most of the MBDA units are in the protonated (neutral) form and at high pH in the ionized one.

Swelling isotherms of hydrogels with different copolymer compositions and with 1.5 wt.‐% of BIS at 22 °C in deionized water.     

The DC‐HIL ligand syndecan‐4 is a negative regulator of T‐cell allo‐reactivity responsible for graft‐versus‐host disease

Acute graft-versus-host disease (GVHD) is the most important cause of mortality after allogeneic haematopoietic stem cell transplantation. Allo-reactive T cells are the major mediators of GVHD and the process is regulated by positive and negative regulators on antigen-presenting cells (APC). Because the significance of negative regulators in GVHD pathogenesis is not fully understood, and having discovered that syndecan-4 (SD-4) on effector T cells mediates the inhibitory function of DC-HIL on APC, we proposed that SD-4 negatively regulates the T-cell response to allo-stimulation in acute GVHD, using SD-4 knockout mice. Although not different from their wild-type counterparts in responsiveness to anti-CD3 stimulation, SD-4^−/− T cells lost the capacity to mediate the inhibitory function of DC-HIL and were hyper-reactive to allogeneic APC. Moreover, infusion of SD-4^−/− T cells into sub-lethally γ-irradiated allogeneic mice worsened mortality, with hyper-proliferation of infused T cells in recipients. Although there my be little or no involvement of regulatory T cells in this model because SD-4 deletion had no deleterious effect on T-cell-suppressive activity compared with SD-4^+/+ regulatory T cells. We conclude that SD-4, as the T-cell ligand of DC-HIL, is a potent inhibitor of allo-reactive T cells responsible for GVHD and a potentially useful target for treating this disease.     

Gamma‐Cyclodextrin‐Recognition‐Responsive Characteristics of Poly(N‐isopropylacrylamide)‐Based Hydrogels with Benzo‐12‐crown‐4 Units as Signal Receptors

Molecular‐recognition‐responsive characteristics of a novel poly(N‐isopropylacrylamide‐co‐benzo‐12‐crown‐4‐acrylamide) (PNB12C4) hydrogel have been investigated. In the prepared PNB12C4 hydrogel, benzo‐12‐crown‐4 (B12C4) groups act as guest molecules and γ‐cyclodextrin (γ‐CD)‐receptors, and poly(N‐isopropylacrylamide) (PNIPAM) networks act as phase‐transition actuators. The formation of stable γ‐CD/B12C4 complexes enhances the hydrophilicity of the PNB12C4 hydrogel networks, and induces positive shift of the volume phase transition temperature (VPTT) of PNB12C4 hydrogel. Moreover, the PNB12C4 hydrogel also shows thermoresponsive adsorption property selectively towards γ‐CD. The γ‐CD‐recognition sensitivity of PNB12C4 hydrogel can be dramatically improved by increasing γ‐CD concentration in solution or B12C4 content in PNB12C4 copolymer networks. The results in this study provide valuable information for developing crown ether‐based smart materials in various applications.

     

Encapsulating Hydrophilic Solution by PU‐PMF Double‐Component Capsule Based on Water‐In‐Oil‐In‐Oil Emulsion Template

This study demonstrates an effective method to encapsulate a hydrophilic payload through the use of polyurethane‐poly(melamine‐formaldehyde) (PU‐PMF) dual‐component capsules based upon the water‐in‐oil‐in‐oil (W/O/O) emulsion template. This emulsion has a middle oil layer that hosts the PU (outer shell) forming reaction while the internal PMF skeleton, fabricated concurrently by polymer precipitation in the aqueous dispersive phase, provides additional mechanical support. The resultant capsules exhibit dense and spherical shape, low permeability, and diameter of ≈50 µm. Remarkably, interfacial tension is the driving factor in the formation of the W/O/O template. This microencapsulation system and the methods used for its fabrication have a great technical potential for use in industrial applications.     

