Endothelial Surface Glycocalyx Can Regulate Flow-Induced Nitric Oxide Production in Microvessels In Vivo

Due to its unique location, the endothelial surface glycocalyx (ESG) at the luminal side of the microvessel wall may serve as a mechano-sensor and transducer of blood flow and thus regulate endothelial functions. To examine this role of the ESG, we used fluorescence microscopy to measure nitric oxide (NO) production in post-capillary venules and arterioles of rat mesentery under reduced (low) and normal (high) flow conditions, with and without enzyme pretreatment to remove heparan sulfate (HS) of the ESG and in the presence of an endothelial nitric oxide synthase (eNOS) inhibitor, NG-monomethyl-L-arginine (L-NMMA). Rats (SD, 250–300g) were anesthetized. The mesentery was gently taken out from the abdominal cavity and arranged on the surface of a glass coverslip for the measurement. An individual post-capillary venule or arteriole was cannulated and loaded for 45 min with 5 μM 4, 5-Diaminofluorescein diacetate, a membrane permeable fluorescent indictor for NO, then the NO production was measured for ~10 min under a low flow (~300 μm/s) and for ~60 min under a high flow (~1000 μm/s). In the 15 min after switching to the high flow, DAF-2-NO fluorescence intensity increased to 1.27-fold of its baseline, DAF-2-NO continuously increased under the high flow, to 1.53-fold of its baseline in 60 min. Inhibition of eNOS by 1 mM L-NMMA attenuated the flow-induced NO production to 1.13-fold in 15 min and 1.30-fold of its baseline in 60 min, respectively. In contrast, no significant increase in NO production was observed after switching to the high flow for 60 min when 1 h pretreatment with 50 mU/mL heparanase III to degrade the ESG was applied. Similar NO production was observed in arterioles under low and high flows and under eNOS inhibition. Our results suggest that ESG participates in endothelial cell mechanosensing and transduction through its heparan sulfate to activate eNOS

Effect of Precursor Solution Aging on the Crystallinity and Photovoltaic Performance of Perovskite Solar Cells

International audiencePerovskite materials due to their exceptional photophysical properties are beginning to dominate the field of thin-film optoelectronic devices. However, one of the primary challenges is the processing-dependent variability in the properties, thus making it imperative to understand the origin of such variations. Here, it is discovered that the precursor solution aging time before it is cast into a thin film, is a subtle but a very important factor that dramatically affects the overall thin-film formation and crystallinity and therein factors such as grain growth, phase purity, surface uniformity, trap state density, and overall solar cell performance. It is shown that progressive aging of the precursor promotes efficient formation of larger seeds after the fast nucleation of a large density of small seeds. The hot-casting method then leads to the growth of large grains in uniform thin-films with excellent crystallinity validated using scanning microscopy images and X-ray diffraction patterns. The high-quality films cast from aged solution is ideal for thin-film photovoltaic device fabrication with reduced shunt current and good charge transport. This observation is a significant step toward achieving highly crystalline thin-films with reliability in device performance and establishes the subtle but dramatic effect of solution aging before fabricating perovskite thin-films

Representative DAF-2 fluorescence images for post-capillary venules.

<p>Images were taken after 10 min low flow (left panel) and an additional 60 min high flow (right panel). A) control (1% BSA Ringer); B) sham control (low flow over entire time); <b>C)</b> 1 h pretreatment of heparinase III; and <b>D)</b> in the presence of L-NMMA. Scale bar is 50 μm.</p

Diameters of post-capillary venules under low (~300 μm/s) and high (~1000 μm/s) flows.

<p>Data shown are Mean ± SE (μm). p > 0.7.</p><p>Diameters of post-capillary venules under low (~300 μm/s) and high (~1000 μm/s) flows.</p

Flow-induced increases in NO production (DAF-2 intensity normalized by that after 45min DAF-2 DA loading) and production rate (df/dt) in arterioles A) control (1% BSA Ringer); B) in the presence of L-NMMA.

