Sensitive detection of DNA by hyperbranched diketopyrrolopyrrole-based conjugated polyelectrolytes

Two water-soluble cationic conjugated polyelectrolytes (linear polymer PF1 and hyperbranched polymer PF3) containing fluorene, diketopyrrolopyrrole (DPP), diacetylene and triphenylamine moieties were synthesized and used for DNA detection. The incorporation of DPP into the polymer backbone offers dual emissive polyelectrolytes with both blue and red emission bands for PF1 and PF3 in the dilute solution resulting from incomplete intramolecular energy transfer. In the solution of PF3, addition of DNA can quench the emission of fluoreneethynylene-triphenylamine units of PF3 more efficiently than that of DPP segments, which causes the fluorescent color change from light blue to light red. However, DNA causes only slight fluorescent quenching of PF1, and the blue color of PF1 solution remains unchanged. Hyperbranched PF3 shows stronger asymmetric emission quenching by DNA than linear PF1, indicating that it might become the first sensor of the hyperbranched conjugated polyelectrolytes for a real-time DNA detection.