[Effect of various storage methods on shear bond strength of enamel of bovine teeth].

PURPOSE：The purpose of this study was to evaluate the effect of various storage methods on shear bond strength of enamel of bovine teeth and find the storage condition that could preserve the similar bond strength as the freshly extracted teeth. METHODS: One hundred and thirty freshly extracted bovine teeth were divided into 13 groups. One was the reference group and 12 were the experimental group. Each group contained 10 teeth. Teeth in the reference group were operated on the same day as the teeth were extracted, while teeth in the experimental groups were stored in different methods (4% formaldehyde solution at 4 ℃, 23 ℃, 1% chloramine T at 4 ℃, 23 ℃, distilled water at 4 ℃, 23 ℃). After stored for 30 days and 90 days, the bovine teeth were taken out and then the shear bond strength was tested. The data were analyzed with SPSS 20.0 software package. RESULTS: The bovine teeth stored in 4% formaldehyde and 1% chloramine T at 23 ℃ and in distilled water at 4 ℃ achieved similar bond strength as freshly extracted teeth at 30 days and 90 days, and the bond strength did not change over time. The bovine teeth stored in 4% formaldehyde solution and 1% chloramine T at 4 ℃ at 30 days had higher shear bond strength than freshly extracted bovine teeth, but over time the bond strength reduced and reached the similar level at 90 days. The bovine teeth stored in distilled water at 23 ℃ obtained similar bond strength as freshly extracted teeth at 30 days but over time the bond strength reduced until 90 days. CONCLUSIONS: Bovine teeth stored in 4% formaldehyde solution and 1% chloramine T at 23 ℃ and in distilled water at 4 ℃ achieved similar bond strength as freshly extracted teeth and does not change over time. These three methods are recommended for storing bovine teeth.

Development of alginate-based hydrogels: Crosslinking strategies and biomedical applications.

Natural polysaccharide-based hydrogels have drawn much concern in the biomedical fields. Among them, alginate, a natural polyanionic polysaccharide, has become one of the research hotspots, because of its abundant source, biodegradability, biocompatibility, solubility, modification flexibility, and other characteristics or physiological functions. Recently, through adopting various physical or chemical crosslinking strategies, selecting suitable crosslinking or modification reagents, precisely controlling the reaction conditions, or introducing organic or inorganic functional materials, a variety of alginate-based hydrogels with excellent performance have been continuously developed, considerably expanding the breadth and depth of their applications. Here, various crosslinking strategies in the preparation of alginate-based hydrogels are comprehensively introduced. The representative application progress of alginate-based hydrogels in drug carrier, wound dressing and tissue engineering is also summarized. Meanwhile, the application prospects, challenges and development trends of alginate-based hydrogels are discussed. It is expected to provide guidance and reference for the further development of alginate-based hydrogels.

An overview of the direct and indirect effects of acid rain on plants: Relationships among acid rain, soil, microorganisms, and plants.

Acid rain (AR) causes numerous environmental problems and complex negative effects on plants globally. Many studies have previously reported on direct effects of AR or its depositional substances on plant injury and performance. However, few studies have addressed the indirect effects of AR on plants as mediated by soil microorganisms and the abiotic environment of the soil rhizosphere. The indirect effects (e.g., AR â†’ soil microorganisms→plants) need greater attention, because acidic deposition not only affects the distribution, composition, abundance, function, and activity of plant-associated microorganisms, but also influences the dynamics of some substances in the soil in a way that may be harmful to plants. Therefore, this review not only focused on the direct effects of AR on plant performance, growth, and biomass allocations from a whole-plant perspective, but also addressed the pathway of AR-soil chemical characteristics-plants, which explains how soil solute leaching and acidification by AR will reduce the availability of essential nutrients and increase the availability of heavy metals for plants, affecting carbon and nitrogen cycles. Mainly, we evaluated the AR-soil microorganisms-plants pathway by: 1) synthesizing the potential roles of soil microbes in alleviating soil acidic stress on plants and the adverse effects of AR on plant-associated soil microorganisms; 2) exploring how plant mycorrhizal types affect the detection of AR effect on plants. The meta-analysis showed that the effects of AR-induced pH on leaf chlorophyll content, plant height, and plant root biomass were dependent on plant mycorrhizal types. Some possible reasons for different synergy between mycorrhizal symbiotic types and plants were discussed. Future research relating to the effects of AR on plants should focus on the combined direct and indirect effects to evaluate how AR affects plant performance comprehensively.

