Characterization and Investigation of the Toxicity, Genotoxicity, Antioxidant, and Radical Scavenging Activity of Highly Fluorescent Nitrogen-Doped Graphene Quantum Dots (NGQDs)

Nitrogen-Doped Graphene Quantum Dots (NGQDs) have recently been used effectively in drug delivery. Our study aimed to characterize NGQDs and investigate their toxicity and genotoxicity using the Brine Shrimp lethality test (BSLT), Allium cepa L assay, and MTT assay on U251 GBM cells. NGQDs were synthesized using citric acid and Tris(hydroxymethyl) aminomethane through the pyrolysis method. Antioxidant and scavenging activities of NGQDs were also measured. LC50, EC50, and IC50 of NGQDs were determined; the Allium cepa L assay was also used to explore the potential mutagenic and carcinogenic effects of NGQDs. NGQDs had an average size of 8.1±1 nm with a zeta(ζ)-potential of −24.4 mV. ATR FT-IR findings demonstrate that NGQDs have functional groups, and TEM analysis revealed heterogeneous morphologies. AFM measurements indicate that the size of the distribution of NGQDs is relatively uniform except for some agglomeration of NGQDs. UV-vis and FL spectra were 335 and 410 nm, respectively. ABTS+ and DPPH radical scavenging activities were 4.13±0.4 and 61.32±0.22%, respectively. Total phenol content and antioxidant power were 23±1.15 µg GAE/g and 577.98±0.28 µmol Fe2+/g, respectively. LC50, EC50, and IC50 values were 3388.4±224.3, 5825.4±703.3, and 3057±156.9 µg/mL, respectively. In conclusion, NGQDs exhibited high photoluminescence and biocompatibility with no significant cytotoxic or genotoxic effects, making them highly safe for drug delivery. Moreover, it was concluded that the BSLT and Allium cepa L assay could be good alternatives to the MTT assay though further research is needed to confirm this.