BENGALURU: Scientists from the Indian Institute of Science (IISc) have developed a simple, glowing paper sensor that could help detect liver cancer early — using the green glow of a rare earth metal called terbium.The sensor works by detecting an enzyme called “β-glucuronidase”, which is found in many living organisms. While it has normal biological roles, high levels of this enzyme are linked to liver cancer, as well as colon, breast, and kidney cancers, and even infections and AIDS.“Traditional detection methods often struggle with background noise or low sensitivity,” said Ananya Biswas, a former PhD student and co-author of the study published in Chemistry. “But terbium has a unique ability — it glows for longer periods, helping us cut through the noise and get a clearer signal,” she added.IISc said the project began nearly 10 years ago when researchers studied metal ions and their gel-forming abilities. They found that terbium, when embedded in a gel made from bile salts, gives off a bright green glow under ultraviolet (UV) light.“To create the sensor, the team added a special organic molecule — 2,3-DHN — coated with a sugar acid called glucuronic acid. This coating keeps it ‘switched off’. But when β-glucuronidase is present, it cuts away the coating, releasing the active molecule. When UV light is shone on the sample, the molecule absorbs the energy and passes it on to the nearby terbium, boosting its green glow,” IISc said.The researchers embedded this glowing gel onto small paper discs, turning it into an easy-to-use sensor. When exposed to samples with β-glucuronidase, the disc glows brighter under UV light.Unlike expensive lab equipment, this sensor can be read using a simple UV lamp and free software called ‘ImageJ’, making it ideal for low-resource settings, IISc said, adding that the sensor can detect enzyme levels as low as 185 nanograms per millilitre — well below the levels usually seen in serious liver disease.Though further clinical trials are needed, researchers believe the sensor could be a low-cost tool for detecting not just liver cancer, but other conditions linked to the enzyme, including jaundice and drug toxicity.