A Cyclometalated Iridium (III) Complex as a Microtubule Probe for Correlative Super-Resolution Fluorescence and...

The visualization of microtubules by combining optical and electron microscopy techniques provides valuable information to understand correlated intracellular activities. However, the lack of appropriate probes to bridge both microscopic resolutions restricts the areas and structures that can be comprehended within such highly assembled structures. Here, a versatile cyclometalated iridium (III) complex is designed that achieves synchronous fluorescence-electron microscopy correlation. The selective insertion of the probe into a microtubule triggers remarkable fluorescence enhancement and promising electron contrast. The long-life, highly photostable probe allows live-cell super-resolution imaging of tubulin localization and motion with a resolution of ≈30 nm. Furthermore, correlative light-electron microscopy and energy-filtered transmission electron microscopy reveal the well-associated optical and electron signal at a high specificity, with an interspace of ≈41 Å of microtubule monomer in cells.