Strong and Facile Adhesives Based on Phase Transitional Poly(acrylic acid)/Poly(ethylenimine) Complexes

Polyelectrolyte complexes have demonstrated their potential application as adhesives to several substrates. However, it is unfortunate that the in-depth study focusing on polyelectrolyte phases as well as rheological analysis is insufficient to uncover the origin of the adhesive properties. Here, we precisely investigated the factors of polyelectrolyte adhesives in terms of electrostatic interaction using conventional rod coating and pH-induced phase transition, followed by a phase study between poly(acrylic acid) and branched poly(ethylenimine). The phase was systemically controlled by parameters such as polymer ratio, concentration of NaCl, and pH level. Then, the rheological modulus of each phase was studied to understand physical cross-linking. In relation to polyelectrolyte adhesives, it was found that a higher viscous phase led to more intensive adhesion strength. In addition, thermal treatment helped to obtain a dramatic increase in adhesion strength (2.4 MPa), which was accomplished by a conversion reaction from carboxylic acid to amide. This chemically cross-linked gel adhesive performance could compete with commercial grade adhesive, and this study creates a pathway to design polyelectrolyte adhesive regarding a facile process and applications

Exercise-Mediated Wall Shear Stress Increases Mitochondrial Biogenesis in Vascular Endothelium

<div><p>Objective</p><p>Enhancing structural and functional integrity of mitochondria is an emerging therapeutic option against endothelial dysfunction. In this study, we sought to investigate the effect of fluid shear stress on mitochondrial biogenesis and mitochondrial respiratory function in endothelial cells (ECs) using <i>in vitro</i> and <i>in vivo</i> complementary studies.</p><p>Methods and Results</p><p>Human aortic- or umbilical vein-derived ECs were exposed to laminar shear stress (20 dyne/cm²) for various durations using a cone-and-plate shear apparatus. We observed significant increases in the expression of key genes related to mitochondrial biogenesis and mitochondrial quality control as well as mtDNA content and mitochondrial mass under the shear stress conditions. Mitochondrial respiratory function was enhanced when cells were intermittently exposed to laminar shear stress for 72 hrs. Also, shear-exposed cells showed diminished glycolysis and decreased mitochondrial membrane potential (Δ<i>Ψ</i>m). Likewise, in <i>in vivo</i> experiments, mice that were subjected to a voluntary wheel running exercise for 5 weeks showed significantly higher mitochondrial content determined by <i>en face</i> staining in the conduit (greater and lesser curvature of the aortic arch and thoracic aorta) and muscle feed (femoral artery) arteries compared to the sedentary control mice. Interestingly, however, the mitochondrial biogenesis was not observed in the mesenteric artery. This region-specific adaptation is likely due to the differential blood flow redistribution during exercise in the different vessel beds.</p><p>Conclusion</p><p>Taken together, our findings suggest that exercise enhances mitochondrial biogenesis in vascular endothelium through a shear stress-dependent mechanism. Our findings may suggest a novel mitochondrial pathway by which a chronic exercise may be beneficial for vascular function.</p></div

Primer Sequences for Real-Time PCR.

<p>Primer Sequences for Real-Time PCR.</p

Increased mitochondrial biogenesis markers by LSS in HAECs.

<p>(a) An overview of LSS protocol used. HAECs were exposed to exercise-mimicking LSS at 20 dyne/cm² for 48 hrs, and then, recovery (Rec) LSS at 5 dyne/cm² was followed for another 24 hrs. (b) Effect of LSS on the mRNA and protein expression of mitochondrial biogenesis markers. mRNA expression of NRF-1, SCO1, SCO2, TFAM, and COX IV were assessed by real-time PCR and protein contents of PGC-1α, VDAC, and p53R2 were analyzed by western blot. (c) Effect of LSS on the mRNA expression of mitochondrial dynamics markers. mRNA expression of Mfn1, Mfn2, OPA1, Fis1, and Drp1 were assessed by real-time PCR. (d) Effect of LSS on mtDNA contents. Relative mtDNA contents are expressed as a ratio of COX I and II to 18s rRNA. (e) Effect of LSS on mitochondrial mass. Mitochondria were labeled with MitoTracker Green in live HAECs. Representative fluorescence micrographs under STT (left panel) and after 48 hrs of LSS at 20 dyne/cm² (right panel) are shown. Bar  = 50 µm. The MitoTracker Green fluorescence intensities were analyzed using the Image J (NIH) software. All densitometry analyses values are shown as mean ± SE; * <i>P</i><0.05 vs. STT; ** <i>P</i><0.01 vs. STT.</p

Effect of LSS on endothelial metabolism.

