Relocation is the key to successful correlative fluorescence and scanning electron microscopy

In this chapter the authors report on an automated hardware and software solution enabling swift correlative sample array mapping of fluorescently stained molecules within cells and tissues across length scales. Samples are first observed utilizing wide-field optical and fluorescence microscopy, followed by scanning electron microscopy, using calibration points on a dedicated sample-relocation holder. We investigated HeLa cells in vitro, fluorescently labeled for monosialoganglioside one (GM-1), across both imaging platforms within tens of minutes of initial sample preparation. This resulted in a high-throughput and high spatially resolved correlative fluorescence and electron microscopy analysis and allowed us to collect complementary nanoscopic information on the molecular and structural composition of two differently distinct HeLa cell populations expressing different levels of GM-1. Furthermore, using the small zebrafish animal model Danio rerio, we showed the versatility and relocation accuracy of the sample-relocation holder to locate fluo-tagged macromolecular complexes within large volumes using long ribbons of serial tissue sections. The subsequent electron microscopy imaging of the tissue arrays of interest enabled the generation of correlated information on the fine distribution of albumin within hepatic and kidney tissue. Our approach underpins the merits that an automated sample-relocation holder solution brings in support of results-driven research, where relevant biological questions can be answered, and high-throughput data can be generated in a rigorous statistical manner.