A barrier against reactive oxygen species: chitosan/acellular dermal matrix scaffold enhances stem cell retention and improves cutaneous wound healing.

BACKGROUND: Stem cell therapies have gained great attention for providing novel solutions for treatment of various injuries and diseases due to stem cells' self-renewal, ability to differentiate into various cell types, and favorite paracrine function. Nevertheless, the low retention of transplanted stem cell still limits their clinical applications such as in wound healing in view of an induced harsh microenvironment rich in reactive oxygen species (ROS) during inflammatory reactions. METHODS: Herein, a novel chitosan/acellular dermal matrix (CHS/ADM) stem cell delivery system is developed, which is of great ROS scavenging activity and significantly attenuates inflammatory response. RESULT: Under ROS microenvironment, this stem cell delivery system acts as a barrier, effectively scavenging an amount of ROS and protecting mesenchymal stem cells (MSCs) from the oxidative stress. It notably regulates intracellular ROS level in MSCs and reduces ROS-induced cellular death. Most importantly, such MSCs delivery system significantly enhances in vivo transplanted stem cell retention, promotes the vessel growth, and accelerates wound healing. CONCLUSIONS: This novel delivery system, which overcomes the limitations of conventional plain collagen-based delivery system in lacking of ROS-environmental responsive mechanisms, demonstrates a great potential use in stem cell therapies in wound healing.

Evaluation of the effect of Tb(IV)-NR complex on herring sperm DNA genetic information by mean of spectroscopic.

The interaction between Tb(IV)-NR complex and herring sperm DNA in buffer solution of Tris-HCl was investigated with the use of acridine orange(AO) as a spectral probe. The binding modes and other information were provided by the UV-spectrophotometry and fluorescence spectroscopy. The thermodynamic functions expressed that the binding constants of Tb(IV)-NR complex with DNA was Kθ298.15K = 4.03 × 105 L·mol-1, Kθ310.15K =1.30 × 107 L·mol-1, and the ΔrGθ m 298.15 K＝-3.20 × 104 J·mol-1. The scatchard equation suggested that the interaction mode between Tb(IV)-NR complex and herring sperm DNA is electrostatic and weak intercalation bindings. FTIR spectroscopy results also indicate that there is a specific interaction between the Tb(IV)-NR complex and the A and G bases of DNA.

Visible and infrared three-wavelength modulated multi-directional actuators.

In recent years, light-guided robotic soft actuators have attracted intense scientific attention and rapidly developed, although it still remains challenging to precisely and reversibly modulate the moving directions and shape morphing modes of soft actuators with ease of stimulating operation. Here we report a strategy of building a multi-stimuli-responsive liquid crystal elastomer soft actuator system capable of performing not only multi-directional movement, but also different shape morphing modes. This strategy is based on the selective stimulation of specific domains of the hierarchical structured actuator through the modulation of three wavelength bands (520, 808, 980 nm) of light stimulus, which release the actuation system from light scanning position/direction restriction. Three near-infrared dual-wavelength modulated actuators and one visible/infrared tri-wavelength modulated multi-directional walker robot are demonstrated in this work. These devices have broad application prospects in robotic and biomimetic technology.

Interpenetrating Liquid-Crystal Polyurethane/Polyacrylate Elastomer with Ultrastrong Mechanical Property.

Liquid-crystal elastomer (LCE) materials, which have been developed and investigated for 4 decades, still lack real industrial applications. The fundamental obstacle is the modest force of LCEs generated in the LC-to-isotropic phase transition process, which is the most important actuation moment. Here, we report an interpenetrating liquid-crystal polyurethane/polyacrylate elastomer material, consisting of one main-chain polyurethane LCE and another liquid-crystal polyacrylate thermoset network, which are simultaneously polymerized. This two-way shape memory material can reversibly shrink/expand under thermal stimulus and show ultrastrong actuation-mechanics properties. With a maximum shrinkage ratio of 86% at 140 °C, which is beyond the LC-to-isotropic phase transition, its actuation blocking stress, actuation work capacity, breaking strength, and elastic modulus reach 2.53 MPa, 1267.7 kJ/m3, 7.9 MPa, and 10.4 MPa, respectively. Such LCE material can lift up a load 30 000 times heavier than its own weight. We hope the outstanding mechanical properties of this interpenetrating polymer network-LCE material would pave the way for real industrial utilizations of LCE-based soft actuators.

