Gold Nanoparticles Allow Controlled Release of Multiple Cancer Agents

Such a system could one day be used to provide more control when fighting diseases typically treated with more than one drug, according to the researchers.

"With a lot of diseases, especially cancer and AIDS, you get a synergistic effect with more than one drug,” said Dr. Kimberly Hamad-Schifferli, assistant professor of biological and mechanical engineering at the Massachusetts Institute of Technology (MIT; Cambridge, MA, USA) and senior author of the study's findings that appeared in the December 16, 2008, issue of the journal American Chemical Society's (ACS) journal ACS Nano.

Delivery devices already exist that can release two drugs, but the timing of the release must be built into the device--it cannot be controlled from outside the body. The new system is controlled externally, and hypothetically, it could deliver up to three or four drugs. The technique takes advantage of the fact that when gold nanoparticles are exposed to infrared light, they melt and release drug payloads attached to their surfaces.

Nanoparticles of different shapes respond to different infrared wavelengths, so "just by controlling the infrared wavelength, we can choose the release time” for each drug, stated Andy Wijaya, graduate student in chemical engineering and lead author of the study.

The team constructed two different shapes of nanoparticles, which they call "nanobones” and "nanocapsules.” Nanobones melt at light wavelengths of 1,100 nm, and nanocapsules at 800 nm. In the study, the researchers tested the particles with a payload of DNA. Each nanoparticle can carry hundreds of strands of DNA, which could also be engineered to transport other types of drugs. In theory, up to four different-shaped particles could be developed, each releasing its cargo at different wavelengths.

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