Aptamer-engineered signal-loaded MCOFs as a turn-on fluorescent platform for trace detection of immunosuppressants and prognostic biomarkers in serum.

The simultaneous detection of immunosuppressive drugs and prognostic biomarkers in the serum of post-transplant patients enables a more accurate assessment of patient status, allowing for timely adjustments to medication regimens and the prevention of graft-versus-host disease (GVHD). In this study, an ordered porous structure based on a covalent organic frameworks (COFs) was constructed. A large number of fluorescent signal molecules were encapsulated within the pores, and aptamers with specific recognition capabilities were subsequently immobilized on the pore walls, thereby establishing a fluorescence sensing platform capable of simultaneous and specific dual-target detection. This study investigated the influence of COF pore size on the encapsulation of fluorescent signal molecules and the quantity of aptamer required to effectively block the pores. The effects of COF pore size on fluorescent-molecule encapsulation and signal confinement were systematically investigated, and the aptamer concentration required for effective pore sealing was optimized. The resulting platform completed the detection within 30 min and exhibited broad linear ranges of 0.5-1000 ng mL-1 for cyclosporine A (CsA) and 0.5-200 ng mL-1 for soluble interleukin-2 receptor alpha (sIL-2Rα), with corresponding limits of detection of 0.094 and 0.26 ng mL-1, respectively. This study demonstrates the simultaneous and specific detection of cyclosporine A (CsA) and the prognostic biomarker soluble interleukin-2 receptor α (sIL-2Rα), highlighting its potential for disease diagnosis and monitoring while expanding the application of COFs with tunable pore sizes in multiplexed biosensing.