Comparison of Toxicity and Cellular Uptake of CdSe/ZnS and Carbon Quantum Dots for Molecular Tracking Using <i>Saccharomyces cerevisiae</i> as a Fungal Model
Sanni M. A. Färkkilä,
Monika Mortimer,
Raivo Jaaniso,
Anne Kahru,
Valter Kiisk,
Arvo Kikas,
Jekaterina Kozlova,
Imbi Kurvet,
Uno Mäeorg,
Maarja Otsus,
Kaja Kasemets
Affiliations
Sanni M. A. Färkkilä
Institute of Ecology and Earth Sciences, University of Tartu, Juhan Liivi 2, 50409 Tartu, Estonia
Monika Mortimer
Laboratory of Environmental Toxicology, National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn, Estonia
Raivo Jaaniso
Institute of Physics, University of Tartu, W. Ostwaldi 1, 50411 Tartu, Estonia
Anne Kahru
Laboratory of Environmental Toxicology, National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn, Estonia
Valter Kiisk
Institute of Physics, University of Tartu, W. Ostwaldi 1, 50411 Tartu, Estonia
Arvo Kikas
Institute of Physics, University of Tartu, W. Ostwaldi 1, 50411 Tartu, Estonia
Jekaterina Kozlova
Institute of Physics, University of Tartu, W. Ostwaldi 1, 50411 Tartu, Estonia
Imbi Kurvet
Laboratory of Environmental Toxicology, National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn, Estonia
Uno Mäeorg
Institute of Chemistry, University of Tartu, Ravila 14a, 50411 Tartu, Estonia
Maarja Otsus
Laboratory of Environmental Toxicology, National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn, Estonia
Kaja Kasemets
Laboratory of Environmental Toxicology, National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn, Estonia
Plant resource sharing mediated by mycorrhizal fungi has been a subject of recent debate, largely owing to the limitations of previously used isotopic tracking methods. Although CdSe/ZnS quantum dots (QDs) have been successfully used for in situ tracking of essential nutrients in plant-fungal systems, the Cd-containing QDs, due to the intrinsic toxic nature of Cd, are not a viable system for larger-scale in situ studies. We synthesized amino acid-based carbon quantum dots (CQDs; average hydrodynamic size 6 ± 3 nm, zeta potential −19 ± 12 mV) and compared their toxicity and uptake with commercial CdSe/ZnS QDs that we conjugated with the amino acid cysteine (Cys) (average hydrodynamic size 308 ± 150 nm, zeta potential −65 ± 4 mV) using yeast Saccharomyces cerevisiae as a proxy for mycorrhizal fungi. We showed that the CQDs readily entered yeast cells and were non-toxic up to 100 mg/L. While the Cys-conjugated CdSe/ZnS QDs were also not toxic to yeast cells up to 100 mg/L, they were not taken up into the cells but remained on the cell surfaces. These findings suggest that CQDs may be a suitable tool for molecular tracking in fungi (incl. mychorrhizal fungi) due to their ability to enter fungal cells.
