Silk and diamonds are the ingredients for a new kind of tiny glowing particle that could provide researchers with a novel technique for biological imaging and drug delivery. The particles, just tens of nanometers across, are made of nanodiamonds covered in silk.

They can be injected into living cells, and because they glow when illuminated with certain kinds of light, biologists can use them to peer inside cells and untangle the molecular circuitry that governs cellular behavior, or to study how cells react to a new drug. The silk-coated diamond particles could also potentially be used in the clinic, allowing doctors to send infection-fighting antibiotics to a targeted area of the body.

A team of researchers from the University of Melbourne, Australia, in cooperation with the Silk Lab at Tufts University, Medford, MA, say nanodiamonds can be made with defects that allow them to absorb and reemit light of certain wavelengths, called fluorescence. Because they are stable, and harmless to living tissue, the researchers have been exploring their use in biological imaging and sensing. But because the particle edges can be rough, the team chose to cover the nanodiamonds in silk, which is transparent, flexible, compatible with biological tissue, and biodegradable, so it won't leave any harmful byproducts inside the body.

When the researchers tested their new hybrid material, they found that the silk remains transparent and does not block the nanodiamonds’ glow, but also enhances their brightness by two to four times. Finally, the new material appears to be safe for use in the body: it left no damaging effects even after spending two weeks implanted inside living tissue, suggesting that it is nontoxic and non-inflammatory, they say.

In the future, the team envisions a range of nanodiamond-silk structures that could help researchers improve techniques for fighting infections in targeted areas of the body. A thin film of the new substance, carrying drugs, could be implanted directly into an infected area, minimizing the patient’s exposure to the drugs.