Two-color in vivo dynamic contrast-enhanced pharmacokinetic imaging.

Optical imaging is unique among in vivo imaging methods because it is possible to simultaneously resolve two or more probes emitting at different wavelengths of light. We employed two near-infrared (NIR) fluorescent optical probes, each labeled with a different protein, to simultaneously evaluate the pharmacokinetics of each probe. Dynamic optical imaging was performed in live mice after the coinjection of bovine serum albumin (BSA) and galactosamine-conjugated bovine serum albumin (GmSA) labeled with either Cy5.5 or Cy7 NIR dyes. The pharmacokinetics of BSA and GmSA were independently and simultaneously visualized. Next, two-color dynamic imaging of biotinylated BSA (b-BSA) and BSA labeled with Cy5.5 or Cy7 was performed before and after an avidin "chase." Following avidin injection, fluorescently labeled b-BSA rapidly accumulated in the liver, while minimal liver uptake of BSA was noted. Thus, multicolor dynamic contrast-enhanced optical imaging can be performed to noninvasively track the pharmacokinetics of different proteins. This imaging technique can be applied to a wide variety of optically labeled proteins in order to simultaneously track their biodistribution.