Soft mechanical metamaterials with unusual swelling behavior and tunable stress-strain curves

Soft adaptable materials that change their shapes, volumes, and properties in response to changes under ambient conditions have important applications in tissue engineering, soft robotics, biosensing, and flexible displays. Upon water absorption, most existing soft materials, such as hydrogels, show a positive volume change, corresponding to a positive swelling. By contrast, the negative swelling represents a relatively unusual phenomenon that does not exist in most natural materials. The development of material systems capable of large or anisotropic negative swelling remains a challenge. We combine analytic modeling, finite element analyses, and experiments to design a type of soft mechanical metamaterials that can achieve large effective negative swelling ratios and tunable stress-strain curves, with desired isotropic/anisotropic features. This material system exploits horseshoe-shaped composite microstructures of hydrogel and passive materials as the building blocks, which extend into a periodic network, following the lattice constructions. The building block structure leverages a sandwiched configuration to convert the hydraulic swelling deformations of hydrogel into bending deformations, thereby resulting in an effective shrinkage (up to around -47% linear strain) of the entire network. By introducing spatially heterogeneous designs, we demonstrated a range of unusual, anisotropic swelling responses, including those with expansion in one direction and, simultaneously, shrinkage along the perpendicular direction. The design approach, as validated by experiments, allows the determination of tailored microstructure geometries to yield desired length/area changes. These design concepts expand the capabilities of existing soft materials and hold promising potential for applications in a diverse range of areas.

Ligase IV inhibitor SCR7 enhances gene editing directed by CRISPR-Cas9 and ssODN in human cancer cells

Background

Precise genome editing is essential for both basic and translational research. The recently developed CRISPR/Cas9 system can specifically cleave a designated site of target gene to create a DNA double-strand break, which triggers cellular DNA repair mechanism of either inaccurate non-homologous end joining, or site-specific homologous recombination. Unfortunately, homology-directed repair (HDR) is challenging due to its very low efficiency. Herein, we focused on improving the efficiency of HDR using a combination of CRISPR/Cas9, eGFP, DNA ligase IV inhibitor SCR7, and single-stranded oligodeoxynucleotides (ssODN) in human cancer cells.

Results

When Cas9, gRNA and eGFP were assembled into a co-expression vector, the disruption rate more than doubled following GFP-positive cell sorting in transfected cells compared to those unsorted cells. Using ssODNs as templates, SCR7 treatment increased targeted insertion efficiency threefold in transfected cells compared to those without SCR7 treatment. Moreover, this combinatorial approach greatly improved the efficiency of HDR and targeted gene mutation correction at both the GFP-silent mutation and the β-catenin Ser45 deletion mutation cells.

Conclusion

The data of this study suggests that a combination of co-expression vector, ssODN, and ligase IV inhibitor can markedly improve the CRISPR/Cas9-directed gene editing, which should have significant application in targeted gene editing and genetic disease therapy.

DFT study on the Au(i)-catalyzed cyclization of indole-allenoate: counterion and solvent effects

The base strength was revealed to be the primary factor controlling the catalytic capability of counterions. The image shows the Au(i)-catalyzed cyclization reaction of indole-allenoate to form dihydrocyclopenta[b]indole derivatives, as reported by Ma.

Investigation on Two Compounds of O,O’-dithiophosphate Derivatives as Corrosion Inhibitors for Q235 Steel in Hydrochloric Acid Solution

In this work, the O,O’-dithiophosphate derivatives of S-4-methylbenzyl-O,O’-di(phenyl) dithiophosphate (Inhi-Ph) and S-4-methyl benzyl-O,O’-di(4-bromophenyl) dithiophosphate (Inhi-BrPh) were synthesized and characterized by elemental analysis, FT-IR, 1H, 13C and 31P NMR. Meanwhile, the corrosion inhibition of Q235 steel in HCl solution by synthesized inhibitors was evaluated by weight loss and electrochemical measurements. Measurement results indicate that the two inhibitors of Inhi-Ph and Inhi-BrPh are mixed-type inhibitor, the inhibition efficiency increase with inhibitor concentration increasing, decrease with HCl concentration and temperature increasing. The adsorption of Inhi-Ph and Inhi-BrPh on Q235 steel surface obeys Langmuir isotherm, which belongs to chemical adsorption.

