Electrochemical Immunosensor for Rapid Detection of SARS-CoV-2 Virus

The COVID-19 pandemic has emphasized the need for rapid, affordable, and reliable SARS-CoV-2 diagnostic tools suitable for decentralized use. Although RT-PCR remains the gold standard, its high cost, technical complexity, and slow processing limit its practicality for point-of-care testing. This study presents a screen-printed electrochemical immunosensor designed for fast and sensitive detection of SARS-CoV-2 antigens in clinical samples. The sensor incorporates a dual-working electrode configuration that enables real-time internal referencing and employs a graphene/titanium dioxide (TiO₂) nanocomposite to improve electron transfer and signal responsiveness. An optimized 90:10 (w/w) graphene-to-TiO₂ ratio, identified through cyclic voltammetry, provided the strongest electrochemical performance. One working electrode was functionalized with anti-SARS-CoV-2 antibodies, while the second acted as a reference; antigen binding caused current suppression measured by differential pulse and square-wave voltammetry. The system achieved a detection limit of 0.58 ng/mL, a quantification limit of 1.77 ng/mL, and demonstrated high accuracy (102 ± 2.6%) and precision (RSD = 4.3%) in spiked serum. By combining nanomaterial synergy with low-cost screen-printing, this immunosensor offers a scalable, field-ready platform that supports rapid and reliable SARS-CoV-2 detection, particularly in resource-limited settings.