An electronic nose in the discrimination of patients with non-small cell lung cancer and COPD

Analysis of volatile organic compounds released from human lung cancer cells and from the urine of tumor-bearing mice

Backgrounds

A potential strategy for the diagnosis of lung cancer is to exploit the distinct metabolic signature of this disease by way of biomarkers found in different sample types. In this study, we investigated whether specific volatile organic compounds (VOCs) could be detected in the culture medium of the lung cancer cell line A549 in addition to the urine of mice implanted with A549 cells.

Results

Several VOCs were found at significantly increased or decreased concentrations in the headspace of the A549 cell culture medium as compared with the culture medium of two normal lung cell lines. We also analyzed the urine of mice implanted with A549 cells and several VOCs were also found to be significantly increased or decreased relative to urine obtained from control mice. It was also revealed that seven VOCs were found at increased concentrations in both sample types. These compounds were found to be dimethyl succinate, 2-pentanone, phenol, 2-methylpyrazine, 2-hexanone, 2-butanone and acetophenone.

Conclusions

Both sample types produce distinct biomarker profiles, and VOCs have potential to distinguish between true- and false-positive screens for lung cancer.

Discrimination between COPD patients with and without alpha 1-antitrypsin deficiency using an electronic nose

BACKGROUND AND OBJECTIVE

To compare the volatile organic compound patterns of patients with COPD with and without alpha 1-antitrypsin (AAT) deficiency using electronic nose technology.

METHODS

Exhaled breath condensate and pure exhaled breath of patients with COPD with (n=10) and without (n=23) AAT deficiency and healthy controls (n=10) were analysed. The effect of human recombinant AAT on the volatile organic compound profile of 11 AAT-deficient patients was also examined. Exhaled breath condensate and pure exhaled breath were measured using the Cyranose 320. Smell prints were analysed by linear discriminant analysis (LDA) using Mahalanobis distance (MD) and cross-validation values (CVVs).

RESULTS

Smell prints of patients with AAT-deficiency were different from those with COPD in exhaled breath condensate (LDA: P<0.0001, sensitivity of 1.00, specificity of 1.00, CVV 82.0%, MD 2.37) and in pure exhaled breath (LDA: P<0.0001, sensitivity of 1.00, specificity of 1.00, CVV 58.3%, MD 2.27). Smell prints of AAT-deficient patients before and after human recombinant AAT augmentation were different (LDA: P=0.001, sensitivity of 1.00, specificity of 1.00, CVV 53.3%, MD 1.79).

CONCLUSIONS

An electronic nose can detect differences in smell prints of COPD patients with and without AAT deficiency. Augmentation therapy changes the volatile organic compound pattern. The electronic nose may be helpful in the diagnosis of AAT deficiency.

Detection of gastro-oesophageal reflux disease (GORD) in patients with obstructive lung disease using exhaled breath profiling

Gastro-oesophageal reflux disease (GORD) has been implicated in the worsening of several respiratory disorders. Current methods of diagnosis lack accuracy, are invasive and can be costly. Recently, novel methods of analysing lung pathophysiology have been developed including the use of an electronic nose and analysis of components of exhaled breath condensate (EBC). We hypothesised that these methods would distinguish patients with GORD from those without GORD in the common obstructive lung diseases and healthy controls. In a cross-sectional study, exhaled breath was analysed using the Cyranose 320 electronic nose, using principal components and canonical discriminant analyses. EBC pH and pepsin were quantified using a pH meter and an enzyme-linked immunosorbent assay, respectively. A standardized reflux disease questionnaire (RDQ) was used to assess reflux symptoms. The Cyranose 320 distinguished exhaled breath profiles of obstructive lung disease patients without GORD from obstructive lung disease patients with GORD (p = 0.023, accuracy 67.6%), asthmatic patients with reflux from asthmatics without GORD (85%, p = < 0.015, interclass M distance > 2.8), but did not produce as robust a profile for patients with COPD and COPD with GORD (p = 0.047, accuracy 64%). Patients with obstructive lung disease and GORD had significantly higher levels of EBC pepsin (9.81 ± interquartile range (IQR) 4.38 ng ml(-1)) than those without GORD (4.6 ± IQR 6.95 ng ml(-1)), as well as healthy controls (3.44 ± IQR 7.87 ng ml(-1); p = < 0.013). EBC pH was not significantly related to the presence of GORD in any group. The RDQ results correlated significantly with the presence of EBC pepsin. This pilot study has shown that exhaled breath profiling can be used for detecting GORD in obstructive lung diseases. While the electronic nose was useful in asthma, EBC pepsin was more helpful in COPD. In this study, several different confounders could potentially have affected results and larger prospective interventional studies are needed.

