Drawing depicting the ILPCR assay format. The antigen (purple, brown, and blue) is bound by an immobilized capture antibody (blue and purple) and a biotinylated secondary antibody (green and purple). The liposome detection reagent (yellow) is coupled to the biotinylated secondary antibody through a NeutrAvidin bridge (aqua and brown). The biotin-labeled PEG phospholipid conjugates are pictured as PEG polymers (dark green) terminating in biotin molecules (red) with the phospholipid component (not visible) embedded in the outermost bilayer leaflet of the liposome. Encapsulated DNA reporters (green with red bars) can be seen inside the liposome. Shown at the bottom right is the biotin-labeled PEG phospholipid conjugate used to prepare the detection liposomes: 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[biotinyl (polyethylene glycol) 2000] ammonium salt. The phospholipid moiety is depicted in blue, the PEG (2000) polymer moiety in green, and the biotin moiety in red.