Figure 2. Pharmacokinetics of gold nanoparticles(a–d) and iodine contrast agent (e–h, Omnipaque®) in mice. (a,e) Before injection. (b,f) 2 min after injection; (c,g) 10 min after injection; (d,h) 60 min after injection. The gold nanoparticles show low liver and spleen uptake and clearance via kidneys and bladder (b–d). At 60 min (d), the contrast in the gold-injected mouse is similar to the uninjected mouse (a), indicating efficient clearance.