Fast analytical methodology based on mass spectrometry for the determination of volatile biomarkers in saliva

We report a methodology for the rapid determination of biomarkers in saliva. The method is based on direct coupling of a headspace sampler with a mass spectrometer. The saliva samples are subjected to the headspace generation process, and the volatiles generated are introduced directly into the mass spectrometer, thereby obtaining a fingerprint of the sample analyzed. The main advantage of the proposed methodology is that no prior chromatographic separation and no sample manipulation is required. The following model compounds were studied to check the possibilities of the methodology: methyl tert-butyl ether and styrene as biomarkers of exposure and dimethyl disulfide, limonene, and 2-ethyl-1-hexanol as biomarkers of diseases. The method was applied to the determination of biomarkers in 28 saliva samples: 24 of them were from healthy volunteers, and the others were from patients with different types of illness (including different types of cancer). Additionally, a separative analysis by GC/MS was performed for confirmatory purposes, and both methods provided similar results.

An electronic nose distinguishes exhaled breath of patients with Malignant Pleural Mesothelioma from controls

BACKGROUND

Malignant Pleural Mesothelioma (MPM) is a tumour of the surface cells of the pleura that is highly aggressive and mainly caused by asbestos exposure. Electronic noses capture the spectrum of exhaled volatile organic compounds (VOCs) providing a composite biomarker profile (breathprint).

OBJECTIVE

We tested the hypothesis that an electronic nose can discriminate exhaled air of patients with MPM from subjects with a similar long-term professional exposure to asbestos without MPM and from healthy controls.

METHODS

13 patients with a histology confirmed diagnosis of MPM (age 60.9±12.2 year), 13 subjects with certified, long-term professional asbestos exposure (age 67.2±9.8), and 13 healthy subjects without asbestos exposure (age 52.2±16.2) participated in a cross-sectional study. Exhaled breath was collected by a previously described method and sampled by an electronic nose (Cyranose 320). Breathprints were analyzed by canonical discriminant analysis on principal component reduction. Cross-validated accuracy (CVA) was calculated.

RESULTS

Breathprints from patients with MPM were separated from subjects with asbestos exposure (CVA: 80.8%, sensitivity 92.3%, specificity 85.7%). MPM was also distinguished from healthy controls (CVA: 84.6%). Repeated measurements confirmed these results.

CONCLUSIONS

Molecular pattern recognition of exhaled breath can correctly distinguish patients with MPM from subjects with similar occupational asbestos exposure without MPM and from healthy controls. This suggests that breathprints obtained by electronic nose have diagnostic potential for MPM.

A novel microreactor approach for analysis of ketones and aldehydes in breath

We report a fabricated microreactor with thousands of micropillars in channels. Each micropillar surface is chemically functionalized to selectively preconcentrate gaseous ketones and aldehydes of exhaled breath and to enhance ultra-trace, rapid analysis by direct-infusion Fourier transform-ion cyclotron resonance (FT-ICR) mass spectrometry (MS). The micropillar reactive coating contains the quaternary ammonium aminooxy salt 2-(aminooxy)ethyl-N,N,N-trimethylammonium iodide (ATM) for capturing trace carbonyl VOCs by means of an oximation reaction. We demonstrate the utility of this approach for detection of C(1) to C(12) aldehydes and ketones in exhaled breath, but the approach is applicable to any gaseous sample.

