Evolving role of radiolabeled particles in detecting infection and inflammation, preliminary data with 99mTc-phytate in rats.

OBJECTIVE

The aim of this study was to evaluate the ability of phytate radiolabeled with technetium-99m (Tc-phytate) to identify inflammatory processes.

METHODS

Radiolabeling efficiency analyses were carried out by thin-layer chromatography on silica gel strips, yielding a radiochemical purity of 92%. In addition, the partition coefficient of Tc-phytate, obtained in a mixture of n-octanol/water (1 : 1), showed hydrophilic features of the radiopharmaceutical. After Tc-phytate was administered into the tail vein of healthy and inflammation focus-bearing rats, induced, in the right tight, by zymosan suspension at 5% (w/v), blood clearance evaluation was performed and showed a short plasma half-life (2.7 min). In the inflammation focus-bearing rats, Tc-phytate scintigraphic images were obtained at 2, 4, and 8 h after radiotracer injection.

RESULTS

A significant radiopharmaceutical uptake was found in mononuclear phagocyte system organs (liver and spleen) and in the inflammation focus (compared with contralateral muscle). Histopathological analysis showed an intense mononuclear infiltration in the inflamed muscle, suggesting that macrophages may be responsible for the greater radiotracer uptake in the inflamed site. Furthermore, the target-to-nontarget ratio (%ID/g of inflamed muscle-to-%ID/g of control muscle ratio) obtained by scintigraphic images performed at 2 h after the radiotracer injection was 10.24±3.49, remaining without any significant difference at 4 and 8 h.

CONCLUSIONS

Inflammation focus was evident in the scintigraphic images from 2 to 8 h after Tc-phytate administration, suggesting that this radiopharmaceutical could be a potential alternative to identify inflamed regions.