Nano diamonds to become a doctor's best friend

Australian scientists have developed a new way to keep tiny nano-sized diamonds separated during production, which could open new avenues in medical imaging.

The research has also allowed scientists to see new light properties not exhibited by larger diamonds.

Led by Associate Professor James Rabeau of Macquarie University in Sydney, the team created and studied the tiny synthetic diamonds, which are between four and five nanometres in size - a thousand times smaller than the width of a human hair.

Their work, which included researchers from the Australian National University, University of Queensland and theCSIRO appears this week in the journal Nature Nanotechnology.

Medical applications

According to the researchers, proteins are hard to track in living bodies, but by attaching bright markers, it's possible to see where they are and where they're going.

Existing techniques employ fluorescent probes which can often extinguish or turn dark and may be toxic in a live body.

Rabeau and colleagues created the synthetic nano diamonds through a detonation process and isolated them from the carbon graphite matrix using acid cleaning and ultrasound.

These nano diamonds attach to the proteins, making it easier to detect with medical imaging devices.

"The key was keeping the nano diamonds separate and stopping them from clumping back together. This gave us a chance to study them in isolation using a laser to see how bright they are," says Rabeau.

"And we were able to determine that the nitrogen impurities which helps them glow, was present in these nano diamonds."

New understanding

Rabeau says discovering that they blink is an important clue about how the light is changed depending on the size of the crystal.

"In larger diamonds, the light emission or fluorescence remains steady, essentially immune to blinking on and off," he says. "But we found that when the atoms are trapped in nano-diamonds which are much smaller, they start to act a bit differently by blinking, most likely because of their closer proximity to the nano diamond surface."

Rabeau and his team found that this irregular fluorescence behaviour could be reversed by encapsulating the nano diamonds in a polymer sheath.

He describes the work as a big step in developing existing ideas on using nano-diamonds for bio-imaging, and says it may herald new technologies, which exploit the blinking optical feature.