Figure 1.

Schematic diagram of NAb LFA principle/mechanism. (1) Fingerstick blood is obtained using a pressure-activated safety lancet. (2) Ten microliters of blood are transferred to the sample port on a test cassette. (3) Buffer is applied to the sample port. (Left to right) RBD of spike (blue) is shown coupled to a green-gold nanoshell (green-GNS). Non-neutralizing antibodies (gold) are shown to bind outside of the RBD, such that in outcome (A) RBD-GNS is available to bind ACE2, seen as a strong test line. Neutralizing antibodies (maroon) are shown binding to RBD, obstructing the interaction between antigen and receptor, such that in outcome (B) RBD does not bind to ACE2, observed as a faint or absent test line.