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We propose a novel competitive mechanism involving the dissolved oxygen (O2) between zirconium-based porphyrinic metal–organic framework nanoparticles (NMOFs) and luminol into a ratiometric electrochemiluminescence (ECL) biosensing interface. Zinc tetrakis(carboxyphenyl)-porphyrin (ZnTCPP) in NMOFs as electron media reduce O2 into reactive oxygen species (ROS) and produce singlet oxygen (1O2), resulting in cathodic ECL. Meanwhile, ROS also react with the luminol anion radical and amplify the anodic ECL emission. Based on the competitive-mechanism-driven ECL process, taking the detection of polynucleotide kinase (PNK) as example, with assembling DNA-functionalized NMOFs on the sensing interface, a lower detection limit of 6.5 × 10–5 U mL–1 and broader linear relationship range from 0.0002 to 10 U mL–1 were obtained compared with that of single-signal-driven ECL sensors. This proposed MOFs-luminol competitive ECL mechanism involving dissolved O2 may provide a new pathway for further research of a green and highly sensitive ECL biosensing system.
Zhang et al. (Wed,) studied this question.