Biodistribution of multi-walled carbon nanotubes functionalized by hydroxyl terminated poly(ethylene glycol) in mice

Poly(ethylene glycol) functionalized carbon nanotubes (CNTs-PEG) have attracted great research interest due to their good biocompatibility and wide applications in biomedical areas, such as drug delivery, bioimaging and photothermal therapy. The biodistribution studies are fundamental and essential to the biomedical applications and toxicological evaluations of CNTs-PEG, while isotopic labeling is the most adopted method for the quantitation of CNTs in vivo. Herein, we studied the biodistribution of hydroxyl terminated CNTs-PEG (CNTs-PEG-OH) in mice using ¹²⁵I-labeling technique. The blood concentrations and accumulation levels of CNTs-PEG-OH in different organs were quantitatively analyzed by detecting the radioactivity of ¹²⁵I labeled on CNTs-PEG-OH. The results indicated that CNTs-PEG-OH were quickly cleared from blood circulation and distributed to the entire body, except brain. CNTs-PEG-OH were mainly sequestrated by liver after intravenous injection. The hepatic accumulation decreased along with time elapse. Prolonging the PEG chains led to the decrease of hepatic accumulation, while the biodistribution pattern was similar. The implications to the biomedical applications and safety evaluations of CNTs-PEG are discussed.