Preparation of radiolabeled polycyclic aromatic hydrocarbon assemblies for biological assessment of diesel exhaust particulates

Abstract

The potential health risk from inhalational exposure of diesel exhaust particulates (DEP) has gained considerable scientific interests. However, the long-term in vivo behavior of DEP have not been clearly understood due to the difficulty of accurate analysis of these substances in a living subject. We herein demonstrate a detail protocol for the preparation of radiolabeled DEP using a radioactive-iodine-tagged pyrene analog. The purified $^{125}I$-labeled pyrene ($[^{125}I]1$) was obtained with a good radiochemical yield ($32{\pm}4%$, n=3) and high radiochemical purity (>99%) from the stannylated precursor 2. Next, the purified $[^{125}I]1$ was successfully assembled into the DEP suspension in an efficient manner. The radiolabeled DEP was highly stable in a mouse serum for 7 days without significant deiodination or dissociation of $[^{125}I]1$. These results clearly indicate that the present radiolabeling method will be useful for biodistribution study of carbonaceous particulates in vivo.

Figure 1. Synthetic procedure of [¹²⁵I]1 and radiolabeled DEP (¹²⁵I-DEP)

Figure 2. Analytical HPLC chromatogram of the purified [¹²⁵I]1. a) UV detector, and b) γ-detector.

Figure 3. Stability test of ¹²⁵I-DEP in mouse serum. (Stability (%) = Cp / (Cp + Cs) x 100, Cp = radioactivity in the pellet, Cs = radioactivity in the supernatant)