Nanotubes used for new cancer imaging technique

The method, described in the Royal Society of Chemistry journal Nanoscale, relies on spectral triangulation. Cancerous tumours are tagged with antibody-linked nanotubes, which naturally fluoresce at short-wave infrared wavelengths when excited by visible light. A highly sensitive detector called an InGaAs (indium gallium arsenide) avalanche photodiode allows for the faint signals from the nanotubes to be identified up to 20mm deep in the simulated tissue used for testing.

"We're using an unusually sensitive detector that hasn't been applied to this sort of work before," said Rice chemist Bruce Weisman, who led the research. "This avalanche photodiode can count photons in the short-wave infrared, which is a challenging spectral range for light sensors. The main goal is to see how well we can detect and localise emission from very small concentrations of nanotubes inside biological tissues. This has potential applications in medical diagnosis."

The Rice team used LED lighting to excite the nanotubes. According to Weisman, lasers are more commonly used for this, but can’t be focused inside tissue because of scattering. However, LED light diffuses through tissue and is able to penetrate to the nanotubes.