Water-Soluble Conjugated Polymers for Amplified Fluorescence Detection of Template-Independent DNA Elongation Catalyzed by Polymerase

A series of water-soluble polyfluorene derivatives containing diketopyrrolopyrrole derivative units are synthesized and characterized. These copolymers, poly[9,9'-bis(6 ''-N,N,N-trimethyl ammonium) hexylfluorene-co-alt-2,5-bis (6 ''-N,N,N-trimethylammonium) hexylpyrrolo[3,4-c]pyrrole-1,4(2H, 5H)-dione] (PFDPN), demonstrate intramolecular energy transfer from the fluorene units to the diketopyrrolopyrrole derivative units, and show red-shifted emissions in aqueous solution. The PFDPN polymers can combine with Cy5-labeled ssDNA by electrostatic interactions and efficiently amplify the fluorescence signal of red Cy5 dye through fluorescence resonance energy transfer. Moreover, based on DNA replacement method, this amplification system can be used to monitor the template-independent DNA elongation process catalyzed by terminal deoxynucleotidyl transferase.