Polyelectrolyte‐in‐Ionic‐Liquid Electrolytes

Novel polymer electrolyte materials based on a polyelectrolyte‐in‐ionic‐liquid principle are described. A combination of a lithium 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid (AMPSLi) and N,N′‐dimethylacrylamide (DMMA) are miscible with the ionic liquid, 1‐ethyl‐3‐methylimidazolium dicyanamide (EMIDCA). EMIDCA has remarkably high conductivity (≥ 2 · 10^?2 S · cm^?1) at room temperature and acts as a good solvating medium for the polyelectrolyte. At compositions of AMPSLi less than or equal to 75 mol‐% in the copolymer (P(AMPSLi‐co‐DMAA)), the polyelectrolytes in EMIDCA are homogeneous, flexible elastomeric gel materials at 10 ? 15 wt.‐% of total polyelectrolyte. Conductivities higher than 8 · 10^?3 S · cm^?1 at 30 °C have been achieved. The effects of the monomer composition, polyelectrolyte concentration, temperature and lithium concentration on the ionic conductivity have been studied using thermal and conductivity analysis, and pulsed field gradient nuclear magnetic resonance techniques.

Comparison of the measured and calculated lithium conductivity at 30 °C.     

Synthesis,Characterization, and Intramolecular End‐to‐End Ring Closure of α‐Isopropylidene‐1,1‐dihydroxymethyl‐ω‐diethylacetal Polystyrene‐block‐polyisoprene Block Copolymers

Cyclic polystyrene‐block‐polyisoprenes of controlled dimensions have been synthesized for the first time by the direct coupling of α‐isopropylidene‐1,1‐dihydroxymethyl‐ω‐diethylacetal‐heterodifunctional linear polystyrene‐block‐polyisoprene precursors previously prepared by living anionic polymerization. Cyclization is achieved under high dilution by intramolecular coupling of the polymer ends under acid catalyst conditions. Using this strategy polystyrene‐block‐polyisoprene macrocycles of controlled chain dimensions are prepared in high yield (> 90%). Pure cycles were finally recovered by flash chromatography. The synthesis and characterization of both the linear α,ω‐heterodifunctional polystyrene‐block‐polyisoprenes block copolymers precursors and of the corresponding cyclized chain architectures are reported.

200 MHz ¹H NMR spectrum (CDCl₃) of cyclized polystyrene‐block‐polyisoprene copolymer (M _n = 12 000).     

4,5‐Ethylene‐2,7‐Carbazole‐Based Medium‐Bandgap Conjugated Polymers with Low‐Lying HOMO Levels Toward Efficient Polymer Solar Cells with High Open‐Circuit Voltage

Three medium‐bandgap polymers based on a 4,5‐ethylene‐2,7‐dithienyl carbazole as the electron‐donating unit and different 5,6‐dialkoxy‐2,1,3‐benzothiadiazoles as the electron‐accepting units, are synthesized as polymer donors for photovoltaic applications. The three copolymers possess highest occupied molecular oribital (HOMO) levels around ?5.47 eV and medium bandgaps of about 1.94 eV. The solar cells with polymer:[6,6]‐phenyl C71‐butyric acid methyl ester (PC₇₁BM) = 1:4 as the active layer, show an especially high open‐circuit voltage (V_oc) of 0.95 V and attain good power conversion efficiency up to 5.91%. The hole mobilities of the active layer films, measured by space‐charge‐limited current (SCLC), are up to 3.5 × 10^?4 cm² V^?1 s^?1. Given the favorable medium bandgaps, low‐lying HOMO levels, and good hole mobilities, these copolymers are promising candidates for the construction of a highly efficient front cell to harvest the shorter wavelength band of the solar radiation in a tandem solar cell with high V_oc.

