Exhaled nitric oxide monitoring by quantum cascade laser: comparison with chemiluminescent and electrochemical sensors

Exhaled Biomarkers for Point-of-Care Diagnosis: Recent Advances and New Challenges in Breathomics

Cancers, chronic diseases and respiratory infections are major causes of mortality and present diagnostic and therapeutic challenges for health care. There is an unmet medical need for non-invasive, easy-to-use biomarkers for the early diagnosis, phenotyping, predicting and monitoring of the therapeutic responses of these disorders. Exhaled breath sampling is an attractive choice that has gained attention in recent years. Exhaled nitric oxide measurement used as a predictive biomarker of the response to anti-eosinophil therapy in severe asthma has paved the way for other exhaled breath biomarkers. Advances in laser and nanosensor technologies and spectrometry together with widespread use of algorithms and artificial intelligence have facilitated research on volatile organic compounds and artificial olfaction systems to develop new exhaled biomarkers. We aim to provide an overview of the recent advances in and challenges of exhaled biomarker measurements with an emphasis on the applicability of their measurement as a non-invasive, point-of-care diagnostic and monitoring tool.

Triphenylamine-embedded copper(II) complex as a "turn-on" fluorescent probe for the detection of nitric oxide in living animals

Nitric oxide (NO) is one of three major signaling molecules, which is involved in a large amount of physiological and pathological processes in biological systems. Furthermore, more and more evidence indicates that NO levels are closely associated with several aspects of human health. Accordingly, it is of great significance to develop a convenient and reliable detection method for NO in biological systems. In this work, a novel triphenylamine-embedded copper(II) complex (NZ-Cu²⁺) has been developed to be used as a fluorescence probe for the detection of NO in living animals. The proposed sensing mechanism of NZ-Cu²⁺ towards NO has been confirmed by high-resolution mass spectrometry, spectroscopic titration and density functional theory calculation. NO induced the conversion of paramagnetic Cu²⁺ to diamagnetic Cu⁺, which blocked the photoinduced electron transfer process of NZ-Cu²⁺, resulting in a remarkable enhancement of the emission spectra. The NZ-Cu²⁺ probe possesses several advantages including high selectivity, low detection limit (12.9 nM), long emission wavelength (640 nm), large Stokes shift (201 nm), fast response time (60 s) and low cytotoxicity. More importantly, NZ-Cu²⁺ has been successfully applied to detect NO in vivo by fluorescence imaging.

Measurement of Exhaled Nitric Oxide in 456 Lung Cancer Patients Using a Ringdown FENO Analyzer

The objective of this study was to investigate the clinical value of exhaled nitric oxide (NO) for diagnosing lung cancer patients by using a relatively large sample. An online and near-real-time ringdown exhaled NO analyzer calibrated by an electrochemical sensor at clinical was used for breath analysis. A total of 740 breath samples from 284 healthy control subjects (H) and 456 lung cancer patients (LC) were collected. The recorded data included exhaled NO, medications taken within the last half month, demographics, fasting status and smoking status. The LC had a significantly higher level of exhaled NO than the H (H: 21.0 ± 12.1 ppb vs. LC: 34.1 ± 17.2 ppb). The area under the receiver operating characteristic curve for exhaled NO predicting LC and H was 0.728 (sensitivity was 0.798; specificity was 0.55). There was no significant difference in exhaled NO level between groups divided by different types of LC, tumor node metastasis (TNM) stage, sex, smoking status, age, body mass index (BMI) or fasting status. Exhaled NO level alone is not a useful clinical tool for identifying lung cancer, but it should be considered when developing a diagnosis model of lung cancer by using breath analysis.

