Luminescence imaging and toxicity assessment of graphene quantum dots using in vitro models

Abstract

Graphene quantum dots (GQDs) have been of high interest due to their size and optical characteristics, which improves when functional groups are added to their borders and defects. In this work, the in vitro toxicity of aqueous dispersion of GQDs (w/wo amino-functionalization) was investigated in two different cellular models (S. cerevisiae and H9c2 cell line). Results in yeast suggest that when at up to 25 % volume concentration, the effect of all tested GQDs was only inhibitory, and, in both cellular models, the toxic effect is rigorously dose-dependent. The comparison of IC₅₀ values of all the tested GQDs reveals no significant variations among them, pointing to non-carbonized citric acid as the more toxic precursor. The obtained data suggest that functionalization makes GQDs less toxic, being the one functionalized with thioacetamide slightly more toxic, followed by the ones functionalized with thiourea and glutathione, respectively. Results confirm that their toxicity is characteristics as a whole, and not as the sum of the toxicity of the precursors. In both models, concentrations up to 2 % showed no significant toxicity. Finally, fluorescence microscopy images suggest that GQDs interact with the cellular membrane and enter in the cell, manifesting fluorescent properties.

Keywords:

• Graphene quantum dots
• cardiomyoblast
• cytotoxicity
• fluorescence imaging
• yeast

Acknowledgments

A.D.F. and E.S.H. thanks to FAPERJ for post-doctoral fellowships and scientific grant (E_02/2016 - CNM - MCTI/FINEP/FNDCT/FAPERJ – 2017). A.G. thanks CNPq and FAPERJ for scholarships. E.S.H. thanks CAPES for PhD fellowship. D.G.L. and C.R.G. thanks scholarships from CNPq. R.Q.A. thanks scholarships from Brazilian agencies FAPERJ (E-26/202.912/2017) and CNPq (303866/2017-9) and scientific grants from CNPq (409090/2018-2) and FAPERJ (E-26/010.101131/2018). This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES) – Finance Code 001.

Disclosure statement

No potential conflict of interest was reported by the authors.