From crosslinking strategies to biomedical applications of hyaluronic acid-based hydrogels: A review.

Hyaluronic acid (HA) is not only a natural anionic polysaccharide with excellent biocompatibility, biodegradability, and moisturizing effect, but also an essential factor that can affect angiogenesis, inflammation, cell behavior, which has a wide range of applications in the biomedical field. Among them, HA-based hydrogels formed by various physical or chemical crosslinking strategies are particularly striking. They not only retain the physiological function of HA, but also have the skeleton function of hydrogel, which further expands the application of HA. However, HA-based natural hydrogels generally have problems such as insufficient mechanical strength and susceptibility to degradation by hyaluronidase, which limits their application to a certain extent. To solve such problems, researchers have prepared a variety of HA-based multifunctional hydrogels with remarkable properties in recent years by adopting various structural modification methods or novel crosslinking strategies, as well as introducing functionally reactive molecules or moieties, which have extended the application scope. This manuscript systematically introduced common crosslinking strategies of HA-based hydrogels and highlighted the development of novel HA-based hydrogels in anticancer drug delivery, cartilage repair, three-dimensional cell culture, skin dressing and other fields. We hope to provide some references for the subsequent development of HA-based hydrogels in the biomedical field.

Efficient preparation of polyoxometalate-junctional cross-linking hybrid nanocomposites by polymerization-induced self-assembly.

We reported a facile method for the preparation of POM-polymer hybrids in one-pot via polymerization-induced self-assembly. Polyoxometalate macroanions were complexed with cations to prepare cross-linking agents. RAFT dispersion polymerization was conducted in the presence of the cross-linking agent. The hybrid nanoparticles can be used as nanoreactors for the photocatalytic synthesis of Au nanoparticles.

[Construction of tissue engineered cell sheet].

Scaffold-free tissue engineered cell sheet is an emerging technology in biomedical field. It can avoid the adverse effects of scaffold materials, and can be further assembled to form more complex three-dimensional functional tissues. The construction of cell sheet is mainly based on the culture substrate composed of sensitive materials. By changing the stimulation factors such as temperature, enzyme, light, ion, redox, pH and sugar, the adhesion behavior of the substrate to the cells could be changed to make the cells detach naturally, thus generating the cell sheet. Recent years have seen the development of various simple and efficient construction technologies of cell sheet due to the development of a variety of novel sensitive culture substrates. The resulted cell sheets with excellent performance have greatly expanded their applications. This review summarized the construction methods of tissue engineered cell sheet and discussed the challenges and future perspectives in this field.

Development, Preparation, and Biomedical Applications of DNA-Based Hydrogels.

Hydrogels have outstanding research and application prospects in the biomedical field. Among them, the design and preparation of biomedical hydrogels with deoxyribonucleic acid (DNA) as building blocks have attracted increasing research interest. DNA-based hydrogel not only has the skeleton function of hydrogel, but also retains its biological functions, including its excellent selection specificity, structural designability, precise molecular recognition ability, outstanding biocompatibility, and so on. It has shown important application prospects in the biomedical field, such as drug delivery, biosensing, and tissue engineering. In recent years, researchers have made full use of the characteristics of DNA molecules and constructed various pure DNA-based hydrogels with excellent properties through various crosslinking methods. Moreover, via introducing functional molecules or elements, or combining with other functional materials, a variety of multifunctional DNA-based hybrid hydrogels have also been constructed, which expand the breadth and depth of their applications. Here, we described the recent development trend in the area of DNA-based hydrogels and highlighted various preparation methods of DNA-based hydrogels. Representative biomedical applications are also exemplified to show the high performance of DNA-based hydrogels. Meanwhile, the existing problems and prospects are also summarized. This review provided references for the further development of DNA-based hydrogels.

Cotton stalk-derived hydrothermal carbon for methylene blue dye removal: investigation of the raw material plant tissues.