Monitoring of endogenous nitric oxide exhaled by pig lungs during ex-vivo lung perfusion

In the context of organ shortage for transplantation, new criteria for better organ evaluation should be investigated. Ex-Vivo Lung Perfusion (EVLP) allows extra-corporal lung re-conditioning and evaluation, under controlled parameters of the organ reperfusion and mechanical ventilation. This work reports on the interest of exhaled gas analysis during the EVLP procedure. After a one-hour cold ischemia, the endogenous gas production by an isolated lung of nitric oxide and carbon monoxide is simultaneously monitored in real time. The exhaled gas is analysed with two very sensitive and selective laser spectrometers developed upon the technique of optical-feedback cavity-enhanced absorption spectroscopy. Exhaled gas concentration measured for an ex-vivo lung is compared to the corresponding production by the whole living pig, measured before euthanasia. On-line measurements of the fraction of nitric oxide in exhaled gas (FENO) in isolated lungs are reported here for the first time, allowing to resolve the respiratory cycles. In this study, performed on 9 animals, FENO by isolated lungs range from 3.3 to 10.6 ppb with a median value of 4.4 ppb. Pairing ex-vivo lung and pig measurements allows to demonstrate a systematic increase of FENO in the ex-vivo lung as compared to the living animal, by a factor of 3 ± 1.2. Measurements of the fraction of carbon monoxide in exhaled gas (FECO) confirm levels recorded during previous studies driven to evaluate FECO as a potential marker of ischemia reperfusion injuries. FECO production by ex-vivo lungs ranges from 0.31 to 2.3 ppm with a median value of 0.8 ppm. As expected, these FECO values are lower than the production by the corresponding whole pig body, by a factor of 6.9 ± 2.7.

The comparision of two exhaled nitric oxide analyzers: NIOX VERO and SUNVOU-CA2122

BACKGROUND

As a marker of eosinophilic airway inflammation, fractional exhaled nitric oxide (FeNO) was widely used in clinical practice. NIOX VERO (VERO) and SUNVOU-CA2122 (CA2122) are two commonly used exhaled nitric oxide (eNO) analyzers in China. However, what's the difference and agreement between the two devices and whether the two types of devices can be replaced by each other in the application of common respiratory diseases have not been reported.

OBJECTIVES

The purpose of this study was to compare the two types of devices and to evaluate the difference between them in clinical use and whether they could be replaced.

METHODS

FeNO levels in 244 respiratory patients (including asthma, COPD, chronic cough) were measured by SUNVOU-CA2122 analyzer (CA2122) and NIOX VERO analyzer (VERO), respectively. FeNO values obtained by the two devices were compared and analyzed for the difference. The success rate, the number of attempts and the total time required for a successful measurement by CA2122 and VERO were compared. The FeNO values measured offline by CA2122 were compared with FeNO values measured online by CA2122 and VERO.

RESULTS

FeNO values obtained by CA2122 were slightly higher than those of VERO [median(range): 29.0(9-271) ppb vs 25.5 (5-263) ppb, P=0.000]. There was a high correlation between FeNO values measured by the two types of devices (r = 0.964, P= 0.000). By comparison, there was a high degree of agreement between the FeNO values measured by two devices, in all patients with different respiratory diseases. FeNO values measured online and offline by CA2122 were highly correlated and there was a high degree of agreement between online and offline methods. The success rate of CA2122 was higher than VERO, and the number of attempts (2.1 vs 2.4) and the total time (110.5±35.7 vs 117.5±48.1 seconds) required for a successful measurement by CA2122 were lower than those of VERO.

CONCLUSIONS

CA2122 and VERO can be replaced by each other, and FeNO values can be converted if necessary. CA2122 has some advantages in success rate, the mean attempts and time required for successful measurement of FeNO.