Solid-phase microextraction and the human fecal VOC metabolome

The diagnostic potential and health implications of volatile organic compounds (VOCs) present in human feces has begun to receive considerable attention. Headspace solid-phase microextraction (SPME) has greatly facilitated the isolation and analysis of VOCs from human feces. Pioneering human fecal VOC metabolomic investigations have utilized a single SPME fiber type for analyte extraction and analysis. However, we hypothesized that the multifarious nature of metabolites present in human feces dictates the use of several diverse SPME fiber coatings for more comprehensive metabolomic coverage. We report here an evaluation of eight different commercially available SPME fibers, in combination with both GC-MS and GC-FID, and identify the 50/30 µm CAR-DVB-PDMS, 85 µm CAR-PDMS, 65 µm DVB-PDMS, 7 µm PDMS, and 60 µm PEG SPME fibers as a minimal set of fibers appropriate for human fecal VOC metabolomics, collectively isolating approximately 90% of the total metabolites obtained when using all eight fibers. We also evaluate the effect of extraction duration on metabolite isolation and illustrate that ex vivo enteric microbial fermentation has no effect on metabolite composition during prolonged extractions if the SPME is performed as described herein.

Breath profiles by electronic nose correlate with systemic markers but not ozone response

BACKGROUND

The evaluation of exhaled breath profiles by electronic nose (eNose) is considered as a promising non-invasive diagnostic tool, and the discrimination of breathprints between patients with COPD and asthma has been reported. The aim of this study was to assess, whether exhaled breath profile analysis can detect the inflammatory airway response induced by ozone inhalation.

METHODS

In a randomized double-blind, cross-over study 14 healthy ozone-responsive subjects were exposed to 250 ppb ozone and filtered room air for 3h with intermittent exercise. Blood biomarkers, exhaled NO, exhaled CO, and breathprints (Cyranose 320(®)) were assessed prior and at 3 time points up to 24h post exposure. Induced sputum was collected at baseline and 3h post exposure. Multivariate analysis of eNose data was performed using transformed and normalized datasets.

RESULTS

Significantly increased numbers of sputum and blood neutrophils were observed after ozone, whereas the eNose signals showed no differences between exposures and no correlation with neutrophilic airway inflammation. However, independent of ozone exposure, sensor data correlated with serum SP-D levels and to a smaller extent with blood neutrophil numbers.

CONCLUSIONS

Exhaled breath profiles as measured by the Cyranose 320(®) did not reflect airway responses to ozone. This suggests that exhaled volatiles did not change with ozone challenges or that the changes were below the detection limits. Conversely, the correlation of eNose signals with blood neutrophils and serum SP-D, i.e. markers of systemic inflammation and lung permeability, suggested that the Cyranose 320(®) can detect volatile organic compounds of systemic origin.

Advances in electronic-nose technologies developed for biomedical applications

The research and development of new electronic-nose applications in the biomedical field has accelerated at a phenomenal rate over the past 25 years. Many innovative e-nose technologies have provided solutions and applications to a wide variety of complex biomedical and healthcare problems. The purposes of this review are to present a comprehensive analysis of past and recent biomedical research findings and developments of electronic-nose sensor technologies, and to identify current and future potential e-nose applications that will continue to advance the effectiveness and efficiency of biomedical treatments and healthcare services for many years. An abundance of electronic-nose applications has been developed for a variety of healthcare sectors including diagnostics, immunology, pathology, patient recovery, pharmacology, physical therapy, physiology, preventative medicine, remote healthcare, and wound and graft healing. Specific biomedical e-nose applications range from uses in biochemical testing, blood-compatibility evaluations, disease diagnoses, and drug delivery to monitoring of metabolic levels, organ dysfunctions, and patient conditions through telemedicine. This paper summarizes the major electronic-nose technologies developed for healthcare and biomedical applications since the late 1980s when electronic aroma detection technologies were first recognized to be potentially useful in providing effective solutions to problems in the healthcare industry.

