Researchers at the Massachusetts Institute of Technology (MIT) have developed a drug-delivery system by using tiny gold particles and infrared light, which may multiple medicines to be released in a controlled fashion.

The researchers believe that the novel system may one day be used to provide more control when battling diseases commonly treated with more than one drug.

"With a lot of diseases, especially cancer and AIDS, you get a synergistic effect with more than one drug," said Kimberly Hamad-Schifferli, assistant professor of biological and mechanical engineering and senior author of a paper on the work that recently appeared in the journal ACS Nano.

The researchers highlight the fact that the existing drug-delivery devices have the ability to release two drugs, and that the timing for drug release cannot be controlled from outside the body. In contrast, according to the researchers, their new system is controlled externally and may be useful for delivering up to three or four drugs.

The novel approach takes advantage of the fact that gold nanoparticles melt and release drug payloads attached to their surfaces when exposed to infrared light. Andy Wijaya, graduate student in chemical engineering and lead author of the paper, said that since nanoparticles of different shapes respond to different infrared wavelengths, "just by controlling the infrared wavelength, we can choose the release time" for each drug.

The researchers have thus far built two different shapes of nanoparticles, namely "nanobones" and "nanocapsules". While the former melt at light wavelengths of 1,100 nanometres, the latter at 800 nanometres.

During the study, the researchers tested the particles with a payload of DNA. The researchers revealed that each nanoparticle could carry hundreds of strands of DNA, and be engineered to transport other types of drugs. They surmise that up to four different-shaped particles can be developed, each releasing its payload at different wavelengths.