Selection of DNA Aptamers for Mycophenolic Acid and Mycophenolate Mofetil Detection in Human Serum

Therapeutic drug monitoring of mycophenolic acid (MPA), the active metabolite of the immunosuppressant mycophenolate mofetil (MMF), is clinically important due to its narrow therapeutic window. In this work, a library-immobilized SELEX strategy was employed to isolate DNA aptamers capable of recognizing both MPA and MMF. Among the selected candidates, a dual-recognition aptamer (MPA-1) exhibited specific binding toward MPA and MMF, with dissociation constants (K_d) of 13.7 µM and 5.5 µM, respectively, as determined by a thioflavin T (ThT) fluorescence assay. Consistent binding affinities were obtained by microscale thermophoresis (MST), yielding K_d values of 3.1 µM for MPA and 0.78 µM for MMF. Notably, MPA-1 displayed negligible binding toward other immunosuppressive drugs and endogenous biomolecules, demonstrating excellent selectivity. Based on a strand-displacement strategy, a turn-on fluorescent aptasensor was subsequently constructed for the determination of MPA and MMF in 10% human serum, achieving limits of detection of 0.46 µM and 0.21 µM, respectively. Satisfactory recoveries in spiked serum samples further demonstrated the feasibility of the sensor for quantitative analysis in diluted serum. These results highlight the potential of the selected aptamer as a versatile recognition element for the future development of biosensors for MPA and MMF monitoring.