The objective of NANOMAGDYE consists in developing tailored biocompatible magneto-optical nanosystems based on magnetic iron oxide nanoparticles. The project will comprise the elaboration of the nanosystems and the characterisation of their structural, optical and magnetic properties. In vitro and in vivo tests will be carried out to test their biocompatibility. The combination of magnetic and optical properties will be achieved through hybrid nanoparticles made of a magnetic iron oxide core on which an organic layer (dye) will be grafted through a dendrimer molecule and a phosphate entity. This grafting strategy will be extended to bubbles on which magnetic nanoparticles will be attached. The grafting sites will be controlled in order to design new geometries and architectures from rings up to submicronic magnetic spheres. Magnetic nanoparticles with monodisperse size between 2 and 100 nm will be elaborated in order to increase the possibility range of achieved properties. The opto-magnetic nanoparticles will be tested in a medical application and a dedicated magneto-optical probe will be fabricated. Current methods for labelling the lymph node system use a dye (vital blue) or radio nuclide injection detected through optical or Gamma probes, respectively, or a combination of both types of markers. Combining optical and magnetic labelling into a single biocompatible nanosystem will provide higher spatial resolution than presently and avoid using ionising radiation to improve patient safety and medical effectiveness. Stabilized submicronic bubbles labelled with the optical-magnetic nanoparticles will play the role of a contrast agent currently used in echography imaging and facilitate the uptake of the iron nanoparticle, and therefore improve node imaging.