05 Dec 2002
Scientists in the US use light-emitting quantum dots that fluoresce in the visible to label breast cancer cells.
A US company has used fluorescent quantum dots to label breast cancer cells for the first time. Quantum Dot Corporation says that its Qdot technology offers several advantages over organic dyes traditionally used for cellular imaging. (Nature Biotechnology to appear)
One advantage is that the Qdots can be fine-tuned to emit different wavelengths simply by altering the size of the core nanostructure. Varying the size of the spherical cdmium selenide (CdSe) core shifts its light emission between 500 and 660 nm. For example, a 3-nm CdSe core emits green light (520 nm) while a 5.5-nm CdSe core emits red light (630 nm). A protective shell of zinc sulphide is then applied making the device up to a standard 8 nm.
A second benefit is that either a single wavelength or broadband source can be used to excite the Qdots. "The excitation wavelength has to be shorter than the emission wavelength," Andy Watson, the company's vice president for business development told Optics.org. "We have used a mercury arc lamp, which is a standard component within any microscope used for fluorescence studies. But you could also think about using lasers or LEDs."
Watson and colleagues have successfully linked their Qdots to biological probes known as streptavidin and IgG. The team used these probes to target a cancer marker, called Her2, that is abundant on the surface of breast cancer cells. According to Watson, the team successfully observed the emission from the Qdots representing the presence of the cancer marker in live cells.
As there are many different forms of breast cancer cell, Watson says the Qdots can also be used to color-code different types of cell.
The company is now looking at different materials to extend the emission range into the near infrared. Cadmium telluride is being used to emit in the red to near infrared while indium arsenide will emit in the near infrared. Watson also says the company is working with other groups to explore other potential biological applications.
Jacqueline Hewett is news reporter on Optics.org and Opto & Laser Europe magazine.