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. Author manuscript; available in PMC: 2010 Dec 1.
Published in final edited form as: Nat Biotechnol. 2010 May 23;28(6):595–599. doi: 10.1038/nbt.1641

Figure 1. Digital ELISA based on arrays of femtoliter wells.

Figure 1

Figure 1

Figure 1

(A) Capturing and labeling single protein molecules on beads using standard ELISA reagents. (B) Loading of beads into femtoliter well arrays for isolation and detection of single molecules. (C) SEM image of a small section of a femtoliter well array after bead loading. 2.7-μm-diam. beads were loaded into an array of wells with diameters of 4.5 μm and depths of 3.25 μm. (D) Fluorescence image of a small section of the femtoliter well array after signals from single enzymes are generated. While the majority of femtoliter chambers contain a bead from the assay, only a fraction of those beads possess catalytic enzyme activity, indicative of a single, bound protein. The concentration of protein in bulk solution is correlated to the percentage of beads that have bound a protein molecule.