Strain-sensitive electrical conductivity of carbon nanotube-graphene-filled rubber composites under cyclic loading.

Conductive rubber nanocomposites have been attracting interest for strain sensing applications owing to their large deformation and high sensitivity. In this paper, the strain sensing behavior of room temperature vulcanized (RTV) hybrid silicone rubber composites containing carbon nanotubes and graphene was systematically investigated. We studied the effects of the nanofiller content and strain amplitude on the strain sensing behavior of the nanocomposites, and found good stability and durability during cyclic loading. The shoulder peaks appeared in the cyclic loading curves owing to the competition between the reconstruction process of the conductive network during deformation and time-dependent features of the polymer material. Furthermore, our test results of different loading histories indicated that a sufficient recovery time could reduce or even eliminate the shoulder peak. Finally, the mechanical structure with a negative Poisson's ratio is designed to regulate the resistance response of the RTV nanocomposites, exhibiting a monotonic and more sensitive resistance response. Our research results explain the main factors contributing to the shoulder peak phenomenon of conductive nanocomposites and provide a regulation strategy for achieving a monotonic and highly sensitive resistance response.

[Study on Autophagy and Apoptosis Induced by Amiodarone Combined with Glycyrrhetinic Acid in HepG2 Cells].

OBJECTIVE: To investigate the effects of amiodarone combined with glycyrrhetinic acid on the activity, apoptosis and autophagy in human hepatoma HepG2 cells. METHODS: After using amiodarone and glycyrrhetinic acid alone or in combination treatment for HepG2 cells, MTT assay was used to detect cell proliferation, Annexin Ⅴ/PI flow cytometry was used to detect apoptosis; Western blot was used to detect the expression of autophagy-related proteins Beclin-1, LC3 and p62. The formation of EGFP-LC3 green fluorescent aggregates was observed under a fluorescence microscope. The effects of autophagy on cell proliferation and apoptosis were studied by autophagy inhibitor hydroxychloroquine (HCQ) and autophagy promoter Rapamycin. RESULTS: The cell viability in combination group was lower than that in single drug group, and the apoptosis rate was higher than that in single drug group. Compared with single-drug group, the expressions of Beclin-1 and LC3Ⅱ protein in the combination group were higher than that in the single-drug group, while the expression of p62 protein was lower in the single-drug group. Fluorescence microscopy results showed that the number of EGFP-LC3 fluorescent aggregates in the combination group were more than that in the single-drug. Using amiodarone and glycyrrhetinic acid treated HepG2 cells, inhibition of auotophagy could decrease cell viability, increase apoptosis rate of cells; promoting autophagy would decrease the apoptosis rate and increase cells viability. CONCLUSION: By increasing apoptosis of hepatocellular carcinoma HepG2 cells and autophagy level, and decreasing the cell activity, amiodarone combining with glycyrrhetinic acid treatment inducing autophagy a protective mechanism for cells.

Optimization of the Linker Length of Mannose-Cholesterol Conjugates for Enhanced mRNA Delivery to Dendritic Cells by Liposomes.

Liposomes (LPs) as commonly used mRNA delivery systems remain to be rationally designed and optimized to ameliorate the antigen expression of mRNA vaccine in dendritic cells (DCs). In this study, we synthesized mannose-cholesterol conjugates (MPn-CHs) by click reaction using different PEG units (PEG100, PEG1000, and PEG2000) as linker molecules. MPn-CHs were fully characterized and subsequently used to prepare DC-targeting liposomes (MPn-LPs) by a thin-film dispersion method. MPn-LPs loaded with mRNA (MPn-LPX) were finally prepared by a simple self-assembly method. MPn-LPX displayed bigger diameter (about 135 nm) and lower zeta potential (about 40 mV) compared to MPn-LPs. The in vitro transfection experiment on DC2.4 cells demonstrated that the PEG length of mannose derivatives had significant effect on the expression of GFP-encoding mRNA. MP1000-LPX containing MP1000-CH can achieve the highest transfection efficiency (52.09 ± 4.85%), which was significantly superior to the commercial transfection reagent Lipo 3K (11.47 ± 2.31%). The optimal DC-targeting MP1000-LPX showed an average size of 132.93 ± 4.93 nm and zeta potential of 37.93 ± 2.95 mV with nearly spherical shape. Moreover, MP1000-LPX can protect mRNA against degradation in serum with high efficacy. The uptake study indicated that MP1000-LPX enhanced mRNA expression mainly through the over-expressing mannose receptor (CD206) on the surface of DCs. In conclusion, mannose modified LPs might be a potential DC-targeting delivery system for mRNA vaccine after rational design and deserve further study on the in vivo delivery profile and anti-tumor efficacy.