     

A Mechanistic and Characteristic Investigation of Electrooxidation of 2‐Amino‐3‐cyano‐4‐methylthiophene

The electrochemical oligomerization of 2‐amino‐3‐cyano‐4‐methylthiophene (ACMT) has been studied by cyclic voltammetry, potential controlled electrolysis and digital simulation. The product analysis after preparative electrolysis was carried out by UV‐vis‐NIR, ¹H and ¹³C NMR and FT‐IR spectroscopic techniques. The kinetic data were estimated using the results of fitting the digitally simulated voltammograms to the experimentally obtained cyclic voltammograms. The oligomerization proceeds according to an ECE mechanism resulting in the formation of an oligomeric mixture containing dimer and tetramer. UV‐vis‐NIR and fluorescence measurements indicated that the isolated dimer and tetramer showed higher conjugation than the monomer unit and the conjugation increased with an increase in the number of monomer units.

     

Clinical characteristics and risk factors of mild‐to‐moderate COVID‐19 patients with false‐negative SARS‐CoV‐2 nucleic acid

This study investigates the clinical and imaging characteristics of coronavirus disease 2019 (COVID‐19) patients with false‐negative nucleic acids. Mild‐to‐moderate COVID‐19 patients, including 19 cases of nucleic acid false‐negative patients and 31 cases of nucleic acid positive patients, were enrolled. Their epidemiological, clinical, and laboratory examination data and imaging characteristics were analyzed. Risk factors for false negatives were discussed. Compared with the nucleic acid positive group, the false‐negative group had less epidemiological exposure (52.6% vs 83.9%; P = .025), less chest discomfort (5.3% vs 32.3%; P = .035), and faster recovery (10 [8, 13] vs 15 [11, 18.5] days; P = .005). The number of involved lung lobes was (2 [1, 2.5] vs 3 [2, 4] days; P = .004), and the lung damage severity score was (3 [2.5, 4.5] vs 5 [4, 9] days; P = .007), which was lighter in the nucleic acid false‐negative group. Thus, the absence of epidemiological exposure may be a potential risk factor for false‐negative nucleic acids. The false‐negative cases of COVID‐19 are worth noting because they have a risk of viral transmission without positive test results, lighter clinical manifestations, and less history of epidemiological exposure.     

Non‐water‐suppressed short‐echo‐time magnetic resonance spectroscopic imaging using a concentric ring k‐space trajectory

Water‐suppressed MRS acquisition techniques have been the standard MRS approach used in research and for clinical scanning to date. The acquisition of a non‐water‐suppressed MRS spectrum is used for artefact correction, reconstruction of phased‐array coil data and metabolite quantification. Here, a two‐scan metabolite‐cycling magnetic resonance spectroscopic imaging (MRSI) scheme that does not use water suppression is demonstrated and evaluated. Specifically, the feasibility of acquiring and quantifying short‐echo (T_E = 14 ms), two‐dimensional stimulated echo acquisition mode (STEAM) MRSI spectra in the motor cortex is demonstrated on a 3 T MRI system. The increase in measurement time from the metabolite‐cycling is counterbalanced by a time‐efficient concentric ring k‐space trajectory. To validate the technique, water‐suppressed MRSI acquisitions were also performed for comparison. The proposed non‐water‐suppressed metabolite‐cycling MRSI technique was tested for detection and correction of resonance frequency drifts due to subject motion and/or hardware instability, and the feasibility of high‐resolution metabolic mapping over a whole brain slice was assessed. Our results show that the metabolite spectra and estimated concentrations are in agreement between non‐water‐suppressed and water‐suppressed techniques. The achieved spectral quality, signal‐to‐noise ratio (SNR) > 20 and linewidth <7 Hz allowed reliable metabolic mapping of five major brain metabolites in the motor cortex with an in‐plane resolution of 10 × 10 mm² in 8 min and with a Cramér‐Rao lower bound of less than 20% using LCModel analysis. In addition, the high SNR of the water peak of the non‐water‐suppressed technique enabled voxel‐wise single‐scan frequency, phase and eddy current correction. These findings demonstrate that our non‐water‐suppressed metabolite‐cycling MRSI technique can perform robustly on 3 T MRI systems and within a clinically feasible acquisition time.     

