Advances in the use of DNA aptamers for bioanalysis of antibody-based therapeutics.

Nucleic acid aptamers are single-stranded oligonucleotides that fold into defined three-dimensional structures and bind molecular targets with high affinity and specificity. Because aptamers are sequence-defined, chemically synthesized reagents, they offer high purity, minimal lot-to-lot variability, and flexible functionalization, positioning them as practical alternatives or complements to antibody-based critical reagents in regulated bioanalysis. This review summarizes the current landscape of DNA aptamer-enabled bioanalysis for therapeutic monoclonal antibodies (mAbs) and antibody-drug conjugates (ADCs), with emphasis on three application areas: (i) ELISA-compatible ligand-binding assays, (ii) immunocapture workflows coupled to liquid chromatography-tandem mass spectrometry or LC-based measurements, and (iii) aptamer-based biosensors for bioanalysis and process analytics. This review highlights key considerations in aptamer acquisition (SELEX design, partitioning, and counter-selection to improve anti-idiotype selectivity) and illustrates representative assay configurations, including drug-to-antibody ratio-responsive formats for ADCs and ratiometric/electrochemical and fluorescence resonance energy transfer-based aptasensors for on-site monitoring. Finally, this review discusses future directions, notably coupling aptamer binding to nucleic acid amplification for ultra-sensitive quantification, and practical challenges, such as nuclease susceptibility, nonspecific interactions with serum proteins, and structure-dependent robustness that must be addressed under fit-for-purpose validation frameworks.