AsianScientist (Nov. 16, 2015) – Diabetic patients have to monitor blood glucose regularly and frequently, but conventional method of taking blood sample for measuring glucose level is painful. In a study published in Advanced Materials, researchers from the Hong Kong Polytechnic University (PolyU) describe their newly developed biosensor that can measure glucose levels in saliva, saving patients the pain of regular blood draws.
The biosensor developed is fabricated with a glucose oxidase enzyme (GOx) layer, which is sensitive to glucose alone and nothing else. By detecting the electrical current, the glucose level can be known.
However, the GOx layer could face interference from other biological elements in saliva, such as dopamine, uric acid and ascorbic acid. To block such interference, researchers have coated Polyaniline (PANI) / Nafion-graphene bilayer films between the top enzyme layer and gate electrode. The strong adhesion of this top layer to the GOx layer enables the latter to stabilize and perform well in glucose detection.
The highly sensitive biosensor showed a detection lower limit of 10-5 mmol/L, which is nearly 1,000 times more sensitive than the conventional devices for measuring blood glucose. This is equivalent to detecting as little as five grams of glucose in a standard swimming pool of 50 m x 25 m x 2 m.
Between the wide range of glucose level from 10-5 mmol/L up to 10 mmol/L (equivalent to 5 g – 5,000 Kg of glucose in a standard swimming pool), the biosensor demonstrates linear response, which is suitable for measuring the possible range of glucose in the human body. The accuracy of the biosensor was determined through laboratory experiments with repeatable results using glucose solutions of known glucose levels.
The glucose biosensor is fabricated with flexible substrates that can be used in a variety of curved and moving surfaces, including human skin, smart textiles and medical bandages. Thus, it has great potential for development into wearable electronic applications, such as a wearable biosensor for the analysis of glucose levels in sweat during exercise.
It can also be mass produced at a low cost of HK$3 to 5 (US$0.40 to 0.65) per test chip, which is comparable or even cheaper than the currently available commercialized products. In addition, this newly invented transistor-based biosensor platform is highly versatile. By changing to suitable enzymes, the platform can be used to measure the level of uric acid and other materials in saliva. For instance, if the biosensor is fabricated with enzyme uricase (UOx) and Polyaniline (PANI) / Nafion-graphene bilayer films, the platform can specifically be sensitive to uric acid only and other interference signals can be blocked.
The article can be found at: Liao et al. (2015) Flexible Organic Electrochemical Transistors for Highly Selective Enzyme Biosensors and Used for Saliva Testing.
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Source: Hong Kong Polytechnic University.
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