Advances in fluorescence microscopy, including super-resolution microscopy, and semi-in-lens type scanning electron microscopy have expanded the field of imaging in biological materials. As a result, there is an increasing demand for more precise analytical methods in correlative light and electron microscopy (CLEM). In-resin CLEM, which involves simultaneous observation and correlative analysis of the same ultrathin section of resin-embedded biological materials using both fluorescence and electron microscopes, has improved correlation accuracy. Ideally, in-resin CLEM should use epoxy resin due to its superior ultrastructural preservation. However, many fluorescent proteins and dyes lose their fluorescence due to the autofluorescence of epoxy resin itself and chemical treatments such as osmium tetroxide staining. Various approaches have been taken to solve these problems, and recently, ‘Immuno in-resin CLEM” at the tissue level was performed by applying immunological reactions.
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