Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.11.16.379206v1?rss=1 Authors: Takahashi, M., Seino, R., Ezoe, T., Ishiyama, M., Ueno, Y. Abstract: The plasma membrane (PM) plays a critical role in many cellular processes, and PM dysfunction is a key biomarker related to the cell status and several diseases. Imaging techniques using small fluorescent probes have become increasingly important tools for visualizing living cells, and particularly, their PMs. Among the commercially available PM-specific probes, PKH dyes are widely used; however, the utility of these dyes is limited by their short membrane retention times and high cytotoxicity. Herein, PlasMem Bright Green and Red are implemented as new PM-specific fluorescent probes, which employ a polycyclic aromatic fluorophore to improve their retention ability and a strong acid moiety to reduce their transmembrane diffusion and cytotoxicity. We demonstrate that the long retention and low cytotoxicity of the PlasMem Bright dyes enable them to be applied for observing neuronal PMs and monitoring PM dynamics involving the endocytic pathway. Furthermore, we successfully detected mitochondria in nerve axons over long periods of time using PlasMem Bright dyes. Finally, the combined use of exosome staining probes and PlasMem Bright dyes allowed clear visualization of the endocytic pathway. Copy rights belong to original authors. Visit the link for more info