Abstract: A composition of metal oxide nanoparticles in which individual nanoparticles comprises a core that optionally is coated and the metal oxide comprises a metal oxide lattice in which 5 there are two, three, four or more different kinds of metal ions: A) one of these metal ions is selected among lanthanide ions (typically ions of elements 57-B 71), and) at least one, two, three or more of the other different kinds of metal ions is selected among 10) i transition metal ions of elements of Groups 3b-7b, 8, 1b, 2b other than the lanthanide b ions of elements 57-71, and/or A) lanthanide ions other than the kind of lanthanide ion selected in A. typical metal ion of (A) is Gd3+, of (B.a) is Fe3+ and of (B.b) is Tb3+. 1 5A v method for coating core forms of the particles, and the use of the particles for visualizing various kinds of biological material, e.g. by magnetic resonance, are also provided.

Abstract: A method for visualizing biological material, preferably by MRI, comprising the steps of: (i) bringing a population of coated nanoparticles into contact with said biological material, each of which nanoparticles comprises a) a metal oxide of a transition metal, said metal oxide preferably being paramagnetic and preferably comprising a lanthanide (+III) such as gadolinium (+III), and b) a coating covering the surface of the core particle, and (ii) recording the image; wherein the coating is hydrophilic and comprises a silane layer which is located next to the surface of the core particle and comprises one or more different silane groups which each comprises an organic group R and a silane-siloxane linkage where a) R comprises a hydrophilic organic group R? and a hydrophobic spacer B, b) O is oxygen directly binding to a surface metal ion of the metal oxide, and c) C is carbon and is also part of B.

Abstract: Superparamagnetic nanoscale particles are disclosed which are useful for providing a contrast agent with high signal intensity, high relaxivity and high intrinsic magnetism. The disclosed contrast agents will have utility and magnetic resonance imaging (MRI) and associated techniques.