Super-antifouling electrochemical biosensor based on a biomimetic gemini zwitterionic interface for sensitive detection of therapeutic antibodies.

Biofouling, arising from the nonspecific adsorption of proteins, cells, and other biomolecules, remains a major challenge that compromises the stability and reliability of diagnostic and therapeutic platforms. To address this issue, a super-antifouling electrochemical aptasensor was developed by integrating a biomimetic "gemini" zwitterionic monomer (BSMMP) with polydopamine (PDA). The covalent assembly of BSMMP and PDA forms a multi-site anchoring layer that enables the stable functionalization of the affinity aptamer GC20. Owing to its dense hydration shell, the PDA-BSMMP hybrid interface acts as a physical barrier against nonspecific adsorption, maintaining electron-transfer stability in undiluted human serum. Differential pulse voltammetry confirmed that this interface markedly reduced biofouling-induced signal loss, limiting attenuation to less than 15%, nearly fourfold lower than that of the unmodified surface. The platform achieved a low limit of detection of 0.97 ng/mL, a broad linear range from 1 ng/mL to 100 μg/mL, and high selectivity for trastuzumab in a label-free format without secondary antibodies or additional signal amplification. Finally, this platform successfully quantified trastuzumab in serum from breast cancer patients, with results consistent with commercial ELISA kits. Overall, this super-antifouling aptasensor offers great potential for therapeutic drug monitoring, advancing zwitterionic interface-based biosensing strategies for point-of-care diagnostics.