The present invention provides a microparticle comprising at least one biocompatible polymer the microparticle encapsulating at least one nanoparticle the nanoparticle comprising: (i) a core comprising a metal and/or a semiconductor and (ii) a corona comprising a plurality of ligands covalently linked to the core wherein said ligands comprise at least one carbohydrate and/or glutathione. The nanoparticle may additionally comprise a biologically active agent or detectable label covalently linked or non covalently bound to said corona and/or said core. Also disclosed are pharmaceutical compositions comprising the microparticles processes for their production and uses of the microparticles in methods of therapy.
