Labelling of human serum albumin (HSA)-nanospheres with technetium-99m radionuclide

Abstract

Labelling of HSA-nanospheres with technetium-99m was carried out by direct and indirect method using sodium pyrophosphate as co-ligand agent. The labelling efficiency was determined by several chromatography system for separation of 99m Tc-HSA-nanospheres labelled compound from its radiochemical impurities. Several parameters influencing the labelling process were studied such as pH, kinds and quantity of reductor agent, labelling method, quantity of HSA-nanospheres and temperature and the duration of incubation. The result show that the optimum direct labelling condition was found by using 0.5 mL HSA-nanospheres solution (which had absorbance of 0.6 at l= 202 nm), 100-150 μg of SnCl2.2H2O as reductor, pH mixture was 2 and the first incubation was done at room temperature for 25 minutes. The labelling process was continued by adding technetium-99m of certain activity, and finally pH was adjusted to 5.5-6.0. The second incubation was carried out at room temperature for 15 minutes. This direct method resulted more than 90% of labelling efficiency, with free 99m Tc-pertechnetate as radiochemical impurity. The indirect labelling process by using 0.5 mL of HSA-nanospheres solution, 100 μg of SnCl 2 .2H 2 O was prior reacted with 1.0 mg of sodium pyrophosphate (1 : 5 mol/mol), the pH was adjusted to 7.4 and incubation was done in the incubator at 37 o C for 15 minutes. After adding 99m Tc-pertechnetate solution, the second incubation was done at room temperature for 15 minutes. This indirect labelling resulted 93.4 ± 1.2 % of labelling efficiency with remain of 99m Tc-pertechnetat and 99m Tc-pyrophosphate as radiochemical impurities. Key words: lymphoscintigraphy , nanocolloid, technetium-99m, radiochemical impurities.