Effect of polyethylene glycol surface charge functionalization of SWCNT on the in vitro and in vivo nanotoxicity and biodistribution monitored noninvasively using MRI.

The current study evaluated in vitro and in vivo toxicity of carboxyl or amine polyethylene glycol (PEG) surface functionalization of single-walled carbon nanotubes (SWCNTs). Assessments of cytotoxicity, genotoxicity, immunotoxicity, and oxidative stress were performed in vitro and in vivo (in a 1-month follow-up study). The SWCNT biodistribution was investigated using noninvasive magnetic resonance imaging (MRI). Results confirmed the enhanced biocompatibility of PEG-functionalized SWCNTs compared to non-functionalized materials with significant decreases (p < 0.05) in the percentage of cell viability and increases in ROS generation, mitochondrial membrane potential, cell apoptosis, oxidative stress generation, and oxidative DNA damage in vitro. PEG-functionalized SWCNTs with amine terminals were found to induce prominent increases in ROS generation, mitochondrial membrane potential, and oxidative stress compared to carboxy functionalization. No significant difference in the biodistribution of either functionalized SWCNTs was observed in MRI. In vivo assessments revealed a statistically significant increase (p < 0.05) in oxidative stress as early as 24 h in serum and liver; however, all values normalized at 2 weeks' investigation time point. DNA damage was minimal with either PEG-COOH or PEG-NH functionalized SWCNTs after 2 weeks' exposure. The negatively charged SWCNTs caused lesser DNA damage compared to positively charged samples. Carboxy-functionalized SWCNTs did not cause substantial changes in inflammatory mediators and were found to be significantly safer than non-functionalized SWCNTs and may pave the way for novel biomedical applications in cancer diagnosis and therapy.