Intramolecular resonance energy transfer-driven self-enhanced p-COFs-based electrochemiluminescence sensor for the...

Cytokeratin 19 fragment (CYFRA21-1) is a clinically significant tumor biomarker, and its ultrasensitive detection is of great importance for early diagnosis. Herein, we report a dual resonance energy transfer (RET)-regulated electrochemiluminescence (ECL) immunosensor enabled by a self-enhanced luminophore. Porphyrin-based covalent organic frameworks (p-COFs) were rationally constructed as an intrinsically self-enhanced ECL luminophore, in which the ordered integration of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin and 4,4',4'',4'''-(ethene-1,1,2,2-tetrayl)tetrabiphenyl units establishes an efficient intraframework RET pathway. This well-defined donor-acceptor architecture facilitates directional energy transfer and effectively suppresses energy loss, thereby significantly amplifying the ECL emission and generating a strong and stable signal output. In addition, Co₃O₄@Co-Fe nanocomposites were introduced as a signal modulation unit to induce interfacial RET with p-COFs. The resultant ECL signal quenching of p-COFs greatly improves the detection sensitivity of the as-fabricated sensor. Under the synergistic dual RET regulation, the ECL immunosensor exhibited an ultrawide linear detection range from 10 fg/mL to 500 ng/mL and an extremely low detection limit of 3.26 fg/mL, along with excellent selectivity and stability. This work develops a facile porphyrin-based COF luminophore and employs dual RET-regulated signal modulation to significantly improve sensitivity, offering a rational design strategy for high-performance ECL sensing platforms.