Prototypical cis-ruthenium(II) complexes present differential fluorescent staining in walled-cell models (yeasts)
cis-Ru(deeb) 3 2+ (R1; where deeb is 4,4′-diethanoate-2,2′-bipyridine) and cis-Ru(phen) 3 2+ (R2; where phen is 1,10-phenanthroline) were synthesized. Although the presence of the cell wall (a structure that is present in yeasts and bacteria,) was previously described as a natural barrier that hampers the uptake of d6-based luminescent complexes, we previously demonstrated that rhenium(I) tricarbonyl complexes were useful to stain both yeasts and bacteria. Even though several studies of classical ruthenium(II) complexes can be found, none of those studies aimed to determine the potential of these compounds as biomarkers for walled cells, testing only cell lines that lack this permeability barrier. Walled cells exhibit a relatively rigid structure, mainly constituted by carbohydrates and proteins, and surround the plasma membrane. In this manuscript, we observed that both R1 and R2 exhibited very low cytotoxicity in different walled-cell models (including bacteria and yeasts). More importantly, we found that both R1 and R2 were able to fluorescently stain Candida albicans (yeast), with a simple and fast procedure, without the need of additional permeabilizer molecules and antibodies. Interestingly, R1 remained retained in a discrete central structure consistent with the cell nucleus, whereas R2 seemed to be accumulated in the cell wall. These results show that these two complexes can be used as biomarkers for walled cells as differential staining, supporting the fact that, as well as with rhenium(I) complexes, biomarkers properties can be modulated by changing the substituents in ruthenium(II)-derivative luminescent stains, even for walled cells.
KeywordsRuthenium(II) complexes Spin–orbit DFT Cytotoxicity Biomarkers Yeasts
We thank FONDECYT 11170637, 1181638, and 1180017. We thank Dr, Ramiro Arratia-Pérez (Center of Applied Nanoscience, Universidad Andres Bello) for the Computational Resources Facilities and Dr. Ivonne Chávez M (Departamento de Química Inorgánica, Pontificia Universidad Católica de Chile) for instrumental facilities.
Compliance with ethical standards
Conflicts of interest
The authors declare no conflicts of interest.
This manuscript is dedicated to Professor Dr. Ramiro Arratia-Pérez (UNAB, director of Center of Applied Nanoscience, Chile), for his relevant contributions to the relativistic quantum chemistry in Chile, where he founded the first Molecular Relativistic School in Latin America, and in the world.
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