Nano Liposomes labeled with 99mTc-HMPAO, A Novel Agent for Blood Pool Imaging

Abstract

In-vitro labeling of RBC with 99mTc is an intricate procedure and there is always a need foran alternate blood pool imaging agent. The aim of this study was to prepare an effective nanosized liposome (NLs) similar to human RBC for blood pool scintigraphy. This study formulatesPEG-NLs and non-PEG-NLs using film method plus high pressure homogenization technique.Biodistribution studies were performed on BALB/C mice 1, 4 and 24 h after tail vein injectionof labeled NLs with 99mTc hexamethylpropylene-amine-oxime (99mTc-HMPAO). Planar imageswere acquired using a 256 × 256 matrix following99m Tc-HMPAO-NLs injection into ear veinof rabbits 1, 2 and 24 h later. SPECT images were obtained 15 minutes after the injection (64slices, 30 second/projection). The mean diameter, zeta potential and polydispersity index (PDI)of the PEG-NLs and the NLs were (80.88 ± 0.594 nm, -12.5 ± 0.56 mv, 0.158 ± 0.025) and(94.14 ± 0.114 nm, -35.5 ± 0.67 mv and 0.198 ± 0.007), respectively. 99mTc-HMPAO-PEG-NLsshowed a significant circulation tracer activity (7.74 ± 1.63%ID/g at 1 h and 4.9 ± 0.77 %ID/gat 4 h), with low liver accumulation (12.07 ± 3.66 %ID/g at 1 h and 14.85 ± 1.3 %ID/g at 4 h).Heart to liver, spleen and background ROIs (region of interests) for 99m c-HMPAO-PEG-NLswere 1.25, 4 and 4.28 respectively at 2 h which changed to 1.06, 1.75 and 2.51 respectivelyat 24 h. The 99mTc-HMPAO-PEG-NLs with a prolonged blood circulation time could be anexcellent RBC alternative for scintigraphy and gastrointestinal bleeding.