Cavity ringdown spectroscopy of nitric oxide in the ultraviolet region for human breath test

We report the spectrum of nitric oxide (NO) in the ultraviolet (UV) (225.4-227.0 nm) region based on cavity ringdown spectroscopy (CRDS). A cavity ringdown system, which consisted of a tunable UV laser source and a vacuum-pumped ringdown cavity, was constructed to measure NO at room temperature and atmospheric or reduced pressure. The measured spectra were validated using LIFBase simulations. The absorption cross-section of NO at the strongest absorption peak at 226.255 nm was measured to be 7.64 × 10^-18 cm² molecule^-1. Using the measured mirror reflectivity of 99.55% at 226.255 nm, the detection limit of NO was determined to be 7.4 ppb (parts per billion) based on the standard 3-σ criteria. The stability and reproducibility of this CRDS system were also tested. Furthermore, exhaled gas samples from 203 human subjects (105 healthy people and 98 lung cancer patients) were measured using the system. Results demonstrated that the cavity ringdown spectroscopy in the deep-UV region has potential for breath NO test.

Fractional Exhaled Nitric Oxide (FENO) in the management of asthma: a position paper of the Italian Respiratory Society (SIP/IRS) and Italian Society of Allergy, Asthma and Clinical Immunology (SIAAIC)

Asthma prevalence in Italy is on the rise and is estimated to be over 6% of the general population. The diagnosis of asthma can be challenging and elusive, especially in children and the last two decades has brought evidences that asthma is not a single disease but consists of various phenotypes. Symptoms can be underestimated by the patient or underreported to the clinician and physical signs can be scanty. Usual objective measures, like spirometry, are necessary but sometimes not significant. Despite proper treatment, asthma can be a very severe condition (even leading to death), however new drugs have recently become available which can be very effective in its control. Since asthma is currently thought to be caused by inflammation, a direct measure of the latter can be of paramount importance. For this purpose, the measurement of Fractional Exhaled Nitric Oxide (FE_NO) has been used since the early years of the current century as a non-invasive, easy-to-assess tool useful for diagnosing and managing asthma. This SIP-IRS/SIAAIC Position Paper is a narrative review which summarizes the evidence behind the usefulness of FE_NO in the diagnosis, management and phenotypization of asthma.

Clinical precision, accuracy, number and durations of exhalations for a novel electrochemical monitor for exhaled nitric oxide

BACKGROUND

Exhaled nitric oxide (FeNO) is a validated marker of eosinophilic inflammation. Fenom Pro^TM is a novel FDA-cleared monitor for FeNO. The American Thoracic Guidelines from 2005 recommend at least 6 s exhalation for adults and in some cases up to 10 s, and 4 s for children, and that the average of the first two valid exhalations is taken as the FeNO value.

METHODS

Clinical precision, 6 versus 10 s exhalations, the first versus the average of the first two valid exhalation methods comparison were evaluated for Fenom Pro^TM, as well as a methods comparison to the NIOX VERO^® monitor.

RESULTS

The intent-to-treat population (n = 126) consisted of 83 adults, and 43 pediatric subjects with 16 subjects under 12 years of age. Clinical precision for 10 s exhalations on Fenom Pro^TM was excellent with a within-subject standard deviation (SD) range of 0.57-3.73 ppb and mean coefficient of variation (CV) range of 4.21% to 9.65%. The clinical precision for the separate adult and pediatric groups as well as for the 6 s exhalations were similar. The 10 and 6 s exhalation comparisons and one versus the average of two valid exhalations showed a high level of agreement. The Fenom Pro^TM and the NIOX VERO^® monitors also demonstrated a high level of agreement with the values from the latter slightly lower (mean bias of -3.2 ppb).

CONCLUSION

Fenom Pro^TM demonstrated eminently acceptable performance supporting its clinical utility. The data suggests that 6 s exhalations can be used in adults and children, and that one exhalation is adequate rather than obtaining the average of two exhalations on Fenom Pro^TM.

Nitric Oxide Analysis Down to ppt Levels by Optical-Feedback Cavity-Enhanced Absorption Spectroscopy

Monitoring nitric oxide at the trace level is required in a large range of applications. We report on a trace gas analyzer optimized for nitric oxide measurements by Optical Feedback Cavity Enhanced Absorption Spectroscopy with an interband cascade laser at 5.3 µm. The short response time of the instrument allows for reaching the level of 50 ppt in only 180 ms. Its stability enables averaging up to 12 min to reach a detection limit of 0.9 ppt. Absolute concentration calibration requires to account for the optical saturation effect that results from the intense absorption line intensity addressed here, in the mid infrared region, in contrast to instruments that are operating in the near infrared region.

