Antibiotic levels can be measured in the breath

Researchers from the University of Freiburg have shown that the concentration of antibiotics in the body can be determined using a biosensor that measures breath samples. Their work has been published in the journal Advanced Materials.

Physicians need to keep antibiotics level within a personalised therapeutic range for patients suffering severe infections, at the risk of threats such as sepsis and organ failure or even the death of the patient. Inadequate administration of antibiotics could also allow bacteria to mutate so that the medicines no longer work. The team’s biosensor — a multiplex chip that allows simultaneous measurement of several specimens and test substances — should thus enable personalised dosing of medicines against infectious diseases and help to minimise the development of resistant strains of bacteria.

The microfluidic biosensor bears synthetic proteins that can recognise beta-lactam antibiotics such as penicillin, affixed to a polymer film. Antibiotics of interest in the sample and an enzyme-coupled beta-lactam are in competition to bind these bacterial proteins. This competition generates a current change, like in a battery: the more antibiotic there is present in the sample, the less enzyme product develops, which leads to a lower measurable current. The process is based on a natural receptor protein that resistant bacteria use to detect the antibiotics that threaten them.

“You could say we are beating the bacteria at their own game,” said Prof Dr Wilfried Weber, co-leader of the research group.

The researchers tested the biosensor on the blood, plasma, urine, saliva and breath samples of pigs who had received antibiotics; the results achieved with the pigs’ plasma were as accurate as the standard medical laboratory process, the researchers found. Furthermore, measurement of antibiotic levels in exhaled breath samples was not previously possible.

“Until now, researchers could only detect traces of antibiotics in the breath,” said research co-leader Dr Can Dincer. “With our synthetic proteins on a microfluidic chip, we can determine the smallest concentrations in the breath condensate and they correlate with the blood values.”

Research co-leader H Ceren Ates concluded that “rapid monitoring of antibiotic levels would be a huge advantage in hospital”, and that “it might be possible to fit the method into a conventional face mask”. Clinical trials to validate the antibiotic biosensor by testing it with human samples are now being planned.

Image caption: The microfluidic multiplex biosensor carries proteins attached to a polymer film that recognise the antibiotics. Image credit: Patrick Seege.

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