Thousandfold Expansion Microscopy

Amazing stuff!

"... In a preprint posted last month to bioRxiv, Boyden and colleagues describe “thousandfold expansion microscopy” or 1000ExM, a method that expands tissues as much as 1000x in every direction—a one billion times increase in volume.

First, they improved upon the expanding gel used to spread things apart. They also figured out how to bind target molecules to this gel, allowing them to break apart proteins and other bonded entities while keeping their pieces relative in space. Lastly, they tinkered with their technique to allow them to repeat the expansion step over and over again. ..."

From the abstract:

"Biological macromolecules, such as proteins, are made of concatenated building blocks. We hypothesized that individual protein residues could be imaged by anchoring their side chains to a swellable polymer, cleaving backbone amide bonds, and expanding residues away from each other to a degree that enables them to be visualized separately.

We introduce thousandfold expansion microscopy (1000ExM), a four-network interpenetrating hydrogel architecture that enables successive expansion from ∼18-fold to >1000-fold (one billion-fold in volume). Protein and peptide structures are maintained across these expansion factors, as verified by analyses of proteins with known structures (nanobodies, GFP) and a well-studied peptide (mCLING). Computational analysis indicates that 1000ExM resolves adjacent amino acid residues, thereby achieving sub-nanometer precision on conventional light microscopes. We anticipate that 1000ExM will find wide utility in protein visualization and identification, potentially even in intact cells and tissues."

ScienceAdviser

Thousandfold Expansion Microscopy (preprint, open access)

A small peptide with one end tagged in purple and certain amino acids in green, showing the difference in resolution between 18x expansion (top; full field on left, zoom in orange on right) and 1000x expansion.

Fig. 1 Design of a four-network interpenetrating polymer network (IPN) architecture enabling ∼1000× linear expansion via recursive ionic-in-ionic casting.