Tetrazine-Based Cycloadditions: Application to Pretargeted Live Cell Imaging

TLDR

Tetrazine cycloadditions are a bioorthogonal chemistry that has been used for live‑cell labeling. The authors functionalized Her2/neu‑targeting antibodies with norbornene and then reacted them with near‑infrared fluorophore‑conjugated tetrazines, exploiting the irreversible norbornene–tetrazine cycloaddition that produces dihydropyrazine and nitrogen gas. The reaction proceeded with high yield, selectivity, and speed in aqueous media, enabling rapid, selective labeling of pretargeted breast cancer cells and suggesting its potential for in vivo pretargeted imaging across multiple modalities.

Abstract

Bioorthogonal tetrazine cycloadditions have been applied to live cell labeling. Tetrazines react irreversibly with the strained dienophile norbornene forming dihydropyrazine products and dinitrogen. The reaction is high yielding, selective, and fast in aqueous media. Her2/neu receptors on live human breast cancer cells were targeted with a monoclonal antibody modified with a norbornene. Tetrazines conjugated to a near-infrared fluorochrome selectively and rapidly label the pretargeted antibody in the presence of serum. These findings indicate that this chemistry is suitable for in vitro labeling experiments, and suggests that it may prove a useful strategy for in vivo pretargeted imaging under numerous modalities.