A Novel Electrochemiluminescence Sensor for Sensitive Detection of Estriol Based on “Three-in-One” Nanocomposite

In this study, chemically polymerized luminol-hydrogen-bonded organic framework (CpL-HOF) is used as the efficient luminophore and POMs@MOFs as the quencher to construct the electrochemiluminescence (ECL) sensor for the ultrasensitive detection of estriol (E3). CpL-HOF is prepared through coordination self-assembly using chemically polymerized luminol (CpL) and three active ligands. The nanoconfinement effect of CpL-HOF exhibits enhanced stability and ECL efficiency compared with the monomer. Mo-based polyoxometalates (Mo POMs) as guests are encapsulated inside a metal-organic framework (Cu-MOF) to synthesize POMs@MOFs nanocomposites with "three-in-one" functions. The distinctive host-guest interaction enhances the activity of superoxide dismutase-like (SOD-like) and catalase-like (CAT-like) enzymes, effectively eliminating reactive oxygen species (ROS). Furthermore, POMs@MOFs exhibit electron-rich redox properties, which can further eliminate ROS by valence switching. Therefore, POMs@MOFs can effectively quench the ECL signal of the CpL-HOF and improve the sensitivity of the sensor. Under optimal conditions, the sensor has a wide linear range (100 fg/mL to 200 ng/mL) and a low limit of detection (92.84 fg/mL). The sensor can be applied to the analysis of real samples, with satisfactory results. The ECL mechanism based on the synergistic interaction of the host-guest provides a theoretical foundation for constructing novel ECL sensing platforms.