Plastic sensors could monitor health conditions

An international team of researchers have developed a low-cost sensor made from semiconducting plastic that can be used to diagnose or monitor a wide range of health conditions, such as surgical complications or neurodegenerative diseases. Described in the journal Science Advances, the new device has a simpler design than existing sensors and opens up new possibilities for health monitoring down to the cellular level.

Semiconducting plastics are currently being developed for use in solar cells and flexible electronics, but have not yet seen widespread use in biological applications. That could all be about to change, thanks to the new work led by the University of Cambridge and King Abdullah University of Science and Technology (KAUST).

“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 at the University of Cambridge. “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, Dr Pappa and her colleagues used a newly synthesised polymer developed at Imperial College 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 to traditional sensors made of metal electrodes.

Additionally, when the sensors are incorporated into more complex circuits, such as transistors, the signal can be amplified and respond to tiny fluctuations in metabolite concentration, despite the tiny size of the devices.

Initial tests of the sensors 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, and the concentration range that the sensor can detect 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: this hasn’t been straightforward until now,” said Dr 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.”

Since the sensor does not consist of metals such as gold or platinum, it can be manufactured at a lower cost and can be easily incorporated in flexible and stretchable substrates, enabling their implementation in wearable or implantable sensing applications.

“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 Dr Pappa.

The researchers now plan to develop the sensor to monitor metabolic activity of human cells in real time outside the body. The Bioelectronic Systems and Technologies group where Dr Pappa is based is focused on developing models that can closely mimic our organs, along with technologies that can accurately assess them in real time, and the sensor technology could be used with these models to test the potency or toxicity of drugs.

This is a modified version of a news item published by the University of Cambridge under CC BY 4.0.

Image caption: The polymer biosensor. Image credit: KAUST.