Dual-color single molecule localization microscopy on transparent polymer waveguide chips

Photonic waveguide chips offer near-field excitation of biological samples, which enables cost-effective, large field-of-view super-resolution microscopy without the need for high numerical aperture (NA) objective lenses. Single molecule localization based super-resolution microscopy that requires high illumination intensities is currently limited to solid state photonic waveguide chips composed of hard-coated, high NA planar waveguides deposited on opaque substrates. These platforms do not permit epi-detection of fluorescence through the substrate, which limits the use of photonic waveguide chips to the upright configuration. Additionally, the detection efficiency is reduced because the majority of the fluorescence emission is directed towards the high refractive index substrate. A low cost waveguide chip based on a polymer core material deposited on common #1.5 coverslips that is easy to produce was recently demonstrated. Here, a platform that is capable of performing single-molecule localization microscopy (SMLM) of biological samples using polymer-based photonic waveguide chips is presented, enabling super-solution microscopy in the inverted microscope configuration. Super-resolved imaging of two different structures of the cytoskeleton in primary liver sinusoidal endothelial cells (LSECs) by two popular SMLM methods, dSTORM and DNA-PAINT, down to 23 nm is demonstrated. ### Competing Interest Statement The authors have declared no competing interest.