Mechanically-Guided Deterministic Assembly of 3D Mesostructures Assisted by Residual Stresses

Formation of 3D mesostructures in advanced functional materials is of growing interest due to the widespread envisioned applications of devices that exploit 3D architectures. Mechanically guided assembly based on compressive buckling of 2D precursors represents a promising method, with applicability to a diverse set of geometries and materials, including inorganic semiconductors, metals, polymers, and their heterogeneous combinations. This paper introduces ideas that extend the levels of control and the range of 3D layouts that are achievable in this manner. Here, thin, patterned layers with well-defined residual stresses influence the process of 2D to 3D geometric transformation. Systematic studies through combined analytical modeling, numerical simulations, and experimental observations demonstrate the effectiveness of the proposed strategy through ≈20 example cases with a broad range of complex 3D topologies. The results elucidate the ability of these stressed layers to alter the energy landscape associated with the transformation process and, specifically, the energy barriers that separate different stable modes in the final 3D configurations. A demonstration in a mechanically tunable microbalance illustrates the utility of these ideas in a simple structure designed for mass measurement.

Targeted integration of genes in Xenopus tropicalis

With the successful establishment of both targeted gene disruption and integration methods in the true diploid frog Xenopus tropicalis, this excellent vertebrate genetic model now is making a unique contribution to modelling human diseases. Here, we summarize our efforts on establishing homologous recombination-mediated targeted integration in Xenopus tropicalis, the usefulness, and limitation of targeted integration via the homology-independent strategy, and future directions on how to further improve targeted gene integration in Xenopus tropicalis.

Large Positive Thermal Expansion and Small Band Gap in Double-ReO3-Type Compound NaSbF6

Double-ReO₃-type structure compound NaSbF₆ undergoes a low-temperature rhombohedral to high-temperature cubic phase between 303 and 323 K, as revealed by temperature-dependent X-ray diffractions. Although many double-ReO₃-type fluorides exhibit either low thermal expansion or negative thermal expansion (NTE), NaSbF₆ exhibits positive thermal expansion (PTE) with a large volumetric coefficient of thermal expansion, α_v = 62 ppm/K, in its cubic phase. Raman spectroscopy reveals that the low-frequency transverse vibration of fluorine atoms is stiffened in NaSbF₆, compared with the typical NTE compound CaZrF₆ with the same structure. The related weak contraction associated with the polyhedral rocking would be overcome by the notable elongation of the Na-F bond length on heating, thus leading to the large volumetric PTE. Unlike ScF₃ and CaZrF₆ which are insulators with a wide band gap, a relative small band gap of 3.76 eV was observed in NaSbF₆. The small band gap can be attributed to the hybridization between the Sb 5s and F 2p orbitals.

Shear Piezoelectricity in Poly(vinylidenefluoride-co-trifluoroethylene): Full Piezotensor Coefficients by Molecular Modeling, Biaxial Transverse Response, and Use in Suspended Energy-Harvesting Nanostructures

The intrinsic flexible character of polymeric materials causes remarkable strain deformations along directions perpendicular to the applied stress. The biaxial response in the shear piezoelectricity of polyvinylidenefluoride copolymers is analyzed and their full piezoelectric tensors are provided. The microscopic shear is exploited in single suspended nanowires bent by localized loading to couple flexural deformation and transverse piezoelectric response.

