Fluorescent nanoparticles from self-assembly of β-cyclodextrin-functionalized fluorenecopolymers for organic molecule sensing and cell labeling

Abstract

Bromide-bearing conjugated fluorene copolymers were prepared by Suzuki coupling polymerization of 2,7-dibromo-9,9-bis(6′-bromohexyl)fluorene and 2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9,9-dihexylfluorene. Thiol-functionalized β-cyclodextrin was subsequently grafted to the bromoalkyl side chains of the fluorene copolymers via the thio-bromo ‘click’ reaction. The resulting fluorene copolymers can self-assemble into fluorescent nanoparticles surrounded by a β-cyclodextrin outer layer in an aqueous medium. Host–guest interactions of the β-cyclodextrin moieties of nanoparticles with the organic guest molecules in the aqueous medium gave rise to variations in the emission intensity of the nanoparticles. The low cytotoxicity of the fluorescent nanoparticles was revealed by incubation with KB cells, a cell line derived from carcinoma of the nasopharynx, in 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assays in vitro. The biocompatible and fluorescent nanoparticles were further used as effective fluorescence labels for KB cells.