亲和素与生物素之间具有极高的亲和力,而且一分子亲和素上有四个生物素结合位点,生物素在血液中又能迅速清除.两步法与三步法预着靶技术都是利用单克隆抗体的肿瘤特异性与亲和素和生物素的上述特点相结合,为肿瘤定位研究中如何迅速降低本底,获得瘤/非瘤高比值提出了新的希望. The affinity between avidin and biotin is very high, and there are four biotin binding sites on one molecule of avidin, and biotin can be rapidly cleared in the blood. Two-step method and three-step method target The technology combines the tumor specificity of monoclonal antibodies with the above features of avidin and biotin, and offers new hope for how to rapidly reduce the background and obtain the tumor / non-tumor high ratio in tumor localization research.