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    The 2018 correlative microscopy techniques roadmap
    (Bristol : IOP Publishing, 2018) Ando, Toshio; Bhamidimarri, Satya Prathyusha; Brending, Niklas; Colin-York, H; Collinson, Lucy; De Jonge, Niels; de Pablo, P J; Debroye, Elke; Eggeling, Christian; Franck, Christian; Fritzsche, Marco; Gerritsen, Hans; Giepmans, Ben N G; Grunewald, Kay; Hofkens, Johan; Hoogenboom, Jacob P; Janssen, Kris P F; Kaufmann, Rainer; Klumpermann, Judith; Kurniawan, Nyoman; Kusch, Jana; Liv, Nalan; Parekh, Viha; Peckys, Diana B; Rehfeldt, Florian; Reutens, David C; Roeffaers, Maarten B J; Salditt, Tim; Schaap, Iwan A T; Schwarz, Ulrich S; Verkade, Paul; Vogel, Michael W; Wagner, Richard; Winterhalter, Mathias; Yuan, Haifeng; Zifarelli, Giovanni
    Developments in microscopy have been instrumental to progress in the life sciences, and many new techniques have been introduced and led to new discoveries throughout the last century. A wide and diverse range of methodologies is now available, including electron microscopy, atomic force microscopy, magnetic resonance imaging, small-angle x-ray scattering and multiple super-resolution fluorescence techniques, and each of these methods provides valuable read-outs to meet the demands set by the samples under study. Yet, the investigation of cell development requires a multi-parametric approach to address both the structure and spatio-temporal organization of organelles, and also the transduction of chemical signals and forces involved in cell–cell interactions. Although the microscopy technologies for observing each of these characteristics are well developed, none of them can offer read-out of all characteristics simultaneously, which limits the information content of a measurement. For example, while electron microscopy is able to disclose the structural layout of cells and the macromolecular arrangement of proteins, it cannot directly follow dynamics in living cells. The latter can be achieved with fluorescence microscopy which, however, requires labelling and lacks spatial resolution. A remedy is to combine and correlate different readouts from the same specimen, which opens new avenues to understand structure–function relations in biomedical research. At the same time, such correlative approaches pose new challenges concerning sample preparation, instrument stability, region of interest retrieval, and data analysis. Because the field of correlative microscopy is relatively young, the capabilities of the various approaches have yet to be fully explored, and uncertainties remain when considering the best choice of strategy and workflow for the correlative experiment. With this in mind, the Journal of Physics D: Applied Physics presents a special roadmap on the correlative microscopy techniques, giving a comprehensive overview from various leading scientists in this field, via a collection of multiple short viewpoints.
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    Oscillatory Microrheology, Creep Compliance and Stress Relaxation of Biological Cells Reveal Strong Correlations as Probed by Atomic Force Microscopy
    (Lausanne : Frontiers Media, 2021) Flormann, D.A.D.; Anton, C.; Pohland, M.O.; Bautz, Y.; Kaub, K.; Terriac, E.; Schäffer, T.E.; Rheinlaender, J.; Janshoff, A.; Ott, A.; Lautenschläger, F.
    The mechanical properties of cells are important for many biological processes, including wound healing, cancers, and embryogenesis. Currently, our understanding of cell mechanical properties remains incomplete. Different techniques have been used to probe different aspects of the mechanical properties of cells, among them microplate rheology, optical tweezers, micropipette aspiration, and magnetic twisting cytometry. These techniques have given rise to different theoretical descriptions, reaching from simple Kelvin-Voigt or Maxwell models to fractional such as power law models, and their combinations. Atomic force microscopy (AFM) is a flexible technique that enables global and local probing of adherent cells. Here, using an AFM, we indented single retinal pigmented epithelium cells adhering to the bottom of a culture dish. The indentation was performed at two locations: above the nucleus, and towards the periphery of the cell. We applied creep compliance, stress relaxation, and oscillatory rheological tests to wild type and drug modified cells. Considering known fractional and semi-fractional descriptions, we found the extracted parameters to correlate. Moreover, the Young’s modulus as obtained from the initial indentation strongly correlated with all of the parameters from the applied power-law descriptions. Our study shows that the results from different rheological tests are directly comparable. This can be used in the future, for example, to reduce the number of measurements in planned experiments. Apparently, under these experimental conditions, the cells possess a limited number of degrees of freedom as their rheological properties change.