Quantum Dots as Fluorescent Labels for Use in Microsphere‐Based Fluoroimmunoassays

Abstract

The use of polystyrene fluorescent microspheres conjugated to antigens and CdTe quantum dots (QDs) conjugated to antibodies as sensitive fluorescent labels in fluoroimmunoassay is described. CdTe QDs were attached to antibodies via electrostatic/hydrophilic self‐assembly. Both CdTe QD–labeled antibodies (anti‐IgGQD) and microsphere‐labeled antigens (IgGFM) were used to form a typical immunoassay on the surface of fluorescent microspheres. The immunoreaction system with different microsphere emissions and QDs can be detected effectively at a single excitation wavelength, because fluorescent QDs have broad excitation spectra and narrow emission bandwidths. This approach allowed detection of goat‐anti‐rabbit IgG in the range of 0.5 to 10 µg/mL. Furthermore, the immunocomplexes of anti‐IgGQD–IgGFM were confirmed by coincidence detection of the fluorescence signals of CdTe QDs and microspheres on a microfluidic on‐chip device.

Keywords:

• Fluorescent polystyrene microspheres
• fluoroimmunoassay
• quantum dots

Acknowledgments

This work was supported financially by the National Natural Science Foundation of China (grant no. 20075009 and no. 20475020). The authors thank Prof. Shuming Nie (Wallace H. Coulter Department of Biomedical Engineering, Emory University and Georgia Institute of Technology) for helpful suggestions.