Pyridinium-conjugated polynorbornenes for nanomolar ATP sensing using an indicator displacement assay and a PET strategy

An indicator displacement assay, namely polymeric PNPY-n/UD consisting of a cationic polynorbornene backbone with pyridinium functional groups (PNPY-1,2,3) and an anionic uranine dye (UD) as an indicator, has been developed for highly sensitive “turn-on” fluorescence sensing of ATP. While PNPY-1/UD itself is non-emissive, a bright green fluorescence signal was observed in the presence of ATP [K_a = 2.17 × 10⁵ M⁻¹, LOD = 5.7 nM]. The potential of a highly photostable system PNPY-1/UD was also validated in detecting ATP levels in live-cell imaging applications.