Nanotoxicology and nanomedicine regulation

Nanotechnologies have enabled the emergence of numerous industrial applications, particularly in the pharmaceutical field, as vectors for active substances. They enable these substances to be targeted at a particular tissue in the body. Nanomedicines, which result from the combination of an active substance and a nanotechnology, are not drugs like any others. They generally consist of a liquid or solid core containing the active substance, surrounded by a crown (figure 1 ). This crown is exposed to the biological environment and performs three important functions: i) colloidal stabilization to prevent aggregation in the biological environment, ii) the ability to circumvent the destruction of nanomedicines by immune system cells, and iii) the association of a ligand on their surface for recognition of a cellular target. Nanomedicines are, however, drugs like any others for part of their development, since they undergo the clinical evaluation required by regulations prior to any marketing application.

However, nanostructured materials have different physico-chemical properties to bulk chemicals. These properties result from their small size and very large surface area for exposure to the surrounding environment, particularly the biological environment. Interactions with the biological environment result in highly specific pharmacokinetic properties and tissue distribution, as well as the ability to cross certain biological barriers that are normally impenetrable. All these properties are considered major assets for the pharmaceutical development of nanomedicines. However, they may also give rise to new toxic effects. These effects, and in some cases the persistence of nanomedicines in the human body, are a cause for concern and require special regulation.

However, it is extremely difficult to establish a single set of regulations, given the diversity of nanomedicines, their chemical nature and their many applications. It is for this reason that in most countries, recommendations have been produced by drug agencies. The aim of this article is to link the fundamental knowledge acquired on the characterization and cellular and tissue fate of nanomedicines to these recommendations.