A comprehensive investigation on adsorption of Ca (II), Cr (III) and Mg (II) ions by 3D porous nickel films

The present study reports the removal of Ca (II), Cr (III), Mg (II) ions from aqueous solution using 3D-porous nickel films (3DNFs) as a novel adsorbent material prepared by hydrogen bubble dynamic template (HBDT) method at room temperature. The structure morphology and the phase constitution of 3DNFs were characterized by FESEM, EDS and XRD. Adsorption process of Ca (II), Cr (III), Mg (II) ions was fast as the equilibrium was established within 30min, and the maximum adsorption at equilibrium was 44.1mg/g, 46.4mg/g and 32.7mg/g, respectively. The adsorption kinetics well fitted using a pseudo second-order kinetic model. The adsorption isotherm data of all the three metals fit well the Langmuir and Freundlich adsorption isotherm model. It was found out that kinetics of adsorption varies with initial concentration of metal ions. Thermodynamic parameters (i.e., the standard Gibbs free energies (ΔG), enthalpy change (ΔH), standard entropy change (ΔS)) were also evaluated. Thermodynamic analysis indicated that a high temperature is favored for the adsorption of metal ions by 3DNFs. These results suggest that 3DNFs have good potential application in effective adsorption of metal ions with satisfactory results.

Epidermal devices for noninvasive, precise, and continuous mapping of macrovascular and microvascular blood flow

Continuous monitoring of variations in blood flow is vital in assessing the status of microvascular and macrovascular beds for a wide range of clinical and research scenarios. Although a variety of techniques exist, most require complete immobilization of the subject, thereby limiting their utility to hospital or clinical settings. Those that can be rendered in wearable formats suffer from limited accuracy, motion artifacts, and other shortcomings that follow from an inability to achieve intimate, noninvasive mechanical linkage of sensors with the surface of the skin. We introduce an ultrathin, soft, skin-conforming sensor technology that offers advanced capabilities in continuous and precise blood flow mapping. Systematic work establishes a set of experimental procedures and theoretical models for quantitative measurements and guidelines in design and operation. Experimental studies on human subjects, including validation with measurements performed using state-of-the-art clinical techniques, demonstrate sensitive and accurate assessment of both macrovascular and microvascular flow under a range of physiological conditions. Refined operational modes eliminate long-term drifts and reduce power consumption, thereby providing steps toward the use of this technology for continuous monitoring during daily activities.

Estrogen receptor α gene PvuII polymorphism and coronary artery disease: a meta-analysis of 21 studies

The association between the estrogen receptor α gene (ESR1) PvuII polymorphism (c.454-397T>C) and coronary artery disease (CAD) is controversial. Thus, we conducted a meta-analysis to evaluate the relationship. Data were collected from 21 studies encompassing 9926 CAD patients and 16710 controls. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the relationship between PvuII polymorphism and CAD. The polymorphism in control populations in all studies followed Hardy-Weinberg equilibrium. We found a significant association between ESR1 PvuII polymorphism and CAD risk in all subjects. When the data were stratified by region, a significant association between ESR1 PvuII polymorphism and CAD risk was observed in Asian populations but not in Western populations. The current study suggests that ESR1 PvuII polymorphism has an important role in CAD susceptibility.

Histone methyltransferase Dot1L plays a role in postembryonic development in Xenopus tropicalis

Histone methylations have been implicated to play important roles in diverse cellular processes. Of particular interest is the methylation of histone H3K79, which is catalyzed by an evolutionarily conserved methyltransferase, disruptor of telomeric silencing (Dot1)-like (Dot1L). To investigate the role of Dot1L during vertebrate development, we have generated a Dot1L-specific transcription activator-like effector nuclease (TALEN) nuclease to knockdown endogenous Dot1L in Xenopus tropicalis, a diploid species highly related to the well-known developmental model Xenopus laevis, a pseudotetraploid amphibian. We show that the TALEN was extremely efficient in mutating Dot1L when expressed in fertilized eggs, creating essentially Dot1L knockout embryos with little H3K79 methylation. Importantly, we observed that Dot1L knockdown had no apparent effect on embryogenesis because normally feeding tadpoles were formed, consistent with the lack of maternal Dot1L expression. On the other hand, Dot1L knockdown severely retarded the growth of the tadpoles and led to tadpole lethality prior to metamorphosis. These findings suggest that Dot1L and H3K79 methylation play an important role for tadpole growth and development prior to metamorphosis into a frog. Our findings further reveal interesting similarities and differences between Xenopus and mouse development and suggest the existence of 2 separate phases of vertebrate development with distinct requirements for epigenetic modifications.

