Amphiphilicity-Controlled Localization of Red Emitting Bicationic Fluorophores in Tumor Cells Acting as Bio-Probes and Anticancer Drugs

Molecules. 2022 Jun 9;27(12):3713. doi: 10.3390/molecules27123713.


Small organic molecules arouse lively interest for their plethora of possible biological applications, such as anticancer therapy, for their ability to interact with nucleic acids, or bioimaging, thanks to their fluorescence emission. Here, a panchromatic series of styryl-azinium bicationic dyes, which have already proved to exhibit high water-solubility and significant red fluorescence in water, were investigated through spectrofluorimetric titrations to assess the extent of their association constants with DNA and RNA. Femtosecond-resolved transient absorption spectroscopy was also employed to characterize the changes in the photophysical properties of these fluorophores upon interaction with their biological targets. Finally, in vitro experiments conducted on tumor cell lines revealed that some of the bicationic fluorophores had a peculiar localization within cell nuclei exerting important antiproliferative effects, others were instead found to localize in the cytoplasm without leading to cell death, being useful to mark specific organelles in light of live cell bioimaging. Interestingly, this molecule-dependent behavior matched the different amphiphilicity featured by these bioactive compounds, which are thus expected to be caught in a tug-of-war between lipophilicity, ensured by the presence of aromatic rings and needed to pass cell membranes, and hydrophilicity, granted by charged groups and necessary for stability in aqueous media.

Keywords: antiproliferative effect; bications; bioimaging; cell-permeant dyes; far-red emission; lipophilicity; nucleic acid binders; ultrafast transient absorption spectroscopy.

MeSH terms

  • Antineoplastic Agents* / pharmacology
  • DNA / chemistry
  • Fluorescent Dyes* / chemistry
  • Ionophores
  • Spectrum Analysis
  • Water / chemistry


  • Antineoplastic Agents
  • Fluorescent Dyes
  • Ionophores
  • Water
  • DNA

Grants and funding

The authors acknowledge support from the Italian “Ministero per l’Università e la Ricerca Scientifica e Tecnologica”, MIUR (Rome, Italy) under the “Dipartimenti di Eccellenza 2018–2022” (grant AMIS) program and from the University of Perugia under the FRB2019 program. V.B. acknowledges the project CONVBORSASTUDIOMAZZUCATO for support to this research.