Acidic pH and High-H2O2 Dual Tumor Microenvironment-Responsive Nanocatalytic Graphene Oxide for Cancer Selective Therapy and Recognition.

It is well known that tumors have an acidic pH microenvironment and contain a high content of hydrogen peroxide (H2O2). These features of the tumor microenvironment may provide physiochemical conditions that are suitable for selective tumor therapy and recognition. Here, for the first time, we demonstrate that a type of graphene oxide nanoparticle (N-GO) can exhibit peroxidase-like activities (i.e., can increase the levels of reactive oxygen species (ROS)) under acidic conditions and catalyze the conversion of H2O2 to ROS-hydroxyl radicals (HO·) in the acidic microenvironment in Hela tumors. The concentrated and highly toxic HO· can then trigger necrosis of tumor cells. In the microenvironment of normal tissues, which has a neutral pH and low levels of H2O2, N-GOs exhibit catalase-like activity (scavenge ROS) that splits H2O2 into O2 and water (H2O), leaving normal cells unharmed. In the recognition of tumors, an inherent redox characteristic of dopamine is that it oxidizes to form dopamine-quinine under neutral (pH 7.4) conditions, quenching the fluorescence of N-GOs; however, this characteristic has no effect on the fluorescence of N-GOs in an acidic (pH 6.0) medium. This pH-controlled response provides an active targeting strategy for the diagnostic recognition of tumor cells. Our current work demonstrates that nanocatalytic N-GOs in an acidic and high-H2O2 tumor microenvironment can provide novel benefits that can reduce drug resistance, minimize side effects on normal tissues, improve antitumor efficacy, and offer good biocompatibility for tumor selective therapeutics and specific recognition.

High-performance double ion-buffering reservoirs of asymmetric supercapacitors based on flower-like Co3O4-G>N-PEGm microspheres and 3D rGO-CNT>N-PEGm aerogels.

Novel 3D flower-like Co3O4-G>N-PEGm composites have been synthesized by employing a solvothermal method, in which the incorporating graphene nanosheets are modified with methoxypolyethylene glycol (mPEG) via nitrene chemistry to form 2D macromolecular brushes. In Co3O4-G>N-PEGm, the flower-like Co3O4 microspheres can anchor on the G>N-PEGm nanosheets, corresponding to the coordination bonds between the lone pair of electrons on the mPEG polymer chains of the G>N-PEGm macromolecular brushes and cobalt ions. Owing to the novel structure, a high specific capacitance value of 1625.6 F g-1 at a current density of 0.5 A g-1 can be achieved in KOH solution. Meanwhile, 3D rGO-CNT>N-PEGm aerogels (GCA), as the negative electrode of electrical double-layer capacitor materials, exhibit a high reversible specific capacitance of 313.8 F g-1 at a current density of 2 A g-1. Based on the high electrochemical performance of both electrode materials, the double ion-buffering reservoirs of asymmetric supercapacitors configured with the Co3O4-G>N-PEGm as the positive electrode and 3D GCA as the negative electrode can deliver a high energy density of 34.4 W h kg-1 at a power density of 400 kW kg-1.

Thienoisoindigo-Based Polymers Bearing Diethynylbenzene and Diethynylanthracene Units for Thin Film Transistors and Solar Cells.

Two thienoisoindigo-based donor-acceptor conjugated polymers were synthesized via Sonogashira coupling reaction with 1,4-diethynylbenzene (P(TII-BEN)) and 9,10-diethynylanthracene (P(TII-ANT)) as donor units, respectively. The optical and electrochemical properties of the polymers were also investigated. The highest hole mobility were 4.38 × 10-3 cm2 V-1 s-1 for P(TII-BEN) and 9.40 × 10-3 cm2 V-1 s-1 for P(TII-ANT) in bottom-gated/top-contact field-effect transistors. The bulk heterojunction organic solar cells consisting of the polymers and PC71BM yielded power conversion efficiencies of 1.59% for P(TII-BEN) and 1.90% for P(TII-ANT). Moreover, the microstructures were investigated by X-ray diffraction and atomic force microscopy.

Thiol-ene photoimmobilization of chymotrypsin on polysiloxane gels for enzymatic peptide synthesis.

