Metallic colloid nanotechnology, applications in diagnosis and therapeutics.

In recent years the fields of medicine and biology assist to an ever-growing innovation related to the development of nanotechnologies. In the pharmaceutical domain, for example, liposomes, polymer based micro and nanoparticles have been subjects of intense research and development during the last three decades. In this scenario metallic particles, which use was already suggested in the first half of the '80, are now experiencing a real renaissance. In the field of diagnosis, magnetic resonance imaging is one of the first and up to now the most developed application of metallic particles. But beside this application, a very new generation of biosensors based on the optical properties of colloidal gold and fluorescent nanocrystals, called quantum dots seems to be ready to be implemented in diagnosis and medical imaging. Concerning therapeutic applications, the potentialities of metal nanoparticles to help fulfilling the need of time and space controlled release of drugs has been intuited for a long time. Nowadays, magnetically guided carriers or thermal responsive matrices, in which drug release is triggered by the heating of metal nanoparticles, are effective examples of their application in drug delivery, while more recently efforts to develop metallic nanoobjects to be used as vectors of nucleic acids for vaccination and transfection have been multiplied. In the future, one of the most interesting challenges is certainly the use of metallic nanoparticles for an innovating, effective and selective physical treatment of solid tumors via targeted intracellular hyperthermia.