Luminescent functional bioprobes based on lanthanide complexes

Les propriétés photophysiques particulières des ions lanthanides, bandes d’émission fines et intenses et temps de vie de luminescence longs, présentent de nombreux avantages pour le développement de sondes biologiques luminescentes. Les travaux de cette thèse portent sur le développement de sondes luminescentes responsives et de bio-sondes pour l’imagerie biologique à base de complexes de lanthanide. Des nouveaux complexes basés sur des plateformes triazacyclononanes ont été synthétisés. La sensibilité de la luminescence de ces complexes à la présence de dioxygène ou d’espèces réactives de l’oxygène (ROS) a été mise en évidence. Cette propriété a été étudiée de manière quantitative pour le développement de sondes responsives. L’étude approfondie des propriétés de luminescence de ces complexes a permis de rationaliser les mécanismes photophysiques impliqués. Dans une seconde partie, une stratégie de synthèse a été développée pour l’obtention d’une nouvelle famille de complexes bioconjugables. Des complexes basés sur des macrocycles tacn et cyclen bioconjugués à des peptides de pénétration cellulaire dérivés du TAT ont été synthétisés et des expériences d’imagerie cellulaire par microscopie à deux photons ont été effectuées. Ces expériences ont permis de mettre en lumière différents paramètres, tels que la lipophilie du complexe ou le choix du peptide, jouant un rôle important lors de l’internalisation cellulaire et offrent de nouvelles perspectives dans le développement de complexes de lanthanide pour l’imagerie cellulaire.The particular photophysical properties of lanthanide ions, fine and intense emission bands and long luminescence lifetimes, offer numerous advantages for the development of luminescent biological probes. This thesis focuses on the development of responsive luminescent probes and bio-probes for biological imaging based on lanthanide complexes. New complexes based on triazacyclononane platforms have been synthesized. The luminescence sensitivity of these complexes to the presence of dioxygen or reactive oxygen species (ROS) was demonstrated. This property was studied quantitatively for the development of responsive probes. Detailed study of these complexes luminescence properties has enabled us to rationalize the photophysical mechanisms involved. In a second part, a synthesis strategy was developed to obtain a new family of bioconjugated complexes. Complexes based on tacn and cyclen macrocycles bioconjugated with TAT derived cell-penetrating peptides were synthesized and cell imaging experiments using two-photon microscopy were carried out. These experiments highlighted various parameters, such as complex lipophilicity and peptide choice, that play an important role in cell internalization and offer new views for the development of lanthanide complexes for cell imaging

Does simplifying the design of macrocyclic lanthanide chelates lead to convincing results in luminescence?

International audienc

Does simplifying the design of macrocyclic lanthanide chelates lead to convincing results in luminescence?

International audienc

The mischievous properties of Ln(III) complexes: switching the luminescence for unexpected reasons

National audiencePrevious works of our team were dedicated to the design and the study of lanthanide complexes with high-brightness due to the sensitization by tailor-made charge-transfer antennas, enabling tridimensional functional imaging through two-photon excitation..

Design of Bifunctional Pyclen-Based Lanthanide Luminescent Bioprobes for Targeted Two-Photon Imaging

In the past, Lanthanide Luminescent Bioprobes(LLBs) based on pyclen-bearing π-extended picolinate antennaswere synthesized and demonstrated well-adapted optical propertiesfor biphotonic microscopy. The objective of this work is to develop astrategy to design bifunctional analogues of the previously studiedLLBs presenting an additional reactive chemical group to allow theircoupling to biological vectors to reach deep in vivo targeted twophotonbioimaging. Herein, we elaborated a synthetic schemeallowing the introduction of a primary amine on the para position ofthe macrocyclic pyridine unit. The photophysical and bioimagingstudies demonstrate that the introduction of the reactive functiondoes not alter the luminescent properties of the LLBs paving the wayfor further applications

Comprehensive photophysical and nonlinear spectroscopic study of thioanisolyl‐picolinate triazacyclononane lanthanide complexes

International audienceAbstract Detailed photophysical studies of luminescent lanthanide complexes are presented and elaborated using a newly developed thioanisolyl‐picolinate antenna and the related tacn macrocyclic ligand. The new ligand proved to sensitise Nd(III), Sm(III), Eu(III) and Yb(III) emission. Eu(III) complex showed complete energy transfer, yielding high quantum yield (44 %) and brightness, while the Tb(III) analogue underwent a thermally activated back‐energy transfer, resulting in a strong oxygen quenching of the triplet excited state. Transient absorption spectroscopy measurements of Gd(III), Tb(III) and Eu(III) compounds confirmed the sensitization processes upon the charge‐transfer antenna excitation. The triplet excited state lifetime of the Tb(III) complex was 5‐times longer than that of the Gd(III) analogue. In contrast, the triplet state was totally quenched by the energy transfer to the 4f ‐metal ion in the Eu(III) species. Nonlinear two‐photon absorption highlighted efficient biphotonic sensitization in Eu(III) and Sm(III) complexes. In case of the Nd(III) compound, one‐photon absorption in 4f–4f transitions was predominant, despite the excitation at the antenna two‐photon band. This phenomenon was due to the Nd(III) 4f–4f transitions overlapping with the wavelength‐doubled absorption of the complex

Comprehensive Photophysical and Nonlinear Spectroscopic Study of Thioanisolyl-Picolinate Triazacyclononane Lanthanide Complexes

Detailed photophysical studies of luminescent lanthanide complexes are presented and elaborated using a newly developed thioanisolyl-picolinate antenna and the related tacn macrocyclic ligand. The new ligand proved to sensitise Nd(III), Sm(III), Eu(III) and Yb(III) emission. Eu(III) complex showed complete energy transfer, yielding high quantum yield (44%) and brightness, while the Tb(III) analogue underwent a thermally activated back-energy transfer, resulting in a strong oxygen quenching of the triplet excited state. Transient absorption spectroscopy measurements of Gd(III), Tb(III) and Eu(III) compounds confirmed the sensitization processes upon the charge-transfer antenna excitation. The triplet excited state lifetime of the Tb(III) complex was 5-times longer than that of the Gd(III) analogue. In contrast, the triplet state was totally quenched by the energy transfer to the 4f-metal ion in the Eu(III) species. Nonlinear two-photon absorption highlighted efficient biphotonic sensitization in Eu(III) and Sm(III) complexes. In case of the Nd(III) compound, one-photon absorption in 4f-4f transitions was predominant, despite the excitation at the antenna two-photon band. This phenomenon was due to the Nd(III) 4f-4f transitions overlapping with the wavelength-doubled absorption of the complex

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

International audienceLanthanide(III) (Ln3+) 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. Several Tb3+ and Eu3+ probes were prepared and characterized. Two-photon microscopy of live cells was attempted using a commercial microscope with the three probes showing the highest quantum yields (>0.15). A diffuse Ln3+ emission was detected in most cells, which is characteristic of cytosolic delivery of the Ln3+ complex. The cytotoxicity of these three probes was evaluated and the IC50 ranged from 7 μM to >50 μM. The addition of a single positive or negative charge to the antenna of the most cytotoxic compound was sufficient to lower significantly or suppress its toxicity under the conditions used for two-photon microscopy. Therefore, the design reported here provides excellent lanthanide-based probes for two-photon microscopy of living cells