Pyclen Based Ln(III) Complexes as Highly Luminescent Bioprobes for in Vitro and in Vivo 1P and 2P Bioimaging Applications

Two pyclen based lanthanide chelators, L^4b and L^4c, bearing two specific picolinate 2P antennas (tailor-made for each targeted metal) and one acetate arm arranged in a dissymmetrical manner, have been synthesized to form, with the already described ligand L^4a, a complete family of lanthanide luminescent bioprobes: [EuL^4a], [SmL^4a], [YbL^4b], [TbL^4c] and [DyL^4c]. Additionally, symmetrically arranged regioisomer L^4a’ was also synthesized as well as its [EuL^4a’] complex to highlight the astonishing positive impact of the dissymmetrical N-distribution of the functional chelating arm. The investigation clearly shows the high performance of each bioprobe, which, depending on the complexed lanthanide, could be used in various applications. Each presents high brightness, quantum yields and lifetimes. Staining of the complexes into living human breast cancer cells was observed. In addition, in vivo 2P-microscopy was performed for the first time on a living Zebrafish model with [EuL^4a]. No apparent toxicity was detected on the growth of the zebrafish and images of high quality were obtained.