Ethylene, an early marker of systemic inflammation in humans

Ethylene is a major plant hormone mediating developmental processes and stress responses to stimuli such as infection. We show here that ethylene is also produced during systemic inflammation in humans and is released in exhaled breath. Traces of ethylene were detected by laser spectroscopy both in vitro in isolated blood leukocytes exposed to bacterial lipopolysaccharide (LPS) as well as in vivo following LPS administration in healthy volunteers. Exposure to LPS triggers formation of ethylene as a product of lipid peroxidation induced by the respiratory burst. In humans, ethylene was detected prior to the increase of blood levels of inflammatory cytokines and stress-related hormones. Our results highlight that ethylene release is an early and integral component of in vivo lipid peroxidation with important clinical implications as a breath biomarker of bacterial infection.

A European Respiratory Society technical standard: exhaled biomarkers in lung disease

Breath tests cover the fraction of nitric oxide in expired gas (F_eNO), volatile organic compounds (VOCs), variables in exhaled breath condensate (EBC) and other measurements. For EBC and for F_eNO, official recommendations for standardised procedures are more than 10 years old and there is none for exhaled VOCs and particles. The aim of this document is to provide technical standards and recommendations for sample collection and analytic approaches and to highlight future research priorities in the field. For EBC and F_eNO, new developments and advances in technology have been evaluated in the current document. This report is not intended to provide clinical guidance on disease diagnosis and management.Clinicians and researchers with expertise in exhaled biomarkers were invited to participate. Published studies regarding methodology of breath tests were selected, discussed and evaluated in a consensus-based manner by the Task Force members.Recommendations for standardisation of sampling, analysing and reporting of data and suggestions for research to cover gaps in the evidence have been created and summarised.Application of breath biomarker measurement in a standardised manner will provide comparable results, thereby facilitating the potential use of these biomarkers in clinical practice.

The measurement of DLNO and DLCO: A manufacturer's perspective

The simultaneous measurement of the lung transfer factor for carbon monoxide (DLCO) and nitric oxide (DLNO) is now available as a powerful method for studying the alveolar-capillary gas exchange. However, application of the DLNO-CO technique in daily settings is still limited by some technical drawbacks. This paper provides a manufacturer's overview of the measuring principles, technical challenges and current available solutions for implementing the DLNO-CO measurement in to a marketed device. This includes the recent developments in technology for NO sensors, latest findings on NO uptake and new statistical methods.

Quantum cascade lasers (QCLs) in biomedical spectroscopy

This review focuses on the recent applications of QCLs in mid-IR spectroscopy of clinically relevant samples.

Fractional exhaled nitric oxide-measuring devices: technology update

The measurement of exhaled nitric oxide (NO) has been employed in the diagnosis of specific types of airway inflammation, guiding treatment monitoring by predicting and assessing response to anti-inflammatory therapy and monitoring for compliance and detecting relapse. Various techniques are currently used to analyze exhaled NO concentrations under a range of conditions for both health and disease. These include chemiluminescence and electrochemical sensor devices. The cost effectiveness and ability to achieve adequate flexibility in sensitivity and selectivity of NO measurement for these methods are evaluated alongside the potential for use of laser-based technology. This review explores the technologies involved in the measurement of exhaled NO.

