ABSTRACT
Many drug delivery systems end up in the lysosome because they are built from covalent or kinetically inert supramolecular bonds. To reach other organelles, nanoparticles hence need to either be made from a kinetically labile interaction that allows re-assembly of the nanoparticles inside the cell following endocytic uptake, or, be taken up by a mechanism that short-circuits the classical endocytosis pathway. In this work, the intracellular fate of nanorods that self-assemble via the Pt Pt interaction of cyclometalated platinum(II) compounds, is studied. These deep-red emissive nanostructures (638 nm excitation, ≈700 nm emission) are stabilized by proteins in cell medium. Once in contact with cancer cells, they cross the cell membrane via dynamin- and clathrin-dependent endocytosis. However, time-dependent confocal colocalization and cellular electron microscopy demonstrate that they directly move to mitochondria without passing by the lysosomes. Altogether, this study suggests that Pt Pt interaction is strong enough to generate emissive, aggregated nanoparticles inside cells, but labile enough to allow these nanostructures to reach the mitochondria without being trapped in the lysosomes. These findings open new venues to the development of bioimaging nanoplatforms based on the Pt Pt interaction.
Subject(s)
Coordination Complexes/chemistry , Nanostructures/chemistry , Platinum/chemistry , Cell Line, Tumor , Coordination Complexes/metabolism , Endocytosis , Humans , Microscopy, Confocal , Microscopy, Electron, Scanning , Mitochondria/chemistry , Mitochondria/metabolism , Quantum TheoryABSTRACT
Josephson junctions are the building blocks of superconducting electronics, with well-established applications in precision metrology and quantum computing. Fabricating a Josephson junction has been a resource-intensive and multistep procedure, involving lithography and wet-processing, which are not compatible with many applications. Here, we introduce a fully additive direct-write approach, where a scanning electron microscope can print substrate-conformal Josephson devices in a matter of minutes, requiring no additional processing. The junctions are made entirely by electron-beam-induced deposition (EBID) of tungsten carbide. We utilize EBID-tunable material properties to write, in one go, full proximity junctions with superconducting electrodes and metallic weak links and tailor their Josephson coupling. The Josephson behavior of these junctions is established and characterized by their microwave-induced Shapiro response and field-dependent transport. Our efforts provide a versatile and nondestructive alternative to conventional nanofabrication and can be expanded to print three-dimensional superconducting sensor arrays and quantum networks.
ABSTRACT
The two-dimensional electron liquid which forms between the band insulators LaAlO3 (LAO) and SrTiO3 (STO) is a promising component for oxide electronics, but the requirement of using single crystal SrTiO3 substrates for the growth limits its applications in terms of device fabrication. It is therefore important to find ways to deposit these materials on other substrates, preferably Si, or Si-based, in order to facilitate integration with existing technology. Interesting candidates are micron-sized nanosheets of Ca2Nb3O10 which can be used as seed layers for perovskite materials on any substrate. We have used low-energy electron microscopy (LEEM) with in-situ pulsed laser deposition to study the subsequent growth of STO and LAO on such flakes which were deposited on Si. We can follow the morphology and crystallinity of the layers during growth, as well as fingerprint their electronic properties with angle resolved reflected electron spectroscopy. We find that STO layers, deposited on the nanosheets, can be made crystalline and flat; that LAO can be grown in a layer-by-layer fashion; and that the full heterostructure shows the signature of the formation of a conducting interface.