Comprehensive assessment of the association of WNK4 polymorphisms with hypertension: evidence from a meta-analysis

The relationship between with-no-lysine [K] kinase 4 (WNK4) gene polymorphisms and hypertension has been widely investigated, However, the studies yielded contradictory results. To evaluate these inconclusive findings comprehensively, we therefore performed a meta-analysis. Ten articles encompassing 16 independent case-control studies with 6089 hypertensive cases and 4881 normotensive controls were selected for this meta-analysis. Four WNK4 gene polymorphisms were identified (G1155942T, G1156666A, T1155547C, and C6749T). The results showed statistically significant associations of G1155942T polymorphism (allelic genetic model: odds ration or OR = 1.62, 95% confidence interval or CI: 1.11–2.38, P = 0.01; dominant model: OR = 1.85, 95% CI: 1.07–3.19, P = 0.03) and C6749T polymorphism (allele contrast: OR = 2.04, 95% CI: 1.60–2.59, P<0.01; dominant model: OR = 2.04, 95%CI: 1.59–2.62, P<0.01; and homozygous model: OR = 5.01, 95% CI: 1.29–19.54, P = 0.02) with hypertension risk. However, neither C1155547T nor G1156666A was associated significantly with hypertension susceptibility. In conclusion, this meta-analysis suggested that WNK4 G1155942T and C6749T gene polymorphisms may contribute to the susceptibility and development of hypertension. Further well-designed studies with larger sample size are required to elucidate the association of WNK4 gene multiple polymorphisms with hypertension risk.

RAG1/2 knockout pigs with severe combined immunodeficiency

Pigs share many physiological, biochemical, and anatomical similarities with humans and have emerged as valuable large animal models for biomedical research. Considering the advantages in immune system resemblance, suitable size, and longevity for clinical practical and monitoring purpose, SCID pigs bearing dysfunctional RAG could serve as important experimental tools for regenerative medicine, allograft and xenograft transplantation, and reconstitution experiments related to the immune system. In this study, we report the generation and phenotypic characterization of RAG1 and RAG2 knockout pigs using transcription activator-like effector nucleases. Porcine fetal fibroblasts were genetically engineered using transcription activator-like effector nucleases and then used to provide donor nuclei for somatic cell nuclear transfer. We obtained 27 live cloned piglets; among these piglets, 9 were targeted with biallelic mutations in RAG1, 3 were targeted with biallelic mutations in RAG2, and 10 were targeted with a monoallelic mutation in RAG2. Piglets with biallelic mutations in either RAG1 or RAG2 exhibited hypoplasia of immune organs, failed to perform V(D)J rearrangement, and lost mature B and T cells. These immunodeficient RAG1/2 knockout pigs are promising tools for biomedical and translational research.

Generation of the SCN1A epilepsy mutation in hiPS cells using the TALEN technique

Human induced pluripotent stem cells (iPSC) can be used to understand the pathological mechanisms of human disease. These cells are a promising source for cell-replacement therapy. However, such studies require genetically defined conditions. Such genetic manipulations can be performed using the novel Transcription Activator-Like Effector Nucleases (TALENs), which generate site-specific double-strand DNA breaks (DSBs) with high efficiency and precision. Combining the TALEN and iPSC methods, we developed two iPS cell lines by generating the point mutation A5768G in the SCN1A gene, which encodes the voltage-gated sodium channel Nav1.1 α subunit. The engineered iPSC maintained pluripotency and successfully differentiated into neurons with normal functional characteristics. The two cell lines differ exclusively at the epilepsy-susceptibility variant. The ability to robustly introduce disease-causing point mutations in normal hiPS cell lines can be used to generate a human cell model for studying epileptic mechanisms and for drug screening.

