Surface plasmon resonance aptasensor based on niobium carbide MXene quantum dots for nucleocapsid of SARS-CoV-2 detection.

A novel label-free surface plasmon resonance (SPR) aptasensor has been constructed for the detection of N-gene of SARS-CoV-2 by using thiol-modified niobium carbide MXene quantum dots (NbC-SH QDs) as the bioplatform for anchoring N-gene-targeted aptamer. In the presence of SARS-CoV-2 N-gene, the immobilized aptamer strands changed their conformation to specifically bind with N-gene. It thus increased the contact area or enlarged the distance between aptamer and the SPR chip, resulting in a change of the SPR signal irradiated by the laser (He-Ne) with the wavelength (λ) of 633 nm. NbC QDs were derived from NbC MXene nanosheets via a solvothermal method, followed by functionalization with octadecanethiol through a self-assembling method. Subsequently, the gold chip for SPR measurements was modified with NbC-SH QDs via covalent binding of the Au-S bond also by self-assembling interaction. NbC-SH QDs not only resulted in high bioaffinity toward aptamer but also enhanced the SPR response. Thus, the NbC-SH QD-based SPR aptasensor had low limit of detection (LOD) of 4.9 pg mL toward N-gene within the concentration range 0.05 to 100 ng mL. The sensor also showed excellent selectivity in the presence of various respiratory viruses and proteins in human serum and high stability. Moreover, the NbC-SH QD-based SPR aptasensor displayed a vast practical application for the qualitative analysis of N-gene from different samples, including seawater, seafood, and human serum. Thus, this work can provide a deep insight into the construction of the aptasensor for detecting SARS-CoV-2 in complex environments. A novel label-free surface plasmon resonance aptasensor has been constructed to detect sensitively and selectively the N-gene of SARS-CoV-2 by using thiol-modified niobium carbide MXene quantum dots as the scaffold to anchor the N-gene-targeted aptamer.