Bionanoprobes with Excellent Two-Photon-Sensitized Eu3+ Luminescence Properties for Live Cell Imaging

Bioimaging or bioanalysis based on nanoprobes encapsulating Eu 3 + complexes with excellent two-photon-sensitized (TPS) luminescence properties combines the advantages of deep penetration, high sensitivity, high signal-to-noise ratio, stable signals during long term observation, low photodamage to biological samples, and desirable target recognizability. The TPS luminescence of lanthanide complexes is produced through the two-photon excitation (TPE) of a lightharvesting antenna ligand and subsequent excitation energy transfer (EET) to the metal ions, which provides a promising manner for extending the excitation windows of lanthanide complexes to the near-infrared (NIR) light wavelength region. In the last two decades, remarkable progress has been achieved in the design and synthesis of two-photonsensitized luminescent lanthanide complexes. [1] Several lanthanide complexes have been applied to the multiphoton-excited bioimaging of cells. [2–4] Due to the characteristic luminescence properties of Eu 3 + complexes, such as the characteristic narrow-line emission in the red-light wavelength region with acceptable transparence for many biosamples, high luminescence quantum yields, large Stokes shifts, and long luminescence lifetime (millisecond order), the TPS Eu 3 + luminescence is of significance for developing bioanal