Online Measurement of Exhaled NO Concentration and Its Production Sites by Fast Non-equilibrium Dilution Ion Mobility Spectrometry

Exhaled nitric oxide (NO) is one of the most promising breath markers for respiratory diseases. Its profile for exhalation and the respiratory NO production sites can provide useful information for medical disease diagnosis and therapeutic procedures. However, the high-level moisture in exhaled gas always leads to the poor selectivity and sensitivity for ion spectrometric techniques. Herein, a method based on fast non-equilibrium dilution ion mobility spectrometry (NED-IMS) was firstly proposed to directly monitor the exhaled NO profile on line. The moisture interference was eliminated by turbulently diluting the original moisture to 21% of the original with the drift gas and dilution gas. Weak enhancement was observed for humid NO response and its limit of detection at 100% relative humidity was down to 0.58 ppb. The NO concentrations at multiple exhalation flow rates were measured, while its respiratory production sites were determined by using two-compartment model (2CM) and Högman and Meriläinen algorithm (HMA). Last but not the least, the NO production sites were analyzed hourly to tentatively investigate the daily physiological process of NO. The results demonstrated the capacity of NED-IMS in the real-time analysis of exhaled NO and its production sites for clinical diagnosis and assessment.

Fluorescence turn-on for the highly selective detection of nitric oxide in vitro and in living cells

A water-soluble, biocompatible, small molecular fluorescent turn-on probe was developed for the highly selective and sensitive detection of NO in vitro and in living cells.

Extended nitric oxide analysis may improve personalized anti-inflammatory treatment in asthmatic children with intermediate F(E)NO50

Exhaled nitric oxide (F(E)NO) is elevated in asthma, and a clinical practice guideline has been published with recommendations for anti-inflammatory treatment. It summarizes that a F(E)NO at an expiratory flow rate of 50 ml s(-1) (F(E)NO50) above 35 ppb in children indicates eosinophilic inflammation, and the most likely response is to use inhaled corticosteroids. Intermediate F(E)NO50 between 20-35 ppb should be interpreted cautiously. The aim of the study was to investigate this guideline in a small group of asthmatic children. Thirty-seven asthmatic children; 23 boys and 14 girls, visited the outpatient clinic, and provided exhaled breath samples for offline NO measurement. These samples were analysed with chemiluminescence techniques. Three flow rates, namely 16, 90 and 230 ml s(-1) were used for the extended NO analysis (Högman-Meriläinen algorithm, HMA) to estimate the alveolar concentration (C(A)NO), diffusion rate of the airway wall (D(aw)NO) and airway wall content (C(aw)NO). For accuracy of the HMA, the estimated value of F(E)NO at 50 ml s(-1) (F(E)NO50) was compared with measured F(E)NO50. In nine children the difference was more than 5 ppb and the data were therefore excluded. Five children with F(E)NO50 <20 ppb had no known allergy and their F(E)NO50 geometrical mean (25th; 75th percentile) was 11 (10;14) and CawNO was 32 (20;43) ppb. Ten children with F(E)NO50  >  35 ppb had an allergy and had F(E)NO50 of 56 (47;60) ppb and C(aw)NO of 140 (121;172) ppb. Thirteen children with allergies, with intermediate F(E)NO50, had F(E)NO50 of 27 (25;30) ppb with a wide range of C(aw)NO. In five of these children, values were comparable to healthy children, 44 (43;50) ppb while eight children had elevated C(aw)NO values of 108 (95;129) ppb. Our data indicate the clinical potential use of extended NO analysis to determine the personal target value of F(E)NO50 for monitoring the treatment outcome. Furthermore, for children with intermediate F(E)NO50 more than half of them could possibly benefit from an adjustment of inhaled corticosteroids if the C(aw)NO value was considered.

New miniaturized exhaled nitric oxide sensor based on a high Q/V mid-infrared 1D photonic crystal cavity