Chemical incorporation of enzymes onto polymeric materials has recently attracted intense scientific attention. Cross-linked polysiloxane gels as a typical super-hydrophobic support, are a good candidate for supporting enzymes in low-water organic medium to efficiently catalyze peptide synthesis because the hydrophobic polysiloxane matrix can prevent water from attacking the acyl-enzyme intermediate, which is beneficial for the shift in equilibrium to peptide formation. In this work, we develop a facile strategy to photoimmobilize olefin-functionalized chymotrypsin onto cross-linked polysiloxane gels via UV-initiated thiol-ene click chemistry. The impacts of water addition amount, heat-treatment and recyclability of the immobilized chymotrypsin influencing the peptide synthesis efficiency are investigated. Compared with the native chymotrypsin, polysiloxane-immobilized chymotrypsin showed advantageous catalytic activity, higher thermal stability and superior recyclability.

Near-Infrared Chromophore Functionalized Soft Actuator with Ultrafast Photoresponsive Speed and Superior Mechanical Property.

In this Communication, we develop a two-step acyclic diene metathesis in situ polymerization/cross-linking method to synthesize uniaxially aligned main-chain liquid crystal elastomers with chemically bonded near-infrared absorbing four-alkenyl-tailed croconaine-core cross-linkers. Because of the extraordinary photothermal conversion property, such a soft actuator material can raise its local temperature from 18 to 260 °C in 8 s, and lift up burdens 5600 times heavier than its own weight, under 808 nm near-infrared irradiation.

A homeotropic main-chain tolane-type liquid crystal elastomer film exhibiting high anisotropic thermal conductivity.

The development of pure polymeric films with anisotropic thermal conductivities for electronic device packaging applications has attracted intense scientific attention. In order to enhance the polymeric film's normal-direction thermal conductivity, homeotropic alignment of macromolecular chains is the primary concern. One of the promising preparation strategies is to perform in situ photopolymerization of homeotropic-oriented liquid crystal monomers. In this work, we design and synthesize a novel tolane-core thiol-ene-tailed liquid crystal monomer. Benefitting from the conjugated and extended tolane π-system of the mesogenic core and length extension of the terminal aliphatic tails, the normal-to-plane thermal conductivity value and the thermal conductivity anisotropy value of the corresponding cross-linked main-chain end-on liquid crystal polymer (xMELCP) film reach 3.56 W m-1 K-1 and 15.0, respectively. Compared with the data of a previously reported ester-type thiol-ene xMELCP film, the two primary values of this novel tolane-type thiol-ene xMELCP material are increased dramatically by 46% and 29%, respectively.

Self-assembly of defect-rich graphene oxide nanosheets with Na2Ti3O7 nanowires and their superior absorptive capacity to toxic dyes.

Graphene sheets, a flexible 2D material with excellent absorptive capacity, have great potential as absorbing materials. However, this material has always suffered from irreversible aggregation and thus loses the abundant active sites and large surface area. In this paper, large-scale graphene oxide (GO) sheets were cut and reduced to tiny reduced graphene oxide (RGO) sheets by a cell-break sonicator, for producing numerous defects, which are the center of chemisorption. Furthermore, sodium titanate nanowires functioned as a framework to help to disperse the tiny RGO sheets uniformly. And, in turn, the flexible tiny RGO sheets glued robust nanowires into a free-standing membrane. This novel composite membrane exhibited an ultra-high decoloration efficiency of 99.8% of rhodamine B in a continuous flow mode, and an outstanding absorptive capability of 1.30 × 10-2 mol g-1 correlated to RGO content in batch reaction, which is about two orders of magnitude higher than other reported graphene-based absorbents. In addition, an efficient and feasible method without any heat treatment for regenerating the membrane is illustrated, and the recycled membrane retains superior decoloration efficiency. The excellent absorptive performance indicates the framework-based disperse strategy has great potential for the construction and application of defect-rich graphene.

Self-Host Blue Dendrimer Comprised of Thermally Activated Delayed Fluorescence Core and Bipolar Dendrons for Efficient Solution-Processable Nondoped Electroluminescence.

