Gianfranco Giubileo

Laser sensors for trace gases in human breath

Ethylene and ethane as biomarkers for lipid peroxidation in humans can be detected in the exhaled breath by means of very sensitive gas sensors based on high-resolution molecular spectroscopy. To this purpose, a laser photoacoustic spectroscopy sensor (PAS) for online ethylene monitoring and a tunable diode laser absorption spectroscopy sensor (TDLAS) for ethane detection were developed at ENEA Frascati Molecular Spectroscopy Laboratory. The sensors have been calibrated by certified mixtures. The main advantages of the breath analysis by spectroscopic technique are the high sensitivity and the absolutely non-invasive character. During an experimental study in cooperation with Umberto I Hospital (Radiology Institute) of Rome, we were able to detect very low concentrations (under 1 ppb) of trace ethylene content in the air exhaled by patients, following X-ray therapy; results are reported in this article.

Medical diagnostics by laser-based analysis of exhaled breath

IMany trace gases can be found in the exhaled breath, some of them giving the possibility of a non invasive diagnosis of related diseases or allowing the monitoring of the disease in the course of its therapy. In the present lecture the principle of medical diagnosis based on the breath analysis will be introduced and the detection of trace gases in exhaled breath by high- resolution molecular spectroscopy in the IR spectral region will be discussed. A number of substrates and the optical systems for their laser detection will be reported. The following laser based experimental systems has been realised in the Molecular Spectroscopy Laboratory in ENEA in Frascati for the analysis of specific substances in the exhaled breath. A tuneable diode laser absorption spectroscopy (TDLAS) appartus for the measurement of 13C/12C isotopic ratio in carbon dioxide, a TDLAS apparatus for the detection of CH4 and a CO2 laser based photoacoustic system to detect trace ethylene at atmospheric pressure. The experimental set-up for each one of the a.m. optical systems will be shown and the related medical applications will be illustrated. The concluding remarks will be focuses on chemical species that are of major interest for medical people today and their diagnostic ability.

Fluorescence spectroscopy of normal and follicular cancer samples from human thyroid

An autofluorescence analysis has been performed on healthy as well as tumour thyroid tissue samples to distinguish follicular cancer from normal thyroid. Complete spectra and synchronous spectra have been recordered from properly stored samples. Fluorescence bands located at 350 nm and 400 nm has been observed in the analysed cancer samples.

Identification of standard explosive traces by infrared laser spectroscopy: PCA on LPAS data

Infrared spectroscopy based methods are promising in the design of an integrated optical system for the real time detection and identification of explosive species to support homeland security. Infrared laser photoacoustic spectroscopy (LPAS) analysis of explosive compounds (DNT; TNT; RDX; HMX; TATP; PETN; TETRYL) and TOLUENE was reported. Standard commercial samples of the explosive species were analyzed in solid phase by a home made PAS apparatus equipped with a stabilized 10 W continuous wave CO2 laser source. A very small amount (less than 100 μg) of the sample was sufficient to produce a clear signal in a 3 cc volume PA cell. The spectral data were treated by a principal component analysis (PCA) based algorithm. In a three principal components representation of the results, every explosive species resulted to be very well distinguishable from each other, as well as from toluene and other solvents. The reported experimental activity was performed in the Molecular Spectroscopy Laboratory of ENEA Research Centre in Frascati in the frame of ISOTREX European Project.

Investigation of human biomarkers in exhaled breath by laser photoacoustic spectroscopy

The paper underlines the importance of breath tests in medicine and the potential of laser techniques to measure in-vivo and in real time human biomarkers. The presence of trace amounts of gases or the metabolites of a precursor in exhaled air could be linked to kidney or liver malfunction, asthma, diabetes, cancer, ulcers or neurological disorders. The measurement of some human biomarkers (ethylene, ammonia), based on laser photoacoustic spectroscopy methods, insure very high sensitivity and selectivity. The technical characteristics of this instrument were measured to determine the detection limits (sub-ppb for ethylene). The results of ethylene release following lipid peroxidation initiated by X-ray irradiation or ingestion of radioactive compounds are presented. The possibility to extend this technique for measurement of breath ammonia levels in patients with end-stage renal disease while they are undergoing hemodialysis is discussed.

