Biodistribution and fate of nanodiamonds in vivo

Nanodiamond (ND) is highly expected to become a versatile material for biological applications, such as biosensors, drug carriers, and imaging probes. Understanding the basic biological consequence of ND is crucial for realizing its biorelevant applications and ascertaining its possible hazards to organisms. In this work, we found that NDs with a diameter of around 50 nm predominantly accumulated in liver after intravenous injection to mouse. Spleen and lung were also target organs for NDs. Analysis of the digested solution of liver and lung by spectroscopic method shows that about 60% of initial NDs were entrapped in liver at 0.5 h post dosing and 8% in lung. The values remained the same at 28 days post injection. The high-resolution transmission electron micrographic imaging and the Raman spectrum of the digested organ solutions confirmed the long-term entrapment of NDs in mouse liver and lung. The NDs were barely detectable in urine and feces by Raman measurement. Considering quite a number of NDs remain in the important organs, potential toxicity study is urgently needed.