Bright red fluorescent conjugated polymer nanoparticles with dibenzopyran as electron donor for cell imaging

Fluorescent conjugated polymers (CPs) have been successfully used to make conjugated polymer nanoparticles (CPNs) for cellular imaging, bio-orthogonal labeling, and in vivo tumor targeting, since CPNs have superior bright fluorescent emission and photostability. However, the preparation of red fluorescent CPNs with reasonably high quantum yield (QY) is still very challenging. We have synthesized bright red fluorescence CPNs based on a conjugated polymer that contains an annulated pyran ring and branched alkoxy chains, which have helped to reduce close packing in the solid phase. We examined the impact of the molecular weight of CPs on the QYs of CPNs. QY as high as 51.8-36.8% was observed in all CPNs with normally used CPs, with a surfactant mass ratio of 1 : 2. Our CPNs provided intense and stable fluorescence which could be traced through several generations in cell imaging, indicating the considerable photostability and biocompatibility of our CPNs.