The biodistribution study of GS-AuNPs and GS-AgNPs. A) 7-min biodistribution of GS-AgNPs and GS-AuNPs in major organs. B) The differences in the clearance of GS-AuNPs (ΔGS-AuNPs) and clearance of GS-AgNPs (ΔGS-AgNPs) in various organs at 7 min and 48 h p.i.. (Kd: kidney, It: intestine, Lv: liver, Hr: heart, Sk: skin, Ms: muscle, St: stomach, Sp: spleen; %ID/g=percentage of the injected dose per gram of tissues). *p<0.005. C) A hypothesized scheme showing the margination of GS-AuNPs (yellow) and GS-AgNPs (green) circulating in the blood stream after tail injection. Due to density-dependent margination, GS-AgNPs reach the kidneys faster than GS-AuNPs.