Applying the Expansion Microscopy Method in Neurobiology

Many biological studies require the analysis of ultrastructural changes at the level of cell organelles and macromolecules. Since the resolution of modern confocal microscope is limited by the diffraction limit (200–300 nm), it is impossible to study such small objects using standard fluorescence microscopy. Ultra-high resolution microscopy methods require expensive equipment and are technically difficult in use, which in turn limits their widespread practical application. However, recently appeared methods make it possible to increase the resolution of microscopy not by improving the image registration system, but by physically isotropic expansion of a biological sample using a controlled chemical process. Due to this method, called expansion or expansive microscopy (ExM), it became possible to obtain three-dimensional images of samples with a resolution sufficient to study individual cell organelles using a conventional confocal microscope. This review covers the history of this method, its basic principles and examples of use in various fields of biology and medicine, as well as reflects future directions for improving this technology. The article discusses the methodological features of the ExM application in a study of brain tissue samples using the algorithm that allows adaptation of the standard protocol to the goals and objectives of a particular study.