Discrimination and characterization of breath from smokers and non-smokers via electronic nose and GC/MS analysis

The objective of this study was to prove the general applicability of an electronic nose for analyzing exhaled breath considering the dependency on smoking. At first, odor compounds from spices (n=6) were detected via the electronic nose and further characterized and classified with gas chromatography/ mass spectrometry to demonstrate the principle ability of the electronic nose. Then, the exhaled breath from smokers and non-smokers were analyzed to prove the influence of smoking on breath analyses with the electronic nose. The exhaled breath was sampled from 11 smokers and 11 non-smokers in a special sampling bag with the mounted sensor chip of the electronic nose. Additionally, solid phase micro-extraction (SPME) technique was established for detection of the specific chemical compounds with gas chromatography and mass spectrometry (GC/MS). For analyses of the sensor signals the principle component analysis (PCA) was applied and the groups were differentiated by linear discriminant function analysis. In accordance to the discrimination between the different spices and between smokers and non-smokers the PCA analysis leads to an optimum accuracy of 100%. The results of this study show that an electronic nose has the ability to detect different changes of odor components and provides separation of smoking side effects in smelling different diseases.

Electronic nose breathprints are independent of acute changes in airway caliber in asthma

Molecular profiling of exhaled volatile organic compounds (VOC) by electronic nose technology provides breathprints that discriminate between patients with different inflammatory airway diseases, such as asthma and COPD. However, it is unknown whether this is determined by differences in airway caliber. We hypothesized that breathprints obtained by electronic nose are independent of acute changes in airway caliber in asthma. Ten patients with stable asthma underwent methacholine provocation (Visit 1) and sham challenge with isotonic saline (Visit 2). At Visit 1, exhaled air was repetitively collected pre-challenge, after reaching the provocative concentration (PC(20)) causing 20% fall in forced expiratory volume in 1 second (FEV(1)) and after subsequent salbutamol inhalation. At Visit 2, breath was collected pre-challenge, post-saline and post-salbutamol. At each occasion, an expiratory vital capacity was collected after 5 min of tidal breathing through an inspiratory VOC-filter in a Tedlar bag and sampled by electronic nose (Cyranose 320). Breathprints were analyzed with principal component analysis and individual factors were compared with mixed model analysis followed by pairwise comparisons. Inhalation of methacholine led to a 30.8 ± 3.3% fall in FEV(1) and was followed by a significant change in breathprint (p = 0.04). Saline inhalation did not induce a significant change in FEV(1), but altered the breathprint (p = 0.01). However, the breathprint obtained after the methacholine provocation was not significantly different from that after saline challenge (p = 0.27). The molecular profile of exhaled air in patients with asthma is altered by nebulized aerosols, but is not affected by acute changes in airway caliber. Our data demonstrate that breathprints by electronic nose are not confounded by the level of airway obstruction.

Breath analysis in asbestos-related disorders: a review of the literature and potential future applications

Asbestos usage was very common worldwide in the last century and continues in several countries today. Several diseases occur due to asbestos exposure, including malignant tumours such as malignant mesothelioma of the pleura and lung cancer, which have a very poor prognosis. Asbestos inhalation may also result in more benign conditions such as asbestosis (or pulmonary fibrosis due to asbestos), pleural plaques and pleural thickening. It is predicted that asbestos-associated mortality and morbidity will continue to increase, but methods for diagnosing asbestos-related disease are currently invasive and unsuitable for an increasingly elderly population. New non-invasive methods such as analysis of exhaled breath biomarkers e.g. exhaled nitric oxide (F(E)NO), exhaled breath condensate or of exhaled volatile organic compounds could potentially be extremely useful in these conditions. This article reviews the current literature on this topic and suggests areas for their application in the future.

Electronic-nose technology using sputum samples in diagnosis of patients with tuberculosis

We investigated the potential of two different electronic noses (EN; code named "Rob" and "Walter") to differentiate between sputum headspace samples from tuberculosis (TB) patients and non-TB patients. Only samples from Ziehl-Neelsen stain (ZN)- and Mycobacterium tuberculosis culture-positive (TBPOS) sputum samples and ZN- and culture-negative (TBNEG) samples were used for headspace analysis; with EN Rob, we used 284 samples from TB suspects (56 TBPOS and 228 TBNEG samples), and with EN Walter, we used 323 samples from TB suspects (80 TBPOS and 243 TBNEG samples). The best results were obtained using advanced data extraction and linear discriminant function analysis, resulting in a sensitivity of 68%, a specificity of 69%, and an accuracy of 69% for EN Rob; for EN Walter, the results were 75%, 67%, and 69%, respectively. Further research is still required to improve the sensitivity and specificity by choosing more selective sensors and type of sampling technique.

