Nanoparticles for cancer detection

A method of detecting a cancer cell or tumor in a subject comprising:

• a) administering into the peritoneum of said subject a nanoparticle, wherein the nanoparticle comprises a detectable agent within the silica nanoparticle and wherein the nanoparticle is an unmodified silica nanoparticle comprising substantially only terminal hydroxyl moieties at the nanoparticle surface;
• and
• b) detecting said nanoparticle at the site of said cancer cell or said tumor in said subject;
• thereby detecting the cancer cell or tumor in said subject.