Formation of Helical Phases in Achiral Block Copolymers by Simple Addition of Small Chiral Additives

Helical superstructures were induced in poly­(ethylene oxide)-<i>b</i>-poly­(<i>tert</i>-butyl acrylate) (PEO-<i>b</i>-PtBA) achiral diblock copolymers (BCPs) through the simple addition of pure enantiomers of tartaric acid. Hydrogen bond interactions between tartaric acid and poly­(ethylene oxide) (PEO) block not only enhance the phase segregation strength of the PEO-based block copolymer but also transfer the chiral information from the additive into the achiral backbone to induce the conformational chirality. The helical phase was formed after thermal annealing with a pitch of ∼25 nm and confirmed by transmission electron microscopy (TEM) and TEM tomography. The handedness of helices can be easily selected by choice of the corresponding enantioisomer of tartaric acid

Precise Preparation of a Multilayer Tubular Cell Sheet with Well-Aligned Cells in Different Layers to Simulate Native Arteries

Compared with artificial vascular grafts, bottom-up tubular cell sheets (TCSs) without scaffolds have shown promise for patients with cardiovascular disease. However, TCS therapy also faces the challenges of lengthy maturation time, elaborate operation, and weak mechanical strength. In this work, a structured small-diameter vascular graft (SDVG), consisting of three layers of TCSs, with different cell types and arrangements, was fabricated using layer-by-layer assembly of naturally formed TCSs and further cell culture. To this end, a surface-patterned collagen-coated cylindrical substrate was designed for the efficient harvesting of naturally formed and well-aligned TCSs. The patterned collagen (type I) layer facilitated the adhesion and orientation of cells, and a continuous tubular cell monolayer was naturally formed after approximately 4 days in cell culture. Biocompatible near-infrared (NIR) light was used to trigger the photothermal phase transition of the collagen coated on the cylindrical substrate to dissociate the collagen layer. As a result, an intact TCS could be harvested within a few minutes. These naturally formed and well-aligned TCSs exhibited outstanding free-standing performance without rugosity, facilitating their operability and practical application. A ring tensile test showed that orientation was critical for improving the mechanical properties of TCSs. The layer-by-layer assembly of SDVGs not only is easy to manipulate and has a short preparation time but also overcomes the bottleneck of forming a hierarchically structured vascular graft. This approach shows promise for repairing damaged blood vessels

Precise Preparation of a Multilayer Tubular Cell Sheet with Well-Aligned Cells in Different Layers to Simulate Native Arteries

Compared with artificial vascular grafts, bottom-up tubular cell sheets (TCSs) without scaffolds have shown promise for patients with cardiovascular disease. However, TCS therapy also faces the challenges of lengthy maturation time, elaborate operation, and weak mechanical strength. In this work, a structured small-diameter vascular graft (SDVG), consisting of three layers of TCSs, with different cell types and arrangements, was fabricated using layer-by-layer assembly of naturally formed TCSs and further cell culture. To this end, a surface-patterned collagen-coated cylindrical substrate was designed for the efficient harvesting of naturally formed and well-aligned TCSs. The patterned collagen (type I) layer facilitated the adhesion and orientation of cells, and a continuous tubular cell monolayer was naturally formed after approximately 4 days in cell culture. Biocompatible near-infrared (NIR) light was used to trigger the photothermal phase transition of the collagen coated on the cylindrical substrate to dissociate the collagen layer. As a result, an intact TCS could be harvested within a few minutes. These naturally formed and well-aligned TCSs exhibited outstanding free-standing performance without rugosity, facilitating their operability and practical application. A ring tensile test showed that orientation was critical for improving the mechanical properties of TCSs. The layer-by-layer assembly of SDVGs not only is easy to manipulate and has a short preparation time but also overcomes the bottleneck of forming a hierarchically structured vascular graft. This approach shows promise for repairing damaged blood vessels

Precise Preparation of a Multilayer Tubular Cell Sheet with Well-Aligned Cells in Different Layers to Simulate Native Arteries

Compared with artificial vascular grafts, bottom-up tubular cell sheets (TCSs) without scaffolds have shown promise for patients with cardiovascular disease. However, TCS therapy also faces the challenges of lengthy maturation time, elaborate operation, and weak mechanical strength. In this work, a structured small-diameter vascular graft (SDVG), consisting of three layers of TCSs, with different cell types and arrangements, was fabricated using layer-by-layer assembly of naturally formed TCSs and further cell culture. To this end, a surface-patterned collagen-coated cylindrical substrate was designed for the efficient harvesting of naturally formed and well-aligned TCSs. The patterned collagen (type I) layer facilitated the adhesion and orientation of cells, and a continuous tubular cell monolayer was naturally formed after approximately 4 days in cell culture. Biocompatible near-infrared (NIR) light was used to trigger the photothermal phase transition of the collagen coated on the cylindrical substrate to dissociate the collagen layer. As a result, an intact TCS could be harvested within a few minutes. These naturally formed and well-aligned TCSs exhibited outstanding free-standing performance without rugosity, facilitating their operability and practical application. A ring tensile test showed that orientation was critical for improving the mechanical properties of TCSs. The layer-by-layer assembly of SDVGs not only is easy to manipulate and has a short preparation time but also overcomes the bottleneck of forming a hierarchically structured vascular graft. This approach shows promise for repairing damaged blood vessels

