Saturday, February 18, 2012

DNA nanorobot delivers drugs to cancer cells

Getting a drug to the place where it needs to do its job is not all that easy. Especially when compounds are toxic, efficient targeting is highly required to ameliorate side effects. Many strategies to get drugs where we need them are currently in development, but scientists from Harvard University have thought of something new: a 'nanorobot' that holds drugs inside, and only releases its load when it finds it predetermined target.

Our genetic code is made up of a specific structure. The building blocks, when fitted together, form a spiralling shape, and Harvard researchers found a way to create structures capable of transporting drugs. Their 'DNA nanorobot' is shaped like a clam, and is 'locked' by a zip. It can only be unzipped, and thus unlocked, when it meets the target it was designed for.

Drug delivery
Specific molecules, for example on the surface of cancer cells, can be targeted by constructing a specific string of DNA that recognizes them. That means the clam will only be unzipped when the nanorobot reaches its target. Unzipping means the clam structure will be opened and the drug inside is free to flow out and hit the target. It's more specific than simply getting the drug into the bloodstream and allowing it to hit every cell it encounters, healthy or malicious.

While the concept is neat, it is of course necessary to prove it actually works. To this end, the scientists designed an experiment where millions of copies of a particular nanorobot recognizing leukaemia cancer cells were added to a cell culture. Filled with a drug that interferes with the growth cycle of the cancer cells, the experiments revealed that their DNA structures were able to effectively deliver their drug load to cancer cells, and managed to kill them in the process. Healthy cells remained alive, which shows the therapy is specific. Cancer and healthy cells were mixed together, which means both of them were exposed to the drug carriers.

Using nanorobots to kill cancer cells sounds exciting, and experiments have shown it is actually a viable therapy. However, so far the drug delivery has only been tested in a cell culture, which is radically different from the environment in live organisms. The next step, therefore, is to test the structures on animal models. That ought to provide us with more proof regarding its efficacy. Because the scientists can design the DNA structures in a shape of their preference, it could very well be an effective therapy for a wide variety of diseases. 

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