Khaw B A, Torchilin V P, Klibanov A L, Nossiff N D, Powers J B, Strauss H W, Haber E
Cardiac Unit, Massachusetts General Hospital, Boston 02114.
J Mol Cell Cardiol. 1989 Feb;21 Suppl 1:31-5. doi: 10.1016/0022-2828(89)90835-3.
Positively charged polymers have been shown to interact nonselectively with cells in vitro by means of an electrostatic binding to a negatively charged cell surface. We reasoned that, if a net negative charge could be introduced onto an antibody molecule, some of the nonspecific antibody interactions with cells could be avoided without affecting the function of the antibody combining site. An important result would be improved target-to-background ratios should such antibodies be used as in vivo imaging agents. To test this hypothesis, we first reacted bifunctional chelators such as diethylenetriamine pentaacetic acid with cationic polylysine polymers to permit radiolabeling with 111In, then rendered the polymer completely anionic by reacting the residual epsilon amino groups with succinic anhydride. These modified polymers were then covalently linked either to monoclonal antimyosin antibody or to its Fab fragment by means of a water soluble carbodiimide. The immunoreactivity of the antibody-polymer conjugates was not significantly diminished. 111In-labeled antimyosin Fab modified with succinylated polylysine permitted visualization of experimental myocardial infarcts as early as 30 min after intravenous injection. An inverse exponential relationship was observed between the distribution of 201Tl and that of polymer-modified antimyosin Fab. 111In-labeled succinylated polymer administered by itself did not localize in the infarct. These observations suggest that anionically modified antibodies may enhance the specificity of antibody imaging.
带正电荷的聚合物已被证明在体外可通过与带负电荷的细胞表面进行静电结合而与细胞发生非选择性相互作用。我们推断，如果能在抗体分子上引入净负电荷，就可以避免一些抗体与细胞的非特异性相互作用，而不会影响抗体结合位点的功能。一个重要的结果是，如果将此类抗体用作体内成像剂，靶本底比会得到改善。为了验证这一假设，我们首先使双功能螯合剂（如二乙三胺五乙酸）与阳离子聚赖氨酸聚合物反应，以便用铟 - 111进行放射性标记，然后通过使残余的ε氨基与琥珀酸酐反应，使聚合物完全呈阴离子性。然后，这些修饰过的聚合物通过水溶性碳二亚胺与单克隆抗肌球蛋白抗体或其Fab片段共价连接。抗体 - 聚合物缀合物的免疫反应性没有显著降低。用琥珀酰化聚赖氨酸修饰的铟 - 111标记的抗肌球蛋白Fab在静脉注射后30分钟即可观察到实验性心肌梗死。观察到铊 - 201的分布与聚合物修饰的抗肌球蛋白Fab的分布呈反指数关系。单独给予铟 - 111标记的琥珀酰化聚合物不会在梗死部位聚集。这些观察结果表明，阴离子修饰的抗体可能会增强抗体成像的特异性。
