Ballistic Microscopy (BaM)

Abstract

Light and electron microscopy utilizes interactions of either photons or electrons with matter to create images from cellular to atomic scale. However, these methods are limited in de novo discovery and spatial mapping of unknown biomolecules. Label free methods such as mass spectrometry or sequencing lack live-cell and subcellular context. Here we introduce a new approach, Ballistic Microscopy (BaM), to image cells with physical nanoparticles. We bombard living cells with millions of nanoparticles traveling at [~]1000 m/s. Each particle passes through cells, piercing and capturing attoliters of cytoplasm on a hydrogel substrate while preserving spatial information (SPLAT-MAP). This "physical image" of a live cell captures a molecular fingerprint of a cell on a hydrogel film that can be processed post-capture via multiple techniques such as TEM, Cryo-EM, mass spectrometry, confocal imaging, and DNA amplification. Using BaM, we discover previously unknown composition of CLIP170 and Tau3R condensates in HEK cells, uncovering Keratin-18 as a structural element. BaM establishes a new paradigm of "physical imaging" with modular readout platform for spatially resolved live sampling across cells, tissues, and organisms.