Extraction, characterization and toxicity evaluation of fluorescent carbon nanoparticles in bamboo charcoal peanut

Heat treatment and the application of additives may introduce nanomaterials into foods. As toxicological investigation and market standards of nanomaterials are still in a state of lack, a growing concern has been raised for their potential health hazards in foods. In this study, the structural properties and cytotoxicity of fluorescent carbon nanoparticles (FCNPs) in fried bamboo charcoal peanuts were investigated for the first time. FCNPs we extracted from charcoal shells and peanut kernels respectively, and were characterized with their structure and properties. Compared with peanut kernel FCNPs (PK-FCNPs), charcoal-shell FCNPs (CS-FCNPs) have smaller particle size, which may be related to the higher cooking temperature of the outer layer. Besides, both FCNPs have good water solubility, possibly due to their abundance of oxygen-containing groups. Additionally, the fluorescence spectra of FCNPs exhibit excitation-dependent emission, and based on this unique feature, FCNPs can be quantified. Finally, the cellular endocytosis and toxic effects of FCNPs were explored. FCNPs could enter the cytoplasm but not the nucleus. The LC50 of CS-FCNPs, PK-FCNPs and mixed FCNPs (M-FCNPs) were calculated as 3.332 mg/mL, 10.64 mg/mL and 5.529 mg/mL, and they induced obvious morphological damage at 10 mg/mL. Moreover, the toxicity of CS-FCNPs was slightly higher than that of PK-FCNPs, possibly derived from CS-FCNPs' smaller particle size.