Quantitative phase microscopy with enhanced contrast and improved resolution through ultra‐oblique illumination (UO‐QPM)

Recent developments in phase contrast microscopy have enabled the label-free visualization of certain organelles due to their distinct morphological features, making this method an attractive alternative in the study of cellular dynamics. However tubular structures such as ER networks and complex dynamics such as the fusion and fission of mitochondria, due to their low phase contrast, still need fluorescent labeling to be adequately imaged. In this paper, we report a quantitative phase microscope with ultra-oblique illumination that enables us to see those structures and their dynamics with high contrast for the first time without labeling. The imaging capability was validated through comparison to the fluorescence images with the same field-of-view. The high image resolution ( ~270nm) was validated using both beads and cellular structures. Further, we were able to record the vibration of ER networks at a frame rate of 250Hz. We additionally show complex cellular processes such as remodelling of the mitochondria networks through fusion and fission and vesicle transportation along the ER without labels. Our high spatial and temporal resolution allowed us to observe mitochondria "spinning", which has not been reported before, further demonstrating the advantages of the proposed method. Keywords: Label free, ultra-oblique illumination, high temporospatial resolution, high contrast, quantitative phase This article is protected by copyright. All rights reserved.