If you give a nanodiamond to your fiancée, you can forget about the wedding. But a new study reports that these tiny flecks of carbon can shrink tumors in mice by delivering chemotherapy drugs to cancer cells.
Lead author Dean Ho, a biomedical engineer at Northwestern University in Evanston, Illinois, says that one of the major challenges in chemotherapy is when tumor cells develop mechanisms to pump drugs right back out. But Ho reasoned that when the drug is bound to a nanoparticle, the combination would be too large for the pump, so tumors would have a hard time evolving resistance.
The value of nanoparticles made of diamond is multifaceted. Made of carbon, they're nontoxic, and the body's immune system doesn't attack them. They can bind tightly to a variety of molecules and deliver them right into a tumor. And because they are only 2 to 8 nanometers in diameter, they are easy for the kidneys to clear from the body before they block up blood vessels, a long-standing problem in nanoparticle therapy.
To study nanodiamonds' usefulness for cancer treatment, Ho's group attached them to doxorubicin, a standard chemotherapy drug, and injected them into mice with drug-resistant breast and liver cancer. With the help of the diamonds, the drug stayed in the bloodstream 10 times longer than usual, making it much more effective. As a result, the tumors shrank significantly, the researchers report  online today in Science Translational Medicine.
Blinging out the drug helped make it less toxic as well. The researchers were able to inject the mice with doses of doxorubicin that normally would be lethal. But the drug stayed bound to the diamond until it reached the tumor, so it didn't damage cells elsewhere in the body, and the animals survived.
In addition, the livers of the mice didn't ramp up enzymatic activity as they normally would in response to high levels of a toxic substance. Most importantly, the doxorubicin-decorated diamonds had no effect on white blood cell count, an indicator of immune system activation that's often the deciding factor in whether a patient can continue chemotherapy.
Ho and colleagues are now planning to try nanodiamond therapy in larger animals such as rabbits. "We're excited about the next step. It looks promising," he says.
Materials science engineer Brij Moudgil of the University of Florida in Gainesville says the study shows that nanodiamonds have potential. However, he's not sure whether they have significant advantages over other materials such as silica and gold, which are also being studied as drug carriers.