Researchers have developed a low-cost sensor made from semi-conducting plastic that can be used to diagnose or monitor a wide range of health conditions, such as surgical complications or neuro-degenerative diseases.

The results, published in the journal Science Advances, suggest that the new device has a far simpler design than the existing ones, and opens up a wide range of new possibilities for health monitoring down to the cellular level. The researchers found that the sensor can measure the amount of critical metabolites -- such as lactate or glucose -- that are present in sweat, tears, saliva or blood. Also, when incorporated into a diagnostic device, it could allow health conditions to be monitored quickly, cheaply and accurately.

"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 lead author Anna-Maria Pappa from the University of Cambridge. For the study, the researchers used a newly-synthesised polymer that acts as a molecular wire, directly accepting the electrons produced during electrochemical reactions.

Initial tests of the sensors were used to measure levels of lactate, which is useful in fitness applications and to monitor patients post-surgery. However, 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.

"In our work, we've overcome many of the limitations of conventional electrochemical biosensors that incorporate enzymes as the sensing material," Pappa said. "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," she added.