Expanding the application of graphene vertical devices to dual femtomolar detection of SARS-CoV-2 receptor binding domain in serum and saliva

• DOI: 10.1016/j.bios.2023.115614
• Publication Date: 2023-08-18T08:03:15Z
• Authors: Isabela A. Mattioli; Karla R. Castro; Graziela C. Sedenho; Lucyano J.A. Macedo; Mona N. Oliveira; Erika R. Manuli; Ester C. Sabino; Frank N. Crespilho
• Keywords: SARS-CoV-2; Humans; COVID-19; Metal Nanoparticles; Graphite; Gold; Biosensing Techniques; Saliva; 3. Good health

The emergence of the graphene-based hybrid electrical-electrochemical vertical device (EEVD) has introduced a promising nanostructured biosensor tailored for point-of-care applications. In this study, we present an innovative EEVD capable of simultaneously detecting the receptor binding domain (RBD) of the SARS-CoV-2 spike protein in both serum and saliva. The foundation of the EEVD lies in a poly-neutral red-graphene heterojunction, which has been enhanced with a bioconjugate of gold nanoparticles and antibodies. The biodevice demonstrates a remarkable limit of detection, registering at the femtomolar scale (2.86 fmol L-1 or 0.1 pg mL-1). Its sensitivity is characterized by a 6.1 mV/decade response, and its operational range spans 10-12 to 10-7 g mL-1 in both serum and saliva samples. With a 20.0 μL of biological samples and a rapid processing time of under 10 min, the EEVD achieves the feat of dual antigen detection. The tests achieved 100.0% specificity, accuracy, and sensitivity in saliva, and 100.0% specificity, 88.9% accuracy, and 80.0% sensitivity in serum. This study highlights the EEVD as a low-cost solution of rapid viral detection during the crucial initial phases of COVID-19 infections.