Fluorescent nanodiamonds can now be made 100 times more cheaply than
before, thanks to work by chemists in Taiwan. The new process should
provide easier access to the tiny diamonds, which could have future
applications in medical imaging and cancer therapy.
Nanodiamonds are made by detonating two explosive compounds, TNT and RDX,
and then collecting the resulting soot - which contains diamonds approximately
4nm in size. But to make the diamonds fluoresce they have to be exposed to a
high-energy electron beam from a van de Graaff accelerator, then heated to 800°C
- a costly procedure.
Image
showing the internalization of green fluorescent diamonds by a cancer cell
photo © Fann et al
Instead, the Taiwanese researchers used a purpose-built
machine to bombard nanodiamonds with high-energy helium ions. This causes
defects to form in the structure of the diamonds so that they fluoresce when
they are hit by laser light.
'Our high-fluence medium-energy (40 keV) helium ion beam can be operated
safely and routinely in ordinary laboratories,' says Huan-Cheng Chang, who led
the team with Wunshain Fann at the National Taiwan University.
The team have already started selling their nanodiamonds - charging around £150
for 10mg - a hundredth of the cost of those made by conventional methods.
In the same way that quantum dots or fluorescent beads are used to
illuminate tumours, the researchers envisage that nanodiamonds could be
connected to tumour-seeking drugs or antibodies to function as beacons.
'Carbon-based nanodiamonds possess several properties that make them very
amenable to biological studies,' says Dean Ho at Northwestern University, Illinois,
who was the first to show that nanodiamond clusters could be used to deliver
chemotherapy drugs to cancer cells. 'They are soluble in water and have
very good biocompatibility: they cause very little inflammation in the body.'
'But work still needs be done to evaluate toxicity and clearance time - how
long the diamonds remain in the body - before clinical trials can begin,' Ho
told Chemistry World.
Lidija Siller of the Nanoscale Science and Nanotechnology Group at Newcastle
University, UK, says that other luminous nanoparticles available for
biological applications are more toxic to cells. 'This work represents a step
forward in fluorescent nanodiamond production and should stimulate research to
further improve separation, size selection, mass production and applications
of this material.'
Lewis Brindley
