Rapid Detection of SARS-CoV-2 Spike Protein Using a Fully 3D-Printed Electrochemical Biosensor

3D printing has been used for the rapid and low-cost fabrication of sensors across various fields. Multimaterial additive manufacturing enables the simultaneous deposition of conductive and structural materials, allowing the development of integrated electrochemical biosensors without the need for postprocessing. In this work, we report a 3-in-1 3D-printed electrochemical biosensor for the rapid detection of the SARS-CoV-2 spike protein (S Ptn). The biosensor consists of a graphite/polylactic acid (G/PLA) working electrode modified with gold nanoparticles conjugated to polyclonal antibodies (pAb-AuNPs), and carbon black/PLA-based reference and auxiliary electrodes. Detection is achieved via an indirect immunoassay, measuring the decrease in cathodic current of a [Fe-(CN)₆]^3-/4- redox probe using cyclic voltammetry. The biosensor exhibited a detection limit of 0.76 pM, a linear range from 2.5 to 10 μg L^-1, and a total assay time of under 5 min. Selectivity was confirmed against other viral proteins, including those from Dengue, Zika, and Chikungunya viruses. Tests in human serum demonstrated the sensor's robustness and applicability for complex matrices. These results highlight the potential of 3D-printed multimaterial biosensors for rapid and selective viral diagnostics.