Transmitted light imaging reveals sarcomeric ultrastructure is preserved in expansion microscopy

Abstract

Expansion Microscopy is a superresolution technique that employs a swellable hydrogel to physically expand a sample to approximately 4x its original size in each dimension. A labeled sample is crosslinked and embedded into acrylamide gel, then cleaved into fragments by a protease. As the gel absorbs water, it expands and pulls protein fragments apart from each other by an equal amount in all directions, enabling increased imaging resolution. Although the relative positions of fluorescent labels are maintained through the process, the optical properties of the proteins themselves were previously thought to be disrupted after protease treatment and expansion.