Comprehensive Investigation of the Temperature-Dependent Electromechanical Behaviors of Carbon Nanotube/Polymer Composites.

The performances of flexible piezoresistive sensors based on polymer nanocomposites are significantly affected by the environmental temperature; therefore, comprehensively investigating the temperature-dependent electromechanical response behaviors of conductive polymer nanocomposites is crucial for developing high-precision flexible piezoresistive sensors in a wide-temperature range. Herein, carbon nanotube (CNT)/polydimethylsiloxane (PDMS) composites widely used for flexible piezoresistive sensors were prepared, and then the temperature-dependent electrical, mechanical, and electromechanical properties of the optimized CNT/PDMS composite in the temperature range from -150 to 150 °C were systematically investigated. At a low temperature of -150 °C, the CNT/PDMS composite becomes brittle with a compressive modulus of ∼1.2 MPa and loses its elasticity and reversible sensing capability. At a high temperature (above 90 °C), the CNT/PDMS composite softens, shows a fluid-like mechanical property, and loses its reversible sensing capability. In the temperature range from -60 to 90 °C, the CNT/PDMS composite exhibits good elasticity and reversible sensing behaviors and its modulus, resistivity, and sensing sensitivity decrease with an increasing temperature. At room temperature (30 °C), the CNT/PDMS composite exhibits better mechanical and piezoresistive stability than those at low and high temperatures. Given that environmental temperature changes have significant effects on the sensing performances of conductive polymer composites, the effect of ambient temperature changes must be considered when flexible piezoresistive sensors are designed and fabricated.

Astragaloside IV inhibits Ang H-induced cell proliferation and collagen expression in cardiac fibroblasts by activating short-chain acyl-CoA dehydrogenase / 中国药理学通报

Aim To explore the effect of astragaloside IV (AS-IV) on cell proliferation and collagen expression in cardiac fibroblasts (CFs) of rats induced with angiotensin II (Ang II) and its mechanism. Methods CFs were pretreated with short-chain acyl-CoA dehydrogenase (SCAD) siRNA1186 for 12 h and then co-treated with Ang TJ and AS-IV for 36 h. The expressions of SCAD, α-SMA, collagen I and collagen III in CFs were detected by Western blot. mRNA expression levels of SCAD, a-SMA, collagen I and collagen III in CFs were detected by quantitative real-time PCR. The SCAD enzymatic activity, the content of ATP, hydroxyproline and free fatty acid were measured by detection kits. Results The expression of α-SMA, collagen I and collagen III were up-regulated (all P < 0. 01) in CFs induced by Ang II compared with the control cells, and the expression and enzymatic activity of SCAD significantly decreased (P < 0. 01, P< 0. 05). The content of ATP decreased (P < 0.01), and the content of hydroxyproline and free fatty acids increased (all P < 0.01). Compared with Ang II group, SCAD expression and enzymatic activity, and ATP content were significantly increased (all P < 0.01) in Ang II + AS-TV group, but the content of hydroxyproline and free fatty acids, and the expression of α-SMA, collagen I and collagen III significantly decreased (all P < 0.01). However, compared with the Ang II + NC group, there was no significant difference in all indices in the Ang II + SiRNA1186 + AS-TV group. The protective effect of AS-TV on Ang II -induced cell proliferation and collagen expression in CFs was eliminated by the interference of SCAD SiRNA1186. Conclusions AS-IV may inhibit Ang II-induced cell proliferation and collagen expression in CFs by activating SCAD.