Complement monitoring of carbon nanotubes

In their survey describing the promises and challenges of carbon nanotubes in imaging and therapeutics, Kostarelos and colleagues state that “…chemically functionalized [carbon] nanotubes have been shown by many groups to be more biocompatible (no immune or acute inflammatory responses) than pristine nanotubes.” We point out below in vitro and in vivo studies that show surface-modified carbon nanotubes can trigger immune responses, notably activation of the complement system2–4. The complement system is a network of over thirty different proteins that orchestrate innate and acquired immunity. Microbial invaders and nanoparticulate systems, depending on their surface properties, size and shape, may trigger the complement cascade through any of the three established classical, alternative and lectin pathways, and more than one pathway may be involved in many cases.