DNA-Functionalized Ti₃C₂T MXenes for Selective and Rapid Detection of SARS-CoV-2 Nucleocapsid Gene

Coronavirus disease 2019 (COVID-19) is an emerging human infectious disease caused by severe acute respiratory syndrome 2 (SARS-CoV-2, initially called novel coronavirus 2019-nCoV) virus. Thus, an accurate and specific diagnosis of COVID-19 is urgently needed for effective point-of-care detection and disease management. The reported promise of two-dimensional (2D) transition-metal carbides (Ti₃C₂T MXene) for biosensing owing to a very high surface area, high electrical conductivity, and hydrophilicity informed their selection for inclusion in functional electrodes for SARS-CoV-2 detection. Here, we demonstrate a new and facile functionalization strategy for Ti₃C₂T with probe DNA molecules through noncovalent adsorption, which eliminates expensive labeling steps and achieves sequence-specific recognition. The 2D Ti₃C₂T functionalized with complementary DNA probes shows a sensitive and selective detection of nucleocapsid (N) gene from SARS-CoV-2 through nucleic acid hybridization and chemoresistive transduction. The fabricated sensors are able to detect the SARS-CoV-2 N gene with sensitive and rapid response, a detection limit below 10⁵ copies/mL in saliva, and high specificity when tested against SARS-CoV-1 and MERS. We hypothesize that the MXenes' interlayer spacing can serve as molecular sieving channels for hosting organic molecules and ions, which is a key advantage to their use in biomolecular sensing.