9 research outputs found

    Microfluidics Reveals a Flow-Induced Large-Scale Polymorphism of Protein Aggregates

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    Amyloid fibrils are characterized by a structural arrangement of cross β-sheet as a common motif. However they can also experience a more complicated packing into a variety of 3D supramolecular structures (polymorphism). Confinement and flow rate play a crucial role in protein aggregation in living systems, but controlling such parameters during in vitro experiments still remains an unsolved problem. Here we present evidence of the effect of flow rate on the aggregation process in a confined environment using microfluidics. Specifically, we show that a gradual transition from spherical aggregates, that is, spherulites, to thick fiber-like structures takes place as a result of increasing the flow rate. Such results have implications both for a basic understanding of the mechanism behind aggregation phenomena and in the development of novel biomaterials

    Soft nanolithography by polymer fibers

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    We report on the use of polymer fibers for large-area soft nanolithography on organic and inorganic surfaces with 50 nm resolution. The morphology of fibers and of the corresponding patterned gap is investigated, demonstrating a lateral dimension downscaling of up to nine times, which greatly increases the achieved resolution during pattern transfer. In this way, we realize poly­mer field effect transistors with channel length and width as low as 250 nm that are expected to show transistor transition frequency up to a few MHz, and are thus exploitable as low-cost radio-frequency identification devices

    Annuaire du club alpin français

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    18921892-1892.Appartient à l’ensemble documentaire : PACA

    Additional file 5: Figure S5. of Investigating the physiology of viable but non-culturable bacteria by microfluidics and time-lapse microscopy

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    Susceptible cells are indistinguishable from untreated cells before drug treatment. Distribution of fluorescence levels in the susceptible phenotype before drug treatment (t = 0) and in untreated control cells before regrowth in LB (t = 0) in the a) tolC, b) tnaC, and c) ptsG reporter strain. The two populations are not statistically different, an unpaired t test with Welch’s correction yielding a P value of 0.07, 0.7, and 0.9, respectively. The bottom and top of the box are the first and third quartiles, the band inside the box is the median, the bottom and top whiskers represent the 10th and 90th percentiles, respectively. Data are obtained at least in biological triplicate (N = 3) for each reporter strain employed for a total of n S  = 6659 and n C  = 3076 susceptible and control cells, respectively. We did not observe any significant difference between the results obtained from different biological replica. (PNG 423 kb

    Soft nanolithography by polymer fibers

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    We report on the use of polymer fibers for large-area soft nanolithography on organic and inorganic surfaces with 50 nm resolution. The morphology of fibers and of the corresponding patterned gap is investigated, demonstrating a lateral dimension downscaling of up to nine times, which greatly increases the achieved resolution during pattern transfer. In this way, we realize poly­mer field effect transistors with channel length and width as low as 250 nm that are expected to show transistor transition frequency up to a few MHz, and are thus exploitable as low-cost radio-frequency identification devices

    Patterning of light-emitting conjugated polymer nanofibres

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    Organic materials have revolutionized optoelectronics by their processability, flexibility and low cost, with application to light-emitting devices for full-colour screens1, solar cells2 and lasers3, 4. Some low-dimensional organic semiconductor structures exhibit properties resembling those of inorganics, such as polarized emission5 and enhanced electroluminescence6. One-dimensional metallic, III–V and II–VI nanostructures have also been the subject of intense investigation7, 8 as building blocks for nanoelectronics and photonics. Given that one-dimensional polymer nanostructures, such as polymer nanofibres, are compatible with sub-micrometre patterning capability9 and electromagnetic confinement within subwavelength volumes8, they can offer the benefits of organic light sources to nanoscale optics. Here we report on the optical properties of fully conjugated, electrospun polymer nanofibres. We assess their waveguiding performance and emission tuneability in the whole visible range. We demonstrate the enhancement of the fibre forward emission through imprinting periodic nanostructures using room-temperature nanoimprint lithography, and investigate the angular dispersion of differently polarized emitted light

    Local Mechanical Properties of Electrospun Fibers Correlate to Their Internal Nanostructure

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    The properties of polymeric nanofibers can be tailored and enhanced by properly managing the structure of the polymer molecules at the nanoscale. Although electrospun polymer fibers are increasingly exploited in many technological applications, their internal nanostructure, determining their improved physical properties, is still poorly investigated and understood. Here, we unravel the internal structure of electrospun functional nanofibers made by prototype conjugated polymers. The unique features of near-field optical measurements are exploited to investigate the nanoscale spatial variation of the polymer density, evidencing the presence of a dense internal core embedded in a less dense polymeric shell. Interestingly, nanoscale mapping the fiber Young’s modulus demonstrates that the dense core is stiffer than the polymeric, less dense shell. These findings are rationalized by developing a theoretical model and simulations of the polymer molecular structural evolution during the electrospinning process. This model predicts that the stretching of the polymer network induces a contraction of the network toward the jet center with a local increase of the polymer density, as observed in the solid structure. The found complex internal structure opens an interesting perspective for improving and tailoring the molecular morphology and multifunctional electronic and optical properties of polymer fibers

    Time-scales and niche-specific relevance of cell viscoelasticity.

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    <p><b>A</b>, <i>In vivo</i>, neutrophils and monocytes navigate constrictions smaller than themselves (<i>y</i>) and deform rapidly as illustrated (<1 s). Macrophages on the other hand, as well as neutrophils and monocytes after extravasation, migrate through tissue, which occurs over much longer time-scales. <b>B</b>, Short time scale advection of cells through the 12 µm×12 µm channel at a pressure of 20 mbar. Macrophages (<i>n</i> = 50) require an average advection time (from entry to exit) of 3.98±1.77 s, an order of magnitude longer than all other cell types and with statistically significant difference (<i>p</i><0.05). There are no statistically significant differences between the advection times of HL60 (<i>n</i> = 24), neutrophils (<i>n</i> = 36), monocytes (<i>n</i> = 50) and macrophages treated with 2 µM Cytochalasin D shown as Mac+ (<i>n</i> = 67). Scale bar is 10 µm. <b>C</b>, Long time scale migration of the three mature cell types and precursors in Boyden chamber assays, where cells squeeze actively through a thick, porous membrane. After 3 h, significantly (<i>p</i><0.0001) more of all three differentiated cell types have migrated than the undifferentiated, more viscous cells. Scale bar is 10 µm.</p

    Creep compliance test distinguishes between cell lineages following differentiation.

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    <p><b>A</b>, Schematic of the optical stretcher (OS), showing two diverging, counter-propagating laser beams emanating from single-mode optical fibres. <b>B</b>, A cell is held at trapping stress of 1.7±0.1 Pa at time <i>t</i> = 0 s. The trapped cell is stretched when the optical stress is increased to 6.0±0.1 Pa, producing an axial strain of 8.17±0.05% at <i>t</i> = 4 s, for the cell shown. The graph shows both the strain and compliance profiles for this one cell, illustrating the single cell resolution of the OS method. Scale bar is 10 µm. <b>C</b>, Representative compliance profiles for all three fully differentiated lineages and for the undifferentiated cells (<i>n</i> = 89). For neutrophils (Neu; <i>n</i> = 75) and monocytes (Mono; <i>n</i> = 85), the compliance increased, while for macrophages (Mac; <i>n</i> = 52) the compliance decreased. <b>D</b>, Box plots of the average compliance during the four seconds of stretching. For all three differentiated lineages, the entire compliance profile, as well as the peak compliance at 4 s (not shown), were significantly different from undifferentiated HL60 cells, where **** and ** indicate significant differences with <i>p</i> values of <0.0001 and <0.01, respectively.</p
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