Visualization of 3D morphological changes in the subcellular structures of a biological specimen is a major challenge in life science. Despite conspicuous refinements in optical nanoscopy, the determination of quantitative changes in subcellular structures, i.e., size and thickness, remains elusive. We present an integrated chip-based optical nanoscopy set-up that provides a lateral optical resolution of 61 nm, combined with a quantitative phase microscopy (QPM) system with a spatial phase sensitivity of ±20 mrad. We used the system to obtain 3D morphology of liver sinusoidal endothelial cells (LSEC) by using chip-based nanoscopy for lateral super-resolution, and high spatially sensitive QPM for nanoscale axial sensitivity. LSEC have unique morphology with small nanopores (50-300 nm in diameter) in the plasma membrane, called fenestrations. The fenestrations are grouped in discrete clusters, which are around 100-200 nm thick. Thus, imaging and quantification of fenestrations and sieve plate thickness requires resolution and sensitivity of sub-100 nm along both the lateral and the axial directions respectively. In chip-based nanoscopy, the optical waveguides are used both for hosting and illuminating the sample through the evanescent field. The fluorescence signal is captured by an upright microscope, which is converted into a Linnik-type interferometer to sequentially acquire both super-resolved images and quantitative phase information of the sample. The multi-modal microscope provided an estimate of the fenestration diameter of 119±53 nm and average thickness of the sieve plates of 136.6±42.4 nm, assuming constant refractive index of cell membrane to be 1.38. Further, to demonstrate the possibility of precise detection of changes in the cell height, LSEC were treated with cytochalasin B. The mean phase value of the fenestrated area in normal and treated cells was found to be 161±50 mrad and 109±49 mrad, respectively. The proposed multi-modal dSTORM and QPM combination offers nanoscale visualization of both the lateral size and the thickness map, which would be of broader interest in the fields of cell biology and bio-imaging.

ThunderSTORM (Fiji Plugin), 1.3