Fluorogenic Squaraine Dimers with Polarity-Sensitive Folding As Bright Far-Red Probes for Background-Free Bioimaging.
Fiche publication
Date publication
décembre 2014
Auteurs
Membres identifiés du Cancéropôle Est :
Pr HIBERT Marcel, Pr MELY Yves, Dr KLYMCHENKO Andrey, Dr RICHERT Ludovic
Tous les auteurs :
Karpenko IA, Collot M, Richert L, Valencia C, Villa P, Mely Y, Hibert M, Bonnet D, Klymchenko AS
Lien Pubmed
Résumé
Polarity-sensitive fluorogenic dyes raised considerable attention because they can turn on their fluorescence after binding to biological targets, allowing background-free imaging. However, their brightness is limited, and they do not operate in the far-red region. Here, we present a new concept of fluorogenic dye based on a squaraine dimer that unfolds on changing environment from aqueous to organic and thus turns on its fluorescence. In aqueous media, all three newly synthesized dimers displayed a short wavelength band characteristic of an H-aggregate that was practically nonfluorescent, whereas in organic media, they displayed a strong fluorescence similar to that of the squaraine monomer. For the best dimer, which contained a pegylated squaraine core, we obtained a very high turn-on response (organic vs aqueous) up to 82-fold. Time-resolved studies confirmed the presence of nonfluorescent intramolecular H-aggregates that increased with the water content. To apply these fluorogenic dimers for targeted imaging, we grafted them to carbetocin, a ligand of the oxytocin G protein-coupled receptor. A strong receptor-specific signal was observed for all three conjugates at nanomolar concentrations. The probe derived from the core-pegylated squaraine showed the highest specificity to the target receptor together with minimal nonspecific binding to serum and lipid membranes. The obtained dimers can be considered as the brightest polarity-sensitive fluorogenic molecules reported to date, having approximately 660,000 M-1 cm-1 extinction coefficient and up to 40% quantum yield, whereas far-red operation region enables both in vitro and in vivo applications. The proposed concept can be extended to other dye families and other membrane receptors, opening the route to new ultrabright fluorogenic dyes.
Référence
J Am Chem Soc. 2014 Dec 29.