Expansion microscopy (ExM) is a technique based on isotropic expansion of a biological specimen by tethering the sample into a swellable polyelectrolyte hydrogel. ExM enables optically clear, superresolution imaging of immunolabeled samples via standard confocal microscopy. We describe ExM hydrogels prepared via thiol-acrylate mixed-mode photopolymerization (PhotoExM), which is highly advantageous for ExM applications, as i) it proceeds rapidly, (i.e. 1 min.) enabling high-throughput fabrication, ii) is oxygen insensitive, preventing depth dependent crosslinking density and expansion and iii) has superior mechanical properties owing to simultaneous step and chain growth. (A) PhotoExM gels are composed of a bisacrylamide crosslinker, chain transfer agent (i.e. -SH), electrolyte monomer (i.e. sodium acrylate) and a photoinitatior. PhotoExM gels were obtained via mild 365 nm light irradiation (I0 = 2-5 mW/cm2) and upon dissociation of the electrolyte monomer, 4-5x expansion was obtained, (B) which was determined by imaging identical area of Lamin A immunolabeled myoblasts pre/post-expansion. (C) PhotoExM allows ~70 nm resolution, as measured from a-tubulin diameter in myoblasts. (D) Furthermore, we used PhotoExM to resolve muscle stem cells on myofibers and in tissue sections, which are difficult to resolve via standard microscopy due to their small size and nuclear morphology. We will further demonstrate the applicability of PhotoExM to carry out superresolution imaging cells/tissues grown in biomaterials. Imaging through biomaterials posit similar challenges to that of tissues (opacity, absorption, aberrations) and circumventing these limitations can enable novel biological investigations.

Photopolymerized hydrogels for expansion microscopy (PhotoExM)

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.