Selective Activation of Cells by Piezoelectric Molybdenum Disulfide Nanosheets with Focused Ultrasound.

An accurate method for neural stimulation within the brain could be very useful for treating brain circuit dysfunctions and neurological disorders. With the aim of developing such a method, this study investigated the use of piezoelectric molybdenum disulfide nanosheets (MoS2 NS) to remotely convert ultrasound energy into localized electrical stimulation in vitro and in vivo. The application of ultrasound to cells surrounding MoS2 NS required only a single pulse of 2 MHz ultrasound (400 kPa, 1,000,000 cycles, and 500 ms pulse duration) to elicit significant responses in 37.9 ± 7.4% of cells in terms of fluxes of calcium ions without detectable cellular damage. The proportion of responsive cells was mainly influenced by the acoustic pressure, number of ultrasound cycles, and concentration of MoS2 NS. Tests using appropriate blockers revealed that voltage-gated membrane channels were activated. In vivo data suggested that, with ultrasound stimulation, neurons closest to the MoS2 NS were 3-fold more likely to present c-Fos expression than cells far from the NS. The successful activation of neurons surrounding MoS2 NS suggests that this represents a method with high spatial precision for selectively modulating one or several targeted brain circuits.

Highly active oxygen evolution integrated with efficient CO2 to CO electroreduction.

Electrochemical reduction of CO2 to useful chemicals has been actively pursued for closing the carbon cycle and preventing further deterioration of the environment/climate. Since CO2 reduction reaction (CO2RR) at a cathode is always paired with the oxygen evolution reaction (OER) at an anode, the overall efficiency of electrical energy to chemical fuel conversion must consider the large energy barrier and sluggish kinetics of OER, especially in widely used electrolytes, such as the pH-neutral CO2-saturated 0.5 M KHCO3 OER in such electrolytes mostly relies on noble metal (Ir- and Ru-based) electrocatalysts in the anode. Here, we discover that by anodizing a metallic Ni-Fe composite foam under a harsh condition (in a low-concentration 0.1 M KHCO3 solution at 85 °C under a high-current ∼250 mA/cm2), OER on the NiFe foam is accompanied by anodic etching, and the surface layer evolves into a nickel-iron hydroxide carbonate (NiFe-HC) material composed of porous, poorly crystalline flakes of flower-like NiFe layer-double hydroxide (LDH) intercalated with carbonate anions. The resulting NiFe-HC electrode in CO2-saturated 0.5 M KHCO3 exhibited OER activity superior to IrO2, with an overpotential of 450 and 590 mV to reach 10 and 250 mA/cm2, respectively, and high stability for >120 h without decay. We paired NiFe-HC with a CO2RR catalyst of cobalt phthalocyanine/carbon nanotube (CoPc/CNT) in a CO2 electrolyzer, achieving selective cathodic conversion of CO2 to CO with >97% Faradaic efficiency and simultaneous anodic water oxidation to O2 The device showed a low cell voltage of 2.13 V and high electricity-to-chemical fuel efficiency of 59% at a current density of 10 mA/cm2.

Flavopereirine induces cell cycle arrest and apoptosis via the AKT/p38 MAPK/ERK1/2 signaling pathway in human breast cancer cells.

Breast cancer, which is the most frequently diagnosed cancer, is quite heterogeneous. For breast cancer subtypes lacking targeted therapies, it is vitally essential to find novel agents that prevent chemoresistance and metastatic relapse. Flavopereirine is a ß-carboline alkaloid that has antiplasmodial activity, and its antiproliferative effect in different cancers remains unclear. The effect of flavopereirine on cell cycle arrest and apoptosis signaling in breast cancer cells was analyzed by flow cytometry. An inhibitor and siRNA were used to confirm the related signaling pathways by Western blot analysis. We found that flavopereirine caused G0/G1 phase arrest in MCF-7 cells and S phase arrest in MDA-MB-231 cells. MDA-MB-231 cells were more sensitive to flavopereirine-induced apoptosis. Furthermore, we found that flavopereirine-induced apoptosis was partially reduced in MDA-MB-231 cells treated with an extracellular regulated kinase (ERK) inhibitor and p38 mitogen-activated protein kinase (MAPK) siRNA. Moreover, p38 siRNA treatment simultaneously reduced phosphorylated ERK expression levels. Conversely, the recovered phosphorylation of AKT decreased the levels of p-ERK and p-p38 MAPK. Overall, flavopereirine induces cell cycle arrest and the AKT/p38 MAPK/ERK signaling pathway, which contribute to flavopereirine-induced apoptosis in MDA-MB-231 cells.