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Abstract

Nanomaterials are increasingly used for the diagnosis and treatment of cancer, including
lung cancer. For the clinical translation of nano-based theranostics, it is vital to detect and monitor their
accumulation in the tumor, as well as their interaction with tumor, immune cells, and the tumor
microenvironment (TME). While high resolution microscopy of fixed tumor specimens can provide some
of this information from individual thin slices, it cannot capture cellular events over time and lacks 3D
information of the tumor tissue. On the other hand, in vivo optical procedures either fall short of providing
the necessary cellular resolution, as in the case of epifluorescence optical imaging, or are very
demanding, as for instance intravital lung microscopy. We describe an alternative approach to
investigate nanoparticle-cell interactions in entire mouse lung lobes, by longitudinal live cell confocal
microscopy at nanometer resolution. By filling the lung ex vivo with 1% agarose, we were able to stabilize
the lung lobes and visualize the interaction of fluorescent cells and nanoparticles for at least 4 hours
post mortem. This high resolution ex vivo live cell imaging approach is an easy 4D tool for assessing
several dynamic processes in tumor tissue, such as the traffic of cells, shedding of extracellular vesicles
(EVs), and the accumulation of nanoparticles in tumor tissue.