Polynuclear SmIII Polyamidoamine‐Based Dendrimer: A Single Probe for Combined Visible and Near‐Infrared Live‐Cell Imaging

We report herein the synthesis of a luminescent polynuclear dendritic structure (Sm^III‐G3P‐2,3Nap) in which eight Sm^III ions are sensitized by thirty‐two 2,3‐naphthalimide chromophores. Upon a single excitation wavelength, the dendrimer complex exhibits two types of emission in the visible and in the near‐infrared (NIR) ranges. Sm^III‐G3P‐2,3Nap was non‐cytotoxic after 24 h of incubation and up to 2.5 μM . The ability of the Sm^III‐based probe to be taken up by cells was confirmed by confocal microscopy. Epifluorescence microscopy validated Sm^III‐G3P‐2,3Nap as a versatile probe, capable of performing interchangeably in the visible or NIR for live‐cell imaging. As both emissions are obtained from a single complex, the cytotoxicity and biodistribution are inherently the same. The possibility for discriminating the sharp Sm^III signals from autofluorescence in two spectral ranges increases the reliability of analysis and reduces the probability of artifacts and instrumental errors.