Wallac wizard 1480 011 automatic gamma counter

Biodistribution experiments were conducted on healthy female Balb/C mice (14–18 weeks old, 20–25 g in weight, n = 3 per administration route). The radioactive exosome [^99mTc]-Exo preparation (250–300 µCi in 300 µL of a PBS 1X solution for the injections and 145–160 µCi in 30 µl of PBS for the intranasal instillation) was administered via the lateral tail vein, intraperitoneally, or intranasally, and the nanotracer was allowed to circulate for 24 h in the 3 groups. After this time, mice were sacrificed and their organs harvested (i.e., brain, trachea/thyroid, lungs, heart, stomach, liver, spleen, kidneys, intestines, muscle, and skin, as well as feces). The activity (exosome content) in the tissue of interest was measured on a Wallac Wizard 1480-011 Automatic Gamma Counter (Perkin Elmer, Waltham, MA, USA) and expressed as mean% ID/g of tissue.

Blood half-life was determined by measuring activity in serial blood samples. Specifically, [^99mTc]-Exo tracer was administered to healthy female Balb/C mice (14–18 weeks old, 20–25 g in weight, n = 3) via intranasal instillation (30 µL in PBS, 110–190 µCi, 9 ± 2 µg), intraperitoneal injection (300 µL, 350–490 µCi, 24 ± 5 µg), or intravenous tail injection (300 µL, 100–170 µCi, 19 ± 8 µg). Except for the intranasal route, tracer was administered under 2% sevoflurane anesthesia (O₂ 100%; 200–400 cc/min; Zoetis, Belgium). Blood samples were extracted from the saphenous vein in awake mice at several time points post-injection. This blood was weighed, and radioactivity was measured on a Wallac Wizard 1480-011 Automatic Gamma Counter (Perkin Elmer, Waltham, MA, USA). Measurements in counts per minute were normalized to the mean% ID/g of tissue. Data were modeled as a two-compartmental kinetic model and analyzed by two-phase decay nonlinear regression with Prism 6.0c (GraphPad Software, La Jolla, CA, USA).