The mechanisms by which chemically functionalized carbon nanotubes flow in blood and are excreted through the kidneys illustrate the unconventional behaviour of these fibrillar nanostructures, and the opportunities they offer as components for the design of advanced delivery vehicles.
In recent times, a wide variety of filamentous, fibre-like nanostructures have been isolated or synthesized, and subsequent attempts have been made to use them in biomedical applications. Such nanostructures can be naturally occurring, protein-based constructs of specific biological activity, for example viruses and amyloid fibrils, or engineered materials such as nanofibres, filomicelles and nanotubes. Fibrillar nanostructures are gaining importance in biomedical research to further our understanding both of the mechanisms involved in pathological conditions (infectious processes or neurodegeneration) and of the interactions between nanoparticles and the biological milieu. In a more practical sense, filamentous nanomaterials are designed as transporters of therapeutic and/or diagnostic agents with much-wanted control over their in vivo tissue navigation, cargo release and clearance profile.