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Graphene oxide exhibits great applications in the rubber industry due to its unique two-dimensional nanosheet structure, significant specific surface area, good barrier property, and high reactivity. However, different rubbers, such as carboxylated nitrile butadiene rubber, natural rubber, and styrene butadiene rubber, have different interactions with graphene oxide, which have a great influence on the reinforcement effect of graphene oxide on the rubber matrix. In this work, the enhancement mechanism of graphene oxide on carboxylated nitrile butadiene rubber, natural rubber, and styrene butadiene rubber was studied and the relationship between the microstructures and properties of GO/rubber nanocomposites was investigated by combining experiments with molecular dynamics simulation. The simulation results showed that graphene oxide had the best compatibility and the strongest interaction with carboxylated nitrile butadiene rubber, resulting in the largest binding energy and the smallest fractional free volume, mean square displacement, and the change of adhesive energy. The solvent resistance and mechanical properties of carboxylated nitrile butadiene rubber were improved by introducing graphene oxide, which was consistent with simulation results. This study provides a new way to explore the macroscopic properties of rubber nanocomposites at the molecular level. [ABSTRACT FROM AUTHOR]

Due to their promising applications in health monitoring, wearable flexible sensors based on hydrogel have gained considerable attention as modern medicine advances. However, it is still challenging for hydrogel-based wearable flexible sensors to be integrated with high stretchability, multifunctionality, and biocompatibility. Herein, we designed novel flexible multifunctional sensors based on ionic conductive double-network (DN) hydrogels composed of poly (acrylamide-co-acrylic acid) (P(AM-co-AAc)), sodium alginate (SA), and calcium chloride (CaCl2) by simple two-step method of copolymerization and soaking. Abundant carboxyl groups on SA and P(AM-co-AAc) chains and their capacity to bind with Ca2+ were utilized to design a double network, providing the hydrogels with high stretchability and toughness. Ca2+ endowed the hydrogels with enhanced conductivity and sensitivity, while P(AM-co-AAc) enabled the hydrogels to respond to multi-stimuli. The SA/P(AM-co-AAc)/Ca2+ hydrogels presented outstanding mechanical properties (elongation at break of 2626%, tensile strength of 372 kPa), great sensitivity (gauge factor up to 7.1), and excellent durability (1000 stretching-releasing cycles). It could detect human movements, touch, physiology (temperature and sweat), pH changes, and organic solvents. Besides, the hydrogel sensors displayed great biocompatibility. Therefore, this work extends the design and preparation of highly stretchable and multifunctional hydrogels to facilitate the applications of skin-friendly wearable sensors. [ABSTRACT FROM AUTHOR]

In this work, a distinguished hydrothermal treatment succeeded in modifying aramid nanofibers (ANFs) with the help of mixed acid, and the hydrothermal-treated ANFs (hANFs) were regarded as a reinforcement agent to be introduced into styrene-butadiene rubber (SBR) via latex co-agglutination treatment. The enhanced comprehensive behaviour of SBR/hANFs composites induced by π-π stacking interaction between hANFs and polymer chains were investigated in details. With respect to virgin SBR, it was found that the temperature at maximum rate of degradation, tear strength and tensile strength of composites with adding 7 phr (parts per hundred rubber) hANFs significantly improved by 14 °C, 148 % and 215 %, respectively. The incorporation of hANFs also endowed SBR with greatly enhanced solvent resistance. [ABSTRACT FROM AUTHOR]

The flexible strain sensors have drawn widespread consideration because of their features with excellent stretchability, durability and sensitivity. In this work, graphene foam (GF) with three-dimensional (3D) network structure was synthesized by employing the polyurethane (PU) sponges as template, and strain sensors based on the natural rubber (NR)/GF composites were fabricated through a dip-coating method. The effects of pore sizes of GF on the strain sensing performance of sensors were systematically investigated. It was founded that the network structure of GF regulated by the sizes of PU sponges had great influence on the strain sensing performance of sensors. The gauge factors of the sensitivity of NR/GF composites decrease from 1350 to 614 with the increase of the pore sizes of GF in the low strain region. Compared with others, sensor based on NR/GF-15 ppi (mesh number, the number of holes per inch) have the most advantages of high strain sensing sensitivity, intense electrical conductivity and superb signal stability. It can be used to monitor body motion behavior such as finger bending, pronunciation of different words and throat micro-motion. [ABSTRACT FROM AUTHOR]

