High‐Contrast Reversible Fluorescence Photoswitching of Dye‐Crosslinked Dendritic Nanoclusters in Living Vertebrates

Dendrimers crosslinked with a photochromic diarylethene (blue in picture) were labeled with the fluorescent dye Cy3 (red) for reversible fluorescence photoswitching. If the obtained nanoclusters are irradiated with UV light, the Cy3 fluorescence is quenched by the diarylethene in its ring-closed form, whereas upon irradiation with visible light, the nanoclusters show fluorescence. High-contrast fluorescence imaging was achieved inside a living zebrafish.