Indian scientists develop low-cost paper biosensor for rapid disease detection 

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The cost of fabricating the paper disc for testing was Rs. 1 or 0.015 USD!

In an attempt to simplify disease diagnosis at the grassroot level, researchers from the Indian Institute of Science (IISc), India have developed a cheap, easy-to-handle single-step sensor that detects lipase, an enzyme associated with several cardiac and liver diseases.

Biosensors are devices used to detect specific biomolecules (often present in samples such as tissues, blood or microorganisms) through their interaction with a chemical, which is usually measured in terms of a light or electrical output. However, more often, such detection systems and chemicals involved in the assay prove to be extremely expensive. Due to practical limitations such as time, cost, space, maintenance, and handling especially during field work in areas with limited resources, developing low-cost detection systems has gained momentum in recent times.

Professor Uday Maitra and his student Tumpa Gorai have fabricated a user-friendly paper-based biosensor that detects the presence of the pancreatic enzyme lipase and can be rapidly quantified by measuring the color change (photoluminescence). Lipase breaks down complex fats into simpler fatty acids and glycerol during digestion and is required only in limited quantities for normal digestive function. Higher lipase levels could be indicative of damage to the pancreas, often leading to further complications in other vital organs.

“Enzymes are one of the important target bioanalytes in the field of biosensors as they play crucial roles in the regulation of metabolic functions in living systems. The detection of enzyme activity through an efficient and simple design is, therefore, of utmost importance. Our lab has fabricated a low-cost paper biosensor that rapidly detects the presence of lipase, a pancreatic enzyme, which breaks down fats into smaller molecules called fatty acids and glycerol during the process of digestion,” said the researchers.  

The biosensor comprises a paper disc, embedded within which is a gel, made with Terbium — a rare earth metal — and doped with a synthetic enzyme substrate. As the disc comes in contact with lipase, it turns green as the Terbium gets illuminated by photoexcitation under UV light.

On digestion of synthetic substrate by lipase, the product interacts with Terbium which in turn glows on 'photoexcitation' by UV light. Source: The Indian Institute of Science.
The schematic of how the paper disc detects lipase. When lipase breaks down the synthetic substrate, the resulting product interacts with Terbium, which in turn glows on ‘photoexcitation’ by UV light. Source: The Indian Institute of Science.

The use of paper as the base material has proven to be extremely advantageous in terms of availability, chemical absorptivity, cost effectiveness, portability, ease of fabrication, and biodegradability. The team adds that it requires very low volumes of biological samples for analysis and the strategy has potential uses in clinical applications.

“The advantage with this system is that the entire sensing material is integrated on the paper surface in a single step. The material cost for the disc fabrication was calculated to be less than Rs 1, so it is a low-cost luminescent assay system. This simple paper-based sensor is useful for detecting the presence of enzymes in real samples, and for rapid screening of an inhibitor. We are currently expanding the scope of this enzyme assay,” said the findings.

The original results were published in ACS Sensors.

Sources: The Times of India, The Better India