When doctors set out to poison cancer cells with drugs, there's always a risk healthy tissues will fall to friendly fire.
And sometimes a drug is kicked out of tumor cells or flushed out of the body before it can do much good.
For help overcoming those hurdles, biomedical engineer Dean Ho and his colleagues at Northwestern University have turned to a surprising material: diamonds.
Well, these aren't the kind of diamonds you might find adorning Kate Middleton's engagement ring. They're nanodiamonds — clusters of a few hundred carbon atoms that Ho tells Shots "kind of look like angular soccer balls." They're so small that when stirred into water the mixture looks pale gray.
Ho's team injected nanodiamonds covered in the drug doxorubicin into mice sick with chemo-resistant breast and liver cancers. The results of their appear in the latest issue of Science Translational Medicine.
Remarkably, the treatment didn't reduce white blood cell count, as the drug usually does, and "no toxic effects on tissues and organs were observed."
When researchers upped the dosage of normal, unbound doxorubicin, the mice all died before they completed the treatment. But when they administered that same dose of doxorubicin in its diamond-bound form, not only did the mice survive, their tumors shrank significantly.
Ho has been searching for a better way to deliver cancer drugs for a while now. He and his collaborators have tried a variety of polymers. They were looking for something off the shelf that could be easily and cheaply mass produced. They also wanted something that could bind tightly to drugs of many different molecular sizes.
"What is promising is that nanodiamonds integrate all of these properties so well into in one drug-delivery platform," Ho tells Shots.
The nanodiamonds are already in use in the automotive industry as a lubricant. They don't cost much (a big bottle of NanoLube goes for about $75), and are pretty uniform in size.
If you're feeling technical, here are some details. When the nanodiamonds are washed in acid, their surfaces gain carboxyl groups and they become "sticky." Small molecules like doxorubicin and large molecules like strands of genetic material can grab on. The nanodiamonds even stick to each other when they are attached to doxorubicin, forming clumps with drug-filled pockets.
These clumps stick around in mice up to ten times longer than unbound doxorubicin and release their drugs in a slow, sustained way. Plus, chemo-resistant cancer cells have trouble expelling the doxorubicin-diamond complex. The high retention of the nanodiamonds within tumors means that smaller, less harmful doses can be used.
But so far, let's be clear, the approach has only been shown to work in mice. Ho says it will be a while before nanodiamonds can even be considered for use in humans. "To continue the push for making this a clinically relevant we have to move to a larger animal model like a rabbit," Ho says. "Given that it's a relatively novel approach, we want to make sure that the material is safe."
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