Water-soluble diketopyrrolopyrrole derivatives for two-photon excited fluorescence microscopy

Five new non-ionic water-soluble two-photon dyes for fluorescence microscopy built around a diketopyrrolopyrrole central core were designed, prepared and characterized by 1H and 13C NMR, UV-Visible spectroscopy, HRMS and IR. Excitation and emission wavelengths were tuned by modifying the lengths of the conjugated systems and the nature of the substituents surrounding the diketopyrrolopyrrole central core. These fluorescent dyes are highly photostable and present high one- and two-photon brightness. Their application in confocal and two-photon excited fluorescence microscopy was performed on HeLa cell cultures with low power excitation.