<p>The filled circles are the measured data, the solid line is the fitting curve and the dashed line is the production rate.</p

Images of fluorescently labeled heparan sulfate in a control vessel (left in Fig. 5A) and a vessel treated with heparinase III for 1 h (right in Fig. 5A).

<p><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0117133#pone.0117133.g005" target="_blank">Fig. 5B</a> shows the comparison of the intensity of the fluorescently labeled heparan sulfate in 5 control vessels and that in 3 heparinase III treated vessels. * p < 0.001.</p

Curve fitting for the flow-induced increases in NO production (DAF-2 intensity normalized by that after 45min DAF-2 DA loading) (smooth solid line) and production rate (df/dt) (dashed line) in post-capillary venules.

<p>A) control (1% BSA Ringer); B) in the presence of L-NMMA; and C) 1 h pretreatment of heparinase III. The filled circles are the measured data.</p

Diameters of arterioles under low (~300 μm/s) and high (~2000–2500 μm/s) flows.

<p>Data shown are Mean ± SE (μm). p > 0.7.</p><p>Diameters of arterioles under low (~300 μm/s) and high (~2000–2500 μm/s) flows.</p

Molecular Origin of Photovoltaic Performance in Donor-<i>block</i>-Acceptor All-Conjugated Block Copolymers

All-conjugated block copolymers may be an effective route to self-assembled photovoltaic devices, but we lack basic information on the relationship between molecular characteristics and photovoltaic performance. Here, we synthesize a library of poly­(3-hexyl­thiophene) (P3HT) <i>block</i> poly­((9,9-dialkyl­fluorene)-2,7-diyl-<i>alt</i>-[4,7-bis­(alkyl­thiophen-5-yl)-2,1,3-benzo­thiadiazole]-2′,2″-diyl) (PFTBT) donor-<i>block</i>-acceptor all-conjugated block copolymers and carry out a comprehensive study of processing conditions, crystallinity, domain sizes, and side-chain structure on photovoltaic device performance. We find that all block copolymers studied exhibit an out-of-plane crystal orientation after deposition, and on thermal annealing at high temperatures the crystal orientation flips to an in-plane orientation. By varying processing conditions on polymer photovoltaic devices, we show that the crystal orientation has only a modest effect (15–20%) on photovoltaic performance. The addition of side chains to the PFTBT block is found to decrease photovoltaic power conversion efficiencies by at least an order of magnitude. Through grazing-incidence X-ray measurements we find that the addition of side chains to the PFTBT acceptor block results in weak segregation and small (<10 nm) block copolymer self-assembled donor and acceptor domains. This work is the most comprehensive to date on all-conjugated block copolymer systems and suggests that photovoltaic performance of block copolymers depends strongly on the miscibility of donor and acceptor blocks, which impacts donor and acceptor domain sizes and purity. Strategies for improving the device performance of block copolymer photovoltaics should seek to increase segregation between donor and acceptor polymer domains

Structural Design of Benzo[1,2‑<i>b</i>:4,5‑<i>b</i>′]dithiophene-Based 2D Conjugated Polymers with Bithienyl and Terthienyl Substituents toward Photovoltaic Applications

In this contribution, six conjugated polymers consisting of benzo­[1,2-<i>b</i>:4,5-<i>b</i>′]­dithiophene–bithiophene (BDT-BT) and benzo­[1,2-<i>b</i>:4,5-<i>b</i>′]­dithiophene–benzothiadiazle (BDT-BTD) as building blocks in the main chain were synthesized by coupling polymerization and utilized for photovoltaic applications. By directly attaching three kinds of alkylthienyl side chains to the conjugated main chain, the resulted two-dimensional configuration revealed a broader absorption range due to the ground state electron transition of their corresponding alkylthienyl units and polymer backbone. Temperature-dependent absorbance, emission spectra, and thermal annealing further verify that the shoulder band(s) were originated from the aggregated (crystalline) species of polymers. The photovoltaic properties of the donor–acceptor polymers revealed well-defined side chain geometries, physical, and electronic structures and showed the highest power conversion efficiency of 4.25% among polymer solar cells based on two-dimensional (2-D) bithienyl- or terthienyl-substituted benzodithiophene