New ICT-based Ratiometric Two-Photon Near Infrared Probe for Imaging Tyrosinase in Living Cells, Tissues and Whole Organisms
Javier Valverde-Pozo, Jose Manuel Paredes, Maria Eugenia García-Rubiño, Thomas Johann Widmann, Carmen Griñan-Lison, Silvia Lobon-Moles, Juan Antonio Marchal, Jose Maria Alvarez-Pez, Eva Maria Talavera
Tyrosinase; NIR sensor; Two-photon excitation; Melanoma; Zebrafish; Bioimaging
Melanoma is a type of highly malignant and metastatic skin cancer. In situ molecular imaging of endogenous levels of the melanoma biomarker tyrosinase (TYR) may decrease the likelihood of mortality. In this study we proposed the weakly fluorescent probe 1-(4-(2-(4-(dicyanomethylene)-4H-chromen-2-yl)vinyl)phenyl)-3-(4-hydroxybenzyl)urea (DCM-HBU), which releases a strong red-shifted fluorescent signal after a TYR-mediated oxidation followed by hydrolysis of the urea linkage. The large Stokes shift of the dye is owed to the recovery of the intramolecular charge transfer (ICT) effect. The resulting probe derivate shows a highly ratiometric fluorescence output. Furthermore, the simultaneous excitation by two near-infrared (NIR) photons of the released DCM-NH2 fluorophore could avoid the usual drawbacks, such as cellular absorption, autofluorescence and light scattering, due to an usually short wavelength of the excitation light on biological systems, resulting in images with deeper tissue penetration. In addition, the probe is useful for the quantitative sensing of TYR activity in vivo, as demonstrated in zebrafish larvae. This new ratiometric two photon NIR fluorescent probe is expected to be useful for the accurate detection of TYR in complex biosystems at greater depths than other one-photon excited fluorescent probes.