Corrosion study of heat exchanger tubes in pressurized water cooled nuclear reactors by conversion electron Mössbauer spectroscopy

A first attempt to label insulin, a small protein with significant affinity to tumors with the α-emitter ²¹¹At was performed by an indirect method using N-succinimidyl 5-(tributylstannyl)-3-pyridinecarboxylate (SPC) as a bi-functional linker, and the stability of the conjugated insulin (²¹¹At-insulin) was evaluated in vitro and in vivo. SPC was synthesized by using 5-bromonicotinic acid as the starting material. With this bi-functional linker, insulin was conjugated with ²¹¹At in a labeling yield of 30–40%, with radiochemical purity of more than 98%. After 24 hours at room temperature, the radiochemical purity was still more than 95%, implying that ²¹¹At-insulin is fairly stable in vitro. Biodistribution of ²¹¹At-insulin was investigated in NIH strain mice. ²¹¹At accumulated rapidly in the liver post injection, with the maximum uptake of 4.29%I.D/g at 30 minutes, and was mainly excreted by kidney. More importantly, ²¹¹At-insulin uptake in some key organs or tissues, especially in thyriod, stomach, lung and spleen, was much less than that of free astatide (²¹¹At^?). This result indicated that ²¹¹At-insulin has considerable stability in vivo as well as in vitro.