Nanotoxicological classification system (NCS) - a guide for the risk-benefit assessment of nanoparticulate drug delivery systems.

There is an increasing discussion about potential toxicity of nanoparticles (nanotoxicity). A classification system is proposed classifying the nanoparticles in four classes (I to IV) from low/no risk to high risk. It is based on the nanoparticle size (>/<100 nm) and size-related differences in interaction with human cells, and on biodegradability/non-biodegradability in the body. This classification is superimposed by biocompatibility (B) and non-biocompatibility (NB) of the nanoparticle surface, resulting in a total of eight classes from I-B (best tolerated) to IV-NB (highest potential risk). The classification should help as a guideline in pharmaceutical formulation development, but also as a guide for risk assessment in other product areas and environmental exposure.