To bioprobes, and beyond

28 May 2020:

When the Reserve Bank of Australia wanted to develop new security technologies for bank notes, Prof Jim Piper’s Advanced Imaging research group in the ARC Centre of Excellence for Nanoscale BioPhotonics (CNBP) at Macquarie University had an answer: timecoded nanoparticles.

Prof Piper and his team could code the fading glow of nanoparticles after exciting them with a pulse of invisible light. This new technology was promising — it would enable infinite possibilities for codes within the inks of bank notes, making it almost impossible to counterfeit them.

However, there was one problem: the nanoparticles were produced manually, and, even though each batch followed the same recipe to the tee, the batches didn’t match. Timecoding was then, also, inconsistent.

‘We needed to get control over the growth of the nanoparticles,’ Prof Piper said.

An example of the ink lighting up under a scanner (credit: MOS Technologies)

But what was a biophotonics team doing working on security technology in the first place?

Rewind a bit, and, as with the start of most good science stories, the team were working on something entirely different when they discovered that nanoparticles could be timecoded at all.

The CNBP’s main focus is developing light-based imaging and sensing tools that can measure the inner workings of living cells within the human body.

‘We were working with biomedical applications, with bioprobes that could analyse a sample for a whole lot of things at the same time,’ Prof Piper said.

Up until then, the signatures needed for each of the probes had been done primarily with colours.

‘But this has a very limited number of choices,’ Prof Piper said. He explains some wavelengths were too broad, making it difficult to distinguish some of the bioproperties.

It was in the search for materials that could provide time signatures that then-PhD students at the CNBP, Jiangbo Zhao and Yiqing Lu*, came across the timecodable properties of nanoparticles.

‘And, as it turns out, this has a lot of different applications,’ Prof Piper said.

With support from industry partner MOS Technologies, Macquarie University, and AusIndustry, the CNBP’s Dr Xianlin Zheng* led the laboratory program responsible for developing a unique automated growth technology. This enabled the highly reproducible production of colour and timecoded nanoparticles that could be used in security inks and applied to almost any material.

Their innovations led to an Australian Research Council grant in April 2020, to support the work of refining the process of growing the nanoparticles consistently, efficiently and cost-effectively on a commercial scale, and introducing timecoded products.

The technology has the potential to not only detect human disease, but to defeat sophisticated counterfeit operations — highlighting the wide-ranging impacts of the CNBP.

*Drs Yiqing Lu and Xianlin Zheng hold independent Faculty positions and are associate investigators of CNBP and co-investigators of the ARC research grant.