Pyrene-doped ZIF-8 possesses high fluorescent quantum yield for sensitive ratiometric immunoassay

Although pyrene-based fluorophores possess some merits including outstanding fluorescent (FL) emission and long-lived excited intermediates, their practicability have been dramatically limited by an obvious aggregation-caused quenching (ACQ) impact. Due to the isolation effect of metal-organic frameworks (MOFs), pyrene-based fluorophores are utilized as the FL dopant rather than organic ligands to anchor onto the porous supports for inferior ACQ effect along with enhanced FL emission. Herein, a one-step alkaline coprecipitation method was proposed to efficiently load 4,4′,4″,4″‘-(1,9-dihydropyrene-1,3,6,8-tetrayl)tetrabenzoic acid onto ZIF-8 MOFs (Py@ZIF-8). Since ZIF-8 effectively rigidified the location of the FL emitter, the decreased ACQ effect of Py@ZIF-8 was realized along with an intriguing FL quantum yield of 77.3 %. Furthermore, the protective activity of the rigid framework endowed Py@ZIF-8 with an attractive long-term FL stability. Note that, green FL microspheres could remarkably quench the luminescent signal of Py@ZIF-8 based on the marked Förster resonance energy transfer (FRET) effect. The FRET donor-acceptor pair of Py@ZIF-8 and green FL microspheres was employed to establish a sandwich ratiometric FL protocol for cardiac troponin I. Superior to a traditional single-signal mode, the dual-signal ratiometric mode displayed an enhanced sensitivity, wherein a low detection limit of 0.5 pg/mL (3σ) was achieved. Moreover, the quantitation results of cardiac troponin I in serum samples by the proposed FL method showed a good agreement with those by a commercial Abbott chemiluminometer. The reliable ratiometric platform exhibited improved precision and preferable feasibility of pyrene-doped MOFs in sensitive diagnosis and trace testing.