Intrareticular Charge Transfer Triggered Self-Electrochemiluminescence of Zirconium-Based Metal–Organic Framework Nanoparticles for Potential-Resolved Multiplex Immunoassays with Isolated Coreactants

In this work, a potential-resolved electrochemiluminescence (ECL) multiplex immunoassay (MIA) was developed using zirconium-based metal–organic framework (MOF) nanoparticles with intense self-ECL as an anodic ECL tag and CdTe nanocrystals (NCs) as a cathodic ECL tag. ECL luminophore 5,5′-(anthracene-9,10-diyl)diisophthalic acid (H4ADIP) and coreactant hexamethylenetetramine (HMT) bound to zirconium nodes in the MOF, giving Zr-ADIP-HMT nanoparticles. Benefiting from the intrareticular charge transfer (ICT) between the oxidized ligands of H4ADIP and HMT via hydrogen bonds, the intense self-ECL from Zr-ADIP-HMT was applied to the potential-resolved ECL MIA without an exogenous anodic coreactant, which can eliminate detrimental effects of multiplex coreactants and anodic ECL emission from CdTe NCs. The ICT within Zr-ADIP-HMT nanoparticles could shorten the electron transport path and reduce the complexity of radical intermediate transport. The ECL intensity from Zr-ADIP-HMT was 18.6-fold that from the mixture of H4ADIP and HMT. In potential-resolved ECL MIA, two lung cancer biomarkers, carcinoembryonic antigen and neuron-specific enolase, were adopted as model analytes, with detection limits of 18 and 5.3 fg·mL–1, respectively. The dual-ligand Zr-ADIP-HMT nanoparticles provide a proof of concept using ICT-based self-ECL luminophores for potential-resolved ECL MIAs with isolated coreactants.