Detection of ethylene in smokers breath by laser photoacoustic spectroscopy

In the experiments reported in this paper small traces of ethylene down to ppb level have been detected by means of photoacoustic spectroscopy in the breath exhaled from humans. The method has been applied in studying how the concentration of the ethylene coming out from human lungs is modified after smoking. We followed up the evolution of ethylene concentration in the case of several people by monitoring the ethylene before and after smoking. In each case the first exhaled air sample was collected prior smoking the cigarette and compared with the samples collected after 30 minutes following the inhalation of cigarette smoke. In all the experiments a high value of ethylene concentration was found immediately after smoking. The experimental laser based photoacoustic system has been realized in ENEA Laboratories in Frascati, Italy.

Detection of ethylene traces by photoacoustic spectroscopy

A laser based photoacoustic system has been designed and built at ENEA in order to monitor bio-gases produced in different processes involving living cells. Experiments aimed to reveal traces of ethylene emitted from tomato plantlets and fruits under temperature stress are here presented and discussed.

Laser photoacoustic spectroscopy: A powerful tool for measurement of trace gases of biological interest at sub-ppb level

A high sensitive photoacoustic system has been developed to monitor trace gases released by biological samples at concentrations of sub-ppb level. We have applied this technique to measure the release of the plant hormone ethylene during seed germination and ripening of climacteric fruits and of the marker ethylene as a result of doping cultures of human cells with heavy metals, of damaging living organisms by ionising radiation(X-ray)and of unleashing lipid peroxidation in lung epithelium following the inhalation of cigarette smoke.

Laser based assessment of lipid peroxidation in humans.

Infrared absorption spectroscopy can be performed at very high resolution by tunable diode laser (TDL) based optical systems for any gas with well resolved absorption spectra. In a double beam setup atmospheric trace gas concentration can be measured down to ppb levels. The analysis of trace gases may have useful applications in detecting chemicals in the human breath for non invasive medical diagnostic. The capability of TDL based breath analysis was well demonstrated by monitoring ammonia and methane. In the human body the formation of free radicals does induce oxidative degradation of polyunsaturated fatty acids (lipid peroxidation) which is a damage for cells and organs in the organism. Specific volatile hydrocarbons generated as end product by lipid peroxidation (LP) can be found inside circulating blood and expired breath. TDL based analysis of those specific hydrocarbons (ethane and pentane) in the expired breath can allow a non invasive assessment of the LP extent.

Comprehensive Infrared Study of Tetryl, Dinitrotoluene, and Trinitrotoluene Compounds.

The present work describes an experimental and theoretical study of energetic materials used for detecting explosives in order to prevent terrorist actions, as well as for de-mining projects. Particular attention was devoted to examining the infrared absorption spectroscopy of classic explosives in order to create a useful mobile apparatus for on-field detection of explosives. This paper reports the vibrational absorption spectra of tetryl, dinitrotoluene, and trinitrotoluene molecules approached using two different spectroscopic techniques, Fourier transform infrared spectroscopy (FT-IR) and laser photoacoustic spectroscopy (LPAS). Diffuse reflectance Fourier transform infrared spectra of all samples were analyzed in a very wide spectral range (400–7500 cm−1) showing for the first time the existence of weak absorption bands attributable to overtones or combination bands, while laser photoacoustic spectroscopy spectra have been investigated in the fingerprint region of organic compounds that share the CO2 laser emission range (∼920–1100 cm−1). The Fourier transform infrared spectra of both matrix isolated dinitrotoluenes have been also investigated. The theoretical treatment of tetryl is reported for the first time.