[Bikanta]

You are correct in the fact that the kidney's are one route of clearance for small agents that are injected. However, these are typically small molecule agents or particles on the lower size range at a couple nms in diameter. To reference a highly sited scientific article from Chemical Rev (Chem. Rev. 2010, 110, 2921–2959), "At 8 nm, observations have been made that hepatic uptake begins to dominate clearance routes, and by 10-12 nm the reticuloendothelial excretion route becomes the dominant route for clearance."

These nanodiamonds range in size from 15-100nm, so the kidneys will not be their primary route of clearance. It is also crucial to note that with any nanoparticle development, coating is a major factor in its biodistribution behavior. Coatings can and have been designed in more recent work regarding nanomedicine that minimize various biodistribution issues.

[rgejman]

If they are in fact small enough to escape via biliary excretion, that would be great. But just skimming the literature it looks like they can accumulate and persist for weeks in the liver—a situation which would suggest hepatotoxicity is another problem (Zhu et al 2012 in "Theranostics" -- never heard of that journal but paper looks 'ok').

Coatings won't help this problem unless you can somehow change the shape of the crystal to fit through the slit OR get it to cross into the renal luminal space via transcytosis or excreted more efficiently in the biliary tree. All difficult propositions.

I really hope novel techniques like this work but this particular on seems very problematic. If I were you I would complete a serious set of toxicity studies very early on to make sure this isn't a fish that's dead in the water.

Edits: clarifying the points

[Bikanta]

Toxicity concerns are always utmost to consider when developing tools for the clinic! Thus far, all studies regarding nanodiamonds have shown biocompatibility and non-toxicity. Coming from a research background and having done a number of in vivo studies myself, these studies we plan to repeat with each targeted version of the nanodiamond (particle + ligand such as antibody) before reaching the clinic. To clarify, we are at the pre-clinical level currently.