Diamonds - girl's best friend, cancer's worst enemy

Scientists have added a sparkle to the arsenal of anti-tumour agents by successfully demonstrating that diamonds can augment the cancer-killing properties of some drugs.

Writing inScience Translational Medicine,旧金山加州大学的科学家George Chow and his colleagues have demonstrated the effective, safe use in mice of tiny diamond particles dubbed "nanodiamonds". These bodies are octahedral in shape and, at 10 nanometres across, roughly equivalent in size to some small viruses. They are made by firing beams of electrons at diamond dust and can be "functionalised" by washing them in acid, which electrically charges the faces, making them sticky.

Drug molecules can then be bound to these adhesive facets, permitting the nanodiamond to act as a carrier for the drug molecule. This makes the drug much more difficult for cancer cells to pump out, overcoming the reason why most chemotherapies currently ultimately fail, because tumours turn on efflux pumps that protect the cell from the harmful effects of the drug.

The research team tested their diamond concept by binding the nanodiamonds to the anti-cancer agent doxorubicin, which kills cells by damaging DNA. Cancer cells grown in a culture dish, including cells expressing the kinds of molecular pumps that make tumours chemotherapy-resistant, were killed when the new preparation was administered. Tests also confirmed that the nanodiamond-coupled drug was retained tenfold longer in the cells compared with doxorubicin administered on its own.

The researchers also successfully tested the agents on mice with liver and breast tumours. Injected via a vein in the tail, the nanodiamond preparation gained access to and was retained within the cancerous cells where it led to significant survival enhancements compared with control animals.

Significantly, the nanodiamond formulation also showed lower rates of systemic toxicity, allowing higher overall doses of drugs to be delivered to tumours. However, this proof of principle is only the first step. Now it needs to be shown that diamonds really are a girl's (or boy's) best friend by demonstrating that the technique is equally safe and effective for humans.