PD‐1 modulates steady‐state and infection‐induced IL‐10 production in vivo

Programmed death‐1 (PD‐1) plays an important role in mediating immune tolerance through mechanisms that remain unclear. Herein, we investigated whether PD‐1 prevents excessive host tissue damage during infection with the protozoan parasite, Toxoplasma gondii. Surprisingly, our results demonstrate that PD‐1‐deficient mice have increased susceptibility to T. gondii, with increased parasite cyst counts along with reduced type‐1 cytokine responses (IL‐12 and IFN‐γ). PD‐1^?/? DCs showed no cell intrinsic defect in IL‐12 production in vitro. Instead, PD‐1 neutralization via genetic or pharmacological approaches resulted in a striking increase in IL‐10 release, which impaired type‐1‐inflammation during infection. Our results indicate that the absence of PD‐1 increases IL‐10 production even in the absence of infection. Although the possibility that such increased IL‐10 protects against autoimmune damage is speculative, our results show that IL‐10 suppresses the development of protective Th1 immune response after T. gondii infection.     

Flower‐Like Multicompartment Micelles with Janus‐Core Self‐Assembled from Fluorocarbon‐Terminated Pluronics

Multicompartment micelles (MCMs), whose cores have at least two compartments, show potential applications in various areas, but the synthesis of polymers for preparing MCMs is usually tedious and time‐consuming. In this work, two well‐defined telechelic fluorocarbon‐terminated triblock copolymers, F₈‐PEO₁₀₀‐PPO₆₅‐PEO₁₀₀‐F₈ (F₈‐F127‐F₈) and F₈‐PEO₁₃₂‐PPO₅₀‐PEO₁₃₂‐F₈ (F₈‐F108‐F₈), are synthesized via a single‐step coupling reaction of Pluronics F127 or F108 with perfluoro‐1‐octanesulfonyl fluoride and characterized by Fourier‐transform infrared and NMR spectroscopies, as well as gel permeation chromatography and surface tensiometry. Both of these fluorocarbon‐terminated Pluronics can self‐assemble into spherical MCMs with Janus‐core in aqueous solution, as evidenced by transmission electron microscopy imaging. Since the lipophilic block (PPO) and fluorophilic segments (F₈) are separated by the hydrophilic blocks (PEO), these fluorocarbon‐terminated Pluronics will loop to give rise to flower‐like MCMs, and the calculations based on thermodynamics and dynamics support the formation of such unique aggregates. A “pre‐self‐assembly” mechanism is proposed to explain the formation process of flower‐like MCMs with Janus‐core prepared by these telechelic fluorocarbon‐terminated triblock copolymers.     

Electrochemical Polymerization of Bis(3,4‐ethylenedioxythiophene)‐Substituted 1,4‐Diketo‐3,6‐diphenyl‐pyrrolo[3,4‐c]pyrrole (DPP) Derivative

Synthesis and electropolymerization of the new bisthienyl‐substituted diketopyrrolopyrrole monomer 1,4‐diketo‐2,5‐di‐hexyl‐3,6‐bis{[2‐(3',4'‐ethylenedi‐oxy)thienyl]phenyl}pyrrolo[3,4‐c]pyrrole (EDOT‐DPP‐EDOT) is reported. EDOT‐DPP‐EDOT exhibits a low oxidation potential of 0.67 V versus ferrocene and can be electropolymerized to form a stable, well adherent polymer thin film at the ITO anode. The polymer film is insoluble in organic solvents, non‐fluorescent, but exhibits reversible electrochromic properties with color changes from deep blue in the neutral state via transparent gray to purple red in the oxidized state. The reversibility in air is excellent.

