[Detection of disease markers in the breath using optoelectronic methods]

Great interest of scientific community is observed recently over non-invasive tests methods dedicated to diagnose disease states using biomarkers. The ability to detect these substances in the human breath can provide valuable information about disorder of biochemical processes in the body. Breath analysis is non-invasive, painless and can provide a quick answer about the existence of the disease. In addition, the sampling process is carried out comfortably for both the patient and the medical staff.

The aim of the study was to present opportunity of application the optoelectronic methods for screening tests in medical diagnostics. The results of the researches carried out at the Institute of Experimental Physics, Department of Physics UW and at the Institute of Optoelectronics MUT are presented.

For the detection of methane and ammonia in breath the Multipass Spectroscopic Absorption Cells (MUPASS ) were used. In the case of nitric oxide and ethane observation, Cavity Enhanced Absorption Spectroscopy (CEAS) was applied. During the investigation modern tunable and sophisticated infrared radiation sources were used: single mode diode lasers (for CH4, NH3 detection), quantum cascade laser (NO sensing), and optical parametric generator (PG711/DFG) for ethane measurements. The investigations of developed sensors were conducted with use of reference samples of biomarkers, which were prepared with gas standards generator 491M from KIN-TEK company.

Experiments showed that sensitivities of the sensors are suitable for human breath analyzing. In case of methane sensor, the detection limit (sensitivity) of ~ 0.1 ppm was obtained. This value is significantly lower than the upper limit of methane concentration in the breath of healthy humans (10 ppm). Therefore, our system well satisfies the requirements for diseases screening (e.g. intestines diseases ) and for methane monitoring in healthy human breath. Ammonia sensor is characterized with linear response in the concentration range higher than 1 ppm. The upper limit of ammonia concentration in healthy human breath is approx. 2 ppm, so this system is well suited for the determination of disease states (e.g. liver diseases). During the observation of nitrogen oxide the detection limit of 30 ppb was obtained. According to the ATS recommendation such NO detection limit is sufficient to monitor people's health state and for the detection of respiratory diseases like asthma or chronic bronchitis. For ethane detection with a wavelength of 3.348 microns the detection limit of 20 ppb was obtained.

Developed sensors are characterized by high sensitivity (ppb-level) and high selectivity, simple and fast measurement procedure. Therefore, they can be applied as medical screening tools enabling biomarkers detection in exhaled air at the molecular level.