<p>(a) Enhanced mitochondrial respiration in LSS-exposed HUVECs. Oxygen consumption of HUVECs was measured after the intermittent LSS exposure for up to 72 hours. Representative strips of the oxygen consumption measured (left panel). Normalized values to the number of cells (right panel). (b) Effect of LSS on Δ<i>Ψ</i>m in ECs. Δ<i>Ψ</i>m was estimated by using MitoTracker Red CMX Ros. Representative fluorescence micrographs for each condition are shown. Bar  = 100 µm. The fluorescence intensities were analyzed using the Image J (NIH) software. (c) Heat map showing the expression of glycolysis markers by microarray analysis. Genes upregulated are presented in yellow and downregulated are in blue (upper panel). Average fold change of each of those glycolysis markers identified by microarray analysis are shown in a bar graph (lower panel). (d) Lactate concentration measured in cell culture medium at 12, 24, 36 hrs of post LSS or STT. Values were normalized to viable cell number. Data shown as means ± SE; * <i>P</i><0.05 vs. STT; ** <i>P</i><0.01 vs. STT.</p

Effect of five weeks of VW running on mitochondrial in mouse endothelium.

<p>(A) Representative fluorescence micrographs of <i>en face</i> immunostaining. Endothelium of the greater curvature (GC), lesser curvature (LC), thoracic aorta (TA), femoral artery (FA), and mesenteric artery (MA) were stained in the sedentary (SED) and voluntary wheel (VW) run C57BL6 mice. The green fluorescent staining indicates mitochondrial density stained by VDAC, and the red color represents ECs stained by CD31 (an endothelial cell specific marker). Nuclei were counterstained with DAPI. Shown are representative images of <i>en face</i> staining labeled. (B) Illustration of mouse arterial tree. (C) Summary of densitometry analysis. Green fluorescence intensities by VDAC staining were analyzed using the Image J (NIH) software. Data shown as mean ± SE; Data shown represent results from a total of 10 mice per group * <i>P</i><0.05 vs. SED. ** <i>P</i><0.01 vs. SED.</p

Effect of five weeks of voluntary wheel (VW) exercise on mitochondrial biogenesis markers in mice abdominal aorta (AA).

<p>(a) Effect of VW running on mRNA expression of mitochondrial biogenesis markers in AA. mRNA expressions of PGC-1α, NRF1, TFAM, p53R2, SCO1, and SCO2 were examined by real-time PCR. Values were normalized to the level of housekeeping gene, TIF. (b) Effect of VW running on protein expression of mitochondrial biogenesis markers in AA. Tissue extracts of the AA from SED and VW group mice were subjected to western blot. The amount of phosphorylated- AMPKα was normalized by the amount of AMPKα protein. Protein content of mitochondrial biogenesis marker VDAC was also measured. The loading volume was normalized by the expression level of α-tubulin. (c) Effect of VW running on mtDNA content in AA. mtDNA contents were compared in between SED and VW run mice. Relative mtDNA content are expressed as a ratio of NADH dehydrogenase subunit 2 (ND II) to 18s rRNA. All densitometry analyses values are shown as means ± SE. Data shown represent results from a total of 5 mice per group; * <i>P</i><0.05 vs. SED; ** <i>P</i><0.01 vs. SED.</p

Harnessing the power of tidal flat diatoms to combat climate change

In approximately one decade, global temperatures will likely exceed a warming level that a United Nations Intergovernmental Panel on Climate Change report considers a “red alert for humanity”. We propose exploring tidal flat diatoms to address climate change challenges. Tidal flats are extensive coastal ecosystems crucial to the provisioning and regulation of aquatic environments. Diatoms contribute to tidal flat biomass production and account for 20% of global primary productivity and 40% of annual marine biomass production, making them crucial for nutrient cycling and sediment stabilization. Potential CO2 removal from Korean tidal flats by diatoms is estimated to be 598,457–683,171 t CO2 equivalents (CO2e) annually, with the economic value of blue carbon (BC) resulting from diatom activity being approximately US$ 17.95–20.50 million. Dissemination of this potential could incentivize coastal wetland protection and climate change mitigation measures. The global estimated CO2e removal potential of tidal flat diatoms is 40,957,346–46,754,961 t CO2e, representing 0.11–0.13% of the annual global greenhouse gas emissions, even though tidal flats cover 0.0025% of the Earth’s surface and diatoms represent less than 0.5% (by weight) of all photosynthetic plants. Researchers should combine ecology and economics to develop standardized approaches for carbon input monitoring and quantification. Further, spatiotemporal analyses of environmental threats to tidal flat diatoms are necessary for conserving their biodiversity and function as a critical BC source. Land-based cultivation for large-scale biomass production and biorefinery processes can contribute to a greener, more prosperous future for humanity and the marine ecosystems upon which we rely.</p