Supramolecular Organic Framework-Enabled Aggregation-Enhanced Electrochemiluminescence for Ultrasensitive Detection of MMP 9

The electrochemiluminescence (ECL) performance of tetraphenylethylene (TPE) derivatives benefits from their intrinsic aggregation-induced emission (AIE) characteristics. Under appropriate aggregation conditions, restricted intramolecular motion and suppressed nonradiative decay facilitate excited-state formation, thereby enhancing ECL efficiency. However, excessive molecular aggregation increases the proportion of ineffective luminescent species, which reduces the excited-state population and ultimately limits the ECL output. To address this, we report the first construction of a supramolecular organic framework (SOF) as an ECL emitter, formed via host-guest complexation between cucurbit[8]uril (CB[8]) and a carboxylated TPE derivative (TPE-4PYCOOH-4Br). The resulting SOF exhibits a 6.49-fold enhancement in ECL intensity compared to the free TPE derivative in the annihilation pathway, attributed to reduced nonradiative losses and suppressed intramolecular motion enabled by its rigid structure. Based on this enhancement, we developed a split-type ECL biosensor for matrix metalloproteinase 9 (MMP 9) detection, using a peptide-modified Fe₃O₄ nanosphere as a coreaction accelerator. Following MMP 9-specific cleavage, Fe₃O₄ nanospheres (Fe₃O₄ NS) become accessible to the sensing system, catalyzing triethylamine (TEA) radical generation and amplifying the ECL signal. The biosensor achieved a limit of detection (LOD) of 0.29 pg/mL, showed excellent linearity from 1 pg/mL to 50 ng/mL (R² = 0.993), and demonstrated high specificity and reproducibility in serum samples. This study introduces SOFs as a new class of ECL emitters and offers an effective strategy to improve AIE-based luminophores for highly sensitive biomarker detection.