4.4.2. Biodistribution of [18F]10

A total of 0.6 <sup>±</sup> 0.1 MBq (*<sup>n</sup>* <sup>=</sup> 15) (43.2 <sup>±</sup> 1.4 <sup>μ</sup>g of protein) of [18F]fluoroalbumin was injected into the tail vein of female CD-1 mice (*n* = 3–4 per time point). The mice were euthanized at selected time-points and the tissues were collected and measured with a gamma counter, as described above. Blood from a cardiac puncture was collected into an Eppendorf tube containing 2 μL of 1% heparin solution in 0.9% NaCl (aq) and was pretreated before analysis, as described above. After centrifugation, a small sample (4 μL) was applied onto a silica TLC plate and 100 μL of the supernatant was injected into HPLC for radiometabolite analysis. For the radiometabolite studies of [18F]**10**, the blood was collected into an 1.5-mL microtube containing 1% heparin solution in 0.9% NaCl (aq), and was centrifuged (at 1000 *g* for 10 min). Plasma was separated from the cell pellet and added onto a 30-kDa molecular weight cut-off (MWCO) centrifugal filter (VWR® Radnor, PA, USA) and centrifuged (at 6500 rpm for 10 min). The filter with over 30 kDa 18F-labeled molecules and the microtube containing the below-30-kDa 18F-labeled molecules in the eluate, were measured with a gamma counter, to determine the percentage of small molecular weight metabolites from over 30 kDa molecules representing the intact BSA in the plasma.
