Wearable sampling of proteins from human exhaled aerosols for nano-liquid chromatography-tandem mass spectrometry analysis: A pilot study

RATIONALE

Human exhaled breath usually contains unique proteins that may provide clues to characterize individual physiological activities and many diseases. However, the concentration of exhaled proteins in exhaled breath is extremely low and usually does not reach the detection limits of all online breath mass spectrometry instruments. Therefore, developing a new breath sampler for collecting and characterizing exhaled proteins is important.

METHODS

In this study, a new mask-based wearable sampler was developed by fixing metal materials into the inner surface of the KN95 mask. Human exhaled proteins could be directly adsorbed onto the metal material while wearing the mask. After sampling, the collected proteins were eluted, digested, and identified using nano-liquid chromatography-tandem mass spectrometry (nano-LC-MS/MS).

RESULTS

The adsorption of exhaled proteins was evaluated, showing that modified gold foil is an effective material for collecting exhaled proteins. Various endogenous proteins were successfully identified from exhaled breath, many of which can be potential biomarkers for disease diagnosis.

CONCLUSIONS

By coupling the newly developed mask sampler with nano-LC-MS/MS, human exhaled proteins were successfully collected and identified. Our results show that the mask sampler is wearable, simple, and convenient, and the method is noninvasive for investigating disease diagnosis and human health.

A clinical proteomics study of exhaled breath condensate and biomarkers for pulmonary embolism

Pulmonary embolism (PE) can be a diagnostic challenge. Current diagnostic markers for PE are unspecific and new diagnostic tools are needed. The air we exhale is a possible new source for biomarkers which can be tapped into by analysing the exhaled breath condensate (EBC). We analysed the EBC from patients with PE and controls to investigate if the EBC is a useful source for new diagnostic biomarkers of PE. We collected and analysed EBC samples from patients with suspected PE and controls matched on age and sex. Patients in whom PE was ruled out after diagnostic work-up were included in the control group to increase the sensitivity and generalizability of the identified markers. EBC samples were collected using an RTube™. The protein composition of the EBCs were analysed using data dependent label-free quantitative nano liquid chromatography-tandem mass spectrometry. EBC samples from 28 patients with confirmed PE, and 49 controls were analysed. A total of 928 EBC proteins were identified in the 77 EBC samples. As expected, a low protein concentration was determined which resulted in many proteins with unmeasurable levels in several samples. The levels of HSPA5, PEBP1 and SFTPA2 were higher and levels of POF1B, EPPK1, PSMA4, ALDOA, and CFL1 were lower in PE compared with controls. In conclusion, the human EBC contained a variety of endogenous proteins and may be a source for new diagnostic markers of PE and other diseases.

Putative Biomarkers for Acute Pulmonary Embolism in Exhaled Breath Condensate

Current diagnostic markers for pulmonary embolism (PE) are unspecific. We investigated the proteome of the exhaled breath condensate (EBC) in a porcine model of acute PE in order to identify putative diagnostic markers for PE. EBC was collected at baseline and after the induction of autologous intermediate-risk PE in 14 pigs, plus four negative control pigs. The protein profiles of the EBC were analyzed using label-free quantitative nano liquid chromatography-tandem mass spectrometry. A total of 897 proteins were identified in the EBCs from the pigs. Alterations were found in the levels of 145 different proteins after PE compared with the baseline and negative controls: albumin was among the most upregulated proteins, with 14-fold higher levels 2.5 h after PE (p-value: 0.02). The levels of 49 other proteins were between 1.3- and 17.1-fold higher after PE. The levels of 95 proteins were lower after PE. Neutrophil gelatinase-associated lipocalin (fold change 0.3, p-value < 0.01) was among the most reduced proteins 2.5 h after PE. A prediction model based on penalized regression identified five proteins including albumin and neutrophil gelatinase-associated lipocalin. The model was capable of discriminating baseline samples from EBC samples collected 2.5 h after PE correctly in 22 out of 27 samples. In conclusion, the EBC from pigs with acute PE contained several putative diagnostic markers of PE.

Comparative proteomic analysis of exhaled breath condensate between lung adenocarcinoma and CT-detected benign pulmonary nodule patients

BACKGROUND

Lung cancer is the leading cause of cancer mortality worldwide. The collection of exhaled breath condensate (EBC) is a non-invasive method that may have enormous potential as a biomarker for the early detection of lung cancer.