1-Butyl 3-methylimidazolium bis(trifluoromethylsulfonyl) imide (BMI)-modified multiwalled carbon nanotubes (MWCNTs) were used as nanofillers for the hydrogenated carboxylated nitrile-butadiene rubber/hydrogenated nitrile-butadiene rubber (HXNBR/HNBR) blends. The multifunctional properties of rubber nanocomposites with various filler loadings were investigated. It was found that in the presence of BMI-MWCNTs, the mechanical strength, dielectric properties, electrical and thermal conductivities of HXNBR/HNBR were significantly improved due to the better dispersibility as well as the intrinsic reinforcement effect of MWCNTs. Particularly, in comparison with unfilled rubber blend, the electrical conductivity of BMI-MWCNTs-filled HXNBR/HNBR composites exhibited three orders of magnitude enhancement with a lower electrical percolation threshold. The tensile strength and thermal conductivity of composites filled with 5 phr (parts per hundred rubber) BMI-MWCNTs increased by 52 and 23%, respectively. In addition, the polarizability of composites was also intensified under the applied electric field, which resulted in remarkable dielectric relaxation compared to neat rubber. Our experimental data have indicated that BMI-MWCNTs can be used as a promising candidate for fabricating multifunctional HXNBR/HNBR nanocomposites. [ABSTRACT FROM AUTHOR]

Aims/hypothesis: Diabetic cardiomyopathy (DCM) is associated with suppressed autophagy and augmented apoptosis in the heart although the interplay between the two remains elusive. The ability of mammalian sterile 20-like kinase 1 to regulate both autophagy and apoptosis prompted us to investigate it as a possible candidate in the progression of DCM. Methods: Wild-type, Mst1 (also known as Stk4) transgenic and Mst1-knockout mice were challenged with streptozotocin to induce experimental diabetes. In addition, cultured neonatal mouse cardiomyocytes were subjected to simulated diabetes to probe mechanisms. Results: Mst1 knockout alleviated while Mst1 overexpression aggravated cardiac dysfunction in diabetes. Diabetic Mst1 transgenic mice exhibited decreased LC3 expression and enhanced protein aggregation. In contrast, typical autophagosomes were observed in diabetic Mst1-knockout mice with increased LC3 expression and reduced protein aggregation. Mst1 downregulation promoted autophagic flux as demonstrated by increased LC3-II and decreased p62 expression in the presence of bafilomycin A1. Furthermore, Mst1 overexpression increased, while Mst1 knockout decreased, cardiomyocyte apoptosis both in vivo and in vitro. Co-immunoprecipitation assays showed that Mst1 overexpression promoted Beclin1 binding to B cell lymphoma 2 (Bcl-2) and induced dissociation of Bcl-2 from Bax in diabetic mice. Conversely, Mst1 knockout disrupted the Beclin1-Bcl-2 complex and enhanced the interaction between Bcl-2 and Bax. Conclusions/interpretation: Mst1 knockout restores autophagy and protects against apoptosis in cardiomyocytes, en route to the rescue against DCM. [ABSTRACT FROM AUTHOR]

Alkaline phosphatases (APs) are non-specific phosphohydrolases, and they are widely used in clinical diagnostics and biological studies. APs are widespread in nature and exhibit different structural formulations. Based on the diversity of biogenetic sources, APs exhibit temperature-propensity traits, and they are classified as psychrophilic, mesophilic, and thermophilic. In this article, the characteristics of psychrophilic APs from marine organisms were described, accompanied by a simple description of APs from other organisms. This review will facilitate better utilization of marine APs in the biotechnology field. [ABSTRACT FROM AUTHOR]

A facile non-covalent surface treatment method is reported in this paper to modify graphene oxide (GO) sheets with the assistance of polyvinylpyrrolidone (PVP). The PVP-modified GO (PGO) was further adopted to fabricate PGO/styrene-butadiene rubber (SBR) nano-composites through the latex compounding method. The properties of PGO were carefully investigated and interaction between GO and PVP molecules was confirmed. The mechanical properties, dynamic mechanical properties, thermal stability, thermal conductivity as well as swelling properties of the PGO/SBR nano-composites were thoroughly studied. It was confirmed that PVP molecules could have strong interaction with GO via hydrogen bond; thus, the PGO significantly improved the strength of SBR matrix, e.g., 517 and 387 % increase in tensile strength and tear strength, respectively, with the presence of only 5 phr (parts per hundred rubber) PGO in the nano-composite. The presence of PGO had also greatly reduced the glass transition temperature ( T) and enhanced the storage modulus of SBR matrix in the nano-composites. Meanwhile, the maximum heat decomposition temperature ( T) was increased by 23.6 °C; equilibrium solvent uptake in toluene was reduced by 41 % and thermal conductivity was increased by 30 %. All the observations indicated that PVP modification of GO can achieve excellent exfoliation and dispersion of GO in the SBR matrix. These findings were further supported by X-ray diffraction and scanning electron microscopy measurements. [ABSTRACT FROM AUTHOR]

