Better biocompatibility of nitrogen-doped graphene compared with graphene oxide by reducing cell autophagic flux blockage and cell apoptosis.

Nitrogen-doped graphene (C 2 N), a novel graphene-based materials, has been proposed as a potential alternative to graphene oxide (GO) in biomedical applications. However, due to the challenges in synthesizing C 2 N, reports in the biomedical field are currently rare. Here, we have modified the reported procedure and successfully synthesized C 2 N nanoparticles at 120°C, which we refer to as C 2 N-120. The toxicity and biocompatibility of GO and C 2 N-120 were evaluated using a mouse model injected with GO/C 2 N-120 via the tail vein, as well as cell models treated with GO/C 2 N-120. In vivo studies revealed that GO/C 2 N-120 showed similar distribution patterns after tail vein injection. The liver, spleen, and lung are the major nanoparticle uptake organs of GO and C 2 N-120. However, GO deposition in the major nanoparticle uptake organs was more significant than that of C 2 N-120. In addition, GO deposition caused structural abnormalities, increased apoptotic cells, and enhanced macrophage infiltration whereas C 2 N-120 exhibited fewer adverse effects. In vitro experiments were conducted using different cell lines treated with GO/C 2 N-120. Unlike GO which induced mitochondrial damage, oxidative stress, inflammatory response, autophagic flux blockage and cell apoptosis, C 2 N-120 showed lower cytotoxicity in cell models. Our data demonstrated that C 2 N-120 exhibits higher biocompatibility than GO, both in vivo and in vitro, suggesting its potential for biomedical application in the future.