OBJECTIVE

To investigate the proteomic differences of EBC between lung cancer and CT-detected benign nodule patients, and determine whether these proteins could be potential biomarkers.

METHODS

Proteomic analysis was performed on individual samples from 10 lung cancer patients and 10 CT-detected benign nodule patients using data-independent acquisition (DIA) mass spectrometry.

RESULTS

A total of 1,254 proteins were identified, and 21 proteins were differentially expressed in the lung adenocarcinoma group compared to the benign nodule group (p< 0.05). The GO analysis showed that most of these proteins were involved in neutrophil-related biological processes, and the KEGG analysis showed these proteins were mostly annotated to pyruvate and propanoate metabolism. Through protein-protein interactions (PPIs) analysis, ME1 and LDHB contributed most to the interaction-network of these proteins.

CONCLUSION

Significantly differentially expressed proteins were detected between lung cancer and the CT-detected benign nodule group from EBC samples, and these proteins might serve as potential novel biomarkers of EBC for early lung cancer detection.

Exhaled Breath Condensate (EBC): Is It a Viable Source of Biomarkers for Lung Diseases?

The exhaled breath condensate is a source of biomarkers with many advantages and benefits compared to other traditional sampling techniques in respiratory medicine. It is a biological product that is formed by cooling the exhaled air via its guidance through a condenser. It is characterized as a cocktail of volatile and non-volatile compounds with water being the predominant constituent. Its composition presents a non-uniformed structure as the volatile and the non-volatile compounds vary in type and ratio. All these compounds originate from the whole respiratory tract. Some of them fulfil the criteria to be characterized as biomarkers since there is a similarity between the content of the exhaled breath condensate and the respiratory tract lining fluid. In addition, the potential biomarkers of the exhaled breath condensate and those from other biological fluids are equivalent.Advantages and Disadvantages Its place in the respiratory medicine as a matrix of biomarkers relies on its various strengths. Some of them are very important and make it exceptional regarding its application, such as its totally non-invasive character and its usage in all ages, while others present a more potential action regarding its purpose such as the categorization of respiratory diseases. However, there are limitations in its application due to the lack of standardization of its conduct which can be minimized by following the official recommendations. Additional studies are needed to develop said standardization.Aim The aim of this paper is to present a brief and comprehensive picture of the sampling technique of the exhaled breath condensate, as well as the criteria to make it a preferred choice as a source of biomarkers.

Breath analysis for detection of viral infection, the current position of the field

The COVID-19 pandemic has highlighted the importance of rapid, cost effective, accurate, and non-invasive testing for viral infections. Volatile compounds (VCs) have been suggested for several decades as fulfilling these criteria. However currently very little work has been done in trying to diagnose viral infections using VCs. Much of the work carried out to date involves the differentiation of bacterial and viral sources of infection and often the detection of bacterial and viral co-infection. However, this has usually been done in vitro and very little work has involved the use of human participants. Viruses hijack the host cell metabolism and do not produce their own metabolites so identifying virus specific VCs is at best a challenging task. However, there are proteins and lipids that are potential candidates as markers of viral infection. The current understanding is that host cell glycolysis is upregulated under viral infection to increase the available energy for viral replication. There is some evidence that viral infection leads to the increase of production of fatty acids, alkanes, and alkanes related products. For instance, 2,3-butandione, aldehydes, 2,8-dimethyl-undecane and n-propyl acetate have all been correlated with viral infection. Currently, the literature points to markers of oxidative stress (e.g. nitric oxide, aldehydes etc) being the most useful in the determination of viral infection. The issue, however, is that there are also many other conditions that can lead to oxidative stress markers being produced. In this review a range of (mainly mass spectrometric) methods are discussed for viral detection in breath, including breath condensate. Currently MALDI-ToF-MS is likely to be the preferred method for the identification of viral strains and variants of those strains, however it is limited by its need for the viral strains to have been sequenced and logged in a database.

