M. Mürtz

Mid-infrared cavity leak-out spectroscopy for ultrasensitive detection of carbonyl sulfide

We present a ringdown absorption spectrometer based on a continuous-wave CO laser in the mid-infrared spectral region near lambda = 5 microm. Using a linear ringdown cavity (length, 0.5 m) with R > = 99.99% mirrors, we observed a noise-equivalent absorption coefficient of 7 x 10(-11) cm(-1) Hz(-1/2). This is 2 orders of magnitude improved compared with previous values. With this setup we studied the spectroscopic detection of carbonyl sulfide (here abbreviated OCS) traces in ambient air and in exhaled breath. We achieved a detection limit of 7 parts in 10(12) (parts per trillion) OCS in ambient air, which is unprecedented and shows great promise for environmental and biomedical applications.

Time resolved simultaneous detection of 14NO and 15NO via mid-infrared cavity leak-out spectroscopy

We present a ring-down absorption spectrometer based on a continuous-wave CO laser in the mid-infrared spectral region near λ = 5 μm. Using a linear ring-down cavity (length: 0.5 m) with high reflective mirrors (R = 99.988 %), we observed a noise-equivalent absorption coefficient of 3 × 10−10 cm−1Hz−1/2. This corresponds to a noise-equivalent concentration of 800 parts per trillion (ppt) for 14NO and 40 ppt for 15NO in 1 s averaging time. We achieve a time resolution of 1 s which allows time resolved simultaneous detection of the two N isotopes. The δ15N value was obtained with a precision of ±1.2‰ in a sample with a NO fraction of 11 ppm. The simultaneous detection enables the use of 15NO as a tracer molecule for endogenous biomedical processes.

Dermal Application of Nitric Oxide In Vivo: Kinetics, Biological Responses, and Therapeutic Potential in Humans

Many local hemodynamic and vascular disorders may be the result of impaired bioavailability of nitric oxide (NO). Previous findings point to a therapeutic potential of dermal NO application in the treatment of hemodynamic disorders, but no reliable data are available on the mechanisms, kinetics, or biological responses relating to cutaneous exposure to NO in humans in vivo. Here we show that, owing to its excellent diffusion capacity, cutaneously applied NO rapidly penetrates the epidermal barrier in significant amounts, strongly enriching skin tissue and blood plasma with its vasoactive derivates. In parallel, it significantly increased vasodilatation and blood flow and reduced thrombocyte aggregation capacity. Data presented here for the first time show that, in humans, dermal application of NO has strong potential for use in the therapy of local hemodynamic disorders arising from insufficient availability of NO or its bioactive derivates.

Mid-infrared laser spectroscopy for online analysis of exhaled CO.

Carbon monoxide (CO) detection in human breath is the focus of much research because of COs possible use as a marker molecule for different diseases. Detecting CO in human breath remains a tough challenge because of the low concentrations of CO (ppm range) that must be detected. Another problem is that many other molecules, which can be found in human breath, can interfere in these measurements. Additionally, a time resolution of less than 1 s is needed to resolve the CO curve of an exhalation. In this study (13)CO instead of (12)CO concentration is measured. The measurements are performed with a cavity leak-out spectroscopy system. The systems properties match the above-mentioned specifications for measurements, even of the rare isotopologue with high specificity, a time resolution of less than 1 s and a detection limit of 7 ppb Hz(-1/2). Two investigations are presented here. The first is a measurement showing intraday changes between 9.5% and 23.3% of the exhaled CO level due to vigorous exercise. The second shows a long-term observation of the CO base level revealing natural variations in the recorded CO concentration. The covered time period is 25 weeks during which the differences between the minimum and maximum CO levels for each test case reached 84%.

Online Monitoring of Exhaled Breath Using Mid-Infrared Laser Spectroscopy

This review describes the merits of laser-assisted analytical instrumentation for biomedical diagnostics. In particular, we present an overview of the recent progress on spec- troscopic online monitoring of exhaled breath with mid-infrared coherent sources. The current detection limits of laser spectroscopic approaches are in the picomolar to nanomolar range, de- pending on the molecular compound. The time resolution of the measurements is down to the sub-second range. This very high sensitivity and time resolution open up exciting perspectives for novel analytical tasks in biomedical research and clinical diagnosis.

Dermal application of nitric oxide releasing acidified nitrite-containing liniments significantly reduces blood pressure in humans

Vascular ischemic diseases, hypertension, and other systemic hemodynamic and vascular disorders may be the result of impaired bioavailability of nitric oxide (NO). NO but also its active derivates like nitrite or nitroso compounds are important effector and signal molecules with vasodilating properties. Our previous findings point to a therapeutical potential of cutaneous administration of NO in the treatment of systemic hemodynamic disorders. Unfortunately, no reliable data are available on the mechanisms, kinetics and biological responses of dermal application of nitric oxide in humans in vivo. The aim of the study was to close this gap and to explore the therapeutical potential of dermal nitric oxide application. We characterized with human skin in vitro and in vivo the capacity of NO, applied in a NO-releasing acidified form of nitrite-containing liniments, to penetrate the epidermis and to influence local as well as systemic hemodynamic parameters. We found that dermal application of NO led to a very rapid and significant transepidermal translocation of NO into the underlying tissue. Depending on the size of treated skin area, this translocation manifests itself through a significant systemic increase of the NO derivates nitrite and nitroso compounds, respectively. In parallel, this translocation was accompanied by an increased systemic vasodilatation and blood flow as well as reduced blood pressure. We here give evidence that in humans dermal application of NO has a therapeutic potential for systemic hemodynamic disorders that might arise from local or systemic insufficient availability of NO or its bio-active NO derivates, respectively.

Laser Spectroscopic Online Monitoring of Volatile Diseasemarkers in Human Breath

We present an overview of the recent progress on spectroscopic online monitoring of exhaled breath with mid-infrared coherent sources. The current detection limits of laser spectroscopic approaches are in the picomolar to nanomolar range, depending on the molecular compound. The time resolution of the measurements is down to the sub-second range. This very high sensitivity and time resolution open up exciting perspectives for novel analytical tasks in biomedical research and clinical diagnosis.