Nanoparticles in biological systems.

Understanding the behavior of nanoparticles in biological systems opens up new directions for medical treatments and is essential for the development of safe nanotechnology. This Review discusses molecules and nanoparticles when in contact with cells or whole organisms, with a focus on inorganic materials. The interaction of particles with biology unravels a series of new mechanisms not found for molecules: altered biodistribution, chemically reactive interfaces, and the combination of solid-state properties and mobility. Externally guided movement of medicaments by using functional nanomagnets brings mechanics into drug design. In subsequent sections, the role of inertness and bioaccumulation is discussed in regard to the long-term safety of nanoparticles.