Figure 2.

A) Principle of Tb‐to‐QD FRET NB displacement immunoassays. Mixing of Tb‐NB1‐H donor conjugate and QD625‐CL4 acceptor results in Tb‐to‐QD FRET (left). The addition of sEGFR (gray arrow in the center) leads to a displacement of Tb‐NB1‐H from the QD surface to sEGFR and disruption of FRET (right). B) NB displacement FRET immunoassay calibration curves with an LOD (3 standard deviations below the zero concentration value – see inset) of 0.08±0.02 nM (16±4 ng mL⁻¹) sEGFR. Data points represent three (10 for the blank samples without sEGFR) independent measurements. Error bars represent standard deviations (σ). The EGFR concentrations are those in the 50 μL sample.