Conversion of the abundant agricultural residual cotton stalk (CS) into useful chemicals or functional materials could alleviate the fossil fuels caused energy shortages and environmental crises. Although some advances have been achieved, less attention has been paid to the plant tissues effect. In this study, the plant tissue of CS was changed by part degradation of some components (hemicelluloses and lignin, for example) with the aid of acid/base (or both). The pretreated CS was transformed into hydrochar by hydrothermal carbonization (HTC) method. Morphological and chemical compositions of CS hydrochar were analyzed by various techniques, including elemental analysis, Fourier transform infrared (FTIR), BET analysis, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Methylene blue (MB) removal of prepared CS hydrochar was used to evaluate CS hydrochar pollutions adsorption capacity. Results reveal acid/base (or both) pretreatment is beneficial for CS raw material to prepare high-quality CS hydrochar. The effects of some parameters, such as initial MB concentration, temperature, pH value and recyclability on the adsorption of MB onto both acid and base-pretreated CS hydrochar (CS-H2SO4 + NaOH-HTC) were studied. The present work exhibits the importance of agricultural waste biomass material plant tissues on its derived materials, which will have a positive effect on the direct utilization of waste biomass.

Modulation of thermodynamic and kinetic inverted phase behavior of block copolymers by inorganic polyoxometalates.

The Keggin polyoxometalates (POM) H3PW12O40 (PW) electrostatically complexed with poly(styrene-block-2-vinyl pyridine) (PS-b-P2VP) in DMF, and ordered microphase separation occurred through solvent evaporation. The phase behaviors of PS-b-P2VP/PW in bulk were systematically investigated by using SAXS and TEM to discover the effect of POM content and molecular weight of the block copolymers. Computational simulation was also performed to reveal the same phase transition sequence as the experimental results. As the POM content increases, the PS-b-P2VP/PW complex with a low molecular weight changed from lamellar phase (LAM) to hexagonal cylindrical phase (HEX), and finally transited into spherical phase (SPH). Unexpectedly, PS-b-P2VP/PW complexes with a high molecular weight were inclined to form a kinetic-trapped intermediate phase (inverted HEX). The mechanism of formation of inverted phases was proposed based on simulation that asymmetric swelling in the concentrated DMF solution would result in the ultimate kinetic-trapped nanostructure in the bulk.

Co-inhibition of BET proteins and PD-L1 as a potential therapy for OSCC through synergistic inhibition of FOXM1 and PD-L1 expressions.

BACKGROUND: Bromodomain and extra-terminal domain (BET) proteins are important epigenetic regulators that facilitate the transcription of genes in chromatin areas linked to acetylated histones. JQ1, a BET inhibitor (BETi), has anti-proliferative and apoptosis activity against many cancers including oral squamous cell carcinoma (OSCC). In this research, we investigated the mechanism underlying the effects of JQ1 in OSCC and investigated strategies to increase its therapeutic potential. METHODS: The OSCC Cal27 and SCC25 cell lines were used for in vitro experiments. Cells were treated with JQ1 and/or siRNA targeting PD-L1 (siPD-L1), and cell viability, apoptosis, and cell cycle were evaluated by cell proliferation assay, colony formation assay, apoptosis, and cell cycle analysis. Levels of cleaved caspase-3, p53, BRD4, PD-L1, and FOXM1 were determined by quantitative real-time PCR and Western blot. The effects of single inhibitor or combination inhibitor treatment on tumors derived from Cal27 cells in mice were monitored. RESULTS: FOXM1 and PD-L1 were downregulated by JQ-1 in a dose-dependent manner. Combined JQ1 and siPD-L1 treatment synergistically inhibited cell growth and induced apoptosis and cell cycle arrest in vitro and synergistically inhibited tumor growth in vivo compared with single treatments. The combination treatment also synergistically suppressed FOXM1 and PD-L1 signaling pathways in OSCC cells. CONCLUSION: Our research suggests that FOXM1 and PD-L1 are targets of BETi in OSCC cells and indicate that combining PD-L1 blockade with BETi may be a useful therapeutic approach in OSCC through further suppressing FOXM1 and PD-L1.

Enantiomer-selective magnetization of conglomerates for quantitative chiral separation.

Selective crystallization represents one of the most economical and convenient methods to provide large-scale optically pure chiral compounds. Although significant development has been achieved since Pasteur's separation of sodium ammonium tartrate in 1848, this method is still fundamentally low efficient (low transformation ratio or high labor). Herein, we describe an enantiomer-selective-magnetization strategy for quantitatively separating the crystals of conglomerates by using a kind of magnetic nano-splitters. These nano-splitters would be selectively wrapped into the S-crystals, leading to the formation of the crystals with different physical properties from that of R-crystals. As a result of efficient separation under magnetic field, high purity chiral compounds (99.2 ee% for R-crystals, 95.0 ee% for S-crystals) can be obtained in a simple one-step crystallization process with a high separation yield (95.1%). Moreover, the nano-splitters show expandability and excellent recyclability. We foresee their great potential in developing chiral separation methods used on different scales.

