pan-ASLM: Axially Swept Light Sheet Microscopy for Fast and High-Resolution Imaging of Expanded Samples

Expansion microscopy, a super-resolution fluorescence microscopy technique in which samples are expanded up to ~8000 times (after 20-fold expansion) their original volume, places high demands on the microscopes used to image the expanded samples. To reveal nanoscale cellular ultrastructure in meaningful sample volumes, the instruments need to feature a large field of view and working distance. Simultaneously, they need to offer a high three-dimensional resolution to avoid counteracting the resolution improvement achieved by the expansion process. Here, we present pan-ASLM, a high resolution, large field-of-view light-sheet microscope developed for expanded samples, based on the Axially Swept Light Sheet Microscopy (ASLM) technique. pan-ASLM allows imaging over a 640 x 640 µm² field of view with lateral and axial resolutions of 586 and 428 nm, respectively, and features an image acquisition speed of up to 20 fps (183 Mvoxels/sec). It offers ~1200× higher imaging speed, a ~7× larger field of view, and ~2× better axial resolution than the standard confocal microscopes typically used for expanded samples. We validate the new microscope design through imaging of pan-expanded HeLa cells as well as mouse kidney and brain tissue.