BIODISTRIBUTION AND IMAGING STUDIES OF TC-99M-LABELED LIPOSOMES IN RATS WITH FOCAL INFECTION

We have recently developed a procedure to label liposomes containing reduced glutathione (GSH) with (TC)-T-99m using the lipophilic chelator, hexamethylpropyleneamine oxime (HMPAO). In the present study, we evaluated the use of Tc-99m-liposomes to detect focal infection sites in rats. Rats were infected in the thigh by intramuscular injection with Staphylococcus aureus followed 24 hr later by an intravenous injection of Tc-99m-liposomes, Ga-67-citrate, or Tc-99m-human serum albumin (HSA). The animals were imaged under a gamma camera and subsequently killed at 4, 24 or 48 hr for tissue biodistribution studies. In contrast to infected rats receiving Ga-67-citrate or Tc-99m-HSA, abscesses were prominently localized within 2 hr in rats after Tc-99m-liposome injection, and continued to increase in activity up to 24 hr. Abscess-to-muscle ratios calculated from 24-hr biodistribution data obtained from tissue sampling were 35.3 +/- 7.6 for (TC)-T-99m-liposomes, 4.1 +/- 0.7 for Ga-67-citrate and 8.0 +/- 1.0 for Tc-99m-HSA. These studies show the potential of using Tc-99m-liposomes to localize infection.