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What Is Best Strategy for Water Soluble Fluorescence Dyes? – a Case Study Using Long Fluorescence Lifetime DAOTA Dyes

submitted on 25.06.2020, 08:55 and posted on 29.06.2020, 06:55 by Niels Bisballe, Bo W. Laursen

The applications of organic fluorophores in biological sciences rely heavily on their properties in aqueous solution. The lipophilic nature of virtually all such chromophores provides several challenges to adapt them to biologically relevant conditions. In this work we investigate three different strategies for achieving water-solubility of the diazaoxatriangulenium (DAOTA+) chromophore: hydrophilic counter ions, aromatic sulfonation of the chromophore core, and attachment of cationic or zwitterionic side chains. The long fluorescence lifetime (FLT, τf » 20 ns) of DAOTA+ makes it a sensitive probe for changes in the rate of non-radiative deactivation and for aggregation leading to multi exponential decay profiles. Direct sulfonation of the chromophore, as applied in several Alexa dyes, does indeed increase solubility drastically, but at the cost of greatly reduced quantum yields (QY) due to enhanced non-radiative deactivation processes. The introduction of either cationic (4) or zwitterionic side chains (5), however, brings the FLT (τf = 18 ns) and QY (φf = 0.56) of the dye to the same level as the parent chromophore in acetonitrile. For these derivatives time-resolved fluorescence spectroscopy also reveals a high resistance to aggregation and non-specific binding in a high loading of bovine serum albumin (BSA). The results clearly show that addition of charged flexible side chains is preferable to direct sulfonation of the chromophore core.


Danish Council of Independent Research (DFF-6111-00483)


Email Address of Submitting Author


University of Copenhagen, Department of Chemistry



ORCID For Submitting Author


Declaration of Conflict of Interest

Bo W. Laursen is associated with the company KU-dyes, which produces and sells fluorescent dyes (including triangulenium dyes).