Labeling IgG with $^{99m}Tc$ using 2-iminothiolane

2-iminothiolane을 이용한 IgG의 $^{99m}Tc$ 표지

2-iminothiolane is known to bind $NH_2$ group of lysine in the protein and deliver SH group, which can be used to label protein with $^{99m}Tc$. In this study, we looked for the best reaction condition in which 2-iminothiolane is conjugated to human polyclonal IgG and labeling condition with $^{99m}Tc$-glucoheptonate. Labeling yield was measured with TSK G4000SW column and HPLC or precipitation with 10% TCA (trichloroacetic acid) and 1% HSA. In vivo distribution was investigated with Staphylococcal abscess bearing rats. With decreasing glucoheptonate, the labeling yield decreased. Without 2-iminothiolane, $^{99m}Tc$-glucoheptonate was bound to IgG, which seemed to be direct labeling. With increasing 2-iminothiolane upto 20 times higher than IgG, the labeling yield increased, and plateau was seen with higher molar excess of 2-iminothiolane. Polymer formation was not observed. The pH for the conjugation of 2-iminothiolane and IgG was best around 6.4. $^{99m}Tc$-2-iminothiolane-IgG showed faster blood clearance, higher renal activity and lower hepatic and splenic activity than $^{99m}Tc$-DTPA-IgG. The biodistribution of $^{99m}Tc$-2-iminothiolane-IgG with higher molar excess of 2-iminothiolane was not different from that with lower molar excess. Labeling antibodies with $^{99m}Tc$ using 2-iminothiolane can afford a possible route to simple labeling and wide clinical use of the immunoscintigraphy.