Radiolabeling, whole-body single photon emission computed tomography/computed tomography imaging, and pharmacokinetics of carbon nanohorns in mice.

In this work, we report that the biodistribution and excretion of carbon nanohorns (CNHs) in mice are dependent on their size and functionalization. Small-sized CNHs (30-50 nm; S-CNHs) and large-sized CNHs (80-100 nm; L-CNHs) were chemically functionalized and radiolabeled with [(111)In]-diethylenetriaminepentaacetic acid and intravenously injected into mice. Their tissue distribution profiles at different time points were determined by single photon emission computed tomography/computed tomography. The results showed that the S-CNHs circulated longer in blood, while the L-CNHs accumulated faster in major organs like the liver and spleen. Small amounts of S-CNHs- and L-CNHs were excreted in urine within the first few hours postinjection, followed by excretion of smaller quantities within the next 48 hours in both urine and feces. The kinetics of excretion for S-CNHs were more rapid than for L-CNHs. Both S-CNH and L-CNH material accumulated mainly in the liver and spleen; however, S-CNH accumulation in the spleen was more prominent than in the liver.