Clinical applications of breath testing

Breath testing has the potential to benefit the medical field as a cost-effective, non-invasive diagnostic tool for diseases of the lung and beyond. With growing evidence of clinical worth, standardization of methods, and new sensor and detection technologies the stage is set for breath testing to gain considerable attention and wider application in upcoming years.

Biomarkers in asthma and allergic rhinitis

A biological marker (biomarker) is a physical sign or laboratory measurement that can serve as an indicator of biological or pathophysiological processes or as a response to a therapeutic intervention. An applicable biomarker possesses the characteristics of clinical relevance (sensitivity and specificity for the disease) and is responsive to treatment effects, in combination with simplicity, reliability and repeatability of the sampling technique. Presently, there are several biomarkers for asthma and allergic rhinitis that can be obtained by non-invasive or semi-invasive airway sampling methods meeting at least some of these criteria. In clinical practice, such biomarkers can provide complementary information to conventional disease markers, including clinical signs, spirometry and PC(20)methacholine or histamine. Consequently, biomarkers can aid to establish the diagnosis, in staging and monitoring of the disease activity/progression or in predicting or monitoring of a treatment response. Especially in (young) children, reliable, non-invasive biomarkers would be valuable. Apart from diagnostic purposes, biomarkers can also be used as (surrogate) markers to predict a (novel) drug's efficacy in target populations. Therefore, biomarkers are increasingly applied in early drug development. When implementing biomarkers in clinical practice or trials of asthma and allergic rhinitis, it is important to consider the heterogeneous nature of the inflammatory response which should direct the selection of adequate biomarkers. Some biomarker sampling techniques await further development and/or validation, and should therefore be applied as a "back up" of established biomarkers or methods. In addition, some biomarkers or sampling techniques are less suitable for (very young) children. Hence, on a case by case basis, a decision needs to be made what biomarker is adequate for the target population or purpose pursued. Future development of more sophisticated sampling methods and quantification techniques, such as--omics and biomedical imaging, will enable detection of adequate biomarkers for both clinical and research applications.

Resection of secondary pulmonary malignancies in head and neck cancer patients

BACKGROUND

This study aimed to evaluate a single institute's experience with resection of metachronous pulmonary malignancy in patients treated for squamous cell carcinoma of the head and neck.

METHODS

Sixty-three consecutive patients treated curatively for head and neck squamous cell carcinoma underwent surgical resection of malignant lung lesions. Survival was estimated and potential prognostic factors investigated.

RESULTS

The median overall survival for the total group was 22.2 months. Fifty-one patients (81 per cent) had one lung lesion, while the remainder had multiple lesions (range, two to seven). In the 63 patients, 35 lobectomies, 4 pneumonectomies and 24 wedge resections were performed. For patients with pulmonary squamous cell carcinoma (n = 52), the three-year survival rate was 35 per cent (95 per cent confidence interval, 22-48); for patients with resected adenocarcinoma (n = 10), it was 50 per cent (95 per cent confidence interval, 18-75). The overall five-year survival rate was 30 per cent (95 per cent confidence interval, 19-42).

CONCLUSION

In patients treated curatively for head and neck squamous cell carcinoma, resection of secondary pulmonary cancer is associated with favourable long term overall survival, especially for patients with adenocarcinoma lesions.

