The neonatal Fc receptor (FcRn) transports maternal IgG across epithelial barriers 1,2 , thereby providing the fetus or newborn with humoral immunity before its immune system is fully functional. In newborn rodents, FcRn transfers IgG from milk to blood by apical-to-basolateral transcytosis across intestinal epithelial cells. The pH difference between the apical (pH 6.0-6.5) and basolateral (pH 7.4) sides of intestinal epithelial cells facilitates efficient unidirectional transport of IgG, since FcRn binds IgG at pH 6.0-6.5 but not pH ≥7 1,2 . As milk passes through the neonatal intestine, maternal IgG is removed by FcRn-expressing cells in the proximal small intestine (duodenum, jejunum); remaining proteins are absorbed and degraded by FcRn-negative cells in the distal small intestine (ileum) [3][4][5][6] . We used electron tomography to directly visualize jejunal transcytosis in space and time, developing new labeling and detection methods to map individual nanogold-labeled Fc within transport vesicles 7 and to simultaneously characterize these vesicles by immunolabeling. Combining electron tomography with a non-perturbing endocytic label allowed us to conclusively identify receptor-bound ligands, resolve interconnecting vesicles, determine if a vesicle was microtubule-associated, and accurately trace FcRn-mediated transport of IgG. Our results present a complex picture in which Fc moved through networks of entangled tubular and irregular vesicles, only some of which were microtubule-associated, as it migrated to the basolateral surface. New features of transcytosis were elucidated, including transport involving multivesicular body inner vesicles/tubules and exocytosis via clathrin-coated pits. Markers for early, late, and recycling Table S1), consistent with AuFc bound to FcRn; and (iii) Au-Fc, but not Au-dextran, was enhanced in proximal (FcRnpositive) cells, whereas both were enhanced in distal (FcRn-negative) cells, reflecting receptormediated and fluid-phase uptake in the proximal and distal intestine, respectively ( Fig.1a; Supplementary Fig.S7).More than 50 tomograms, each ~1.8 μm 3 , were recorded from jejunal cells from Au-Fc-fed neonatal rats (steady-state experiments) (Supplementary Table S1). For kinetic analysis, ligated intestinal lumens were incubated with Au-Fc (>50 pulse or pulse/chase tomograms or projections) (Supplementary Table S3). We defined three jejunal cell regions ( Table S1 , Fig.S8): clathrin-coated pits at the apical/basolateral membranes, regular ~60nm diameter tubular vesicles (RTVs -uniform diameters; variable lengths), coated buds/tips on RTVs, coated and uncoated spherical vesicles, irregular >70nm tubular vesicles (ITVs -variable diameters/lengths), irregular nontubular vesicles (INTVs), coated/uncoated bulbs in ITVs/INTVs, multivesicular bodies (MVBs), and MVB inner vesicles, protrusions, and tubules. Compartments that contained enlarged Au-Fc were further characterized by immunolabeling using antibodies against early (EEA1 and Rab5), late (Rab7 and Rab9), and rec...
In this work, a new approach to modifying poly(dimethylsiloxane) (PDMS) as a negative triboelectric material using graphene oxide (GO) and a sodium dodecyl sulfate (SDS) surfactant was reported. A porous PDMS@GO@SDS composite triboelectric nanogenerator (TENG) could deliver an output voltage and current of up to 438 V and 11 μA/cm, respectively. These values were 3-fold higher than those of the flat PDMS. The superior performance is attributed to the intensified negative charges on PDMS from the oxygen functional groups of GO and anionic head groups of the SDS molecules. The outstanding performance and straightforward, low-cost fabrication process of the PDMS@GO@SDS TENG would be beneficial for the further development of powerful NGs integrated into wearable electronics and self-charging power cells.
