Shining a light on small diseased tissues

Singaporean researchers have created polymer nanoagents that can ‘light up’ tiny areas of diseased tissues that conventional methods fail to detect. Described in the journal Nature Biotechnology, the nanoagents can store light energy from sources such as sunlight, near-infrared light or even light from mobile phones, and then emit long-lasting ‘afterglow light’.

Led by Nanyang Technological University, Singapore (NTU Singapore), the research team tailored highly sensitive nanoagents known as semiconductor polymer nanoparticles (SPNs) to track down and lock on to diseased tissues in the body, such as cancerous cells, sending back near-infrared signals which can be received and interpreted by standard imaging equipment.

The result is that scientists and doctors now have more time to look at test results, as the nanoagents continue self-illuminating and their light intensity decreases by half only after 6 min. Alternatively, if stored at -20°C, the sample will maintain its results for a month, making it convenient for other diagnostic experts to interpret and review the results at a later time.

When tested in mice, the method provided results 20 to 120 times more sensitive than current optical imaging methods and 10 times faster in showing up diseased tissues. Furthermore, unlike conventional optical afterglow agents that are less bright and contain rare-earth heavy-metal ions that are toxic to biological cells, the nanoagents are organic, biodegradable and contain biologically benign ingredients that are non-toxic.

“The new polymer nanoagents we have designed and built show a great deal of promise for clinical applications,” said NTU Associate Professor Pu Kanyi, who led the research team. “They can detect diseased tissue much faster than current optical imaging techniques, and are much safer to use.

“We hope this may lead to technology that allows doctors to diagnose and treat patients much earlier than is possible at present. Potential use may be in image-guided surgery, where surgeons could use the technology to help them precisely remove diseased tissues in real time.”

Associate Professor Pu Kanyi and his research team. Image credit: NTU Singapore.

The technology can also be used to evaluate the behaviour and therapeutic outcomes of drugs in the body; for example, whether drugs induce liver damage as a side effect. Drug-induced liver damage is one of the most common reasons that the US FDA withholds drug approval.

Evaluation of potential damage in advance of regulatory approval is challenging, as studies performed in a controlled environment outside of a living organism often have low predictive power of how the drug reacts inside the organism. Furthermore, existing methods only track activity at the tissue level.

The new technology, however, works at a molecular level, monitoring increased or decreased levels of biomarkers to determine how the drugs are working, before their therapeutic action is complete. This provides much greater predictive power for drug development.

The study took two years and a patent is currently being filed for the technology. The research team now intends to conduct further trials in larger animal models.

Top image caption: Nanoagents can be customised to be in different colours to facilitate tracking of more than one type of biomarker in the body. Image credit: NTU Singapore.