Homogeneous near-infrared emissive polymeric nanoparticles based on amphiphilic diblock copolymers with perylene diimide and PEG pendants: self-assembly behavior and cellular imaging application

An amphiphilic diblock copolymer, poly(perylene diimide acrylate)-block-poly(poly(ethyleneglycol)methacrylate) (PPDA-b-P(PEGMA)), has been synthesized via the reversible addition fragmentation transfer polymerization (RAFT) method. The polymer shows self-assembly behavior in water due to the synergistic effects of the strong hydrophobic interactions and π–π stacking of perylene diimide (PDI) groups. Homogeneous polymer nanoparticles (PNPs) in aqueous solution with good water solubility and stability were formed with an average size of 64.3 ± 3.3 nm, revealed by dynamic light scattering (DLS). The PNPs showed near-infrared (NIR) emission at 660 nm instead of the traditional emission of individual PDI groups at 530 nm. The aggregation-enhanced π–π stacking and the resulting NIR emission of the PDI groups were demonstrated by spectroscopy and 1H-NMR characterization. Cellular imaging of human pancreatic cancer cells was conducted with the obtained PNPs. Confocal microscopy results showed that the PNPs were located specifically within the cell cytoplasm. This study provides a new design concept to take full advantage of polymer amphipathy to fabricate nanoparticles with NIR emission for applications in bio-imaging.