Different volatile signals emitted by human ovarian carcinoma and healthy tissue

Many cancers are detected at a late stage resulting in high mortality rates. Thus, it is essential to develop inexpensive and simple methods for early diagnosis. Detection of different malignancies using canine scent, as well as other technical methods, has been reported in peer-reviewed journals, indicating that this may represent a new diagnostic tool for malignancies. Aim: This study aims to test the detection of different volatile organic compound signals emitted by ovarian carcinoma and normal tissues. Materials & methods: A previously tested electronic nose is used in the pilot study to analyze human grade 3 seropapillary ovarian carcinoma samples. The recorded signals were compared with healthy human Fallopian tube specimens. A variety of algorithms were tested and confusion matrices compared. In parallel, an external validation study was performed using the same type and grade of human ovarian carcinomas with healthy myometrium (first part) and postmenopausal ovarium (second part) specimens as controls. Both sample types were obtained from individuals who did not participate in the pilot study. Results: Method sensitivity was 100% (15 of 15) in the pilot study. The first part of the validation study demonstrated that 84.8% of cancer tissues (sensitivity: 84.8%) and 88.6% of the control samples (specificity: 88.6%) were correctly classified. In the second part the JRip algorithm correctly classified 75% of cancer tissues (sensitivity: 75%) and 80% of the control ovarian tissues (specificity: 80%). Collating results gives a sensitivity of 84.4%, whereas overall specificity was 86.8%. Conclusion: Although based on a limited number of samples, our results strongly suggest that specific volatile organic compound signals emitted by ovarian carcinomas may be used for early diagnosis of the disease.

Urinary volatile compounds as biomarkers for lung cancer: a proof of principle study using odor signatures in mouse models of lung cancer

A potential strategy for diagnosing lung cancer, the leading cause of cancer-related death, is to identify metabolic signatures (biomarkers) of the disease. Although data supports the hypothesis that volatile compounds can be detected in the breath of lung cancer patients by the sense of smell or through bioanalytical techniques, analysis of breath samples is cumbersome and technically challenging, thus limiting its applicability. The hypothesis explored here is that variations in small molecular weight volatile organic compounds (“odorants”) in urine could be used as biomarkers for lung cancer. To demonstrate the presence and chemical structures of volatile biomarkers, we studied mouse olfactory-guided behavior and metabolomics of volatile constituents of urine. Sensor mice could be trained to discriminate between odors of mice with and without experimental tumors demonstrating that volatile odorants are sufficient to identify tumor-bearing mice. Consistent with this result, chemical analyses of urinary volatiles demonstrated that the amounts of several compounds were dramatically different between tumor and control mice. Using principal component analysis and supervised machine-learning, we accurately discriminated between tumor and control groups, a result that was cross validated with novel test groups. Although there were shared differences between experimental and control animals in the two tumor models, we also found chemical differences between these models, demonstrating tumor-based specificity. The success of these studies provides a novel proof-of-principle demonstration of lung tumor diagnosis through urinary volatile odorants. This work should provide an impetus for similar searches for volatile diagnostic biomarkers in the urine of human lung cancer patients.

Diagnostic performance of an electronic nose, fractional exhaled nitric oxide, and lung function testing in asthma

BACKGROUND

Analysis of exhaled breath by biosensors discriminates between patients with asthma and healthy subjects. An electronic nose consists of a chemical sensor array for the detection of volatile organic compounds (VOCs) and an algorithm for pattern recognition. We compared the diagnostic performance of a prototype of an electronic nose with lung function tests and fractional exhaled nitric oxide (FENO) in patients with atopic asthma.

METHODS

A cross-sectional study was undertaken in 27 patients with intermittent and persistent mild asthma and in 24 healthy subjects. Two procedures for collecting exhaled breath were followed to study the differences between total and alveolar air. Seven patients with asthma and seven healthy subjects participated in a study with mass spectrometry (MS) fingerprinting as an independent technique for assessing between group discrimination. Classification was based on principal component analysis and a feed-forward neural network.

RESULTS

The best results were obtained when the electronic nose analysis was performed on alveolar air. Diagnostic performance for electronic nose, FENO, and lung function testing was 87.5%, 79.2%, and 70.8%, respectively. The combination of electronic nose and FENO had the highest diagnostic performance for asthma (95.8%). MS fingerprints of VOCs could discriminate between patients with asthma and healthy subjects.

CONCLUSIONS

The electronic nose has a high diagnostic performance that can be increased when combined with FENO. Large studies are now required to definitively establish the diagnostic performance of the electronic nose. Whether this integrated noninvasive approach will translate into an early diagnosis of asthma has to be clarified.

TRIAL REGISTRATION

EUDRACT https://eudralink.emea.europa.eu; Identifier: 2007-000890-51; and clinicaltrials.gov; Identifier: NCT00819676.

