Figure 3.

Radiolabelling efficiency and radiochemical stability of membrane-labelled B16F10 exosomes. (A) B16F10 exosomes with covalently attached DTPA (DTPA-Exo_B16) were purified from excess ¹¹¹InCl₃ by gel filtration (Sepharose® CL-2B). Free ¹¹¹In in ammonium acetate buffer (¹¹¹In-AA) was also eluted through the column as control. Eight 500 µl fractions were collected and the radioactivity for each fraction and the column itself post-purification was measured by gamma counting, and are expressed as the percentage of activity relative to the initial activity added to the column. Radiolabelling efficiency was calculated as the sum of % radioactivity recovered from F1 and F2. Values are expressed as mean ± SD, where n=3. Statistical analysis was done on F1 and F2 (p** < 0.01, p*** <0.001). (B) Radiolabelled exosomes ([¹¹¹In]DTPA-Exo_B16) were incubated in either PBS or 50% serum for 24 h at 37°C, and then spotted on a TLC paper. The paper was then run on 0.1 M ammonium acetate with 0.25mM EDTA (pH 5.5) as the mobile phase and imaged using a phosphorimager. Radiochemical stability was calculated as % radioactivity remaining at the application point. Values are expressed as mean ± SD, where n=3.