Carbon dots from thermally processed Spirulina: Properties, biodistribution and cytotoxicity

Foodborne carbon dots (FCDs) are ubiquitous nanoparticles in thermally processed foods that have received attention for potential health risks. Herein, FCDs were extracted from Spirulina by hydrothermal (H-FCDs) and microwave (M-FCDs) methods, and their properties, biodistribution, and biotoxicity were explored. The results showed that H-FCDs had higher nitrogen content, quantum yield, fluorescence stability, and smaller molecular weight than M-FCDs. In vivo experiments indicated that FCDs could distribute in intestine, kidney, liver, and brain of mice, but caused no obvious acute toxicity at 2 g/kg. In vitro studies showed that FCDs were internalized by HT29 and C6 cells, inducing oxidative stress, disrupting Ca²⁺ homeostasis, and mitochondrial membrane potential. Besides, compared with M-FCDs, H-FCDs significantly upregulated Bax, downregulated Bcl-2, promoted the release of Cyt-C, and activated Caspase-3, thereby inducing apoptosis in HT29 cells. These findings provide insights for the potential health risks of FCDs in thermally processed Spirulina foods.