Conjugation of Luminescent Quantum Dots with Antibodies Using an Engineered Adaptor Protein To Provide New Reagents for Fluoroimmunoassays

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Abstract
We describe the preparation and characterization of bioinorganic conjugates made with highly luminescent semiconductor CdSe−ZnS core−shell quantum dots (QDs) and antibodies for use in fluoroimmunoassays. The conjugation strategy employs an engineered molecular adaptor protein, attached to the QDs via electrostatic/hydrophobic self-assembly, to link the inorganic fluorophore with antibodies. In this method, the number of antibodies conjugated to a single QD can be varied. In addition, we have developed a simple purification strategy based on mixed-composition conjugates of the molecular adaptor and a second two-domain protein that allows the use of affinity chromatography. QD−antibody conjugates were successfully used in fluoroimmunoassays for detection of both a protein toxin (staphylococcal enterotoxin B) and a small molecule (2,4,6-trinitrotoluene).