Hnatowich D J, Mardirossian G, Rusckowski M, Winnard P
Department of Nuclear Medicine, University of Massachusetts Medical Center, Worcester 01655, USA.
Nucl Med Commun. 1996 Jan;17(1):66-75. doi: 10.1097/00006231-199601000-00012.
A novel method of radiolabelling antibodies and other proteins is described. A small single-stranded DNA was covalently conjugated to an antibody and labelled by hybridization following the addition of the complementary single-stranded DNA labelled with technetium-99m (99Tc(m)) or indium-111 (111In). Antibody labelling efficiencies were 100% in about 1 h at room temperature with specific activities of up to 30 microCi micrograms-1 of IgG for 99Tc(m). Both diester and thioate DNAs were used. Both the diester- and thioate-labelled antibodies showed complete label stability in 37 degrees C saline. After 24 h in 37 degrees C serum, however, about 40% of the label in the case of the diester antibody was on low molecular weight species--probably labelled catabolites from nuclease degradation of the phosphodiester DNA. In contrast, the 99Tc(m) label on the thioate antibody was immediately and quantitatively bound to serum proteins--probably due to non-specific binding through the sulphur groups. Biodistribution studies in normal mice reflect these in vitro observations: 99Tc(m) on the diester antibody was rapidly cleared through the kidneys, probably as low molecular weight catabolite, while on the thioate antibody, the 99Tc(m) label was predominately deposited in the liver. In conclusion, by modifying with a single-stranded DNA, proteins may be readily labelled with a variety of radionuclides by DNA hybridization. The properties of the radiolabel are strongly influenced by the nature of the DNA.
本文描述了一种放射性标记抗体及其他蛋白质的新方法。将一小段单链DNA与抗体共价结合，然后加入用99m锝（99Tc(m)）或111铟（111In）标记的互补单链DNA进行杂交标记。在室温下约1小时内，抗体标记效率可达100%，99Tc(m)标记的IgG比活度高达30微居里/微克。使用了二酯DNA和硫代磷酸酯DNA。二酯标记和硫代磷酸酯标记的抗体在37℃盐水中标记稳定性良好。然而，在37℃血清中放置24小时后，二酯抗体约40%的标记存在于低分子量物质上，可能是磷酸二酯DNA经核酸酶降解产生的标记代谢产物。相比之下，硫代磷酸酯抗体上的99Tc(m)标记立即定量地与血清蛋白结合，可能是通过硫基团发生非特异性结合。正常小鼠的生物分布研究反映了这些体外观察结果：二酯抗体上的99Tc(m)通过肾脏迅速清除，可能是以低分子量代谢产物的形式，而硫代磷酸酯抗体上的99Tc(m)标记主要沉积在肝脏。总之，通过单链DNA修饰，蛋白质可通过DNA杂交轻松用多种放射性核素标记。放射性标记的性质受DNA性质的强烈影响。
