In vitro toxicity assessment of fungal-synthesized cadmium sulfide quantum dots using bacteria and seed germination models

Abstract

There is currently controversy over the use of quantum dots (QDs) in biological applications due to their toxic effects. Therefore, the purpose of the present study was to evaluate the toxic effect of chemical and biogenic (synthesized by Fusarium oxysporum f. sp. lycopersici) cadmium sulfide quantum dots (CdSQDs) using a bacterial model of Escherichia coli and sprouts of Lactuca sativa L. with the aim to foresee its use in the near future in biological systems. Physicochemical properties of both types of CdSQDs were determined by TEM, XRD, zeta potential and fluorescence spectroscopy. Both biogenic and chemical CdSQDs showed agglomerates of spherical CdSQDs with diameters of 4.14 nm and 3.2 nm, respectively. The fluorescence analysis showed a band around 361 nm in both CdSQDs, the zeta potential was −1.81 mV for the biogenic CdSQDs and −5.85 mv for the chemical CdSQDs. Results showed that chemical CdSQDs, presented inhibition in the proliferation of E. coli cell in a dose-dependent manner, unlike biogenic CdSQDs, that only at its highest concentration showed an antibacterial activity. Also, it was observed that after incubation with chemical and biogenic CdSQDs of L. sativa L. seeds, only the biogenic CdSQDs showed no inhibition on seed germination. In summary, our results suggest that the production route has a significant effect on the toxicity of QDs; in addition, it seems that the biological coating of the CdSQDs from F. oxysporum f. sp. lycopersici inhibit their toxic effect on bacterial strains and plant seeds.

Keywords:

• Fusarium oxysporum
• CdS quantum dots
• green synthesis
• sulfur waste
• toxicity assessment

Acknowledgments

The authors gratefully acknowledge Dr. Barceinas Sánchez (CICATA-Querétaro) for helping with the DRX analyses and Msc. Ma. Lourdes Palma Tirado (UNAM-Querétaro) for support in TEM analyses.

Disclosure statement

The authors declare no conflict of interest.

Additional information

Funding

This research was supported by CONACYT CB A1-S-31777.