Detection of specific antibodies against SARS-CoV-2 spike protein via ultra-sensitive bio-functionalized carbonnitride-reduced graphene oxide electrochemical immunosensing platform in real samplesAbubakar Sadique, Mohd. (Avtor) Yadav, Shalu (Avtor) Ranjan, Pushpesh (Avtor) Chouhan, Raghuraj S. (Avtor) Jerman, Ivan (Avtor) Kumar, Ashok (Avtor) Saigal, Saurabh (Avtor) Khadanga, Sagar (Avtor) Khan, Raju (Avtor) Srivastava, Avanish K. (Avtor) SARS-CoV-2detectionnanomaterialsIn this work, we fabricate a facile de novo synthesis route to prepare bio-functionalized carbon nitride-reduced graphene oxide with chitosan (Chi) nanocomposite (C3N4/RGO/Chi). The nitrogen-rich C3N4 has been synthesized through facile and low-cost thermal oxidation and offers a metal-free and highly active surface for synergistic modification with RGO and Chi. Moreover, the synergistically incorporated C3N4/RGO and biopolymer improve the electrocatalytic activity, provide surface functionalities, and enhance electroconductivity for immunosensing applications. Consequently, the bio-functionalized C3N4/RGO nanocomposite provides a suitable substrate for the immobilization of SARS-CoV-2 RBD spike protein. The immunosensor detects SARS-CoV-2 antibodies in a wide detection range from 10 zg mL−1 (10 × 10−21 g mL−1) to 100 ng mL−1 with an ultra-low detection limit (LOD) of 3.31 zg mL−1. The validation of the immunosensor was also carried out on spiked serum samples, which show a linear detection range of 100 ag mL−1 to 100 ng mL−1 and a LOD of 1.73 ag mL−1. Nevertheless, the clinical diagnostic application of the immunosensor is validated through the examination of real serum samples from COVID-19 patients. The results suggest that the immunosensor can be efficiently used as a screening platform to distinguish between positive and negative samples with high accuracy. The findings of the work have the potential to translate the immunosensing strategy into next-generation point-of-care testing (POCT) of various infectious diseases.The Royal Society of Chemistry20232025-12-16 13:46:30Neznano24748Združeno kraljestvosl© 2023 The Author(s).