Electrochemiluminescence (ECL)-functionalized metal–organic frameworks (MOFs) have attracted increasing attention in biosensing in virtue of their diverse and tunable optical properties. A famous ECL luminophore, carboxyl-rich tris­(4,4′-dicarboxylic acid-2,2′-bipyridyl) ruthenium­(II) (Ru­(dcbpy)3 2+), possesses the characteristics of good water solubility and excellent ECL performance and also has the potential to be the organic ligand of metal–organic frameworks. Herein, functionalized MOF nanosheets (RuMOFNSs) containing plenty of Ru­(dcbpy)3 2+ in the frameworks were synthesized in aqueous solution by a simple one-pot method. In this protocol, Ru­(dcbpy)3 2+ acted as organic ligand to coordinate with Zn2+ originated from Zn­(NO3)2, and polyvinylpyrrolidone (PVP) was used as structure-directing agent to control the formation of sheetlike structure. For practical application, a “signal-on” ECL immunosensor was designed for cardiac troponin I (cTnI) detection by employing RuMOFNSs as ECL probe. The immunosensor exhibited high sensitivity and excellent selectivity for cTnI detection in the range from 1 fg/mL to 10 ng/mL with a detection limit as low as 0.48 fg/mL. Finally, the biosensor was successfully applied for the detection of cTnI in human serum sample with satisfactory results, demonstrating its potential application in bioanalysis and clinical diagnosis.

Ratiometric electrochemiluminescence (ECL) has attracted special focus in the biological analysis field, because it could eliminate the environmental interference and allow for precise measurement. Herein, a dual-wavelength ratiometric ECL biosensor was designed for the detection of cardiac troponin I (cTnI), where (4,4′-dicarboxylic acid-2,2′bipyridyl) ruthenium(II) (Ru(dcbpy) 3 2+ ) and Au nanoparticle-loaded graphene oxide/polyethylenimine (GPRu− Au) nanomaterial acts as an acceptor, and Au nanoparticlemodified graphitic phase carbon nitride nanosheet composite (Au−CNN) acts as donor. Au−CNN shows a high and steady ECL signal centered at 455 nm, which is well-matched with the adsorption of GPRu−Au; thereby, a highly efficient electrochemiluminescent resonance energy transfer (ECL-RET) sensing platform is designed. AuNPs facilitate the immobilization of antibody on the nanomaterials through a Au−N bond. The high surface area of graphene oxide/polyethylenimine allows a large number of Ru(dcbpy) 3 2+ to be loaded, immensely amplifying the ECL signal. This sensing platform exhibits outstanding analytical performance toward cTnI with a detection limit of 3.94 fg/mL (S/N = 3). The high reliability, selectivity, and sensitivity of this ratiometric ECL biosensor provides a versatile sensing platform for the bioanalysis.