Figure 1. Schematics of sandwich (A-D) and reverse-phase (E-H) assays.

(A) The sensors are immobilized with capture probes. In this case, antibodies are selected as capture probes. (B) After blocking the rest of surface, the sample containing target proteins is introduced and incubated. The complementary pairs of antibody and its antigen are displayed in the same color. Thus, irrelevant proteins shown as green pentagons are not captured by capture probes. (C) After washing, the detection probes are added. They can be pre-conjugated with tags, which are shown as grey circles, or additional steps can be performed to attach the tags to them. (D) If the detection probes do not cross-react with other proteins or capture probes, the final assembly becomes three-layered structure of sandwich assays. (E) In the reverse-phase assays, the samples containing target proteins are spotted on the sensors. (F) After neutralizing the surface, the primary antibodies are added and incubated. These antibodies can recognize their target proteins which are shown as blue squares. (G) After washing unbound primary antibodies, the secondary antibodies with tags are introduced. These secondary antibodies bind to the other parts of the primary antibodies, which are indicated in orange. (H) The final assembly of reverse-phase assays.