     

Water‐Induced Transitions from Ellipsoidal Micelles to Chain‐Like Nanostructures Self‐Assembled by the Coil‐Rod‐Coil Block Copolymer Based on Hydrogen‐Bonding Urea Groups

Herein, a novel coil‐rod‐coil triblock copolymer with the coil blocks composed of poly(ethylene glycol) methyl ether and the rigid midterm block alternatively connected with isophorone diisocyanate and isophorone diamine is developed. The triblock copolymer can self‐assemble into ellipsoidal micelles in 1‐methyl‐2‐pyrrolidinone. After the addition of a second coil‐selective solvent (water) to the micellar solutions, these ellipsoidal micelles can further transform into chain‐like nanostructures. The self‐assembly behavior is highly influenced by the additional order of the solvents, which is considerably due to the impacts of the hydrogen‐bonding urea groups and rigid motifs. The transition of the ellipsoidal micelles to chain‐like nanostructures is governed by the water molar fractions. The sizes of the chain‐like nanostructures increase first and then decrease with the growth of the water molar fractions in the mixed solutions.

     

Simultaneous multi‐slice spin‐ and gradient‐echo dynamic susceptibility‐contrast perfusion‐weighted MRI of gliomas

Although combined spin‐ and gradient‐echo (SAGE) dynamic susceptibility‐contrast (DSC) MRI can provide perfusion quantification that is sensitive to both macrovessels and microvessels while correcting for T₁‐shortening effects, spatial coverage is often limited in order to maintain a high temporal resolution for DSC quantification. In this work, we combined a SAGE echo‐planar imaging (EPI) sequence with simultaneous multi‐slice (SMS) excitation and blipped controlled aliasing in parallel imaging (blipped CAIPI) at 3 T to achieve both high temporal resolution and whole brain coverage. Two protocols using this sequence with multi‐band (MB) acceleration factors of 2 and 3 were evaluated in 20 patients with treated gliomas to determine the optimal scan parameters for clinical use. ΔR₂*(t) and ΔR₂(t) curves were derived to calculate dynamic signal‐to‐noise ratio (dSNR), ΔR₂*‐ and ΔR₂‐based relative cerebral blood volume (rCBV), and mean vessel diameter (mVD) for each voxel. The resulting SAGE DSC images acquired using MB acceleration of 3 versus 2 appeared visually similar in terms of image distortion and contrast. The difference in the mean dSNR from normal‐appearing white matter (NAWM) and that in the mean dSNR between NAWM and normal‐appearing gray matter were not statistically significant between the two protocols. ΔR₂*‐ and ΔR₂‐rCBV maps and mVD maps provided unique contrast and spatial heterogeneity within tumors.     

Dimorphic HLA‐B signal peptides differentially influence HLA‐E‐ and natural killer cell‐mediated cytolysis of HIV‐1‐infected target cells

As a mechanism of self‐protection, signal peptides cleaved from human leukocyte antigen (HLA) class I products bind to HLA‐E before the complex interacts with the natural killer (NK) cell receptor CD94/NKG2A to inhibit NK‐mediated cell lysis. Two types of the signal peptides differ in their position 2 (P2) anchor residue, with P2‐methionine (P2‐M) having higher HLA‐E binding affinity than P2‐threonine (P2‐T). All HLA‐A and HLA‐C molecules carry P2‐M, whereas HLA‐B products have either P2‐M or P2‐T. Epidemiological evidence suggests that P2‐M is unfavourable in the context of HIV‐1 infection, being associated with accelerated acquisition of HIV‐1 infection in two African cohorts. To begin elucidating the functional mechanism, we studied NK‐mediated killing of CD4⁺ T cells and monocyte‐derived macrophages infected with two laboratory‐adapted HIV‐1 strains and two transmitted/founder (T/F) viruses. In the presence of target cells derived from individuals with the three HLA‐B P2 genotypes (M/M, M/T and T/T), NK‐mediated cytolysis was elevated consistently for P2‐T in a dose‐dependent manner for all cell and virus combinations tested (P = 0·008–0·03). Treatment of target cells with an anti‐HLA‐E monoclonal antibody restored NK‐mediated cytolysis of cells expressing P2‐M. Observations on cell lysis were also substantiated by measurements of HIV‐1 p24 antigen in the culture supernatants. Overall, our experiments indicate that the anti‐HIV‐1 function mediated by NK cells is compromised by P2‐M, corroborating the association of HLA‐B genotype encoding P2‐M with accelerated HIV‐1 acquisition.