Photonic waveguide chip-based nanoscopy visualizes rearrangements of the cortical actin cytoskeleton in activated Jurkat T cells.

The actin cytoskeleton in activated T cells undergoes rapid structural changes during the formation of an immunological synapse. Superresolution fluorescence microscopy provides excellent means to visualize such antibody-triggered changes. Here, we use single-molecule localization microscopy (SMLM) enabled by transparent polymer waveguide chips to resolve the filamentous-actin (F-actin) cytoskeleton in activated Jurkat T cells in comparison to nonactivated T cells across a large field of view. Transparent polymer waveguides enable a wide array of imaging modalities. In combination, these modalities reveal the structural differences between lamellipodial and ramified actin networks within the immunological synapse of activated T cells. SMLM images recorded by using narrow-width waveguide total internal reflection illumination resolve the double-stranded helical structure of actin filaments in activated Jurkat T cells. The average crossover length of the filaments is measured to be ~40 nanometers, which corroborates similar observations of isolated actin filaments by electron microscopy.