Fig. 4

The performance of (a–c) commercial ELISA kits and (d–f) recent nanobiosensors for the detection of SARS-CoV-2 antigens. The X-axis and Y-axis display the limit of detection (M) and working range (order of magnitude): a/d S1 protein; b/e S(RBD) protein; c/f N protein. In the plot of nanobiosensors, orange, yellow and blue circles indicate electrochemical, electronic, and optical detection. The black solid lines indicate the median value of the group, and the red dotted line marks a picomolar (physiologically relevant) level of viral proteins