Biodistribution study and identification of inflammation sites using 99mTc-labelled stealth pH-sensitive liposomes.
OBJECTIVE
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.


CONCLUSIONS
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.
Faculdade de Farmácia, Universidade Federal de Minas Gerais, Minas Gerais, Brazil.
Vildete A S
VA
Carmo
Cristiano S
CS
Ferrari
Eduardo C O
EC
Reis
Gilson A
GA
Ramaldes
Maira A
MA
Pereira
Mônica C
MC
De Oliveira
Valbert N
VN
Cardoso
D000818:Animals; D004337:Drug Carriers / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007249:Inflammation / Q000000981:diagnostic imaging* / Q000378:metabolism*; D008081:Liposomes / Q000737:chemistry*; D008297:Male; D008657:Metabolic Clearance Rate; D009928:Organ Specificity; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000737:chemistry / Q000493:pharmacokinetics; D051381:Rats; D017208:Rats, Wistar; D019690:Technetium Tc 99m Exametazime / Q000737:chemistry / Q000493:pharmacokinetics*; D014018:Tissue Distribution
D004337:Drug Carriers; D008081:Liposomes; D019275:Radiopharmaceuticals; D019690:Technetium Tc 99m Exametazime