Performance comparison of electrochemically deposited mussel-inspired polycatecholamine coatings for SARS-CoV-2 biosensing: a competitive evaluation of polydopamine, polynorepinephrine, and poly-α-methylnorepinephrine.

The first comparative evaluation is presented of three electrochemically synthesized mussel-inspired polycatecholamine (PCA) nanocoatings, polydopamine (PDA), polynorepinephrine (PNE), and poly-α-methylnorepinephrine (PAMN), for the development of high-performance electrochemical biosensors. The PCA nanocoatings were directly deposited onto graphene (Gr)-modified screen-printed electrodes (SPEs) and subsequently functionalized with either SARS-CoV-2 antigens or antibodies, enabling dual-mode detection of the respective targets. Comprehensive physicochemical and electrochemical characterizations were performed to evaluate the structure, surface morphology, and redox behaviour of the fabricated platforms. Biosensing studies using linear sweep voltammetry demonstrated a remarkable linear detection range for SARS-CoV-2 antigen detection, spanning from 10 ag/mL–50 ng/mL, with a detection limit (LOD) of 0.269 ag/mL. Similarly, for SARS-CoV-2 antibody detection, the sensors showed excellent linearity across 1 ng/mL to 1 fg/mL, with a LOD of 0.185 fg/mL. Among the three platforms, PAMN-Gr/SPE exhibited the highest sensitivity, while PDA-Gr/SPE and PNE-Gr/SPE demonstrated superior storage stability, retaining functionality for up to three months. Overall, PDA-based electrodes offered the most balanced performance, combining high sensitivity, antifouling capability, long-term stability, and cost-effectiveness, rendering them ideal for scalable and practical biosensor development. This work provides a robust foundation for the rational design of PCA-based biosensors and underscores the potential of mussel-inspired nanocoatings in enabling next-generation point-of-care diagnostic platforms, particularly for emerging infectious diseases.