HOW鈥橲 this for a clever robot? Tiny probes built from DNA can seek and destroy cancer cells, leaving healthy cells untouched. These clam-like bots, which release a drug only when they reach and identify their target, could improve the treatment of many diseases.
Shawn Douglas and colleagues at Harvard University鈥檚 Wyss Institute used 鈥淒NA origami鈥� to build the nanorobot. They used software that understands how DNA base pairs bind together, as well as the shapes they create. When the team enter a chosen shape the software returns a list of DNA strands that can be mixed together to create it.
Douglas鈥檚 team chose a clam-like cage, so that the nanorobot could hold a drug dose inside until it was time to deliver it.
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To ensure that the cage only opened when it found its target, the team fitted it with two locks. Each lock is a strand of DNA called an aptamer that can be designed to recognise a specific molecule. When the aptamer and target molecule connect, the DNA strand unzips and the clam opens up, releasing its payload.
To test its potential, Douglas鈥檚 team created a nanorobot with locks that unzip in response to molecules on the surface of leukaemia cells. The team then loaded it with a molecule that kills the cancer cells by interfering with their growth cycle. Finally, they released millions of nanorobots into a mixture of healthy and cancerous human blood cells.
Three days later, around half of the leukaemia cells had been destroyed, leaving healthy cells unharmed (Science, ).
Douglas reckons that by adding additional drugs to cripple more of the cells鈥� normal functioning, his team could target every last one of the leukaemia cells. What鈥檚 more, with different locks, the nanorobots could be designed to target any type of cell.
Having two locks means that a nanorobot is better able to distinguish between cells, says Douglas. 鈥淭wo different signals have to be present to open it, increasing its specificity,鈥� he says. He hopes the cancer-targeting nanorobots will steer clear of other rapidly dividing cells, such as those in the gut and at hair follicles, which often suffer collateral damage during chemotherapy.
J酶rgen Kjems at Aarhus University in Denmark agrees. 鈥淭he group provides proof of principle that DNA origami has the capacity to create highly intelligent drugs that activate only on encountering diseased cells,鈥� he says. 鈥淭his will lower the toxicity and side effects of the drugs carried within the device.鈥�
聯DNA origami creates highly intelligent drugs that are released only on meeting diseased cells聰
Paul Rothemund at the California Institute of Technology in Pasadena is also hopeful. 鈥淭he ability to [match] the binding of the clam shell to the targeted cell type and use this as a trigger for delivery is a major step beyond the smart drugs of today.鈥�
鈥淭he next step will be to ensure the nanorobot can withstand the destructive environment of living organisms,鈥� says Kjems.
