Spreading of Cell Aggregates on Zwitterion-Modified Chitosan Films

The sulfobetaine (SB) moiety, which comprises a quaternary ammonium group linked to a negatively charged sulfonate ester, is known to impart nonfouling properties to interfaces coated with polysulfobetaines or grafted with SB-polymeric brushes. Increasingly, evidence emerges that the SB group is, overall, a better antifouling group than the phosphorylcholine (PC) moiety extensively used in the past. We report here the synthesis of a series of SB-modified chitosans (CH-SB) carrying between 20 and 40 mol % SB per monosaccharide unit. Chitosan (CH) itself is a naturally derived copolymer of glucosamine and N-acetyl-glucosamine linked with a beta-1,4 bond. Analysis by quartz crystal microbalance with dissipation (QCM-D) indicates that CH-SB films (thickness similar to 20 nm) resist adsorption of bovine serum albumin (BSA) with increasing efficiency as the SB content of the polymer augments (surface coverage similar to 15 mu g cm(-2) for films of CH with 40 mol % SB). The cell adhesivity of CH-SB films coated on glass was assessed by determining the spreading dynamics of CT26 cell aggregates. When placed on chitosan films, known to be cell-adhesive, the CT26 cell aggregates spread by forming a cell monolayer around them. The spreading of CT26 cell aggregates on zwitterion-modified chitosans films is thwarted remarkably. In the cases of CH-SB30 and CH-SB40 films, only a few isolated cells escape from the aggregates. The extent of aggregate spreading, quantified based on the theory of liquid wetting, provides a simple in vitro assay of the nonfouling properties of substrates toward specific cell lines. This assay can be adopted to test and compare the fouling characteristics of substrates very different from the chemical viewpoint.Peer reviewe

MicroRNA-187 inhibits pentylenetetrazol-induced neuronal apoptosis and alleviates development of epilepsy in epileptic rats by regulating SPRY1 expression

Purpose: To explore the role of microRNA-187 on the pathological process of epilepsy. Methods: The seizure score of epileptic rats was evaluated according to Racine’s scale. Real-time quantitative polymerase chain reaction (RT-qPCR) was performed to determine the expression levels of microRNA-187 (miR-187). Western blot technique was conducted to assess the expression levels of caspase 3, B-cell lymphoma-2 (BCL-2), and poly (ADP-ribose) polymerase (PARP)] and activation of phosphatase and tensin homolog (PTEN)/PI3K/AKT cascade. Caspase 3 colorimetric assay kit was employed to evaluate the activity of caspase 3. Dual-luciferase reporter gene system was used to explore the regulating mechanisms of miR-187 and protein sprouty homolog 1 gene (SPRY1). Results: The results showed that miR-187 was aberrantly downregulated in the hippocampus regions of pentylenetetrazol (PTZ)-treated rats compared to normal rats (p < 0.05). Furthermore, PTZ promoted caspase 3-dependent neuronal apoptosis by increasing the expression of pro-apoptosis protein PARP and decreasing the expression levels of BCL-2 in rats. On the other hand, overexpression of miR-187 downregulated SPRY1 as well as PTEN (p < 0.05), thereby activating the downstream PI3K/AKT signaling pathway. Notably, the effects of upregulated miR-187 on neuronal apoptosis and epilepsy development in PTZ-induced rats was reversed by the concomitant overexpression of SPRY1 (p < 0.05). Conclusion: The results of this research show that overexpressed miR-187 alleviates the development of PTZ-induced neuronal apoptosis and epilepsy in epileptic rat models by regulating SPRY1 expression. These findings can hopefully be beneficial for the discovery of new therapeutic strategies for epilepsy treatment

Hierarchical bismuth vanadate/reduced graphene oxide composite photocatalyst for hydrogen evolution and bisphenol A degradation

Bismuth vanadate (BiVO4) is a widely studied photocatalyst for the depollution of contaminated wastewater, production of hydrogen by water splitting, and organic synthesis. The photophysical properties of BiVO4 are sensitive to morphology and quantum confinement effects, and can exhibit enhanced photocatalytic performance in nanocomposites with graphene. Synthesis of hierarchical BiVO4 plates decorated by nanoparticles (h-BiVO4) in contact with reduced graphene oxide (RGO) is reported via a facile one-pot solution phase approach using ethanolamine and a polyethylene glycol stabilizer. The resulting h-BiVO4/RGO photocatalyst exhibited superior photoactivity for bisphenol A (BPA) degradation and hydrogen evolution under visible light irradiation compared to single component h-BiVO4 or a μm-sized block-like BiVO4 morphology. Rates of BPA photocatalytic degradation and apparent quantum efficiency (AQE) decreased in the order h-BiVO4/RGO (4.5 × 10−2 mmol.g−1.min−1; 15.1% AQE) > h-BiVO4 (3.5 × 10−2 mmol.g−1.min−1; 11.7% AQE) > BiVO4 (1 × 10−2 mmol.g−1.min−1; 3.4% AQE), representing a 4.5 fold enhancement for h-BiVO4/RGO versus BiVO4. Liquid phase photodegradation products included benzene-1,4-diol, cyclohexa-2,5-diene-1,4-dione and (2Z)-but-2-enedioic acid. The rate of photocatalytic hydrogen production under visible light was 11.5 µmol.g−1.h−1 for h-BiVO4/RGO, ~383.3 times greater than for BiVO4 (0.03µmol.g−1.h−1). The superior photocatalytic performance of h-BiVO4/RGO is largely attributed to its higher surface area, aided by enhanced visible light absorption and charge separation across the semiconductor-RGO interface, which together confer a higher density and lifetime of photoexcited charge carriers

Effect of Mo₂C Addition on the Tribological Behavior of Ti(C,N)-Based Cermets

Due to the excellent properties of Ti (C,N)-based ceramics, such as high hardness, excellent wear resistance, exceptional thermal deformation resistance, and sound chemical stability, they have been widely used in cutting tools or molds. Thus, revealing their tribological behavior against hard materials is of great significance. Some studies have reported the tribological behavior of Ti(C,N)-based cermets and hard cermets, but so far, the effects of Mo2C additions on the frictional properties of Ti(C,N)-based cermets are still unclear. In this study, Ti(C,N)-10WC-1Cr3C2-5Co-10Ni-x Mo2C cermets (x = 4, 6, 8, 10 and 12 wt.%) were sintered using a vacuum hot-pressing furnace. Furthermore, the core–rim morphologies of the sintered samples were observed in SEM images. Then, the wear resistance of the cermets was studied against a Si3N4 ball at a 50 N load using the fretting wear test. Finally, the wear mechanism was characterized using a combination of SEM, EDS and XPS. The experimental results indicated that the wear mechanisms of the cermets were mainly abrasive wear, adhesive wear, and the formation of an oxide film. As the content of Mo2C increased from 4 wt.% to 12 wt.%, the friction coefficient and wear volume had a variation law of first decreasing and then decreasing, and reached minimum values at 6 wt.% and 12 wt.%, and the lowest friction coefficient and wear rate were 0.49 and 0.9 × 10−6 mm3/Nm, respectively. The 6 wt.% Mo2C greatly improved the hardness and fracture toughness of the cermet, while the 12 wt.% Mo2C promoted the formation of an oxide film and protected the friction surface. The cermet with 6 wt.% Mo2C is recommended because it has comprehensive advantages in terms of its mechanical properties, tribological properties, and cost