New luminescent hydrophilic iridium(III) nanoflower at low potential for electrochemiluminescence immunosensing

Screening effective luminophore is always one of the most essential concerns in highly sensitive electrochemiluminescence (ECL) bioanalysis. Here, a new nanoflower-like iridium(III) J-aggregate (T-Ir) was prepared via nonionic surfactant assisted reprecipitation technique, which possessed good reductive-oxidative ECL activity and performed a strong ECL emission around 626 nm at low potential (−1.10 V) in the presence of potassium persulfate. Thus, T-Ir was employed as a luminophore and good biocompatible matrix to load large amounts of capture antibodies (Ab1). Meanwhile, gold nanoparticles capped cuprous oxide nanocubes (Cu2O@Au) were used as the efficient quencher to label detection antibodies (Ab2). While different dosages of carcinoembryonic antigen (CEA) were introduced via sandwich immunoreaction, the ECL intensity was significantly dropped due to electrochemiluminescence resonance energy transfer from energy donor (T-Ir) to the acceptor (Cu2O@Au), achieving the highly sensitive detection of CEA. The proposed immunosensor showed a linear concentration range from 1 fg·mL−1 to 80 ng·mL−1 with a low limit of detection of 0.93 fg·mL−1 (S/N = 3). It featured superior stability, selectivity, reproducibility and practicability. With the successful demonstration of hydrophilic iridium(III)-based nanomaterials, sensing strategies for various biomarkers detection in diseases diagnosis will flourish.