Synthesis of coumarin-containing conjugated polymer for naked-eye detection of DNA and cellular imaging

Three novel coumarin-containing conjugated polyelectrolytes (P1–P3) containing coumarin, carbazole, fluorene and phenylene moieties were successfully synthesized by Suzuki coupling reaction. The narrow bandgap coumarin–carbazole units and the wide bandgap fluorene–phenylene units in P1–P3 might form energy donor–acceptor molecule architectures, in which coumarin–carbazole units serve as an acceptor of the fluorescent resonance energy transfer (FRET). The addition of calf thymus DNA resulted in efficient FRET from fluorene–phenylene (energy donor) to coumarin–carbazole (energy acceptor) unit for P1, which caused the solution fluorescent color to change from blue to light green. In addition, P1 can be utilized as a reliable fluorescent probe for cellular imaging of human adult skin fibroblast cells, where blue and green fluorescence were observed in the cytoplasm by use of different excitation wavelength. Subsequently, the water-soluble and fluorescent P1 were used as high sensitive DNA sensor and effective fluorescent cell labeling agents with dual emission pathways.