An investigation on electronic nose diagnosis of lung cancer

The use of gas sensor arrays as medical diagnosis instruments has been proposed several years ago. Since then, the idea has been proven for a limited number of diseases. The case of lung cancer is particularly interesting because it is supported by studies that have shown the correlation between the composition of breath and the disease. However, it is known that many other diseases can alter the breath composition, so for lung cancer diagnosis it is necessary not only to detect generic alterations but those specifically consequent to cancer. In this paper an experiment, performed in the bronchoscopy unit of a large hospital, aimed at discriminating between lung cancer, diverse lung diseases and reference controls is illustrated. Results show not only a satisfactory identification rate of lung cancer subjects but also a non-negligible sensitivity to breath modification induced by other affections. Furthermore, the effects of some compounds frequently found in the breath of lung cancer subjects have also been studied. Results indicate that breath samples of control individuals drift towards the lung cancer group when added with either single or mixtures of these alleged cancer-related compounds.

Diagnosing lung cancer in exhaled breath using gold nanoparticles

Conventional diagnostic methods for lung cancer are unsuitable for widespread screening because they are expensive and occasionally miss tumours. Gas chromatography/mass spectrometry studies have shown that several volatile organic compounds, which normally appear at levels of 1-20 ppb in healthy human breath, are elevated to levels between 10 and 100 ppb in lung cancer patients. Here we show that an array of sensors based on gold nanoparticles can rapidly distinguish the breath of lung cancer patients from the breath of healthy individuals in an atmosphere of high humidity. In combination with solid-phase microextraction, gas chromatography/mass spectrometry was used to identify 42 volatile organic compounds that represent lung cancer biomarkers. Four of these were used to train and optimize the sensors, demonstrating good agreement between patient and simulated breath samples. Our results show that sensors based on gold nanoparticles could form the basis of an inexpensive and non-invasive diagnostic tool for lung cancer.

Noninvasive detection of lung cancer by analysis of exhaled breath

Background

Lung cancer is one of the leading causes of death in Europe and the western world. At present, diagnosis of lung cancer very often happens late in the course of the disease since inexpensive, non-invasive and sufficiently sensitive and specific screening methods are not available. Even though the CT diagnostic methods are good, it must be assured that "screening benefit outweighs risk, across all individuals screened, not only those with lung cancer". An early non-invasive diagnosis of lung cancer would improve prognosis and enlarge treatment options. Analysis of exhaled breath would be an ideal diagnostic method, since it is non-invasive and totally painless.

Methods

Exhaled breath and inhaled room air samples were analyzed using proton transfer reaction mass spectrometry (PTR-MS) and solid phase microextraction with subsequent gas chromatography mass spectrometry (SPME-GCMS). For the PTR-MS measurements, 220 lung cancer patients and 441 healthy volunteers were recruited. For the GCMS measurements, we collected samples from 65 lung cancer patients and 31 healthy volunteers. Lung cancer patients were in different disease stages and under treatment with different regimes. Mixed expiratory and indoor air samples were collected in Tedlar bags, and either analyzed directly by PTR-MS or transferred to glass vials and analyzed by gas chromatography mass spectrometry (GCMS). Only those measurements of compounds were considered, which showed at least a 15% higher concentration in exhaled breath than in indoor air. Compounds related to smoking behavior such as acetonitrile and benzene were not used to differentiate between lung cancer patients and healthy volunteers.

Results

Isoprene, acetone and methanol are compounds appearing in everybody's exhaled breath. These three main compounds of exhaled breath show slightly lower concentrations in lung cancer patients as compared to healthy volunteers (p < 0.01 for isoprene and acetone, p = 0.011 for methanol; PTR-MS measurements). A comparison of the GCMS-results of 65 lung cancer patients with those of 31 healthy volunteers revealed differences in concentration for more than 50 compounds. Sensitivity for detection of lung cancer patients based on presence of (one of) 4 different compounds not arising in exhaled breath of healthy volunteers was 52% with a specificity of 100%. Using 15 (or 21) different compounds for distinction, sensitivity was 71% (80%) with a specificity of 100%. Potential marker compounds are alcohols, aldehydes, ketones and hydrocarbons.

