Complement sensing of PEGylated carbon nanotubes

As a result of their unique thermal and spectroscopic properties as well as their ability to traverse cellular membranes, carbon nanotubes have attracted considerable attention as entities for disease diagnosis and treatment.
The interaction of carbon nanotubes with elements of the innate immunity, and particularly the complement system has not received much attention. Complement is the first line of defense against intruders and its uncontrolled activation may induce adverse effects. Our investigations show that both methoxypoly(ethylene glycol) (PEG)-phospholipid coated and PEG functionalized carbon nanotubes can trigger complement system in human serum. Activation is triggered through surface sensing by the pattern recognition molecule L-ficolin, which in turn activate the zymogen mannose-binding lectin associated serine protease-2. Complement activation by PEGylated carbon nanotubes proceeds regardless of PEG molecular mass and surface packing density. Further treatment of PEGylated carbon nanotubes with serum albumin did not prevent complement activation. The immune safety of carbon nanotubes is therefore questionable.