The present invention provides carbohydrate encapsulated nanoparticles. In particular, the present invention provides metallic nanoparticles (e.g. gold nanoparticles) that are encapsulated in biologically important carbohydrate molecules, such as sugars, sugar derivatives, P-blood group antigens and analogues thereof. The present invention also provides methods of employing these carbohydrate encapsulated nanoparticles in diagnostic and therapeutic applications.