A water soluble probe with near infrared two-photon absorption and polarity-induced fluorescence for cerebral vascular imaging

A water soluble Lemke chromophore derivative shows an unusual polarity dependence of its emission efficiency, leading to strong red-NIR fluorescence in water when fitted with appropriate water-solubilizing polymer chains. In this edge article, the synthesis of the chromophore is described. The dependence of its fluorescence on solvent polarity is investigated experimentally and rationalized on the basis of ab initio calculations. Finally, we demonstrate that this chromophore is a valuable candidate for in vivo two-photon imaging of cerebral vasculature, with two-photon absorption and emission in the biological transparency window.