Conclusion

GCMS-SPME is a relatively insensitive method. Hence compounds not appearing in exhaled breath of healthy volunteers may be below the limit of detection (LOD). PTR-MS, on the other hand, does not need preconcentration and gives much more reliable quantitative results then GCMS-SPME. The shortcoming of PTR-MS is that it cannot identify compounds with certainty. Hence SPME-GCMS and PTR-MS complement each other, each method having its particular advantages and disadvantages. Exhaled breath analysis is promising to become a future non-invasive lung cancer screening method. In order to proceed towards this goal, precise identification of compounds observed in exhaled breath of lung cancer patients is necessary. Comparison with compounds released from lung cancer cell cultures, and additional information on exhaled breath composition in other cancer forms will be important.

Detection of cutaneous myiasis in sheep using an 'electronic nose'

Cutaneous myiasis (flystrike), in Australia caused primarily by Lucilia cuprina [Diptera: Calliphoridae], is a debilitating, painful and potentially lethal disease of sheep. Early detection of flystrike is difficult and continual flock surveillance is required to enable timely treatment of struck sheep. Electronic nose technology offers the potential for early and automated detection of flystrike. An electronic nose consisting of six metal oxide semiconductor sensors and temperature and humidity sensors was used to measure odours collected by dynamic headspace sampling during flystrike development in four experiments and from urine- and faeces-stained fleece in one experiment. Non-linear signal measurement techniques and linear discriminant analysis (LDA) were used to extract signal features and process those features for analysis of categorical separation of odour groups. The results from LDA indicated that the electronic nose accurately distinguished flystrike odour on days 1, 2 and 3 of development from that of dry wool in all experiments (P<0.05). The electronic nose was also able to discriminate flystrike odour on the day of larval implantation (day 0) in three of the four studies. In the experiment with urine- and faeces-stained wool, these odours were accurately distinguished from both dry wool and flystrike (P<0.05). This study provides proof-of-concept for the detection of flystrike using electronic nose technology. Practical methods for collection of odour in the field and suitable detection algorithms will be required for development to commercial application.

Exhaled breath profiling enables discrimination of chronic obstructive pulmonary disease and asthma

RATIONALE

Chronic obstructive pulmonary disease (COPD) and asthma can exhibit overlapping clinical features. Exhaled air contains volatile organic compounds (VOCs) that may qualify as noninvasive biomarkers. VOC profiles can be assessed using integrative analysis by electronic nose, resulting in exhaled molecular fingerprints (breathprints).

OBJECTIVES

We hypothesized that breathprints by electronic nose can discriminate patients with COPD and asthma.

METHODS

Ninety subjects participated in a cross-sectional study: 30 patients with COPD (age, 61.6 +/- 9.3 years; FEV(1), 1.72 +/- 0.69 L), 20 patients with asthma (age, 35.4 +/- 15.1 years; FEV(1) 3.32 +/- 0.86 L), 20 nonsmoking control subjects (age, 56.7 +/- 9.3 years; FEV(1), 3.44 +/- 0.76 L), and 20 smoking control subjects (age, 56.1 +/- 5.9 years; FEV(1), 3.58 +/- 0.78). After 5 minutes of tidal breathing through an inspiratory VOC filter, an expiratory vital capacity was collected in a Tedlar bag and sampled by electronic nose. Breathprints were analyzed by discriminant analysis on principal component reduction resulting in cross-validated accuracy values (accuracy). Repeatability and reproducibility were assessed by measuring samples in duplicate by two devices.

MEASUREMENTS AND MAIN RESULTS

Breathprints from patients with asthma were separated from patients with COPD (accuracy 96%; P < 0.001), from nonsmoking control subjects (accuracy, 95%; P < 0.001), and from smoking control subjects (accuracy, 92.5%; P < 0.001). Exhaled breath profiles of patients with COPD partially overlapped with those of asymptomatic smokers (accuracy, 66%; P = 0.006). Measurements were repeatable and reproducible.

CONCLUSIONS

Molecular profiling of exhaled air can distinguish patients with COPD and asthma and control subjects. Our data demonstrate a potential of electronic noses in the differential diagnosis of obstructive airway diseases and in the risk assessment in asymptomatic smokers. Clinical trial registered with www.trialregister.nl (NTR 1282).