Sequential assembly of in situ grown Ti₃C₂Tₓ MXene–PBA composite for enhanced electrochemiluminescent sensing of factor XIa activity and inhibitor screening

Factor XIa (FXIa), a pivotal target in anticoagulant therapy, requires precise activity monitoring to assess coagulation status and bleeding risks. To address the limited sensitivity of conventional chromogenic methods, we developed a novel electrochemiluminescence (ECL) biosensor exploring the synergistic effects of MXene's superior conductivity and Prussian blue analogue's (PBA) large specific surface area. Transient absorption spectrometry was employed to determine the excited-state lifetime and to elucidate the functional role of MXene@PBA. Molecular docking and specificity constant analysis identified Mpr(mercaptopropionic acid)-TEARK-Fc(ferrocene) as an optimal peptide substrate. The MXene@PBA-enhanced biosensor quantifies FXIa-induced ECL signal changes via peptide cleavage, achieving a linear range of 1.0 × 10⁻⁵ mIU/mL to 1 mIU/mL and an LOD of 3.7 × 10⁻⁶ mIU/mL (S/N = 3) in human serum. Furthermore, the ECL biosensor demonstrated efficacy in FXIa inhibitor screening, firstly revealing salvianolic acid A and C as potent inhibitors (>60 % inhibition) and apigenin as a moderate inhibitor (~40 %). Molecular docking confirmed that these inhibitors competitively bind to FXIa's catalytic pocket (His57, Cys58, Ala190, Lys192, Ser195), overlapping with the substrate recognition site. This MXene@PBA-enhanced ECL biosensor establishes a robust strategy for both FXIa activity monitoring and therapeutic agent development.