A self-host thermally activated delayed fluorescence (TADF) dendrimer POCz-DPS for solution-processed nondoped blue organic light-emitting diodes (OLEDs) was designed and synthesized, in which the bipolar phosphine oxide carbazole moiety was introduced by alkyl chain to ensure balanced charge transfer. The investigation of physical properties showed that the bipolar dendrons not only improve the morphological stability but also restrain the concentration quenching effect of the TADF emissive core. The spin-coated OLEDs featuring POCz-DPS as the host-free blue emitter achieved the highest external quantum efficiency (7.3%) and color purity compared with those of doped or nondoped devices based on the parent molecule DMOC-DPS, which indicates that incorporating the merits of encapsulation and bipolar dendron is an effective way to improve the electroluminescent performance of the TADF emitter used for a solution-processed nondoped device.

Single-layer dual-phase nematic elastomer films with bending, accordion-folding, curling and buckling motions.

In this communication, we describe a two-stage temperature-varied photopatterning protocol to synthesize a series of single-layer dual-phase liquid crystalline elastomer films, which have the capabilities to perform versatile three-dimensional motions, such as bending, accordion-folding, wrinkling, curling, and buckling, under thermal stimulus.

Comparison of the Optical and Electrochemical Properties of Bi(perylene diimide)s Linked through Ortho and Bay Positions.

The Ullmann homocoupling of 2-bromo-perylene diimides (PDIs) gave [2,2'-biperylene]-3,4:9,10:3',4':9',10'-tetrakis(dicarboximide)s, 2,2'-bi(PDI)s, and the Suzuki coupling of a PDI-2-boronic ester and a 1-bromo-PDI gave a [1,2'-biperylene]-3,4:9,10:3',4':9',10'-tetrakis(dicarboximide), 1,2'-bi(PDI). These were compared with [1,1'-biperylene]-3,4:9,10:3',4':9',10'-tetrakis(dicarboximide)s, 1,1'-bi(PDI)s. Solution absorption spectra suggest that the PDIs in 2,2'-bi(PDI)s are more planar and less strongly coupled than those in 1,1'-bi(PDI)s, which is consistent with density functional theory calculations. 2,2'-Bi(PDI)s are less easily reduced than 1,1'- and 1,2'-bi(PDI)s by ca. 70-90 mV. Bulk heterojunction organic solar cells incorporating a 2,2'-bi(PDI) acceptor behaved similarly to those employing its 1,1'-bi(PDI) analogue.

Constructing a Novel Dendron for a Self-Host Blue Emitter with Thermally Activated Delayed Fluorescence: Solution-Processed Nondoped Organic Light-Emitting Diodes with Bipolar Charge Transfer and Stable Color Purity.

Self-host thermally activated delayed fluorescence (TADF) materials have recently been identified as effective emitters for solution-processed nondoped organic light-emitting diodes (OLEDs). However, except for the carbazole unit, few novel dendrons have been developed to build self-host TADF emitters. This study reports two self-host blue materials, tbCz-SO and poCz-SO, with the same TADF emissive core and different dendrons. The influence of the peripheral dendrons on the photophysical properties and electroluminescent performances of the self-host materials were systematically investigated. The transient fluorescence and electroluminescence spectra indicated that the diphenylphosphoryl carbazole units could effectively encapsulate the emissive core to reduce the concentration quenching effect and to enhance reverse intersystem crossing. By using tbCz-SO and poCz-SO as host-free blue emitters, the performance of the solution-processed nondoped OLED device demonstrated that a more balanced charge transfer from the bipolar dendrons would offer a better current efficiency of 10.5 cd A-1 and stable color purity with Commission Internationale de L'Eclairage units of (0.18, 0.27).

A plant tendril mimic soft actuator with phototunable bending and chiral twisting motion modes.

In nature, plant tendrils can produce two fundamental motion modes, bending and chiral twisting (helical curling) distortions, under the stimuli of sunlight, humidity, wetting or other atmospheric conditions. To date, many artificial plant-like mechanical machines have been developed. Although some previously reported materials could realize bending or chiral twisting through tailoring the samples into various ribbons along different orientations, each single ribbon could execute only one deformation mode. The challenging task is how to endow one individual plant tendril mimic material with two different, fully tunable and reversible motion modes (bending and chiral twisting). Here we show a dual-layer, dual-composition polysiloxane-based liquid crystal soft actuator strategy to synthesize a plant tendril mimic material capable of performing two different three-dimensional reversible transformations (bending versus chiral twisting) through modulation of the wavelength band of light stimuli (ultraviolet versus near-infrared). This material has broad application prospects in biomimetic control devices.

