Biodistribution was performed as previously described.[24 (link)] Either 24 or 48 hours after tail vein injection with fluorescent hRS7, mice were euthanized and organs were then resected and mechanically disrupted. A solution of 5 mg/mL collagenase IV (Worthington Biochemical) in 1X RIPA cell lysis buffer (Fisher Scientific) was then added to the organs for a 1 hour incubation. Organs were sonicated using an FB-120 Sonic Dismembrator and incubated for another hour after adding 1X RIPA buffer with 0.025% trypsin-EDTA. Cells were sonicated again to complete tissue homogenization, then serially diluted and scanned on the Odyssey CLx Scanner. A calibration curve of known concentration was used to calculate the concentration of fluorescent probe, which was then normalized to organ weight and dose to calculate the percent injected dose per gram (%ID/g).