Sustainable Electrochemical-Magnetic Biosensor Fabricated from Recycled Materials for Label-Free Detection of SARS-CoV-2 in Human Saliva

The COVID-19 pandemic has highlighted the critical need for scalable, rapid, and cost-effective diagnostic solutions, especially in resource-limited settings. In this study, we developed a sustainable magnetic electrochemical biosensor for the mass testing of SARS-CoV-2, emphasizing affordability, environmental impact reduction, and clinical applicability. By leveraging recycled materials from spent batteries and plastics, we achieved a circular economy-based fabrication process with a recyclability rate of 98.5%. The biosensor employs MnFe₂O₄ nanoparticles functionalized with anti-SARS-CoV-2 antibodies, integrated into a 3D-printed electrochemical device for decentralized testing. Advanced characterization confirmed the biosensor's robust performance, including high sensitivity (LOD: 3.46 pg mL^-1) and specificity, with results demonstrating a 95% correlation to RT-PCR gold standard testing. The cost of materials used per biosensor test is only USD 0.2, making it highly affordable and suitable for large-scale production using additive manufacturing. Key features include simple preparation, rapid response, and reusability, making it ideal for point-of-care diagnostics. Beyond COVID-19, this platform's modularity allows for adaptation to other viral diseases, offering a versatile solution to global diagnostic challenges. This work highlights the potential of integrating electrochemical sensing with sustainable practices to address healthcare inequities and reduce environmental impact.