Quantitative phase imaging of adherent mammalian cells: a comparative study.

The Quantitative phase imaging methods have several advantages when it comes to monitoring cultures of adherent mammalian cells. Because of low photo-toxicity and no need for staining, we can follow cells in a minimally invasive way over a long period of time. The ability to measure the optical path difference in a quantitative manner allows the measurement of the cell dry mass, an important metric for studying the growth kinetics of mammalian cells.

Large field-of-view phase and fluorescence mesoscope with microscopic resolution.

Phase and fluorescence are complementary contrasts that are commonly used in biology. However, the coupling of these two modalities is traditionally limited to high magnification and complex imaging systems. For statistical studies of biological populations, a large field-of-view is required.

Photothermal Control of Heat-Shock Protein Expression at the Single Cell Level.

Laser heating of individual cells in culture recently led to seminal studies in cell poration, fusion, migration, or nanosurgery, although measuring the local temperature increase in such experiments remains a challenge. Here, the laser-induced dynamical control of the heat-shock response is demonstrated at the single cell level, enabled by the use of light-absorbing gold nanoparticles as nanosources of heat and a temperature mapping technique based on quadriwave lateral shearing interferometry (QLSI) measurements. As it is label-free, this approach does not suffer from artifacts inherent to previously reported fluorescence-based temperature-mapping techniques and enables the use of any standard fluorescent labels to monitor in parallel the cell's response.

Polarized super-resolution structural imaging inside amyloid fibrils using Thioflavine T.

Thioflavin T (ThT) is standardly used as a fluorescent marker to detect aggregation of amyloid fibrils by conventional fluorescence microscopy, including polarization resolved imaging that brings information on the orientational order of the fibrils. These techniques are however diffraction limited and cannot provide fine structural details at the fibrils scales of 10-100 nm, which lie beyond the diffraction limit. In this work, we evaluate the capacity of ThT to photoswitch when bound to insulin amyloids by adjusting the redox properties of its environment.

Quantitative nanoscale imaging of orientational order in biological filaments by polarized superresolution microscopy.

Essential cellular functions as diverse as genome maintenance and tissue morphogenesis rely on the dynamic organization of filamentous assemblies. For example, the precise structural organization of DNA filaments has profound consequences on all DNA-mediated processes including gene expression, whereas control over the precise spatial arrangement of cytoskeletal protein filaments is key for mechanical force generation driving animal tissue morphogenesis. Polarized fluorescence is currently used to extract structural organization of fluorescently labeled biological filaments by determining the orientation of fluorescent labels, however with a strong drawback: polarized fluorescence imaging is indeed spatially limited by optical diffraction, and is thus unable to discriminate between the intrinsic orientational mobility of the fluorophore labels and the real structural disorder of the labeled biomolecules.