Development of 99mTc-neomannosyl human serum albumin (99mTc-MSA) as a novel receptor binding agent for sentinel lymph node imaging.

Development of 99mTc-neomannosyl human serum albumin (99mTc-MSA) as a novel receptor binding agent for sentinel lymph node imaging.
Jeong, Jae Min; Hong, Mee Kyung; Kim, Young Joo; Lee, Jaetae; Kang, Joo Hyun; Lee, Dong Soo; Chung, June-Key; Lee, Myung Chul
Nuclear Medicine Communications. 25(12):1211-1217, December 2004.
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Abstract:
Background and aim: Various mannose receptor-binding agents, for example 99mTc-diethylenetriaminepentaacetic acid (DTPA)-mannosyl-polymer, have been developed for sentinel lymph node (SLN) imaging. In order to simplify the synthesis and labelling procedure and to improve the biological properties, we developed a novel mannose receptor-binding agent, 99mTc-neomannosyl human serum albumin (99mTc-MSA), for SLN imaging.
Methods: MSA was synthesized by conjugating mannopyranosylphenylisothiocyanate to human serum albumin (HSA). After reducing MSA with [beta]-mercaptoethanol and PD-10 column purification, a medronate solution containing stannous fluoride was added, divided into aliquots and freeze-dried. Reduced MSA was labelled with 99mTc-pertechnetate solution. The stability was checked for 24 h at 37[degrees]C in human serum. The biodistribution of 99mTc-MSA in mice was investigated by intravenous injection through the tail vein and subcutaneous injection into the foot pad. The biodistributions of 99mTc-HSA and 99mTc-antimony sulphur colloid (99mTc-ASC) were also investigated for comparison. Dynamic whole-body images were obtained for 30 min after subcutaneous injection into the rats' foot pads.
Results: The number of mannose molecules conjugated per MSA was 15.9. The number of thiol groups produced was 19.4 per MSA after reduction with [beta]-mercaptoethanol. Labelling yields were always higher than 97%. 99mTc-MSA was stable for 24 h at 37[degrees]C in human serum. The biodistribution in mice after intravenous injection showed high liver uptake (50.7+/-5.5% and 42.7+/-3.7% injected dose per gram at 10 and 60 min, respectively). 99mTc-MSA and 99mTc-ASC showed high accumulation in the lymph nodes after subcutaneous injection, whereas 99mTc-HSA and 99mTc-tin colloid did not, in both biodistribution and imaging studies.
Conclusions: We have successfully developed a novel 99mTc-MSA for lymphoscintigraphy. The results of animal studies show that 99mTc-MSA has promising properties for SLN imaging.
(C) 2004 Lippincott Williams & Wilkins, Inc.