The best way of applying medicines powerful enough to kill cancerous tumours is to ensure that they wind up in those tumours and nowhere else in the body. In a recent Nature Nanotechnology paper, researchers at the University of Toronto point the way to just this kind of targeted delivery, which takes advantage of the properties of gold nanoparticles. 

DNA can be employed to manipulate these nanoparticles and the polymer polyethylene glycol to form intricate structures, which can contain and carry drugs to the tumour site. Just as importantly, these structures subsequently break down and are flushed from the body, preventing any build-up of unwanted material.

The success of this strategy depends upon the size of the structures. If they are too small, less than 10 nanometres, they will pass through pores in blood vessel walls and fail to reach their destination. Instead, they must be large enough to continue travelling in the bloodstream until they reach a tumour, which has its own system of incomplete blood vessels with much larger pores that vary from 50-500 nanometres across. If a drug-laden nanoparticle structure exits there, it will wind up inside the tumourous tissue, where the medicine can go to work.
As straightforward as this sounds, paper co-author Warren Chan points out just how much work has gone into learning how to use DNA to assemble nanoparticle cage-like structures to contain the drug molecules in the desired way. “We’ve spent eight years just trying to understand the basics,” says Chan, a professor at U of T’s Institute of Biomaterials and Biomedical Engineering. “Now we’re at the point where we have design parameters to make this nanotechnology work effectively and be safe.”

Those parameters are crucial, Chan adds, if such treatments are ever going to obtain approval from Health Canada and the US Food and Drug Administration. “The DNA allows us to build up a nanoparticle system but now we don’t have to worry about long-term toxicity because it will be degraded and get eliminated from the body.”