In contrast, there was only ICB accumulation in the intestines, with negligible ICB signal in any other excised organ including the liver. We attribute the desirable pharmacokinetic features of ICB to a favorable combination of: (a) high ICB affinity for blood proteins which inhibits passive ICB extravasation from the bloodstream, 51 and (b) rapid uptake into hepatocytes, presumably by OATP1B, with negligible retention within these liver cells due in part to ICB hydrophilicity (negative LogP value) which diminishes hydrophobic interaction with the efflux transporters and cell membranes. These mouse biodistribution results suggested to us that ICB would likely be an effective deep-red fluorescent marker for imaging blood perfusion. We tested this possibility by conducting mouse imaging experiments that monitored changes in blood perfusion induced by inflammation. In recent years, fluorescence imaging has emerged as a valuable tool for diagnosing inflammatory diseases and conditions .52 Inflammation is associated with changes in micro vascularization and blood vessel permeability leading to increased accumulation of blood proteins within inflamed tissue. We employed a standard mouse inflammation model that injected lipopolysaccharide (LPS) into a mouse paw and used in vivo fluorescence imaging to visualize blood flow compared to the contralateral paw. More specifically, a 50 μL of a solution containing 100 ng LPS/μL was injected into the right posterior paw to induce inflammation, while a control saline dose was administrated to the left posterior paw (Figure ). Two fluorescence imaging paradigms were evaluated. One was a single-agent imaging experiment, where each mouse was given an intravenous injection of either ICB or ICG (100 nmol) and the mouse was imaged over time. Representative mouse fluorescence images are provided in Figure and Figure with a graph in Figure showing the rise and fall in mean pixel intensity for dye fluorescence in each mouse paw over time. The images show significantly higher dye accumulation in the inflamed paw compared to the control paw at 2 hours, with extensive dye clearance from both posterior paws by 6 hours. The mice were sacrificed at the 6 hour time point and in each case, the exposed abdomen was imaged (Figure ). The organs were then excised and imaged separately to produce a dye biodistribution profile (Figure ). As above, there was much higher background accumulation of ICG in the clearance organs.