The topoisomerase inhibitor CPT-11 prevents the growth and metastasis of lung cancer cells in nude mice by inhibiting EGFR/MAPK signaling pathway

Objective: The topoisomerase inhibitor CPT-11 has been applied in treatment of multiple cancer types. Here, we probed into the possible mechanism of CPT-11 in affecting growth and metastasis of lung cancer (LC) cells, with involvement of the EGFR/MAPK pathway. Methods: The target protein of CPT-11 was screened through bioinformatics analysis, and the LC-related microarray datasets GSE29249, GSE32863 and GSE44077 were obtained for differential analysis for identifying the target protein. A subcutaneous xenograft tumor model and a metastatic tumor model were constructed in nude mice for in vivo mechanism verification of the regulatory role of CPT-11 in LC through modulation of EGRF/MAPK pathway. Results: Bioinformatics analysis showed that EGFR was the target protein of CPT-11. In vivo animal experiments confirmed that CPT-11 enhanced LC cell growth and metastasis in nude mice. CPT-11 could inhibit activation of EGFR/MAPK pathway. EGFR promoted LC cell growth and metastasis in nude mice through activation of the MAPK pathway. Conclusion: The topoisomerase inhibitor CPT-11 may prevent LC growth and metastasis by inhibiting activation of EGFR/MAPK pathway

Ultrathin 2D Photodetectors Utilizing Chemical Vapor Deposition Grown WS₂ With Graphene Electrodes

In this report, graphene (Gr) is used as a 2D electrode and monolayer WS₂ as the active semiconductor in ultrathin photodetector devices. All of the 2D materials are grown by chemical vapor deposition (CVD) and thus pose as a viable route to scalability. The monolayer thickness of both electrode and semiconductor gives these photodetectors ∼2 nm thickness. We show that graphene is different to conventional metal (Au) electrodes due to the finite density of states from the Dirac cones of the valence and conduction bands, which enables the photoresponsivity to be modulated by electrostatic gating and light input control. We demonstrate lateral Gr–WS₂–Gr photodetectors with photoresponsivities reaching 3.5 A/W under illumination power densities of 2.5 × 10⁷ mW/cm². The performance of monolayer WS₂ is compared to bilayer WS₂ in photodetectors and we show that increased photoresponsivity is achieved in the thicker bilayer WS₂ crystals due to increased optical absorption. This approach of incorporating graphene electrodes in lateral TMD based devices provides insights on the contact engineering in 2D optoelectronics, which is crucial for the development of high performing ultrathin photodetector arrays for versatile applications

Utilizing Interlayer Excitons in Bilayer WS₂ for Increased Photovoltaic Response in Ultrathin Graphene Vertical Cross-Bar Photodetecting Tunneling Transistors

Here we study the layer-dependent photoconductivity in Gr/WS₂/Gr vertical stacked tunneling (VST) cross-bar devices made using two-dimensional (2D) materials all grown by chemical vapor deposition. The larger number of devices (>100) enables a statistically robust analysis on the comparative differences in the photovoltaic response of monolayer and bilayer WS₂, which cannot be achieved in small batch devices made using mechanically exfoliated materials. We show a dramatic increase in photovoltaic response for Gr/WS₂(2L)/Gr compared to monolayers because of the long inter- and intralayer exciton lifetimes and the small exciton binding energy (both interlayer and intralayer excitons) of bilayer WS₂ compared with that of monolayer WS₂. Different doping levels and dielectric environments of top and bottom graphene electrodes result in a potential difference across a ∼1 nm vertical device, which gives rise to large electric fields perpendicular to the WS₂ layers that cause band structure modification. Our results show how precise control over layer number in all 2D VST devices dictates the photophysics and performance for photosensing applications

Doping graphene transistors using vertical stacked monolayer WS2 heterostructures grown by chemical vapor deposition.

We study the interactions in graphene/WS2 2D layered vertical heterostructures with variations in the areal coverage of graphene by the WS2. All 2D materials were grown by chemical vapour deposition and transferred layer by layer. Photoluminescence (PL) spectroscopy of WS2 on graphene showed PL quenching along with an increase in the ratio of exciton/trion emission, relative to WS2 on SiO2 surface, indicating a reduction in the n-type doping levels of WS2 as well as reduced radiative recombination quantum yield. Electrical measurements of a total of 220 graphene field effect transistors with different WS2 coverage showed double-Dirac points in the field effect measurements, where one is shifted closer towards the 0V gate neutrality position due to the WS2 coverage. Photo-irradiation of the WS2 on graphene region caused further Dirac point shifts, indicative of a reduction in the p-type doping levels of graphene, revealing that the photogenerated excitons in WS2 are split across the heterostructure by electron transfer from WS2 to graphene. Kelvin probe microscopy showed that regions of graphene covered with WS2 had a smaller work function and supports the model of electron transfer from WS2 to graphene. Our results demonstrate the formation of junctions within a graphene transistor through the spatial tuning of the work function of graphene using these 2D vertical heterostructures

High-Performance All 2D-Layered Tin Disulfide: Graphene Photodetecting Transistors with Thickness-Controlled Interface Dynamics

Tin disulfide crystals with layered two-dimensional (2D) sheets are grown by chemical vapor deposition using a novel precursor approach and integrated into all 2D transistors with graphene (Gr) electrodes. The Gr:SnS₂:Gr transistors exhibit excellent photodetector response with high detectivity and photoresponsivity. We show that the response of the all 2D photodetectors depends upon charge trapping at the interface and the Schottky barrier modulation. The thickness-dependent SnS₂ measurements in devices reveal a transition from the interface-dominated response for thin crystals to bulklike response for the thicker SnS₂ crystals, showing the sensitivity of devices fabricated using layered materials on the number of layers. These results show that SnS₂ has photosensing performance when combined with Gr electrodes that is comparable to other 2D transition metal dichalcogenides of MoS₂ and WS₂

Doping Graphene Transistors Using Vertical Stacked Monolayer WS₂ Heterostructures Grown by Chemical Vapor Deposition

We study the interactions in graphene/WS₂ two-dimensional (2D) layered vertical heterostructures with variations in the areal coverage of graphene by the WS₂. All 2D materials were grown by chemical vapor deposition and transferred layer by layer. Photoluminescence (PL) spectroscopy of WS₂ on graphene showed PL quenching along with an increase in the ratio of exciton/trion emission, relative to WS₂ on SiO₂ surface, indicating a reduction in the n-type doping levels of WS₂ as well as reduced radiative recombination quantum yield. Electrical measurements of a total of 220 graphene field effect transistors with different WS₂ coverage showed double-Dirac points in the field effect measurements, where one is shifted closer toward the 0 V gate neutrality position due to the WS₂ coverage. Photoirradiation of the WS₂ on graphene region caused further Dirac point shifts, indicative of a reduction in the p-type doping levels of graphene, revealing that the photogenerated excitons in WS₂ are split across the heterostructure by electron transfer from WS₂ to graphene. Kelvin probe microscopy showed that regions of graphene covered with WS₂ had a smaller work function and supports the model of electron transfer from WS₂ to graphene. Our results demonstrate the formation of junctions within a graphene transistor through the spatial tuning of the work function of graphene using these 2D vertical heterostructures