Guest Controlled Pillar[5]arene and Polyoxometalate Based Two-Dimensional Nanostructures toward Reversible Iodine Capture.

The two-dimensional (2D) nanostructures comprised of polyoxometalate based building blocks are of great value in nanoarchitectures, which have unique properties and widespread potential applications, but it is still challenging in mature preparation. Herein a new strategy to build Cr(III) centered Anderson type polyoxometalate 2D nanostructures based on the modulation of host-guest interaction between cationic pillar[5]arenes and sodium dodecyl sulfonate (SDS) in aqueous media was exploited in this work. Through regulating stoichiometry of SDS, the morphology of assemblies vary from nanobones to 2D nanosheets. The fine assembled structure was discovered by combined 1H NMR, SAXS, and element analyses. The nanomaterials can be used as adsorbents for I2 in various solutions, including n-hexane, cyclohexane, water, and chloroform, where the polyoxometalates play a key role in the effective adsorption of iodine since they can expand the interspace between pillar[5]arenes in the as-prepared nanostructure. Furthermore, such adsorbents are easily regenerated and reused as iodine can be released spontaneously from nanobones@I2 and nanosheets@I2 solids when being immersed in dimethyl sulfoxide.

Surface plasmon resonance-assisted circularly polarized luminescent hybrid assemblies of Eu-containing polyoxometalates.

The circular dichroism and circularly polarized luminescence of achiral inorganic Eu-containing clusters in an electrostatically coassembled supramolecular assembly were induced by a cationic chiral copolymer with the help of an enhanced electromagnetic field generated by Ag nanoparticles.

Induced Circular Dichroism of Isotactic Poly(2-vinylpyridine) with Diverse and Tunable "Sergeants-and-Soldiers" Type Chiral Amplification.

Facile and efficient construction of the helical structure with diverse and tunable chiral amplification from an achiral polymer is attractive but remains a challenge to develop multiple functional materials. We report herein a macromolecular acid-base complex of highly isotactic poly(2-vinylpyridine) (mmmm > 99%), (+)-camphorsulfonic acid, and dodecylbenzensulfonic acid. The asymmetric induction of the chiral additive through the ionic interactions between pyridinium pendants and acid ions drives the polymer backbone to twist in a preferred direction in CHCl3 and its mixture with CH3CN. The sign and intensity of induced circular dichroism rely on the base to acid ratio, the chiral acid content, and the solvent nature. By systematically tuning the solvent composition, four distinct types of "sergeants-and-soldiers" mode chiral amplification are achieved for the first time within a single system owing to the solvent dependent bias of chiral-chiral and chiral-achiral ion pairs.

A Supramolecular Catalyst Self-Assembled From Polyoxometalates and Cationic Pillar[5]arenes for the Room Temperature Oxidation of Aldehydes.

Oxidizing aldehydes to generate carboxylic acids is a crucial reaction in nature and in chemical industry. The aldehyde oxidation, an easily achieved process in liver cells, is inert toward autoxidation in industrial production and difficultly achieved under enzymatic condition (in water, at pH 7, at room temperature). Herein, we prepared a supramolecular catalyst which are nanospheres assembled in aqueous media by chromium centered Anderson polyoxometalates Na3[CrMo6O18(OH)3] (namely, CrMo6) and cationic pillar[5]arenes (namely, P5A) with 10 positive charges which can be used as the phase transfer catalysts (PTCs). This supramolecular catalyst was exploited on aldehydes oxidation under enzymatic condition with relatively good conversion. Through DLS monitoring, the diameters of nanospheres were variable while changing the charge ratios of the ionic complexes (P5A-CrMo6), and it is probably because of the closer charge ratios causing the more compact assemblies. Also, the nano-morphologies were monitored by TEM and SEM, and the nanostructures were characterized by zeta potential, the X-ray energy-dispersive spectroscopy (EDS), elemental analysis.

Piezoresistive temperature sensors fabricated by a surface micromachining CMOS MEMS process.

This paper presents a micromachined monocrystalline silicon piezoresistive temperature sensor fabricated by a surface micromachining CMOS (Complementary Metal Oxide Semiconductor) MEMS (Micro-Electro-Mechanical System) process. The design of the temperature sensor is based on the structure of the multi-layer cantilever beam and the bimetallic effect. The temperature change of the cantilever beam is translated into the change of the piezoresistance's value. The test results show that the sensitivities of the sensors are 27.9 mV/°C with 100 Ω/▯ piezoresistance between -40 °C to 60 °C and 7.4 mV/°C with 400 Ω/▯ piezoresistance between -90 °C to 60 °C. The temperature sensor proposed in this paper can be used in radiosondes for its low operating temperature (as low as -90 °C), small size (below 1 mm2) and low heat capacity.

