Ru(dcbpy)32+-functionalized γ-cyclodextrin metal-organic frameworks as efficient electrochemiluminescence tags for the detection of CYFRA21-1 in human serum

Electrochemiluminescence (ECL)-functionalized metal-organic frameworks (MOFs) have become one of the most favored topics in biomarker immunoassays. Herein, a biocompatible tris(4,4′-dicarboxylic acid-2,2′-bipyridyl) ruthenium(II) [Ru(dcbpy)32+] functionalized γ-cyclodextrin MOF was freshly prepared as an ECL tag for analyzing cytokeratin 19 fragment 21–1 (CYFRA21–1), a quintessential biomarker of non-small cell lung cancer. As a green ECL carrier, γ-CD-MOF possessed a large cavity that can absorb enormous Ru(dcbpy)32+ molecules, obtaining consecutive stable ECL signals using N,N-dibutyl-2-hydroxyethylamine (DBAE) as a coreactant. Further functionalization of palladium nanoparticles with Ru@ γ-CD-MOF not only facilitated the electron-transfer rate to boost the ECL emission but also immobilized the detection antibody (Ab2) via a Pd-N bond. To fabricate the sensing substrate, a porous NH2-MIL-125 (Ti) MOF was coated on the electrode to provide many binding sites for the capture antibody (Ab1). Through the traditional sandwich-type sensing format, the assembled immunosensor manifested a linear range with a limit of detection of 0.048 pg/mL (S/N = 3) within a concentration gradient of 0.0001–50 ng/mL for CYFRA21–1 detection. Given this strategy's merits of favorable specificity, reliable accuracy and remarkable stability, this study highlighted the feasibility of fabricating γ-CD-based ECL tags for immunosensor construction, revealing this strategy's promising aptitude for bioanalysis and the clinical diagnosis of biomarkers.