Robust Covalent Aptamer Strategy Enables Sensitive Detection and Enhanced Inhibition of SARS-CoV‑2 Proteins

Aptamer-based detection and therapy have made substantial progress with cost control and easy modification. However, the conformation lability of an aptamer typically causes the dissociation of aptamer–target complexes during harsh washes and other environmental stresses, resulting in only moderate detection sensitivity and a decreasing therapeutic effect. Herein, we report a robust covalent aptamer strategy to sensitively detect nucleocapsid protein and potently neutralize spike protein receptor binding domain (RBD), two of the most important proteins of SARS-CoV-2, after testing different cross-link electrophilic groups via integrating the specificity and efficiency. Covalent aptamers can specifically convert aptamer–protein complexes from the dynamic equilibrium state to stable and irreversible covalent complexes even in harsh environments. Covalent aptamer-based ELISA detection of nucleocapsid protein can surpass the gold standard, antibody-based sandwich ELISA. Further, covalent aptamer performs enhanced functional inhibition to RBD protein even in a blood vessel-mimicking flowing circulation system. The robust covalent aptamer-based strategy is expected to inspire more applications in accurate molecular modification, disease biomarker discovery, and other theranostic fields.