Figure 3
ATPS ELISA can be used to pattern 9-plex and 16-plex arrays of detection antibodies.
(a) A 9-plex version of the experiment shown in Figure 1 c that demonstrates how ATPS-ELISA suppresses cross-reactions. Goat anti-ST2 detection antibody solutions are dispensed as ATPS droplets only to the 5 regions with spotted ST2 capture antibodies and ST2 antigen. These 5 regions generated true-positive signals. The 4 other regions spotted with anti-goat capture antibodies that would cross-react and give false positive signals with the goat anti-ST2 detection antibody did not receive any detection antibody solution droplets and thus resulted in no signal, demonstrating suppression of false positive signals. (b) A 9-plex version of the experiment shown in Figure 1 d. Bath applied goat anti-ST2 detection antibodies become sequestered by the 4 anti-goat antibody spots. This produces 4 false positive readouts and interestingly 5 false negative signals with very low (but detectable) signal levels because there is insufficient ST2 detection antibody available to bind to the ST2 sandwich regions despite the fact that the anti-ST2 capture antibodies are bound to ST2. (c) Representative image of a 16-plex ATPS sandwich ELISA for ST2 with bath application of the capture antibody and localized dispensing of detection antibody in DEX droplets. (d) Same experiment as in c but without localized dispensing of detection antibody in the DEX droplets. The result is a signal from the entire well rather than localized signals.
