Nanoparticles offer new ways to combat cancer

Nanoparticles are offering a promising new way to strike at cancer, according to researchers working at MIT and Brigham and Women's Hospital.

In a paper published in April in the online edition of the Proceedings of the National Academy of Sciences, the team reported a way to custom design nanoparticles so they home in on dangerous cancer cells, then enter the cells to deliver lethal doses of chemotherapy. Normal, healthy cells remain unscathed.

Experiments were conducted first on cells growing in laboratory dishes, and then on mice bearing human prostate tumors. The tumors shrank dramatically, and all the treated mice survived, although the untreated control animals did not.

"A single injection of our nanoparticles completely eradicated the tumors in five of the seven treated animals, and the remaining animals also had significant tumor reduction, compared with the controls," said Dr Omid C. Farokhzad, an assistant professor at Brigham and Women's Hospital and Harvard Medical School.

In the study, Farokhzad and colleagues tailor-made tiny sponge-like nanoparticles laced with docetaxel. The particles are specifically designed to dissolve in a cell's internal fluids, releasing the anticancer drug either rapidly or slowly, depending on what is needed. These nanoparticles were purposely made from materials that are familiar and approved for medical applications by the US FDA.

To make sure only the correct cells are hit, the nanoparticles are "decorated" on the outside with targeting molecules called aptamers. Like homing devices, the aptamers specifically recognise the surface molecules on cancer cells, while avoiding normal cells. In addition, the nanoparticles also display polyethylene glycol molecules, which keep them from being rapidly destroyed by macrophages.

The team chose nanoparticles as drug delivery vehicles because they are so small that living cells readily swallow them when they arrive at the cell's surface. They created particles that are about 150 nanometers in size as particles larger than 200 nanometers are less likely to get through a cell's membrane.

The scientists said that further testing is needed. Although all the parts and pieces of their new system are known to be safe, the system itself must yet be proven safe and effective in humans.

Further, from an engineering perspective, Farokhzad said the team wanted to develop a broadly applicable system that other investigators could alter for their own purposes. The technology could be applied to almost any disease by re-engineering the nanoparticles' properties.