Synthesis and in vivo evaluation of 99m Tc-Transferrin conjugate for detection of inflamed site.

Transferrin is one of acute phase reactants in inflamed lesion. Expression of transferrin receptor is increased in activated macrophage during inflammation process. Conjugates of target ligand with novel water-soluble chitosan for fast excretion of background radioactivity have been shown to be selectively taken up via the target molecules. In this study, radiolabeled 99m Tc-Transferrin conjugate was synthesized and evaluated its efficacy in vivo as a targeted agent for the rapid detection of inflamed lesion that expresses relatively high level of transferrin receptors. Transferrin was conjugated with HYNIC-chitosan and radiolabeled with 99m Tc. The biodistribution and scintigraphic images with the 99m Tc-HYNIC-chitosan-Transferrin conjugate (99m Tc-Tfc) were studied in a murine infection model in which the infection was induced with Escherichia coli (2 x 10(6) colonies). The %ID/g was as follows: 1.612 +/- 0.098, 2.473 +/- 0.202 and 2.617 +/- 0.646% at 30, 120 min and 6 h after injection, respectively. Gamma camera imaging rapidly visualized the infection/inflammation lesion, with the lesion-to-background ratio improving with time up to 5.68 +/- 0.48. 99m Tc-Tfc scintigraphy allows rapid and good imaging of an inflamed lesion.