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

Document Type: Research article

Authors

1 Nuclear Medicine Research Center, Mashhad University of Medical Sciences, Mashhad, Iran.

2 Biotechcology Research Center, Nanotechnology Research Center, School of Pharmacy, MUMS, Mashhad, Iran

3 Nuclear Medicine Research Center, Mashhad University of Medical Sciences, Mashhad, Iran

4 Nuclear Science and Technology Research Institute, Tehran, Iran

Abstract

In-vitro labeling of RBC with 99mTc is an intricate procedure and there is always a need for
an alternate blood pool imaging agent. The aim of this study was to prepare an effective nano
sized liposome (NLs) similar to human RBC for blood pool scintigraphy. This study formulates
PEG-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 injection
of labeled NLs with 99mTc hexamethylpropylene-amine-oxime (99mTc-HMPAO). Planar images
were acquired using a 256 × 256 matrix following99m Tc-HMPAO-NLs injection into ear vein
of rabbits 1, 2 and 24 h later. SPECT images were obtained 15 minutes after the injection (64
slices, 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-NLs
showed a significant circulation tracer activity (7.74 ± 1.63%ID/g at 1 h and 4.9 ± 0.77 %ID/g
at 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-NLs
were 1.25, 4 and 4.28 respectively at 2 h which changed to 1.06, 1.75 and 2.51 respectively
at 24 h. The 99mTc-HMPAO-PEG-NLs with a prolonged blood circulation time could be an
excellent RBC alternative for scintigraphy and gastrointestinal bleeding.

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