Ultrathin two-dimensional (2D) charge density wave (CDW) materials, with sharp resistance change at the phase-transition temperature, yet with ultrathin thickness, hold great potential for electrical device applications. However, chemical synthesis of high-quality samples and observation of the CDW states down to the monolayer limit is still of great challenge. Chemical vapor deposition of 1T-TaS sheets on hexagonal boron nitride (h-BN) with robust CDW states even down to the monolayer extreme is reported here. Further, based on the near commensurate CDW to incommensurate CDW phase transition with a high temperature coefficient of resistance (TCR), highly responsive room-temperature bolometers are fabricated by suspending the as-grown 1T-TaS sheets.
This work is a systematic experimental and theoretical study of the in‐plane dielectric functions of 2D gallium and indium films consisting of two or three atomic metal layers confined between silicon carbide and graphene with a corresponding bonding gradient from covalent to metallic to van der Waals type. k‐space resolved free electron and bound electron contributions to the optical response are identified, with the latter pointing towards the existence of thickness dependent quantum confinement phenomena. The resonance energies in the dielectric functions and the observed epsilon near‐zero behavior in the near infrared to visible spectral range, are dependent on the number of atomic metal layers and properties of the metal involved. A model‐based spectroscopic ellipsometry approach is used to estimate the number of atomic metal layers, providing a convenient route over expensive invasive characterization techniques. A strong thickness and metal choice dependence of the light–matter interaction makes these half van der Waals 2D polar metals attractive for quantum engineered metal films, tunable (quantum‐)plasmonics and nano‐photonics.
Ionic thermocells have relatively high thermopowers based on thermogalvanic effect, but their small electricity output is still insufficient for practical applications. We demonstrated a highly ionic conductive, anti-freezing stretchable thermogalvanic...
We have developed methods to locate individual ligands that can be used for electron microscopy studies of dynamic events during endocytosis and subsequent intracellular trafficking. The methods are based on enlargement of 1.4 nm Nanogold attached to an endocytosed ligand. Nanogold, a small label that does not induce misdirection of ligand-receptor complexes, is ideal for labeling ligands endocytosed by live cells, but is too small to be routinely located in cells by electron microscopy. Traditional pre-embedding enhancement protocols to enlarge Nanogold are not compatible with high pressure freezing/freeze substitution fixation (HPF/FSF), the most accurate method to preserve ultrastructure and dynamic events during trafficking. We have developed an improved enhancement procedure for chemically-fixed samples that reduced autonucleation, and a new pre-embedding goldenlarging technique for HPF/FSF samples that preserved contrast and ultrastructure and can be used for high-resolution tomography. We evaluated our methods using labeled Fc as a ligand for the neonatal Fc receptor. Attachment of Nanogold to Fc did not interfere with receptor binding or uptake, and gold-labeled Fc could be specifically enlarged to allow identification in 2D projections and in tomograms. These methods should be broadly applicable to many endocytosis and transcytosis studies.
The development of an effective mechanical to electrical energy conversion device and its functional integration with an energy storage device for self-powered portable gadgets are cutting-edge research fields. However, the generated power and the mechanical stability of these integrated devices are still not efficient to power up portable electronics. We fabricated a rectifier-free piezoelectric nanogenerator (NG) integrated with a supercapacitor (SC). A multifunctional composite matrix was prepared by the incorporation of ultrathin (<10 nm) ZnO nanoflakes and reduced graphene oxide in polyvinylidene fluoride to enhance the piezoelectric output characteristics and mechanical stability of the device while minimizing the additional energy losses during the integration. The as-fabricated SC-based power unit through the energy conversion and storage processes showed a remarkable self-charging performance. We obtained the maximum output voltage, current density, and power density of about 44 V, 1000 nA cm–2, and 193.6 μW cm–2 under the applied mechanical force of 10 N, respectively. The self-charging behavior of the device showed that it can store 1.5 × 10–3 mC within 100 s without resorting to a rectifier. We obtained the total energy density of about 10.34 mW h kg–1 under palm impact. Our results present a step forward in the development of the NG and SC-based flexible and self-charging devices.
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