Cancer killer

Researchers in Japan have developed a nanoprobe that can spot cancer cells and demonstrated that it could also be used to treat cancer using photodynamic therapy.

The researchers, Rumiana Bakalova and Dr. Hideki Ohba of the Single-Molecule Bioanalysis Laboratory (SMBL), developed the nanoprobe with funding from the Japanese National Institute of Advanced Industrial Science and Technology.

The probe itself comprises a quantum dot made from Cadmium Selenide (CdSe) joined with lectin which specifically identifies sugar chains existing on the surface of a cancer cell.

When the quantum dot-lectin complex is fed to cancer cells and irradiated with UV rays, quantum dots incorporated with the surface and interior of the cancer cell emit brilliant green fluorescent light allowing the researchers to spot where the cancerous cells are.

But better yet, continued irradiation with the UV light triggers selective death in 20 to 45% of cancer cells after 60 minutes.

That’s because although the quantum dots absorb the UV energy and emit fluorescence, a part of the energy absorbed from the UV light reacts with oxygen around the dots to produce poisonous oxygen species – such as a singlet oxygen and free radicals – that induce apoptosis in the cancer cells.

On the other hand, the complex probe does not react with normal cells, and exposure to UV rays gives no fluorescence.

Although the researchers have only carried out experiments on cultured cells at the moment, they expect to repeat the procedure using animals in the near future.

Earlier in the year, Emory University scientists used luminescent “quantum dot” nanoparticles in living animals to simultaneously target and image cancerous tumours (see Related Stories).