Electrochemical Detection of SMN Protein by Immunosensors: The Role of Surface Modifications in Screen-Printed Carbon Electrodes

Point-of-care (POC) technologies are promising tools to decentralize and accelerate the diagnosis of rare diseases. Among them, electrochemical immunosensors offer advantages such as high sensitivity, low cost, portability, low sample consumption, and suitability for use in resource-limited settings. However, the performance of these devices is dependent on electrode surface properties, which influence electron transfer, biomolecule immobilization, and analytical sensitivity. In this work, screen-printed carbon electrodes (SPCEs) were modified through two strategies: (i) gold electrodeposition and (ii) cold plasma treatment. The modified electrodes were functionalized with EDC/NHS, followed by the immobilization of anti-SMN antibodies and electrochemical characterization using cyclic voltammetry and differential pulse voltammetry. The impact of each modification approach on the electrochemical response and reproducibility of the sensor was evaluated. Gold electrodeposition resulted in higher and more reproducible electrochemical responses, demonstrating improved electron transfer properties and surface homogeneity. The primary objective of this study was to investigate how different surface modification strategies affect the electrochemical performance of SPCE-based immunosensors, employing the detection of Survival Motor Neuron (SMN) protein, a biomarker associated with Spinal Muscular Atrophy (SMA), as a proof-of-concept application. The resulting platform successfully differentiated specific and non-specific protein recognition events through distinct electrochemical patterns, demonstrating the suitability of gold-modified SPCEs for immunosensing applications. These findings provide insights into the influence of surface engineering strategies on sensor performance and support the future development of optimized electrochemical platforms for biomarker detection.