In vivo imaging of carbon nanotube biodistribution using magnetic resonance imaging.

As novel engineered nanoparticles such as carbon nanotubes (CNTs) are extensively used in nanotechnology due to their superior properties, it becomes critical to fully understand their biodistribution and effect when accidently inhaled. A noninvasive follow-up study would be beneficial to evaluate the biodistribution and effect of nanotube deposition after exposure directly in vivo. Combined helium-3 and proton magnetic resonance resonance (MRI) were used in a rat model to evaluate the biodistribution and biological impact of raw single-wall CNTs (raw-SWCNTs) and superpurified SWCNTs (SP-SWCNTs). The susceptibility effects induced by metal impurity in the intrapulmonary instilled raw-SWCNT samples were large enough to induce a significant drop in magnetic field homogeneity detected in 3He MR image acquired under spontaneous breathing conditions using a multiecho radial sequence. No MRI susceptibility variation was observed with SP-SWCNT exposition even though histological analysis confirmed their presence in instilled lungs. Proton MRI allowed detection of intravenously injected raw-SWCNTs in spleen and kidneys using gradient echo sequence sensitive to changes of relaxation time values. No signal modifications were observed in the SP-SWCNT injected group. In instilled groups, the contrast-to-noise ratio in liver, spleen, and kidneys stayed unchanged and were comparable to values obtained in the control group. Histological analysis confirms the absence of SWCNTs in systemic organs when SWCNTs were intrapulmonary instilled. In conclusion, the presence of SWCNTs with associated metal impurities can be detected in vivo by noninvasive MR techniques. Hyperpolarized 3He can be used for the investigation of CNT pulmonary biodistribution while standard proton MR can be performed for systemic investigation following injection of CNT solution.