Nuclear Techniques ›› 2015, Vol. 38 ›› Issue (1): 10301-010301.

### Chemical kinetics study on the labeling of BAT-AV-45 with 99mTc

CAO Guoxian ZHOU Xingqin MAO Shishi ZHANG Jiankang QIN Xiaofeng

1. (Key Laboratory of Nuclear Medicine, Ministry of Health, Key Laboratory of Molecular Nuclear Medicine of Jiangsu, Jiangsu Institute of Nuclear Medicine, Wuxi 214063, China)
• Received:2014-06-06 Revised:2014-11-18 Online:2015-01-10 Published:2015-01-07

Abstract: Background: In recent years, a new amyloid-?-peptide (A?) protein imaging agent 18F-AV-45 which can be used to diagnose Alzheimer’s disease (AD), was developed. Whereas single-photon emission computed tomography (SPECT) was widely applied in medical clinic in China, a two function compound BAT was connected to the end of AV-45 to successfully synthesize a new compound BAT-AV-45, and its chemical kinetics of labeling reaction with 99mTc was studied. Purpose: 99mTc-BAT-AV-45 was synthesized via direct reaction and ligand exchange for obtaining high labeling yield. Methods: The labeling reactions were performed with three modes: (1) adding BAT-AV-45, GH and 99mTc; (2) adding BAT-AV-45 and 99mTc but non GH; (3) adding GH and 99mTc but non BAT-AV-45. Reactants were incubated at 4°C, 25°C and 100°C, respectively. Samples were taken with capillary from vials at 2 min, 5 min, 10 min, 20 min and 30 min, respectively. Labeling yields were determined by thin layer chromatography (TLC). Order of reaction n, rate constant k, average activation energy Ea and reaction half life t1/2 of labeling reaction were calculated with chemical kinetics software compiled by ourselves. Results: The results expressed that the labeling yields of 99mTc-BAT-AV-45 with direct reaction and ligand exchange were proportional to reaction temperature and reaction time. The highest labeling yields with direct reaction and ligand exchange were 3.45%±0.05% and 93.81%±0.91%, respectively. The parameters of chemical kinetics were calculated. n was 1. k were 2.00×10?4 min?1, 3.00×10?4 min?1, 1.40×10?3 min?1 with direct reaction and 0.108 min?1, 0.115 min?1, 0.265 min?1 with ligand exchange at 4°C, 25°C and 100°C, respectively. Ea were 17.11 kJ?mol?1 with direct reaction and 6.84 kJ?mol?1 with ligand exchange, respectively. t1/2 were 3 890.60 min, 2779.51 min, 481.39 min with direct reaction and 6.43 min, 6.00 min, 2.62 min with ligand exchange at 4 °C, 25 °C and 100°C, respectively. Conclusion: The results indicated that the high labeling yield of 99mTc-BAT-AV-45 could be obtained by using ligand exchange to reduce activation energy Ea of labeling reaction so as to accelerate the reaction.