Plastic sensor enables low-cost medical monitoring and diagnostics

A low-cost sensor made from semiconducting plastic can be used to diagnose or monitor a wide range of health conditions, including surgical complications or neurodegenerative diseases. The sensor was developed by a research team led by the University of Cambridge in the United Kingdom and King Abdullah University of Science and Technology in Saudi Arabia (KAUST).

Plastic medical sensor
Image courtesy King Abdullah University of Science and Technology/University of Cambridge.

The sensor can measure the amount of critical metabolites, such as lactate or glucose, that are present in sweat, tears, saliva or blood, reports the University of Cambridge in a press release. When incorporated into a diagnostic device, the sensor could allow health conditions to be monitored quickly, cheaply and accurately. 

The researchers used semiconducting plastics that are being developed for use in solar cells and flexible electronics, but have not yet seen widespread use in biological applications. Since the sensor does not contain metals such as gold or platinum, it can be manufactured at a low cost and can be easily incorporated in flexible and stretchable substrates, enabling implementation in wearable or implantable sensing applications. The research is published in the journal Science Advances.

“In our work, we’ve overcome many of the limitations of conventional electrochemical biosensors that incorporate enzymes as the sensing material,” said lead author Dr Anna-Maria Pappa, a postdoctoral researcher in Cambridge’s Department of Chemical Engineering and Biotechnology. “In conventional biosensors, the communication between the sensor’s electrode and the sensing material is not very efficient, so it’s been necessary to add molecular wires to facilitate and ‘boost’ the signal.”

To build their sensor, Pappa and her colleagues used a synthesized polymer developed at Imperial College in London that acts as a molecular wire, directly accepting the electrons produced during electrochemical reactions. When the material comes into contact with a liquid such as sweat, tears or blood, it absorbs ions and swells, becoming merged with the liquid. This leads to significantly higher sensitivity compared with traditional sensors made of metal electrodes.

Initial tests of the sensor were used to measure levels of lactate, which is useful in fitness applications or to monitor patients following surgery. However, according to the researchers, the sensor can be easily modified to detect other metabolites, such as glucose or cholesterol, by incorporating the appropriate enzyme. The sensor’s detectable concentration range can be adjusted by changing the device’s geometry.

“This is the first time that it’s been possible to use an electron-accepting polymer that can be tailored to improve communication with the enzymes, which allows for the direct detection of a metabolite,” said Pappa. “It opens up new directions in biosensing, where materials can be designed to interact with a specific metabolite, resulting in far more sensitive and selective sensors.

“An implantable device could allow us to monitor the metabolic activity of the brain in real time under stress conditions, such as during or immediately before a seizure and could be used to predict seizures or to assess treatment,” said Pappa.

The researchers now plan to develop the sensor to monitor metabolic activity of human cells in real time outside the body. 

The research was funded by the Marie Curie Foundation, the KAUST Office of Sponsored Research, and the Engineering and Physical Sciences Research Council. 

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