Premium
Quantum Dot–Based FRET Immunoassay for HER2 Using Ultrasmall Affinity Proteins
Author(s) -
Wu YuTang,
Qiu Xue,
Lindbo Sarah,
Susumu Kimihiro,
Medintz Igor L.,
Hober Sophia,
Hildebrandt Niko
Publication year - 2018
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.201802266
Subject(s) - förster resonance energy transfer , quantum dot , immunoassay , chemistry , conjugate , ligand (biochemistry) , biophysics , fluorescence , nanotechnology , antibody , materials science , biochemistry , receptor , biology , immunology , mathematical analysis , physics , mathematics , quantum mechanics
Engineered scaffold affinity proteins are used in many biological applications with the aim of replacing natural antibodies. Although their very small sizes are beneficial for multivalent nanoparticle conjugation and efficient Förster resonance energy transfer (FRET), the application of engineered affinity proteins in such nanobiosensing formats has been largely neglected. Here, it is shown that very small (≈6.5 kDa) histidine‐tagged albumin‐binding domain‐derived affinity proteins (ADAPTs) can efficiently self‐assemble to zwitterionic ligand–coated quantum dots (QDs). These ADAPT–QD conjugates are significantly smaller than QD‐conjugates based on IgG, Fab', or single‐domain antibodies. Immediate applicability by the quantification of the human epidermal growth factor receptor 2 (HER2) in serum‐containing samples using time‐gated Tb‐to‐QD FRET detection on the clinical benchtop immunoassay analyzer KRYPTOR is demonstrated here. Limits of detection down to 40 × 10 −12 m (≈8 ng mL −1 ) are in a relevant clinical concentration range and outperform previously tested assays with antibodies, antibody fragments, and nanobodies.