Chang, J.-B., Chen, F., Yoon, Y.-G., Jung, E. E., Babcock H., Kang J.-S., Asano S., Suk H.-J., Pak N., Tillberg P.W., Wassie A., Cai D., Boyden E.S. (2017) Iterative expansion microscopy, Nature Methods 14:593-599.
April 17, 2017
Chang, J.-B., Chen, F., Yoon, Y.-G., Jung, E. E., Babcock H., Kang J.-S., Asano S., Suk H.-J., Pak N., Tillberg P.W., Wassie A., Cai D., Boyden E.S. (2017) Iterative expansion microscopy, Nature Methods 14:593-599.
We recently developed a method called expansion microscopy, in which preserved biological specimens are physically magnified by embedding them in a densely crosslinked polyelectrolyte gel, anchoring key labels or biomolecules to the gel, mechanically homogenizing the specimen, and then swelling the gel–specimen composite by ~4.5× in linear dimension. Here we describe iterative expansion microscopy (iExM), in which a sample is expanded ~20×. After preliminary expansion a second swellable polymer mesh is formed in the space newly opened up by the first expansion, and the sample is expanded again. iExM expands biological specimens ~4.5 × 4.5, or ~20×, and enables ~25-nm-resolution imaging of cells and tissues on conventional microscopes. We used iExM to visualize synaptic proteins, as well as the detailed architecture of dendritic spines, in mouse brain circuitry.