Potential-Resolved Differential Electrochemiluminescence Immunosensor for Cardiac Troponin I Based on MOF-5 Wrapped CdS Quantum Dots Nanoluminophores.

Recently, nanoluminophores with potential-resolved multicolor electrochemiluminescence (PRMCECL) property emerge and show promising applications in sensitive, selective and accurate bioassays, bioimaging, and multicolor emitting devices. However, only limited PRMCECL nanoluminophores and their applications in ratiometric biosensors eliminating proportional errors have been reported. Herein, a novel PRMCECL nanoluminophore was synthesized by encapsulating CdS quantum dots (CdSQDs) into MOF-5 (CdSQDs@MOF-5). Using K2S2O8 as a coreactant, two electrochemiluminescence (ECL) peaks, ECL-1 centered at 685 nm and ECL-2 centered at 475 nm, were observed at -1.4 V and -1.8 V, respectively. Related ECL mechanisms have been proposed. Based on the potential-resolved ECL signals, a label-free differential ECL immunosensor for the determination of cardiac troponin I (cTnI) was established by assembly of poly(diallyldimethylammonium chloride), CdSQDs@MOF-5 and cTnI antibody functionalized silver nanoparticles on the surface of fluorine doped tin oxide electrode subsequently. In the presence of cTnI, cTnI was captured by the sensing interface, leading to an increase in ECL-1 and ECL-2 intensity. cTnI could be determined in the range of 0.01 - 1000 pg/mL with a detection limit of 5.01 fg/mL by using intensity difference between ECL-1 and ECL-2. This work provides a new family member of PRMCECL nanoluminophores. The proposed label-free differential ECL immunosensor provides a new strategy based on potential-resolved ECL signals, which could effectively eliminate the additive error and show better sensitivity, selectivity and accuracy for the detection of cTnI than single-signal strategy and ratiometric strategy.