99m Tc-tricarbonyl labeling of paclitaxel as an antimicrotubule agent and its evaluation in B16-F10 melanoma tumor-bearing mice.

In the present study paclitaxel (taxol) was labeled with [99m Tc(CO)3 (H2 O)3 ]+ core. Labeling was optimized, and radiochemical analysis was determined by thin layer chromatography and high performance liquid chromatography. Radiocomplex was evaluated and verified further as a tumor characterization agent in B16-F10 melanoma tumor-bearing mice. The [99m Tc(CO)3 (H2 O)3 ]+ -paclitaxel complex with high specific activity (0.77 GBq/μmol) and labeling yield (96.8 ± 1.3) was obtained. No decrease in labeling was observed up to 6 hours, and the stability of the radiocomplex was found adequate. Our main achievement was high accumulation of radiolabeled paclitaxel in tumor (4.51 ± 0.65 percentage injected dose per gram [%ID/g] at 2-h postinjection) followed by significant reduction (1.86 ± 0.27%ID/g) at 4-hour postinjection. Because paclitaxel is a substrate for multidrug resistance,99m Tc-tricarbonyl-paclitaxel imaging would be useful for tumor characterization rather than tumor detection.