Expansion Microscopy: Recent Developments in Gelation, Labeling, and Imaging Strategies

Abstract

Light microscopy is a powerful approach for studying the dynamic spatiotemporal organization of the molecular processes in cellular life. However, the resolution that can be obtained using conventional light microscopy is insufficient to resolve many macromolecular structures. While various super-resolution imaging approaches have been developed that overcome this resolution limit, they require specialized equipment that is largely inaccessible to most scientists. Recently, an alternative method for super-resolution imaging was developed, called expansion microscopy, which bypasses the resolution limit by spatially separating biomolecules through expansion of the sample. Unlike previous super-resolution imaging approaches, expansion microscopy can be performed using commercially available compounds and widely-available conventional microscopes, making super-resolution imaging more accessible for non-expert researchers. In this review, the original expansion microscopy concept and followed by early developments in its workflow will first be described. Next, this review will focus on challenges within the field of expansion microscopy, including labeling density, expansion factor, and expansion isotropy, and critically review recent developments aimed at addressing these challenges. Finally, recently developed alternative labeling strategies for expansion microscopy and the possibility to combine expansion microscopy with other super-resolution microscopy approaches will be discussed.