Bright Quantum-Dot-Sized Single-Chain Conjugated Polyelectrolyte Nanoparticles: Synthesis, Characterization and Application for Specific Extracellular Labeling and Imaging

We report a simple method to fabricate quantum-dot-sized nanoparticles (NPs) from poly[9,9-bis((6-N,N,N-trimethylammonium)hexyl)fluorene-alt-co-2,1,3-benzoxadiazole dibromide] (PFBD). The transmission electron microscope results reveal that the obtained NPs have a mean diameter of approximate to 4 nm, which is composed of a single PFBD chain. The NPs show bright fluorescence with an emission maximum at approximate to 636 nm and a quantum yield of approximate to 26% in water. The fluorescence properties of the NPs are characterized by steady fluorescence microscopy, fluorescence dynamic study and single nanoparticle microscopy, which show superior brightness over commercial quantum dots QD655. The NPs are further conjugated with streptavidin to yield PFBD-SA NPs, which serve as a specific extracellular labeling and imaging probe with high specificity and good photostability.