Magnet-assisted electrochemical immunosensor based on surface-clean Pd-Au nanosheets for sensitive detection of SARS-CoV-2 spike protein.

Tracking and monitoring of low concentrations of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can effectively control asymptomatic transmission of current coronavirus disease 2019 (COVID-19) in the early stages of infection. Here, we highlight an electrochemical immunosensor for sensitive detection of SARS-CoV-2 antigen marker spike protein. The surface-clean Pd-Au nanosheets as a substrate for efficient sensing and signal output have been synthesized. The morphology, chemical states and excellent stable electrochemical properties of this surface-clean heterostructures have been studied. Functionalized superparamagnetic nanoparticles (MNPs) were introduced as sample separators and signal amplifiers. This biosensor was tested in phosphate buffered saline (PBS) and nasopharyngeal samples. The results showed that the sensor has a wide linear dynamic range (0.01 ng mL to 1000 ng mL) with a low detection limit (0.0072 ng mL), which achieved stable and sensitive detection of the spike protein. Therefore, this immunosensing method provides a promising electrochemical measurement tool, which can furnish ideas for early screening and the reasonable optimization of detection methods of SARS-CoV-2.