Key Points

The team focussed on the potential of terbium -- a rare earth metal -- to develop a unique luminescent probe that can sense the presence of an enzyme called beta-glucuronidase.

While its core function is to break down a sugar acid called glucuronic acid, the enzyme also doubles as a critical biomarker for liver cancer.

An increase in beta-glucuronidase levels has been associated with the risk of colon, breast, and renal cancers, as well as infections of the urinary tract and AIDS.

Thus, the novel sensor offers a potentially powerful screening tool against different types of cancers, neonatal jaundice, and NSAID-induced toxicity, said the researchers.

“Conventional methods of colorimetry and fluorescence for detecting such enzymes are often restricted by sensitivity or interference from background signals. The ability of rare earth metals to have long-lived excited states allows us to filter out short-lived background fluorescence, resulting in a much clearer signal,” said Ananya Biswas, former PhD student at IISc and co-first author of the paper published in the journal Chemistry, on Monday.

The innovation began with research into the gel-forming properties of metal ions. The IISC team discovered that terbium ions, when incorporated into a gel matrix derived from bile salts, emitted a bright green glow.

To this, the researchers added a molecule called 2,3-DHN ((2,3-Dihydroxynaphthalene), masked with glucuronic acid.

In the presence of beta-glucuronidase, terbium ions cleave the mask, releasing 2,3-DHN, which then acts as an “antenna,” absorbing UV light. It also transfers energy to nearby terbium ions, amplifying the green fluorescence, explained Uday Maitra, Professor in the Department of Organic Chemistry, IISc.

Further, to make the technology accessible, the team embedded the gel matrix onto paper discs, creating a simple and portable sensor.

Exposing the samples containing beta-glucuronidase, these discs emitted a pronounced green glow under UV light.

These sensors could also be analysed using a UV lamp and ImageJ -- an open source, freely accessible software, making this technique ideal for resource-limited settings, the team said.

The sensor showed a detection limit, which was significantly below the beta-glucuronidase levels typically seen for cirrhosis -- an advanced stage of liver disease.

While more clinical studies are needed to validate the findings, such sensors can bring down the cost of detecting clinically significant biomarkers, the researchers said.

- IANS