Amphiphilic Diblock Co-polymers Bearing a Cysteine Junction Group: Synthesis, Encapsulation of Inorganic Nanoparticles, and Near-Infrared Photoresponsive Properties.

Encapsulation of inorganic nanoparticles (NPs) in the interfaces of amphiphilic vesicles is a challenging task. The traditional strategy is to use amphiphilic triblock co-polymers, which possess two outer blocks for building the walls and coronas of the vesicles, and one middle NP binding block for localizing NPs at the vesicle interfaces. In this manuscript, we describe the design and synthesis of an amphiphilic diblock co-polymer, that is, PEG-SH-b-PS (PEG=poly(ethylene glycol), PS=polystyrene) bearing a cysteine junction with one free pendant thiol group at the center point between the hydrophilic poly(ethylene glycol) block and the hydrophobic polystyrene block. The amphiphilicity-driven self-assembly in aqueous solution of the pure linear diblock co-polymer PEG-SH-b-PS and the corresponding amphiphilic PEG-SH-b-PS/gold NPs (GNPs) nanocomposites is examined. From TEM observations of the self-assembled samples containing the conjugated GNPs, it can be concluded that most of the GNPs are dispersed at the interfaces of the formed vesicles. In addition, near-infrared (NIR)-absorbing copper monosulfide (CuS) NPs are also encapsulated into the PEG-SH-b-PS vesicles. Due to the photothermal heating effect of the CuS NPs, the corresponding PEG-SH-b-PS/CuSNPs vesicles can disassemble and release the embedded cargos under NIR illumination, which endows this nanocomposite material with potential in biomedical applications, such as cancer imaging, photothermal therapy, and drug delivery.

Generation of liquid crystallinity from a Td-symmetry central unit.

A series of new columnar liquid crystals containing an adamantane central unit with its four bridgehead positions partially or fully decorated with different numbers (1-4) of 3,4,5-tris(dodecyloxy)phenyl carbamoyl groups were designed and investigated carefully to explore the structure-property correlations. The molecular structures and mesomorphic properties of the DLCs were characterized by (1)H-NMR, (13)C-NMR, IR, UV-vis, POM, DSC and XRD. It was found that the mesophase symmetry and thermal stability were extremely dependent on the structures of the adamantane derivatives. No mesophase was observed for the 1-adamantanecarboxylic acid derivative ADLC1, while two different mesophases were observed for ADLC2, a 1,3-disubstituted derivative functionalized with two 3,4,5-tris(dodecyloxy)phenyl carbamoyl groups at two symmetric bridgehead positions. At lower temperature ADLC2 exhibited a rectangular columnar phase, which switched to a square columnar phase possessing a wide temperature range. Similarly, a hexagonal columnar mesophase was observed for the bridgehead trisubstituted adamantane molecule ADLC3. Interestingly, the fully bridgehead-functionalized 1,3,5,7-tetrasubstituted adamantane compound ADLC4 completely lost liquid crystallinity.

Homeotropically-aligned main-chain and side-on liquid crystalline elastomer films with high anisotropic thermal conductivities.

Homeotropically-aligned main-chain and side-on liquid crystalline elastomer films are prepared by using LC thiol-ene and acrylate systems respectively. Evaluated by laser flash analysis, the room temperature thermal conductivities of these two LCP films in the film normal direction are both dramatically higher than those along the horizontal direction.

A calamitic mesogenic near-infrared absorbing croconaine dye/liquid crystalline elastomer composite.

In this work, we report the first example of a calamitic mesogenic near-infrared (NIR) absorbing organic dye, made by functionalizing a thiophene-croconaine chromophore rigid core with two symmetric long flexible alkyl chains. The liquid crystal (LC) NIR dye YHD796 exhibits a sharp and intense NIR absorption band with a maximum absorption peak at 796 nm. Taking advantage of the improved solubility of YHD796 dispersed in mesogenic molecules, a homogeneously-aligned mono-domain liquid crystalline elastomer (LCE)/YHD796 composite film is successfully prepared by applying the classical LC-cell-alignment method and in situ photo-polymerization of photocurable LC monomer mixtures. This LCE/YHD796 composite film performs a fully reversible contraction/expansion response towards NIR light stimulus due to the photo-thermal heating effect induced by the YHD796 dye well-dispersed in the LCE matrix.