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Lab-on-a-chip detects ammonia in human breath

May 28, 2004

A lab-on-a-chip that is sensitive enough to detect just a tiny ammount of ammonia in human breath has been developed by Björn Timmer of University of Twente in The Netherlands. Ammonia is an indicator for the development of a bacterial infection in the stomach. The tiny dimensions of this lab-on-a-chip have several advantages: it just needs a tiny sample, it is fast, and a compact handheld analyzer can be built. Timmer has finished his PhD research on this system within MESA+ research institute, on May 28. The concentration of ammonia in human breath provides the doctor with information about the presence of the bacterium Helicobacter Pyloris in the stomach. This could lead to an ulcer. The bactery disturbs the ureum household in the body, and this change can be detected. The present ureum breath tests involve detecting CO2, as the marker for the bacterium. For this, the patient drinks a fluid containing some -radioactive or non-radioactive- ureum. In case of the radioactive C14-ureumtest, the CO2 exhaled is radioactive as well. Although these tests are far more comfortable than the old methods using a tube in the stomach, they are quite expensive, not very fast and available at just a limited number of hospitals. An alternative should be fast, very sensitive and relatively cheap. The ammonia detectors available, e.g. for environmental monitoring are in fact too large and slow; apart from that they need quite a volume to do the analysis. Miniaturization is the key word there. Timmer has combined all the necessary components on one single chip. This reduces the detection time from twenty minutes to about one minute, and a 100 times smaller sample will suffice. For this, components of the detected gas are mixed with fluid and subsequently they are separated. The electrical conductivity of the separate fluid channels will be different, and by measuring this the concentration of ammonia can be deduced. The system is sensible enough for breath analysis. And selective enough, as well: as breath has a higher concentration of carbon dioxide than air, the selectivity of the system must be high. Björn Timmer did his research within the BIOS Lab-on-a-chip Group of prof. Albert van den Berg. This group is part of the MESA+ Institute for Nanotechnology of the University of Twente.

Twente, University of