Coreactant-Free Zirconium Metal–Organic Framework with Dual Emission for Ratiometric Electrochemiluminescence Detection of HIV DNA

Owing to the limitations of dual-signal luminescent materials and coreactants, constructing a ratiometric electrochemiluminescence (ECL) biosensor based on a single luminophore is a huge challenge. This work developed an excellent zirconium metal–organic framework (MOF) Zr-TBAPY as a single ECL luminophore, which simultaneously exhibited cathodic and anodic ECL without any additional coreactants. First, Zr-TBAPY was successfully prepared by a solvothermal method with 1,3,6,8-tetra(4-carboxyphenyl)pyrene (TBAPY) as the organic ligand and Zr4+ cluster as the metal node. The exploration of ECL mechanisms confirmed that the cathodic ECL of Zr-TBAPY originated from the pathway of reactive oxygen species (ROS) as the cathodic coreactant, which is generated by dissolved oxygen (O2), while the anodic ECL stemmed from the pathway of generated Zr-TBAPY radical itself as the anodic coreactant. Besides, N,N-diethylethylenediamine (DEDA) was developed as a regulator to ECL signals, which quenched the cathodic ECL and enhanced the anodic ECL, and the specific mechanisms of its dual action were also investigated. DEDA can act as the anodic coreactant while consuming the cathodic coreactant ROS. Therefore, the coreactant-free ratiometric ECL biosensor was skillfully constructed by combining the regulatory role of DEDA with the signal amplification reaction of catalytic hairpin assembly (CHA). The ECL biosensor realized the ultrasensitive ratio detection of HIV DNA. The linear range was 1 fM to 100 pM, and the limit of detection (LOD) was as low as 550 aM. The outstanding characteristic of Zr-TBAPY provided new thoughts for the development of ECL materials and developed a new way of fabricating the coreactant-free and single-luminophore ratiometric ECL platform.