Biodistribution of intravenous [Tc-99m]Tc-phytate in mouse models of chemically and foreign-body induced sterile inflammation

When injected intravenously, [Tc-99m]Tc-phytate forms particles in the nanometer range. This size can favor its extravasation into tumor and inflammation through pores of the vasculature. The aim of this work is the evalua-tion of the use of [Tc-99m]Tc-phytate to assess sterile inflammation in mouse models. Biodistribution studies of [Tc-99m] Tc-phytate were performed in two groups of male Swiss Albino mice. Sterile inflammation was induced after intra-muscular injection of turpentine in the first group (chemically induced sterile inflammation model) and after implan-tation of sterile metal bolts in the second group (foreign-body induced sterile inflammation model). [Tc-99m]Tc-phytate was intravenously injected after the development of inflammation in both groups and ex vivo biodistribution of the radiolabelled complex followed at different time-points. Biodistribution was expressed as percent injected dose per gram (%ID/g). Target-to-background ratios were also recorded. For the chemically induced sterile inflammation model, ex vivo biodistribution evaluation measurements revealed a pronounced uptake in the inflamed muscle when compared to uptake in the control/non-inflamed muscle. Moreover, as expected, there is a high uptake in the liver and spleen. For the foreign-body induced sterile inflammation model, a significantly higher uptake was observed in the inflamed muscle post [Tc-99m]Tc-phytate injection, both for the 24 hours post-bolt implantation and for the 7 days post-bolt implantation groups. The nanoparticle properties of [Tc-99m]Tc-phytate are potentially useful in the imaging of different types of sterile inflammation with translational potential clinical SPECT (single photon emission computed tomography) imaging applications in humans.