Morphology Evolution of Stimuli-Responsive Triblock Copolymer Modulated by Polyoxometalates.

Polyoxometalate (POM) H3PMo12O40 was coassembled with stimuli-responsive triblock copolymer poly(ethylene oxide)- block-polystyrene- block-poly(2-(dimethylamino)ethyl methacrylate) (PEO- b-PS- b-PDMAEMA) by electrostatic interactions. Depending on the POM contents, the hybrid complexes can self-assemble into a series of morphologies: micelles, rods, toroids, and vesicles. Unlike traditional morphology transition of amphiphilic block copolymer derived from a broad range of hydrophobic volume fractions, POM-induced morphology transitions just occurred in a narrow range of volume fractions. The length of rod micelles exponentially decreased with solvent compositions (tetrahydrofuran/H2O). The hybrid assemblies showed acid-base responsibility due to the PDMAEMA block. Rod micelles could further assemble and disassemble reversibly upon adding acid/base. Fluorescent polyoxometalate Na9EuW10O36 was also complexed with PEO- b-PS- b-PDMAEMA to prepare fluorescent vesicles. The vesicles showed off-on switchable fluorescence behavior accompanied with reversible vesicle-to-micelle transformation in response to pH stimuli.

Comparative experiments of fibril formation from whey protein concentrate with homogeneous and secondary nuclei.

Two types of special structures, homogeneous and secondary nuclei, form during fibril formation. The structural and functional properties of amyloid fibrils in whey protein concentrate (WPC) with different ratios of added homogeneous nuclei to secondary nuclei were investigated. Thioflavin T fluorescence analysis and kinetic equations indicated that two types of nuclei could accelerate WPC fibrillation compared with WPC self-assembling into amyloid fibrils, thereby reducing the lag time and increasing the number of fibrils. However, there were considerable differences in the nucleation-inducing capability of WPC fibrillation between homogeneous and secondary nuclei. The number of fibrils formed by adding homogeneous nuclei was higher than that obtained with secondary nuclei, the increase in the Th T fluorescence intensity induced by homogeneous nuclei was 1.83-fold much than secondary nuclei. Meanwhile, secondary nuclei yielded a 2.71-fold faster aggregation rate of WPC than homogeneous nuclei, particularly during the first hour of thermal treatment (protein mass ratio of nuclei to WPC 1:1). The gelation time of WPC after secondary nuclei addition was shorter, from 10 h (WPC (2.0/6.5)) to 4 h (WPC + HN) to 2 h (WPC + SN); however, the gel microstructure of WPC after the addition of homogeneous nuclei was denser, yielding a preferred water holding capacity.

Dual electrical switching permeability of vesicles via redox-responsive self-assembly of amphiphilic block copolymers and polyoxometalates.

Electro-responsive vesicles were demonstrated based on an amphiphilic block copolymer PEO114-b-P(DCH-Ru)n and an inorganic nanoparticle polyoxometalate H3PMo12O40 (PMo12) via electrostatic interactions. After undergoing electrochemical reactions, vesicle membranes allow the migration of electrolyte ions and release of loaded cargos.

The structure and amphipathy characteristics of modified γ-zeins by SDS or alkali in conjunction with heating treatment.

γ-Zein was modified by SDS or alkali combined with heating treatments in water and in 70% ethanol to change its amphipathic properties and explore the relationship between amphipathic characteristic and structure. γ-Zein water-dispersibility was dramatically increased via alkali or SDS combined with heating treatments, but their ethanol-dispersibilities were significantly different during ethanol evaporation. High both water-dispersibility and ethanol-dispersibility were found from alkali modified γ-zein while high water-dispersibility but low ethanol-dispersibility were obtained from SDS modified γ-zein, indicating that alkali modified γ-zein had better amphipathic characteristic compared with SDS modified γ-zein. Alkali modified γ-zein with higher amphipathic characteristic possessed higher structural inversion ability since it was easy to recover its native state as solvent changing from water to ethanol, contrary to SDS modified γ-zeins whose amphipathic characteristic was not improved. Moreover, the higher structural inversion ability of alkali modified γ-zein depended on the recovery capability of α-helix structure as solvent altering.