A high Q/V mid-infrared 1D photonic crystal cavity in chalcogenide glass AMTIR-1 (Ge₃₃As₁₂Se₅₅) resonating at λ_R=5.26  μm has been proposed as a key element of a sensor able to evaluate the nitric oxide (NO) concentration in the exhaled breath, namely fraction exhaled NO. The cavity design has been carried out through 3D finite-element method simulations. A Q-factor of 1.1×10⁴ and a mode volume V=0.8  (λ/n)³, corresponding to a Q/V ratio of 1.4×10⁴(λ/n)^-3, have been obtained with a resonance transmission coefficient T=15%. A sensitivity of 10 ppb has been calculated with reference to the photothermal physical property of the material. Such a result is lower than the state-of-the-art of NO sensors proposed in literature, where hundreds of parts per trillion-level detection seem to have been achieved, but comparable with the performance obtained by commercial devices. The main advantages of the new device are in terms of footprint (=150  μm²), smaller at least 1 order of magnitude than those in literature, fast response time (only few seconds), and potential low cost. Such properties make possible in a handheld device the sensor integration in a multi-analysis system for detecting the presence of several trace gases, improving prevention, and reducing the duration of drug treatment for asthma and viral infections.

Quantitative detection of nitric oxide in exhaled human breath by extractive electrospray ionization mass spectrometry

Exhaled nitric oxide (eNO) is a useful biomarker of various physiological conditions, including asthma and other pulmonary diseases. Herein a fast and sensitive analytical method has been developed for the quantitative detection of eNO based on extractive electrospray ionization mass spectrometry (EESI-MS). Exhaled NO molecules selectively reacted with 2-phenyl-4, 4, 5, 5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO) reagent, and eNO concentration was derived based on the EESI-MS response of 1-oxyl-2-phenyl-4, 4, 5, 5-tetramethylimidazoline (PTI) product. The method allowed quantification of eNO below ppb level (~0.02 ppbv) with a relative standard deviation (RSD) of 11.6%. In addition, eNO levels of 20 volunteers were monitored by EESI-MS over the time period of 10 hrs. Long-term eNO response to smoking a cigarette was recorded, and the observed time-dependent profile was discussed. This work extends the application of EESI-MS to small molecules (<30 Da) with low proton affinity and collision-induced dissociation efficiency, which are usually poorly visible by conventional ion trap mass spectrometers. Long-term quantitative profiling of eNO by EESI-MS opens new possibilities for the research of human metabolism and clinical diagnosis.

Breath analysis as a potential and non-invasive frontier in disease diagnosis: an overview

Currently, a small number of diseases, particularly cardiovascular (CVDs), oncologic (ODs), neurodegenerative (NDDs), chronic respiratory diseases, as well as diabetes, form a severe burden to most of the countries worldwide. Hence, there is an urgent need for development of efficient diagnostic tools, particularly those enabling reliable detection of diseases, at their early stages, preferably using non-invasive approaches. Breath analysis is a non-invasive approach relying only on the characterisation of volatile composition of the exhaled breath (EB) that in turn reflects the volatile composition of the bloodstream and airways and therefore the status and condition of the whole organism metabolism. Advanced sampling procedures (solid-phase and needle traps microextraction) coupled with modern analytical technologies (proton transfer reaction mass spectrometry, selected ion flow tube mass spectrometry, ion mobility spectrometry, e-noses, etc.) allow the characterisation of EB composition to an unprecedented level. However, a key challenge in EB analysis is the proper statistical analysis and interpretation of the large and heterogeneous datasets obtained from EB research. There is no standard statistical framework/protocol yet available in literature that can be used for EB data analysis towards discovery of biomarkers for use in a typical clinical setup. Nevertheless, EB analysis has immense potential towards development of biomarkers for the early disease diagnosis of diseases.

Dopant titrating ion mobility spectrometry for trace exhaled nitric oxide detection

Ion mobility spectrometry (IMS) is a promising non-invasive tool for the analysis of exhaled gas and exhaled nitric oxide (NO), a biomarker for diagnosis of respiratory diseases. However, the high moisture in exhaled gas always brings about extra overlapping ion peaks and results in poor identification ability. In this paper, p-benzoquinone (PBQ) was introduced into IMS to eliminate the interference of overlapping ion peaks and realize the selective identification of NO. The overlapping ions caused by moisture were titrated by PBQ and then converted to hydrated PBQ anions (C6H4[Formula: see text](H2O)n). The NO concentration could be determined by quantifying gas phase hydrated nitrite anions (N[Formula: see text](H2O)n), product ions of NO. Under optimized conditions, a limit of detection (LOD) of about 1.4 ppbv and a linear range of 10-200 ppbv were obtained for NO even in 100% relative humidity (RH) purified air. Furthermore, this established method was applied to measure hourly the exhaled NO of eight healthy volunteers, and real-time monitoring the exhaled NO of an esophageal carcinoma patient during radical surgery. These results revealed the potential of the current dopant titrating IMS method in the measurement of exhaled NO for medical disease diagnosis.

