Multicolor Conjugate Polyelectrolyte/Peptide Complexes as Self-Assembled Nanoparticles for Receptor-Targeted Cellular Imaging

An anionic conjugated polyelectrolyte (CPE, P1) with energy donor−acceptor architecture is synthesized and assembled with an Arg-Gly-Asp (RGD) terminated peptide to form fluorescent nanoparticles (FNs) with targeting capability. Complexation between oppositely charged P1 and the peptide at different molar ratio results in FNs with different size and fluorescence varying from sky-blue to orange-red because of aggregation-enhanced fluorescence resonance energy transfer (FRET). At the P1/peptide molar ratio of 8:0.9, the FNs exhibit bright orange-red fluorescence with a quantum yield of 16% and a large Stokes shift of 195 nm. In addition, these FNs also possess low cytotoxicity and good photostability. By virtue of the specific binding between RGD and integrin receptors, the P1/peptide FNs serve as an effective probe for receptor-targeted fluorescence imaging of HT29 cancer cells. This study thus provides a facile and generic strategy to prepare a new generation of multicolor polymeric FNs with native targeting capability and controllable properties for biological applications.