Novel NAC Transcription Factor TaNAC67 Confers Enhanced Multi-Abiotic Stress Tolerances in <i>Arabidopsis</i>

<div><p>Abiotic stresses are major environmental factors that affect agricultural productivity worldwide. NAC transcription factors play pivotal roles in abiotic stress signaling in plants. As a staple crop, wheat production is severely constrained by abiotic stresses whereas only a few NAC transcription factors have been characterized functionally. To promote the application of NAC genes in wheat improvement by biotechnology, a novel NAC gene designated <i>TaNAC67</i> was characterized in common wheat. To determine its role, transgenic <i>Arabidopsis</i> overexpressing <i>TaNAC67-GFP</i> controlled by the CaMV-35S promoter was generated and subjected to various abiotic stresses for morphological and physiological assays. Gene expression showed that <i>TaNAC67</i> was involved in response to drought, salt, cold and ABA treatments. Localization assays revealed that TaNAC67 localized in the nucleus. Morphological analysis indicated the transgenics had enhanced tolerances to drought, salt and freezing stresses, simultaneously supported by enhanced expression of multiple abiotic stress responsive genes and improved physiological traits, including strengthened cell membrane stability, retention of higher chlorophyll contents and Na⁺ efflux rates, improved photosynthetic potential, and enhanced water retention capability. Overexpression of <i>TaNAC67</i> resulted in pronounced enhanced tolerances to drought, salt and freezing stresses, therefore it has potential for utilization in transgenic breeding to improve abiotic stress tolerance in crops.</p></div

Comparisons of relative transcript levels of <i>DREB1A</i>, <i>DERB2A</i>, <i>RD29A</i>, <i>RD29B</i>, <i>Rab18</i>, <i>Cor15</i>, <i>RD22 ABI1</i>, <i>ABI2</i> and <i>ABI5</i> in WT and vector control and <i>TaNAC67</i> overexpressing lines treated for 3 h with PEG-6000 (−0.5 MPa) and assessed by qRT-PCR.

<p>Seedlings harvested before water deficit stress were used as control (CK). Ten seedlings were pooled as a sample, three samples were prepared for qRT-PCR on each line, and the experiments were triplicate. Vertical columns indicate relative transcript levels. Values (and error bars) were calculated using data from three independent assays.</p

<i>Cis</i>-acting regulatory elements identified in the promoter region of <i>TaNAC67</i> involved in response to biotic and abiotic stimuli.

<p><i>Cis</i>-acting regulatory elements identified in the promoter region of <i>TaNAC67</i> involved in response to biotic and abiotic stimuli.</p

<i>TaNAC67</i> transgenics have higher K⁺ and Na⁺ ion efflux rates than WT.

<p>A. The transgenics had a higher K⁺ ion efflux rate than WT plants after a 30 min NaCl shock. <i>Arabidopsis</i> seedlings were pre-incubated in buffer (0.5 mM KCl, 0.1 mM MgCl₂, 0.1 mM CaCl₂, 0.2 mM Na₂SO₄, and 0.3 mM MES, pH 6.0) for 30 min and assayed in the same buffer containing 100 mM NaCl at pH 6.0. Five plants were measured for each line. Values are means ± SE. B. <i>TaNAC67</i> transgenics had higher Na⁺ ion efflux rates after treatment with 100 mM NaCl. <i>Arabidopsis</i> seedlings were pretreated on MS medium with 100 mM NaCl for 24 h, and then subjected to measurement of Na⁺ ion flux rates. Five plants were measured for each line, and the values are means ± SE.</p

Chromosome location of <i>TaNAC67</i>.

<p>A. Genomic origin of <i>TaNAC67</i> among 20 accessions of wheat and related species. B. Three <i>TaNAC67</i> genes were identified in the A, B and D genomes of hexaploid wheat. AA, <i>T</i>. <i>urartu</i>; SS, <i>Ae</i>. <i>speltoides</i>; DD, <i>Ae</i>. <i>tauschii</i>; AABB, <i>T</i>. <i>diccocoides</i>; AABBDD, <i>T</i>. <i>aestvium</i>; M, 200 bp DNA ladder. C. Chromosome location of <i>TaNAC67</i> genes using 41 nulli-tetrasomic (NT) lines of Chinese Spring. Different <i>TaNAC67</i> genes were missing in each of the NT lines for homoeologous group 6. NT, nulli-tetrasomic line; M, 200 bp DNA ladder. Arrow, pointing at the missing bands in corresponding NT lines.</p

Expression patterns of <i>TaNAC67</i> in common wheat.

<p>Expression patterns of <i>TaNAC67</i> in different tissues at different developmental stages (A) and under stress treatments with ABA, PEG (−0.5 MPa), salt (NaCl) and low temperature (LT) (B). Two-leaf seedlings of common wheat cv. Hanxuan 10 were exposed to abiotic stresses as described in Materials and Methods. The 2^−ΔΔCT method was used to measure relative expression levels of the target gene in stressed and non-stressed leaves. Three samples were collected for each time point per treatment, and the experiments for each sample were triplicate. Means were generated from three biological replications; bars indicate standard errors. SL, seedling leaves; SR, seedling roots; BS, booting spindles; ES, emerging spikes; PEG, PEG-6000; LT, low temperature.</p