Generation of knockout rabbits using transcription activator-like effector nucleases

Zinc-finger nucleases and transcription activator-like effector nucleases are novel gene-editing platforms contributing to redefine the boundaries of modern biological research. They are composed of a non-specific cleavage domain and a tailor made DNA-binding module, which enables a broad range of genetic modifications by inducing efficient DNA double-strand breaks at desired loci. Among other remarkable uses, these nucleases have been employed to produce gene knockouts in mid-size and large animals, such as rabbits and pigs, respectively. This approach is cost effective, relatively quick, and can produce invaluable models for human disease studies, biotechnology or agricultural purposes. Here we describe a protocol for the efficient generation of knockout rabbits using transcription activator-like effector nucleases, and a perspective of the field.

Anatomical information for intercostobrachial nerve preservation in axillary lymph node dissection for breast cancer

This study aimed to provide additional anatomical information for axillary lymph node dissection (ALND) through in vivo anatomy studies of intercostobrachial nerve (ICBN) preservation in order to provide theoretical and practical experience for clinicians. A total of 156 patients with breast cancer underwent ALND at the Department of Gynecology of Baotou Tumor Hospital between June 2009 and March 2010. The origin, destination, main source, length, branch type, and direction of ICBN in axilla were observed, as well as its relationship with adjacent major blood vessels and nerves within the axilla. There were 120 cases of single trunk, 23 cases of double trunks, 9 cases of multiple trunks, and 4 cases without trunks in 156 patients with ICBN preservation. The transverse diameter at the origin of the ICBN was 1.89 ± 0.44 mm with a length of 94.45 ± 12.08 mm; the distances were 77.19 ± 21.04 mm, 29.34 ± 6.73 mm, 90.04 ± 13.13 mm, and 28.63 ± 13.01 mm from origin to the inferior margin at the midpoint of the clavicle, inferior margin of the axillary vein, the bottom of axilla, and branch point, respectively. The identification, dissection, and preservation of ICBN was simple and easy in a modified radical mastectomy for breast cancer and breast-conserving surgery, which only took 10-20 min, but effectively reduced the incidence of post-mastectomy pain syndrome and significantly improved the quality of life for patients after surgery.

Efficient RNA/Cas9-mediated genome editing in Xenopus tropicalis

For the emerging amphibian genetic model Xenopus tropicalis targeted gene disruption is dependent on zinc-finger nucleases (ZFNs) or transcription activator-like effector nucleases (TALENs), which require either complex design and selection or laborious construction. Thus, easy and efficient genome editing tools are still highly desirable for this species. Here, we report that RNA-guided Cas9 nuclease resulted in precise targeted gene disruption in all ten X. tropicalis genes that we analyzed, with efficiencies above 45% and readily up to 100%. Systematic point mutation analyses in two loci revealed that perfect matches between the spacer and the protospacer sequences proximal to the protospacer adjacent motif (PAM) were essential for Cas9 to cleave the target sites in the X. tropicalis genome. Further study showed that the Cas9 system could serve as an efficient tool for multiplexed genome engineering in Xenopus embryos. Analysis of the disruption of two genes, ptf1a/p48 and tyrosinase, indicated that Cas9-mediated gene targeting can facilitate direct phenotypic assessment in X. tropicalis embryos. Finally, five founder frogs from targeting of either elastase-T1, elastase-T2 or tyrosinase showed highly efficient transmission of targeted mutations into F1 embryos. Together, our data demonstrate that the Cas9 system is an easy, efficient and reliable tool for multiplex genome editing in X. tropicalis.