Gold/Silica Particles for Various Applications in (CLEM) Microscopy

The field of Correlative Light and Electron Microscopy (CLEM), has expanded rapidly in the last decade. Especially in biology it turns out to be very useful to combine these two techniques. Light microscopy, or more specifically fluorescence microscopy (FM), is used to visualize, localize, and track specific fluorescent molecules in cells over large areas with high sensitivity, while electron microscopy (EM) provides high resolution ultrastructural information of cells and materials. To gain additional information from CLEM experiments, it is important to properly overlay or register (stacks of) images obtained in the two modalities. This process is complicated by the vast different field of view of FM and EM, as well as the different contrast mechanisms of these techniques. Particles, or fiducial markers, that are visible in both modalities can be used to overcome this problem. In this work, nanocomposite core-shell particles based on a gold core and a fluorescently labelled silica shell are deployed as fiducial markers for 2D and 3D (integrated)CLEM. Within this particle, the gold core provides contrast for EM while fluorophores covalently incorporated in the silica shell provide fluorescence for FM. For FM, it is important that the fiducial markers are bright and visible over a longer period of time. As both properties are strongly influenced by the fluorophore labelling density this topic is also addressed. The work finishes with the presentation of a single sample based on similar core-shell particles to check and optimize the full performance of a high-end 3D super-resolution (STED) light microscope