RADIONUCLIDE-LABELED LIPOSOMES - NEW LYMPH-NODE IMAGING AGENT

The regional lymph node localisation of technetium-99mlabelled liposomes in rats, following interstitial injection, was studied by external γ-camera imaging and tissue radioassay. Liposomes were labelled with the radionuclide using a stannous chloride method. Liposome charge, size and the time from injection were factors found to influence regional lymph node uptake. Small, well-sonicated, liposomes of neutral or cationic charge, as detemined by their lipid composition, were found to localise well in regional lymph nodes. Anionic liposomes were poorly localised. Neutral liposome size, as determined by length of exposure to ultrasound, was measured by electron microscopy. Kinetic studies of 99mTc labelled neutral liposomes of different sizes showed that the smallest liposomes (mean diameter 33 nm) were well localised in regional lymph nodes 6 h after injection and were maintained at a high concentration for 24 h. The clearance of the technetium label from the injection site and blood levels were also measured. Detailed studies of the tissue distribution of 99mTc labelled neutral, cationic and anionic liposomes, using both γ-camera imaging and radioassay, were carried out. The localisation of 99mTc labelled liposomes in regional lymph nodes may be of value in lymphoscintigraphy and further studies are required to investigate their potential in the detection of tumours in the lymphatic system. © 1979.