Scientists have designed a set of shape-shifting nanoparticles attached to strands of DNA that can deliver drugs directly to cancer cells, while minimizing side effects such as skin damage and hair loss.

Professor Warren Chan from the University of Toronto has been trying to figure out how to deliver chemotherapy drugs into tumors - and nowhere else.

The researchers said that no two tumors are identical. Early-stage breast cancer might react differently to a given treatment than pancreatic cancer, or even breast cancer at a more advanced stage

Which particles can get inside which tumors depends on multiple factors such as the particle's shape, size and surface chemistry. The researchers analyzed how these factors dictate the delivery of small molecules and nano technologies to tumors, and have been able to design a targeted molecular delivery system that uses modular nanoparticles whose size, shape and chemistry can be changed by the presence of specific DNA sequences.

Chan said that the component pieces can be built into many shapes, with binding sites exposed or hidden. They are designed to respond to biological molecules by changing shape, like a key fitting into a lock. These shape shifters are made of tiny chunks of metal with strands of DNA attached to them.

Chan imagines that the nanoparticles will float harmlessly in the blood stream, until a DNA strand binds to a sequence of DNA known to be a marker for cancer. When this happens, the particle changes shape, then carries out its function, it can target the cancer cells, expose a drug molecule to the cancerous cell.

The study has been published in the journals PNAS and Science.