Nanoscale sensing method has potential in medical treatment

These super-bright, photostable nanocrystals are said to enable a new approach to highly advanced sensing technologies using optical fibres.

This discovery, by a team of researchers from Macquarie University, the University of Adelaide, and Peking University, is said to open the way for rapid localisation and measurement of cells within a living environment at the nanoscale, such as the changes to a single living cell in the human body in response to chemical signals.

Published in Nature Nanotechnology, the research outlines a new approach to advanced sensing that has been facilitated by bringing together a specific form of nanocrystal, a so-called SuperDot, with a special kind of optical fibre that enables light to interact with nanoscale volumes of liquid.

‘Up until now, measuring a single nanoparticle would have required placing it inside a very bulky and expensive microscope,’ said Prof Tanya Monro, director of the University of Adelaide’s Institute for Photonics and Advanced Sensing (IPAS) and ARC Australian Laureate Fellow. ‘For the first time, we’ve been able to detect a single nanoparticle at one end of an optical fibre from the other end. That opens up all sorts of possibilities in sensing.’

‘Using optical fibres we can get to many places such as inside the living human brain, next to a developing embryo, or within an artery ‒ locations that are inaccessible to conventional measurement tools.

‘This advance ultimately paves the way to breakthroughs in medical treatment. For example, measuring a cell’s reaction in real time to a cancer drug means doctors could tell at the time treatment is being delivered whether or not a person is responding to the therapy.’

The performance of sensing at single molecular level had previously been limited by insufficient signal strength and interference from background noise.

The optical fibre engineered at IPAS also proved useful in understanding the properties of nanoparticles.

‘Material scientists have faced a huge challenge in increasing the brightness of nanocrystals,’ said Dr Jin, ARC Fellow at Macquarie University’s Advanced Cytometry Laboratories. ‘Using these optical fibres, however, we have been given unprecedented insight into the light emissions. Now, thousands of emitters can be incorporated into a single SuperDot – creating a far brighter, and more easily detectable nanocrystal.’

Under infrared illumination, these SuperDots selectively produce bright blue, red and infrared light, with a thousand times more sensitivity than existing materials.

‘Neither the glass of the optical fibre nor other background biological molecules respond to infrared, so that removed the background signal issue. By exciting these SuperDots we were able to lower the detection limit to the ultimate level – a single nanoparticle,’ Jin said in a statement.