Contribution of exhaled nitric oxide measurement in airway inflammation assessment in asthma. A position paper from the French Speaking Respiratory Society

Nitric oxide (NO) is both a gas and a ubiquitous inter- and intracellular messenger with numerous physiological functions. As its synthesis is markedly increased during inflammatory processes, NO can be used as a surrogate marker of acute and/or chronic inflammation. It is possible to quantify fractional concentration of NO in exhaled breath (FENO) to detect airway inflammation, and thus improve the diagnosis of asthma by better characterizing asthmatic patients with eosinophilic bronchial inflammation, and eventually improve the management of targeted asthmatic patients. FENO measurement can therefore be viewed as a new, reproducible and easy to perform pulmonary function test. Measuring FENO is the only non-invasive pulmonary function test allowing (1) detecting, (2) quantifying and (3) monitoring changes in inflammatory processes during the course of various respiratory disorders, including corticosensitive asthma.

Taking your breath away: metabolomics breathes life in to personalized medicine

Breath-based metabolomics (breathomics) is an exciting developing area of biotechnology that centers on the capture, identification, and quantification of volatile organic compound (VOC) patterns in human breath and their utilization as tools in the diagnosis of a broad spectrum of medical problems. With the age of personalized medicines demanding rapid bespoke diagnosis and treatment, this area of molecular diagnostics is beginning to see an upsurge in biotechnological advancement. Here, we discuss recent improvements and directions in the development of breath VOC analysis and diagnosis platforms that offer the potential for disease biomarker discovery and disease prognosis.

A mitochondria-targetable fluorescent probe for dual-channel NO imaging assisted by intracellular cysteine and glutathione

A mitochondria-specific fluorescent probe for NO (1) was synthesized by the direct conjugation of a pyronin dye with one of the amino groups of o-phenylenediamino (OPD). The probe could selectively detect NO over dehydroascorbic acid (DHA), ascorbic acid (AA), and methylglyoxal (MGO) as well as the reactive oxygen/nitrogen species (ROS/RNS) with the significant off-on response due to the production of a red-emission triazole 2. In the presence of cysteine/glutathione (Cys/GSH), 2 could be further transformed into a green-emission aminopyronin 4 and a red-emission thiopyronin 5, respectively. Assisted by intracellular Cys and GSH, the probe demonstrated its potential to monitor mitochondrial NO in a dual-channel mode.

A review of the volatiles from the healthy human body

A compendium of all the volatile organic compounds (VOCs) emanating from the human body (the volatolome) is for the first time reported. 1840 VOCs have been assigned from breath (872), saliva (359), blood (154), milk (256), skin secretions (532) urine (279), and faeces (381) in apparently healthy individuals. Compounds were assigned CAS registry numbers and named according to a common convention where possible. The compounds have been grouped into tables according to their chemical class or functionality to permit easy comparison. Some clear differences are observed, for instance, a lack of esters in urine with a high number in faeces. Careful use of the database is needed. The numbers may not be a true reflection of the actual VOCs present from each bodily excretion. The lack of a compound could be due to the techniques used or reflect the intensity of effort e.g. there are few publications on VOCs from blood compared to a large number on VOCs in breath. The large number of volatiles reported from skin is partly due to the methodologies used, e.g. collecting excretions on glass beads and then heating to desorb VOCs. All compounds have been included as reported (unless there was a clear discrepancy between name and chemical structure), but there may be some mistaken assignations arising from the original publications, particularly for isomers. It is the authors' intention that this database will not only be a useful database of VOCs listed in the literature, but will stimulate further study of VOCs from healthy individuals. Establishing a list of volatiles emanating from healthy individuals and increased understanding of VOC metabolic pathways is an important step for differentiating between diseases using VOCs.

