Figure 1.

Example of a modern approach to sandwich immunoarrays. On left, a gold nanoparticle-decorated spot (to achieve high surface area) on the array is represented with attached primary antibodies (Ab₁). Sample is delivered to the array, which can have a number of different Ab₁ spots to capture a range of different antigens in a multiplexed assay. For our example SPOT, the antigen is prostate specific antigen, a biomarker protein for prostate cancer.² The antigens are captured by Ab₁’s on their specific spots, usually during an incubation period. After washing, secondary or detection antibodies (Ab₂) are introduced, shown here by two examples. The conventional approach employs a single labeled antibody, while a more sensitive assay can be designed with multiple labels to amplify the signals.¹ This step is followed by another incubation period, washing, and detection. These kinds of arrays can be integrated with microfluidics for sample and reagent delivery and automation.