Carbazole-Based Eu Complexes for Two-Photon Microscopy Imaging of Live Cells.

Lanthanide(III) complexes with two-photon absorbing antennas are attractive for microscopy imaging of live cells because they can be excited in the NIR. We describe the synthesis and luminescence and imaging properties of two Eu complexes, and , with (-carbazolyl)-aryl-alkynyl-picolinamide and (-carbazolyl)-aryl-picolinamide antennas, respectively, conjugated to the TAT cell-penetrating peptides. Contrary to what was previously observed with related Eu complexes with carbazole-based antennas in a mixture of water and organic solvents, these two complexes show very low emission quantum yield (Φ < 0.

Efficient cytosolic delivery of luminescent lanthanide bioprobes in live cells for two-photon microscopy.

Lanthanide(iii) (Ln) complexes have desirable photophysical properties for optical bioimaging. However, despite their advantages over organic dyes, their use for microscopy imaging is limited by the high-energy UV excitation they require and their poor ability to cross the cell membrane and reach the cytosol. Here we describe a novel family of lanthanide-based luminescent probes, termed dTAT[Ln·L], based on (i) a DOTA-like chelator with a picolinate moiety, (ii) a two-photon absorbing antenna to shift the excitation to the near infrared and (ii) a dimeric TAT cell-penetrating peptide for cytosolic delivery.