July 24, 2006
New Nano Approaches to In Vivo and Cell-Based Imaging
Nanomaterials are revolutionizing biological imaging thanks to their unique nanoscale properties. The ability to tailor physical and chemical characteristics at the nanoscale makes it possible to create imaging probes that are brighter, longer-lasting and multifunctional. A new report illustrates the versatility and promise of nanoscale imaging agents.
Writing in the journal Biomacromolecules, a team of investigators at the Center of Nanotechnology for Treatment, Understanding, and Monitoring of Cancer, led by Tomas Mustelin, M.D., Ph.D., of the Burnham Institute, has developed an intracellular imaging probe using carbon nanotubes and quantum dots. The researchers formed the nanotube-quantum dot conjugate by first attaching the protein streptavidin to standard quantum dots. Streptavidin then wraps itself around the sidewalls of single-walled carbon nanotubes, creating a stable complex that, unlike pristine carbon nanotubes, was readily dispersible in water.
Streptavidin is famous for its ability to bind to biotin with incredible strength, and the researchers used this property to their advantage by creating a tumor-cell labeling conjugate between biotin and an antibody that recognizes CD3, a protein on the surface of leukemia and other cells that many viruses use to gain entry to cells. Adding the biotin-antibody conjugate to the leukemia cells first, and then adding the quantum dot-labeled nanotubes, resulted in the leukemia cells taking up the labeled nanotubes in large numbers. Thanks to the attached quantum dots, the nanotubes were readily visible in the cells using a fluorescent microscope.
The researchers note that taking advantage of the CD3-mediated uptake mechanism boosts the number of nanoscale imaging constructs that make it into the cell’s interior, reducing the concentration of nanotubes and quantum dots needed for intracellular imaging and any potential toxicities. The investigators found that this same mechanism may be useful for delivering drug-loaded nanotubes into tumor cells.
This work, which was supported by the NCI’s Alliance for Nanotechnology in Cancer, is detailed in a paper titled, “Full-length single-walled carbon nanotubes decorated with streptavidin-conjugated quantum dots as multivalent intracellular fluorescent nanoprobes.” Investigators from the University of Rome, Italy, also participated in this study. This paper was published online in advance of print publication. An abstract is available at the journal’s website.