Applications of absorption spectroscopy using quantum cascade lasers

Infrared laser absorption spectroscopy (LAS) is a promising modern technique for sensing trace gases with high sensitivity, selectivity, and high time resolution. Mid-infrared quantum cascade lasers, operating in a pulsed or continuous wave mode, have potential as spectroscopic sources because of their narrow linewidths, single mode operation, tunability, high output power, reliability, low power consumption, and compactness. This paper reviews some important developments in modern laser absorption spectroscopy based on the use of quantum cascade laser (QCL) sources. Among the various laser spectroscopic methods, this review is focused on selected absorption spectroscopy applications of QCLs, with particular emphasis on molecular spectroscopy, industrial process control, combustion diagnostics, and medical breath analysis.

Pulmonary infection, and not systemic inflammation, accounts for increased concentrations of exhaled nitric oxide in patients with septic shock

Nitric oxide (NO) is a key mediator in the pathophysiology of septic shock that can be measured in exhaled breath. To assess whether a pulmonary infection itself or systemic inflammation is responsible for NO production, we determined exhaled NO in ventilated patients with respiratory and non-respiratory septic shock and compared it with the concentration in ventilated intensive care patients without systemic inflammation. In addition, the change of NO production over time and correlations with haemodynamic instability were evaluated. The controls without systemic inflammation, as witnessed by the absence of systemic inflammatory response syndrome criteria and low levels of interleukin-6, had similar concentrations of NO as the patients with non-respiratory septic shock. The respiratory sepsis patients exhaled more NO than the non-respiratory sepsis patients (p = 0.05), and a time dependent decline in time in both groups (p = 0.04). Exhaled NO did not correlate with markers of disease severity, systemic inflammation and haemodynamic instability. These data indicate that the infected lungs are the source of exhaled NO.

Highly water-soluble BODIPY-based fluorescent probe for sensitive and selective detection of nitric oxide in living cells

A highly water-soluble BODIPY dye bearing electron-rich o-diaminophenyl groups at 2,6-positions was prepared as a highly sensitive and selective fluorescent probe for detection of nitric oxide (NO) in living cells. The fluorescent probe displays an extremely weak fluorescence with fluorescence quantum yield of 0.001 in 10 mM phosphate buffer (pH 7.0) in the absence of NO as two electron-rich o-diaminophenyl groups at 2,6-positions significantly quench the fluorescence of the BODIPY dye via photoinduced electron transfer mechanism. The presence of NO in cells enhances the dye fluorescence dramatically. The fluorescent probe demonstrates excellent water solubility, membrane permeability, and compatibility with living cells for sensitive detection of NO.

Methods of NO detection in exhaled breath

There is still an unexplored potential for exhaled nitric oxide (NO) in many clinical applications. This study presents an overview of the currently available methods for monitoring NO in exhaled breath and the use of the modelling of NO production and transport in the lung in clinical practice. Three technologies are described, namely chemiluminescence, electrochemical sensing and laser-based detection with their advantages and limitations. Comparisons are made in terms of sensitivity, time response, size, costs and suitability for clinical purposes. The importance of the flow rate for NO sampling is discussed from the perspective of the recent recommendations for standardized procedures for online and offline NO measurement. The measurement of NO at one flow rate, such as 50 ml s(-1), can neither determine the alveolar site/peripheral contribution nor quantify the difference in NO diffusion from the airways walls. The use of NO modelling (linear or non-linear approach) can solve this problem and provide useful information about the source of NO. This is of great value in diagnostic procedures of respiratory diseases and in treatment with anti-inflammatory drugs.