Triblock near-infrared fluorescent polymer semiconductor nanoparticles for targeted imaging

Polymer semiconductors have attracted significant attention as fluorescent probes due to their high extinction coefficients, high fluorescence quantum yields, and excellent photostability. However, semi-conducting polymers that exhibit emission in near-infrared (NIR) with high quantum yields and narrow bandwidth remain scarce. Furthermore, functionalization and bioconjugation of polymer semiconductors usually rely on physical encapsulation or surface modification. Here, we report an approach that utilizes robust covalent functionalization of semiconducting polymers with multiple components including biomolecules for targeted delivery and a hydrogel while maintaining a degree of independent tuning of the optical properties. The multiblock copolymers consist of an ABA architecture, where the core block consists of a NIR-emitting polymer semiconductor, and the shell block is composed of oligo(ethylene glycol) and folic acid pendant groups to provide water solubility and specificity for cell recognition. The synthesis, photophysics, self-assembly and cell studies of a series of polymer semiconductors as NIR-emitting fluorescent probes and triblock copolymer nanoparticles are presented. We demonstrate that the polymer semiconductors can exhibit emission that spans the NIR spectrum while maintaining a high fluorescent quantum yield and narrow emission. This design of block copolymers results in stable core-shell nanoparticles with the ability to specifically target and label folate-receptor positive cancer cells.