Study of chemical kinetics on labeling of ^99mTc-N-ethyl-N₂S₂-Memantine

Study of chemical kinetics on labeling of 99m Tc-N-ethyl-N 2 S 2 -Memantine 1 2 3 corresp first-author Corresponding author. E-mail address: jswxcgx@sina.com Corresponding author. E-mail address: jswxcgx@sina.com jswxcgx@sina.com 1 2 3 1 2 3 1 2 3 1 2 3 Key Laboratory of Nuclear Medicine, Ministry of Health, Wuxi 214063, China Key Laboratory of Nuclear Medicine, Ministry of Health, Wuxi 214063, China Key Laboratory of Molecular Nuclear Medicine of Jiangsu, Wuxi 214063, China Key Laboratory of Molecular Nuclear Medicine of Jiangsu, Wuxi 214063, China Jiangsu Institute of Nuclear Medicine, Wuxi 214063, China Jiangsu Institute of Nuclear Medicine, Wuxi 214063, China In this work, a calculation method of chemical kinetics was established for labeling reaction of 99m Tc-N-ethyl-N 2 S 2 -memantine, a potential NMDA receptor imaging agent prepared in our laboratory. Four groups of vials (3 vials per group) were added with 0.02 mL (1 mg/mL) N-ethyl-N 2 S 2 - Memantine, 0.08 mL (40 mg/mL) GH, 0.05 mL (10 mg/mL) EDTA-2Na, 0.035 mL (2 mg/mL) SnF 2 , 0.8 mL phosphate buffer(1 mol/L, pH 6.5) and 37 MBq Na 99m TcO 4 . The vials were incubated at 70°C, 80°C, 90°C or 100°C. Samples were taken with capillary from the vials at 2, 5, 10, 20, 30, 40 and 60 min. Labeling yields were determined by TLC. Order of reaction n , rate constant k , activation energy E a and half life t 1/2 of labeling reaction were calculated with the kinetics software we compiled. Mean labeling yields of 99m Tc-N-ethyl-N 2 S 2 -memantine at 2, 5, 10, 20, 30, 40 and 60 min were (1) 13.5, 15.7, 34.0, 64.8, 81.9, 91.4 and 95.4 at 70°C; (2) 13.2, 20.5, 40.1, 70.0, 88.2, 94.5 and 95.6 at 80°C; (3) 15.6, 22.9, 43.7, 74.3, 87.2, 93.4 and 96.1 at 90°C; and (4) 20.5, 25.8, 45.3, 81.1, 92.2, 95.6 and 96.0 at 100°C. The other parameters were; n =1; k =0.053, 0.061, 0.063 and 0.076 L/min at 70°C, 80°C, 90°C and 100°C, respectively; E a =12.38 kJ/L ; t 1/2 =13.11, 11.45, 11.05 and 9.07 min at 70°C, 80°C, 90°C and 100°C, respectively. The mean labeling yield increased with temperature and time, optimized at 100°C and 40–60 min. The concentration of 99m Tc-N-ethyl-N 2 S 2 -Memantine was larger than that of Na 99m TcO 4 , so n =1. The k increased with reaction, hence the accelerated reaction rate at higher temperatures. The labeling reaction was not so difficult because of the low E a . The t 1/2 decreased with increasing reaction temperature, hence the acceleration of labeling reaction. 99m Tc-N-ethyl-N 2 S 2 -Memantine NMDA receptor Labelling Chemical kinetics References Paoletti P , Neyton J . Curr Opin Pharmacol , 2007 , 7 : 39 - 47 . Curr Opin Pharmacol Liu Y T , Wong T P , Aarts M , et al . J Neuroscience , 2007 , 27 : 2846 - 2857 . J Neuroscience Lau C G , Zukin R S . Nat Rev Neurosci , 2007 , 8 : 413 - 426 . Nat Rev Neurosci Labrie V , Lipina T , Roder J C . Psychopharmacology , 2008 , 200 : 217 - 230 . Psychopharmacology Liu Y T , Zhou X Q , Cao G X , et al . Nucl Sci Teth , 2010 , 21 : 171 - 176 . Nucl Sci Teth Fu X C , Shen W X , Yao T Y . Physical chemistry . Fourth edition, Beijing : Higher Education Press , 1990 , 700 - 755 . Physical chemistry 10.13538/j.1001-8042/nst.23.52-56 Supported by the Jiangsu Natural Science Foundation (BK2008111, BK2010157) and the National Natural Science Foundation of China (30770602) 2011-07-18 2012-02-20 2021-01-19 2012 Nuclear Science and Techniques 01 23