Bacterial cellulose whisker (BCW) reinforced carboxylated acrylonitrile-butadiene rubber (xNBR) vulcanizates were fabricated by mixing BCW suspension with xNBR latex, followed by coagulating and vulcanization. The BCW, prepared from acid hydrolysis of bacterial cellulose, has as rod-like nanofiber structure according to transmission electron microscopy. BCW maintained its crystal structure in BCW/xNBR vulcanizates as confirmed by X-ray diffraction. The incorporation of BCW improved the curing rate of xNBR. Compared with unfilled xNBR, the tensile strength, Young's modulus, and tear strength of BCW/xNBR vulcanizates were increased considerably: by 320, 150, and 150 %, respectively.The storage modulus ( E′) and glass transition temperature ( T) also increased because of the addition of BCW. [ABSTRACT FROM AUTHOR]

The poor viability of transplanted stem cells hampers their therapeutic efficacy for treatment of myocardial infarction. The aim of this study was to investigate whether rosuvastatin improved survival of adipose-derived mesenchymal stem cells (AD-MSCs) after transplantation into infarcted hearts. AD-MSCs isolated from Tg( Fluc- egfp) mice which constitutively express both firefly luciferase (Fluc) and enhanced green fluorescent protein were transplanted into infarcted hearts with or without rosuvastatin administration. Longitudinal in vivo bioluminescence imaging and histological staining revealed that rosuvastatin enhanced the survival of engrafted AD-MSCs. Furthermore, combined therapy of AD-MSC and rosuvastatin reduced fibrosis, decreased cardiomyocyte apoptosis, and preserved heart function. AD-MSCs were then subjected to hypoxia and serum deprivation injury in vitro to mimic the ischemic environment. Rosuvastatin (10 mmol/L) enhanced the viability and paracrine effect of AD-MSCs, and decreased their apoptotic rate. Western blotting revealed that rosuvastatin supplementation increased Akt and ERK phosphorylation, which resulted in FoxO3a phosphorylation and nuclear export. In addition, rosuvastatin administration decreased the pro-apoptotic proteins Bim and Bax, and increased the anti-apoptotic proteins Bcl-xL and Bcl-2. Furthermore, these effects were abolished by PI3K inhibitor LY294002 and MEK1/2 inhibitor U0126. This study demonstrates that rosuvastatin may improve the survival of engrafted AD-MSCs at least in part through the PI3K/Akt and MEK/ERK1/2 signaling pathways. Combination therapy with rosuvastatin and AD-MSCs has a synergetic effect on improving myocardial function after infarction. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO)/carboxylated acrylonitrile butadiene rubber (xNBR) vulcanizates were prepared in this study by mixing exfoliated GO aqueous dispersion with xNBR latex. The GO monolayers were exfoliated from natural flake graphite by Hummers' method. This study shows that GO could be dispersed homogeneously in xNBR matrix up to 1.2 vol.%. Adding GO nanosheets has a great effect on the mechanical, thermal stability, thermal conductivity, and thermal diffusivity of GO/xNBR vulcanizates. With the incorporation of GO nanosheets, the thermal stability, thermal conductivity, and thermal diffusivity of GO/xNBR vulcanizates increased significantly. The mechanical property of GO/xNBR vulcanizates reached its peak with 1.2 vol.% of GO content. The addition of 1.2 vol.% of GO nanosheets largely enhanced the tensile strength and modulus at 100 % elongation of xNBR by more than 370 and 230 %, respectively. The thermal conductivity and diffusivity of the GO/xNBR vulcanizates with 1.6 vol.% of GO had 1.4- and 1.2-fold improvements, respectively, compared to that of unfilled xNBR vulcanizate. [ABSTRACT FROM AUTHOR]