Sensitive monitoring of RNA transcription by optical amplification of cationic conjugated polymers.

We reported a new strategy for sensitive monitoring in vitro RNA synthesis in real time based on fluorescence resonance energy transfer (FRET) from water-soluble conjugated polymer poly (9, 9-bis (6'-N, N, N,-trimethylammonium) hexyl) fluorene-co-alt-1,4-phenylene) bromide (PFP) to fluorogenic RNA aptamer/fluorophore (Spanich2/DFHBI and Broccoli/DFHBI) system. In this strategy, RNA of interest was transcribed accompanied by the Spanich2 or Broccoli. Then the 3, 5-difluoro-4-hydroxybenzylidene imidazolinone (DFHBI) bound to the RNA aptamer sequence and thereby induced a fluorescence signal. PFP was used as the fluorescence energy donor, and Spanich2/DFHBI was the fluorescence energy acceptor. The fluorescence signal of Spanich2/DFHBI was amplified by light-harvesting and fluorescence amplification ability of PFP via FRET. And the limit of detection (LOD) (0.29 nM) was near 10-fold lower than that of RNA aptamer/DFHBI (LOD is 2.8 nM) alone by measuring the FRET ratio, which greatly reduced the variation of background signals. Most importantly, the addition of PFP did not interfere with RNA transcription in vitro, so this method was successfully applied to sensitively monitor RNA transcription and effect of T7 RNA polymerase inhibitor in real time, supplying a sensitive and simple method to study the modulation and inhibitor of RNA polymerase in vitro.