Expansion microscopy: principles and uses in biological research

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Abstract

Many biological investigations require 3D imaging of cells or tissues with nanoscale spatial resolution. We recently discovered that preserved biological specimens can be physically expanded in an isotropic fashion through a chemical process. Expansion microscopy (ExM) allows nanoscale imaging of biological specimens with conventional microscopes, decrowds biomolecules in support of signal amplification and multiplexed readout chemistries, and makes specimens transparent. We review the principles of how ExM works, advances in the technology made by our group and others, and its applications throughout biology and medicine.

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Fig. 1: ExM concept and example outcomes.
Fig. 2: Applications of ExM in biology and medicine.
Fig. 3: ExM decrowds biomolecules, facilitating post-expansion staining, signal amplification, and multiplexed readout.
Fig. 4: Results of 25-nm-resolution imaging of neural circuitry and synapses with iExM.

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Acknowledgements

E.S.B. acknowledges the NIH (1R01NS102727, 1R01EB024261, 1R41MH112318, 1R01MH110932, 1RM1HG008525, and Director's Pioneer Award 1DP1NS087724), the Open Philanthropy Project, DARPA, John Doerr, the NSF (grant 1734870), the MIT Aging Brain Initiative/Ludwig Foundation, the HHMI-Simons Faculty Scholars Program, IARPA D16PC00008, the US Army Research Laboratory and the US Army Research Office under contract/grant number W911NF1510548, the US–Israel Binational Science Foundation (grant 2014509), the MIT Media Lab, the MIT Brain and Cognitive Sciences Department, and the McGovern Institute. A.T.W. acknowledges the Hertz Foundation Fellowship.

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A.T.W., Y.Z., and E.S.B. all contributed to the writing of the manuscript and have read and agreed to its content.

Correspondence to Edward S. Boyden.

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Competing interests

E.S.B. is a co-inventor on multiple patents related to ExM and is also a co-founder of a company (http://extbio.com/) commercializing ExM. Y.Z. and A.T.W. are inventors on several inventions related to ExM.

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Wassie, A.T., Zhao, Y. & Boyden, E.S. Expansion microscopy: principles and uses in biological research. Nat Methods 16, 33–41 (2019) doi:10.1038/s41592-018-0219-4

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