Surface chemistry effects on electrochemical impedance spectroscopy of biomacromolecule interactions

Electrochemical impedance spectroscopy (EIS) has become a cornerstone technique for probing the intricate interactions of biological macromolecules at electrode interfaces. Owing to its exceptional sensitivity, EIS provides valuable mechanistic insights into the binding kinetics, thermodynamic behavior, and conformational transitions of proteins, nucleic acids, and polysaccharides. A key determinant of these analytical capabilities is the interfacial surface chemistry, which governs how biomolecules are immobilized, oriented, and functionally retained. To exert precise control over these parameters, researchers have developed a wide array of surface modification strategies, including self-assembled monolayers, nanostructured coatings, and functional polymers. Such engineered interfaces enhance molecular selectivity while minimizing nonspecific adsorption, thereby improving signal fidelity. Recent innovations in nanostructured electrode design have further amplified the impedance response, enabling the detection of a broad spectrum of biomolecular interactions ranging from protein-protein and protein-DNA recognition to antibody-antigen binding and enzyme-substrate catalysis. Beyond simple detection, EIS allows the extraction of kinetic and thermodynamic parameters under surface-confined conditions, offering a powerful framework for dissecting molecular recognition phenomena. Nevertheless, data interpretation remains challenging, primarily due to the inherent complexity of biological interfaces and their deviation from idealized electrochemical models. To overcome these limitations, current research is increasingly turning toward bioinspired interfacial engineering, advanced equivalent circuit modeling, and the integration of EIS with complementary analytical methods such as calorimetry and computational modeling. Collectively, these approaches promise to enhance both the accuracy and interpretability of impedance measurements. This review critically examines recent progress in EIS-based bioanalysis, highlighting the central role of surface chemistry in shaping biosensor performance, and delineates emerging research directions that are likely to broaden the technique's impact in biomolecular diagnostics and mechanistic studies.