Ultrabright benzoselenadiazole-based semiconducting polymer dots for specific cellular imaging

Semiconducting polymer dots (Pdots) have recently emerged as a new class of extraordinarily bright fluorescent probes with promising applications in biological imaging and sensing. Herein we synthesized a novel series of highly emissive orange-fluorescent copolymers, poly[9,9-dioctylfluorenyl-2,7-diyl)-co-1,4-benzo-{2,1'-3}-selenadiazole)] (PFBS) and tuned the ratio of fluorene to benzoselenadiazole (BS) from 98 : 2 to 50 : 50 to investigate the influence of BS molar ratio on the emission properties of the resulting Pdots. An optimal quantum yield of 44% could be obtained for PFBS Pdots at a fluorene to BS ratio of 70 : 30. These PFBS Pdots also exhibited great photostability and superior single-particle brightness. We next conjugated biomolecules onto the surface of these PFBS Pdots and demonstrated their ability for specific cellular labeling without any noticeable nonspecific binding. We are now working on the synthesis of near-infrared Pdots based on this BS unit and anticipate this series of ultrabright Pdots will be very useful in a variety of in vitro and in vivo bioimaging applications.