Labeling of native proteins with fluorescent RAFT polymer probes: application to the detection of a cell surface protein using flow cytometry

Conjugation of fluorescent polymer chains synthesized by RAFT controlled radical polymerization with native proteins was achieved by introducing an activated ester function at their ω-chain-end via a very efficient thiol–ene click post-polymerization functionalization strategy. These fluorescent polymer probes covalently reacted with the lysine amino groups of native proteins to form bright protein–polymer fluorescent conjugates. In particular, streptavidin was labeled with various polymer probes and it was shown that it retained in each case its ability to selectively bind biotinylated compounds. Finally, streptavidin labeled with fluorescent polymer chains was used to reveal biotinylated antibodies, enabling the detection of CD40 receptors at the surface of live dendritic cells.