Scientists from Taiwan have developed nanodiamonds that, when swallowed, harmlessly coat the digestive track. When coated with special sugars or proteins, the nanodiamonds are absorbed into the body and attach themselves to specific cells.
The research, which is currently limited to animals, could eventually diagnose and eventually treat diseases in humans.
"This research work demonstrates that nanodiamonds are non-toxic in both cellular and organismic levels," said Yi-Chun Wu, a scientist who, along with Huan-Cheng Chang and their colleagues in Taiwan, co-authored a new study in the journal ACS Nano Letters.
Nanodiamonds are tiny pieces of pure carbon only a few of nanometers across. (One nanometer is about 100,000 times smaller than a human hair.) Most nanodiamonds are formed by blowing up TNT or other explosives to create high temperate and high pressures that bond carbon atoms together in a classic 3D diamond nanostructure.
These nanodiamonds are not solid, however. Inside those tiny structures are tiny holes, called vacancies, where a nitrogen atom from the air has replaced two carbon atoms. Nitrogen vacancies in diamonds are common. Natural diamonds with lots of nitrogen have a yellow tint to them. The nanodiamonds the scientists from Taiwan used absorb yellow light and emit violet light.
Next, the scientists fed two types of nanodiamonds to the round worm C. elegans. The first batch of nanodiamonds were uncoated, just pure carbon with a few nitrogen atoms. Those nanodiamonds coated the digestive tract of the transparent roundworm.
The second batch of nanodiaonds the roundworms ate were coated with a special sugar. Once inside the roundworm, the nanodiamonds passed through the digestive tract and into the body of the worm, congregating at various points inside the body.
Both the coated and uncoated nanodiamonds glowed purple when yellow light was shined onto the roundworms, revealing their location inside the worm. All the bejeweled worms had normal lifespans, and none of them showed any sign of distress, said the scientists.
The scientists fed the nanodiamonds to the worms just to measure their toxicity and to see where the diamonds ended up. More specific functions will come soon though, said Vadym Mochalin, a scientist at Drexel University who uses nanodiamonds in his own research.
Virtually any kind of protein or chemical can coat nanodiamonds. When placed into the body, those coated nanodiamonds could seek out and attach themselves to cancer cells, immune cells, pathogens and other cells.
At first, coated and glowing nanodiamonds will likely help doctors and scientists find and map cancers and other things that harm humans. After that nanodiamonds will likely be used to deliver low doses of powerful drugs to help treat those diseases.
Some researchers are most excited about using nanodiamonds to track stem cells.
"One of the most exciting applications of [fluorescent nanodiamonds] in humans is the long-term imaging, tracking, and sorting of human stem cells," said Chang.
Those stem cells could jump-start immune responses, help repair nerve damage, and potentially even regenerate entire organs if the research pans out. Those kinds of advanced therapies are still years, if not decades away however, caution scientists. But this research, along with dozens of other papers and groups working with nanodiamonds, opens the door for powerful therapies in the future.
"The nanodiamond looks very promising compared with other carbon-based nanoparticles," said Mochalin. "It's the least toxic carbon-based nanomaterial to date."