Escort aptamers: a delivery service for diagnosis and therapy

In 1990, the discovery of aptamers by Tuerk and Gold (1) and subsequently by Ellington and Szostak (2) spawned significant interest within academia and industry. Aptamers have quickly become valuable research tools (3-5). More than that, a therapeutic aptamer (6) has entered clinical evaluation just eight years after the inception of the technology. While aptamers have built inroads into therapeutic applications, they may also become important in vitro diagnostic tools (7). Here, we discuss a new development: the use of "escort aptamers" as targeting agents for in vivo diagnosis and therapy. Instead of directly interrupting a disease process, as would a function-blocking aptamer, escort aptamers are designed to deliver radionuclides, toxins, or cytotoxic agents to diseased tissue. Specifically, we focus on the delivery of benign radionuclides for in vivo diagnosis of disease. For discussion of function-blocking aptamers, see White et al., this Perspective series (8).