Effects of individual ozone exposure on lung function in the elderly: a cross-sectional study in China

The aim of this study was to assess the acute health effects of individual ozone (O₃) exposure on the respiratory system in the elderly. A total of 40 non-smoking elderly volunteers completed personal 24 h of measurement for O₃ and fine particulate matter (PM_2.5). To assess health effects, we measured the pulmonary function and five inflammatory biomarkers in exhaled breath condensate (EBC), including interleukin-2 (IL-2), interferon-γ (IFN-γ), prostaglandin E₂ (PGE₂), and tumor necrosis factor α/β (TNFα/β). We used the generalized additive model to analyze the association between O₃ and these health effects, after adjusting PM_2.5, BMI, and sex as confounders. As a result, we found a negative correlation between O₃ and forced vital capacity (FVC) or forced expiratory volume-one second (FEV1). With the increasing of O₃ by 10 μg/m³, FVC and FEV1 decreased by 0.13 L (95% CI 0.01, 0.26) and 0.11 L (95% CI 0.02, 0.20), respectively. We found no statistical significance between O₃ and biomarkers in EBC. The results suggested that individual 24-h O₃ exposure was associated with decreased pulmonary function in the elderly.

Determining the presence of asthma-related molecules and salivary contamination in exhaled breath condensate

Background

Researchers investigating lung diseases, such as asthma, have questioned whether certain compounds previously reported in exhaled breath condensate (EBC) originate from saliva contamination. Moreover, despite its increasing use in ‘omics profiling studies, the constituents of EBC remain largely uncharacterized. The present study aims to define the usefulness of EBC in investigating lung disease by comparing EBC, saliva, and saliva-contaminated EBC using targeted and untargeted mass spectrometry and the potential of metabolite loss from adsorption to EBC sample collection tubes.

Methods

Liquid chromatography mass spectrometry (LC-MS) was used to analyze samples from 133 individuals from three different cohorts. Levels of amino acids and eicosanoids, two classes of molecules previously reported in EBC and saliva, were measured using targeted LC-MS. Cohort 1 was used to examine contamination of EBC by saliva. Samples from Cohort 1 consisted of clean EBC, saliva-contaminated EBC, and clean saliva from 13 healthy volunteers; samples were analyzed using untargeted LC-MS. Cohort 2 was used to compare eicosanoid levels from matched EBC and saliva collected from 107 asthmatic subjects. Samples were analyzed using both targeted and untargeted LC-MS. Cohort 3 samples consisted of clean-EBC collected from 13 subjects, including smokers and non-smokers, and were used to independently confirm findings; samples were analyzed using targeted LC-MS, untargeted LC-MS, and proteomics. In addition to human samples, an in-house developed nebulizing system was used to determine the potential for EBC samples to be contaminated by saliva.

Results

Out of the 400 metabolites detected in both EBC and saliva, 77 were specific to EBC; however, EBC samples were concentrated 20-fold to achieve this level of sensitivity. Amino acid concentrations ranged from 196 pg/mL – 4 μg/mL (clean EBC), 1.98 ng/mL – 6 μg/mL (saliva-contaminated EBC), and 13.84 ng/mL – 1256 mg/mL (saliva). Eicosanoid concentration ranges were an order of magnitude lower; 10 pg/mL – 76.5 ng/mL (clean EBC), 10 pg/mL – 898 ng/mL (saliva-contaminated EBC), and 2.54 ng/mL – 272.9 mg/mL (saliva). Although the sample size of the replication cohort (Cohort 3) did not allow for statistical comparisons, two proteins and 19 eicosanoids were detected in smoker vs. non-smoker clean-EBC.

Conclusions

We conclude that metabolites are present and detectable in EBC using LC-MS; however, a large starting volume of sample is required.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-017-0538-5) contains supplementary material, which is available to authorized users.

Exhaled breath condensate for lung cancer protein analysis: a review of methods and biomarkers

Lung cancer is a leading cause of cancer-related deaths worldwide, and is considered one of the most aggressive human cancers, with a 5 year overall survival of 10-15%. Early diagnosis of lung cancer is ideal; however, it is still uncertain as to what technique will prove successful in the systematic screening of high-risk populations, with the strongest evidence currently supporting low dose computed tomography (LDCT). Analysis of exhaled breath condensate (EBC) has recently been proposed as an alternative low risk and non-invasive screening method to investigate early-stage neoplastic processes in the airways. However, there still remains a relative paucity of lung cancer research involving EBC, particularly in the measurement of lung proteins that are centrally linked to pathogenesis. Considering the ease and safety associated with EBC collection, and advances in the area of mass spectrometry based profiling, this technology has potential for use in screening for the early diagnosis of lung cancer. This review will examine proteomics as a method of detecting markers of neoplasia in patient EBC with a particular emphasis on LC, as well as discussing methodological challenges involving in proteomic analysis of EBC specimens.