A High-Affinity Antibody for Rapid Screening of PFAS: Breaking Immunological Inertness through Descriptor-Guided Hapten Design

Per- and polyfluoroalkyl substances (PFAS) are ubiquitous emerging contaminants in indoor environments, yet the development of high-affinity antibodies for immunoassays remains hindered by the intrinsic immunological inertness of PFAS. Here, we present a descriptor-guided hapten design strategy that addresses this limitation by quantitatively linking the physicochemical features of PFAS to hapten spacer engineering. Using quantum-chemistry-derived molecular descriptors, we designed three perfluorooctanoic acid (PFOA)-based haptens that preserved the structural identity of the perfluoroalkyl chain while enhancing the immunogenic suitability of the resulting immunogens. As predicted, all three spacer-engineered haptens elicited markedly improved immune responses compared with direct PFOA conjugation. Among them, H1 emerged as the optimal design owing to its most balanced descriptor profile, enabling the generation of a high-affinity monoclonal antibody, mAb12 × 10 8 . This antibody recognized four perfluoroalkyl carboxylic acids (C6–C9) and four perfluoroalkyl sulfonates (C5–C8), with icELISA IC 50 values of 9.6–117.4 ng/mL. Surface plasmon resonance (SPR) analysis further confirmed the high-affinity of mAb12 × 10 8, yielding a KD of 36.6 nM toward PFOA. Structural modeling and molecular docking revealed a chain-length-dependent recognition mechanism governed by the geometry of the antibody binding pocket. Based on mAb12 × 10 8, a chemiluminescent indirect competitive ELISA (CL-icELISA) was established for indoor dust analysis, achieving a limit of detection of 2.19 μg/kg. In practical validation, 40 field-collected indoor dust samples were screened within 1.5 h, and high-positive samples were further confirmed by UPLC–MS/MS with concentration deviations of less than 20%, demonstrating a practical screen-then-confirm workflow for high-frequency PFAS monitoring.