Quantum Dot Streptavidin Conjugates (Invitrogen™)

PI Institution Title IMAT Award
Robert Daniels
Marcel Bruchez
Quantum Dot Corporation Sensitive, Multiplexed Analysis of Breast Cancer Markers R44

Quantum dot (Qdot) nanocrystals have strong photostability, which lets them detect low-abundance antigens. Because the nanocrystals have narrow and symmetric emission spectra, they can also be used for multicolor, multiplexed fluorescence detection using one excitation source, such as the 405-nm laser. Qdot streptavidin conjugates take advantage of the photostability of Qdot nanocrystals and streptavidin’s very specific binding properties so they can be used as fluorescence detection reagents in tissue-labeling and flow-cytometry experiments. Unlike conventional dye conjugates, the Qdot streptavidin conjugates can be excited efficiently using the 405-nm violet laser, and Qdot nanocrystal fluorescence resists photobleaching.

An IMAT award contributed to the development of Qdot-protein conjugates. The goals of the IMAT award were to differentially identify multiple, spectrally distinct probes (i.e., multiplexing) in cell sections, use Qdot conjugates to characterize breast tissue sections, manufacture and characterize the Qdot conjugates, stain tissue microarrays with Qdot conjugates, and perform in situ hybridization with Qdot conjugates. By the end of the funding period, the researchers had successfully manufactured Qdot conjugates of antibodies and proteins to Qdot nanocrystals, developed staining protocols, and showed that Qdots were superior to existing conjugate probes for multiplex microscopy experiments. They also developed five Qdot streptavidin-conjugated probes.

After the funding period, the investigators developed two additional Qdot-streptavidin conjugates. All seven Qdot-streptavidin conjugates are commercially available through Invitrogen.

Streptavidin-conjugated Qdots have been used to detect Her2 cancer markers on the surface of human breast cancer cells through a biotinylated secondary antibody to human and a humanized antibody to Her2. The technology has also been used to show that the N-terminal region of mortalin is involved in the in vivo and in vitro interactions of two proteins. Suppression of heat shock protein 60 (HSP60) expressed by short hairpin RNA (shRNA) plasmids caused the growth arrest of cancer cells similar to that obtained by suppressing mortalin expression by ribosomes.

PubMed lists 38 publications on quantum dot or Qdot conjugation with streptavidin. Of these, 6 focus on the use of these conjugates in cancer research.

1 Michalet X, Pinaud FF, Bentolila LA, Tsay JM, Doose S, Li JJ, Sundaresan G, Wu AM, Gambhir SS, Weiss S. Quantum dots for live cells, in vivo imaging, and diagnostics.ScienceJanuary 28; 307(5709):538-44, 2005.