Investigations of avidin and biotin for imaging applications.

TLDR

Avidin and biotin bind with extremely high affinity (Kd ≈ 10⁻¹⁵ M), making them attractive for imaging applications. The study aims to enhance ¹¹¹In targeting in animals using avidin–biotin chemistry. Antibodies were conjugated with biotin and injected unlabeled, then radiolabeled DTPA‑avidin/streptavidin was administered, or antibodies were conjugated with avidin and injected before radiolabeled biotin. In a mouse peritoneal bead model, the avidin–biotin approach markedly improved target‑to‑nontarget radioactivity ratios compared to conventional methods.

Abstract

The attractive properties of avidin (streptavidin) and biotin, in particular their strong affinities (Kd = 10(-15)M), may be used to advantage in imaging applications. These molecules have been used in this preliminary investigation to improve the targeting of 111In in animals. Antibodies have been conjugated with biotin and administered unlabeled while, at a later time, the radiolabel was administered attached to DTPA-coupled avidin or streptavidin. An alternative procedure was also considered whereby the antibodies were conjugated with avidin and administered before the administration of radiolabeled biotin. Using a model in which the target consisted of conjugated agarose beads deposited in the peritoneum of mice, it has been shown that the target/nontarget radioactivity ratios may be significantly improved with respect to the conventional procedures through the use of this approach.