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Biodistribution study and identification of inflammation sites using 99mTc-labelled stealth pH-sensitive liposomes
Vildete A S Carmo1, Cristiano S Ferrari, Eduardo C O Reis
1Faculdade de Farmácia, Universidade Federal de Minas Gerais, Minas Gerais, Brazil.
Purpose:
To investigate the biodistribution and the ability of stealth pH-sensitive liposomes radiolabelled with 99mTc to identify inflammatory regions in a rat focal inflammation model.
Methods:
Preformed glutathione-containing stealth pH-sensitive liposomes were labelled with 99mTc-hexamethylpropylene amine oxime (99mTc-HMPAO). The 99mTc-HMPAO radiolabelled stealth pH-sensitive liposomes (99mTc-SpHL) were administered intravenously in Wistar male rats with inflammation induced by injection subplantar of carrageenan in the right foot. At pre-established time intervals the animals were anaesthetized and tissues were removed and analysed for 99mTc content using an automatic scintillation apparatus. Scintigraphic imaging was also performed after 2, 4 and 8 h of intravenous injection of 99mTc-SpHL.
Results:
The 99mTc-SpHL was significantly taken up by the spleen (19.21+/-2.98%ID/g at 30 min post-injection). Low radioactivity levels were found in the liver, lungs, and kidney. Moreover, the 99mTc-SpHL uptake was significantly higher in the inflamed foot when compared to the respective control (0.386+/-0.059 and 0.215+/-0.018%ID/g at 2 h post-injection, respectively). As early as 30 min after administration of 99mTc-SpHL, the focus of inflammation could be visualized scintigraphically. The value of the inflammatory and non-inflammatory site radioactivity counting ratio was greater than 5.
Conclusion:
This result indicates that the 99mTc-SpHL presents a high tropism for inflammatory regions and may be useful as a radiopharmaceutical to identify these foci.
