An organically surface-bonded metal or metal oxide material including an inorganic metal or metal oxide and an organic material. The organic material is coated on the surface of the inorganic metal or metal oxide. The inorganic metal or metal oxide and the organic material are linked through a strong chemical bond. The strong chemical bond includes a covalent bond between a metal in the inorganic metal or metal oxide and a nitrogen in the organic material.

Nanoclusters comprising inorganic nanocrystals and a biodegradable polymer are disclosed. The inorganic nanocrystals have a mean particle size of 1 to 500 nm. The inorganic nanocrystals are contained within a core of the nanoclusters, on the surface of the nanoclusters, contained within a core of the nanoclusters, dispersed throughout the nanoclusters, or a combination thereof. The biodegradable polymer allows the inorganic nanocrystals to be excreted renally over a period of time. The nanoclusters can be used for medical imaging or other biomedical applications.

There are described magnetic nanoparticles the surface of which is functionalized with catechol and constructs comprising a plurality of said nanoparticles encapsulated in a biocompatible polymer matrix, wherein a molecule with therapeutic action is optionally dispersed, said polymer matrix optionally being in turn further functionalized; there are further described cells of the immune system incorporating said polymeric constructs giving rise to their engineering.

The invention relates to novel biocompatible hybrid nanoparticles of very small size, useful in particular for diagnostics and/or therapy. The purpose of the invention is to offer novel nanoparticles which are useful in particular as contrast agents in imaging (e.g. MRD and/or in other diagnostic techniques and/or as therapeutic agents, which give better performance than the known nanoparticles of the same type and which combine both a small size (for example less than 20 nm) and a high loading with metals (e.g. rare earths), in particular so as to have, in imaging (e.g. MRI), strong intensification and a correct response (increased relaxivity) at high frequencies. Thus, the nanoparticles according to the invention, with diameter d.sub.1 between 1 and 20 nm, each comprise a polyorganosiloxane (POS) matrix including gadolinium cations optionally associated with doping cations; a chelating graft C.sup.1 DTPABA (diethylenetriaminepentaacetic acid bisanhydride) bound to the POS matrix by an SiC covalent bond, and present in sufficient quantity to be able to complex all the gadolinium cations; and optionally another functionalizing graft Gf* bound to the POS matrix by an SiC covalent bond (where Gf* can be derived from a hydrophilic compound (PEG); from a compound having an active ingredient PA1; from a targeting compound; from a luminescent compound (fluorescein). The method for the production of these nanoparticles and the applications thereof in imaging and in therapy also form part of the invention.