Washington, October 13 : Scientists at Harvard Medical School have found that a new nanoparticle can multitask as a drug courier and a delivery reporter by glowing, when it finds or enters tumour cells.

They say that the technique may enable doctors to see exactly which cells have successfully received a drug, once it is approved for use in humans.

About 1000th of the width of a human hair, ‘Quantum dots’ are reflective crystals that show much promise as medicinal tools due to their extremely bright fluorescence, and the ability to carry other molecules on their surface.

Omid Farokhzad of Harvard Medical School and his colleagues used cell culture experiments to create quantum dots that switch this fluorescence on when they enter the target cells, and delivered the drug.

The researcher has revealed that the key to the design are molecules called aptamers, which sit on the quantum dot's surface. He said that one of the qualities of aptamers, made of nucleic acids such as DNA, is that it can bind to specific target molecules.

In this case, the ends of the aptamers recognise molecules only found on the outside of prostate cancer cells, while the stems accommodate molecules of the anti-cancer drug doxorubicin (dox).

"Normally, dox is fluorescent, but when it binds to the aptamer, the interaction between the two molecules switches the fluorescence off. Dox also absorbs all the light reflected from the quantum dot, so that then doesn't fluoresce either," New Scientist quoted Farokhzad as saying.

The researchers further said that only when the nanoparticle has entered a cancer cell does it lights up again. It so happens because the dox is removed from the aptamers, allowing the dot to recover its fluorescence. In the lab, the quantum dots' coloured light can be detected with a fluorescence microscope.

"Using nanotechnology to target drugs to cancer cells is an exciting technique and the nanoparticles engineered in this study are smarter than ever before," Alison Ross, science information officer at Cancer Research UK, said.

She, however, added that "more research is needed to discover whether these particles could be used to benefit cancer patients in the future."

Farokhzad believes that by varying the molecules used, his system can be adapted to target a wide range of diseases. He now aims to test the particles in animals with prostate cancer. (ANI)