Analytical methods based on exhaled breath for early detection of lung cancer

A visualization method for quickly detecting nitrite ions in breath condensate using a portable closed bipolar electrochemical sensor

A portable and non-invasive sensor presents an innovative way to measure inflammation biomarkers in exhaled breath condensate (EBC). This research is focused on developing a miniaturized bipolar electrochemical sensor that can be connected to a smartphone app. This device will be able to detect adding known amounts of nitrite (spikes) to a salt solution and small amounts of nitrite ions in collected real samples in EBC. The sensor was fabricated and tested for its rapid electron transfer capability and ability to detect nitrite ions even at very low concentrations and low real sample levels. In the proposed setup, when the required potential was applied by using a direct power supply, the nitrite ions were oxidized electrocatalytically at amine-functionalized graphene oxide (AGO) decorated with gold nanoparticles on a carbon paper anodic pole. On the other hand, the reduction reaction of Prussian blue occurred at the cathodic pole of the bipolar electrode simultaneously. This strategy led to a change in color from blue to white as a result of the reduction process and the color change is proportional to the concentration of nitrite ions in the analytical solution. The combination of smartphones with the colorimetric method has resulted in a platform for the detection of test strips that is more visual and convenient. The amperometry and voltammetric methods of nitrite detection showed a linear range of up to 1230 μM. The bipolar electrochemical sensor was able to detect the clinically relevant range of nitrite from 0.5 to 85 μM in a buffer with an ultralow detection limit (LOD) of 250 nM (S/N = 3), fast response and excellent selectivity. It was benchmarked by utilizing pre-characterized real EBC samples to differentiate patients with respiratory diseases from healthy volunteers. By tracking the results of nitrite measurements over time, it has become possible to detect trends and changes in an individual's nitrite ion concentration and to potentially identify lung inflammation earlier.

Online breath analysis using metal oxide semiconductor sensors (electronic nose) for diagnosis of lung cancer

The analysis of exhaled breath is drawing a high degree of interest in the diagnostics of various diseases, including lung cancer. Electronic nose (E-nose) technology is one of the perspective approaches in the field due to its relative simplicity and cost efficiency. The use of an E-nose together with pattern recognition algorithms allow 'breath-prints' to be discriminated. The aim of this study was to develop an efficient online E-nose-based lung cancer diagnostic method via exhaled breath analysis with the use of some statistical classification methods. A developed multisensory system consisting of six metal oxide chemoresistance gas sensors was employed in three temperature regimes. This study involved 118 individuals: 65 in the lung cancer group (cytologically verified) and 53 in the healthy control group. The exhaled breath samples of the volunteers were analysed using the developed E-nose system. The dataset obtained, consisting of the sensor responses, was pre-processed and split into training (70%) and test (30%) subsets. The training data was used to fit the classification models; the test data was used for the estimation of prediction possibility. Logistic regression was found to be an adequate data-processing approach. The performance of the developed method was promising for the screening purposes (sensitivity-95.0%, specificity-100.0%, accuracy-97.2%). This shows the applicability of the gas-sensitive sensor array for the exhaled breath diagnostics. Metal oxide sensors are highly sensitive, low-cost and stable, and their poor sensitivity can be enhanced by integrating them with machine learning algorithms, as can be seen in this study. All experiments were carried out with the permission of the N.N. Petrov Research Institute of Oncology ethics committee no. 15/83 dated March 15, 2017.

Ion mobility spectrometry: the diagnostic tool of third millennium medicine

Ion mobility spectrometry (IMS) is a fast, low cost, portable, and sensitive technique that separates ions in a drift tube under the influence of an electric field according to their size and shape. IMS represents a non-invasive and reliable instrumental alternative for the diagnosis of different diseases through the analysis of volatile metabolites in biological samples. IMS has applications in medicine in the study of volatile compounds for the non-invasive diagnose of bronchial carcinoma, chronic obstructive pulmonary disease, and other diseases analysing breath, urine, blood, faeces, and other biological samples. This technique has been used to study complex mixtures such as proteomes, metabolomes, complete organisms like bacteria and viruses, monitor anaesthetic agents, determine drugs, pharmaceuticals, and volatile compounds in human body fluids, and others. Pharmaceutical applications include analysis of over-the-counter-drugs, quality assessment, and cleaning verification. Medical practice needs non-invasive, robust, secure, fast, real-time, and low-cost methods with high sensitivity and compact size instruments to diagnose different diseases and IMS is the diagnostic tool that meets all these requirements of the Medicine of the future.

Evolution of clinical and environmental health applications of exhaled breath research: Review of methods and instrumentation for gas-phase, condensate, and aerosols

Human breath, along with urine and blood, has long been one of the three major biological media for assessing human health and environmental exposure. In fact, the detection of odor on human breath, as described by Hippocrates in 400 BC, is considered the first analytical health assessment tool. Although less common in comparison to contemporary bio-fluids analyses, breath has become an attractive diagnostic medium as sampling is non-invasive, unlimited in timing and volume, and does not require clinical personnel. Exhaled breath, exhaled breath condensate (EBC), and exhaled breath aerosol (EBA) are different types of breath matrices used to assess human health and disease state. Over the past 20 years, breath research has made many advances in assessing health state, overcoming many of its initial challenges related to sampling and analysis. The wide variety of sampling techniques and collection devices that have been developed for these media are discussed herein. The different types of sensors and mass spectrometry instruments currently available for breath analysis are evaluated as well as emerging breath research topics, such as cytokines, security and airport surveillance, cellular respiration, and canine olfaction.

Techniques and issues in breath and clinical sample headspace analysis for disease diagnosis

Analysis of volatile organic compounds (VOCs) from breath or clinical samples for disease diagnosis is an attractive proposition because it is noninvasive and rapid. There are numerous studies showing its potential, yet there are barriers to its development. Sampling and sample handling is difficult, and when coupled with a variety of analytical instrumentation, the same samples can give different results. Background air and the environment a person has been exposed to can greatly affect the VOCs emitted by the body; however, this is not an easy problem to solve. This review investigates the use of VOCs in disease diagnosis, the analytical techniques employed and the problems associated with sample handling and standardization. It then suggests the barriers to future development.

Sensitivity enhancement in the determination of volatile biomarkers in saliva using a mass spectrometry-based electronic nose with a programmed temperature vaporizer

With a view to improving the sensitivity of direct coupling of a headspace sampler (HS) with a mass spectrometer (MS), here we propose the use of a programmed temperature vaporizer (PTV) in solvent-vent injection mode before the sample is introduced into the MS. This preconcentration scheme has been used for some time in many methods based on gas chromatography (GC), but to the best of our knowledge it has not yet been used in an electronic nose based on MS. The increase in the S/N ratio with the proposed instrumental configuration (HS-PTV/MS) lies between 6.9- and 22-fold. The main advantage of using this injector lies in the fact that it does not involve time-consuming steps. To check the possibilities of this methodology, saliva samples from healthy volunteers and patients with different types of illnesses (including some types of cancer) were analyzed. None of the compounds studied was detected in the samples corresponding to the healthy volunteers. One or more biomarkers, at levels ranging from 13 to 500 μg/L, were found in five of the samples from the patients. Additionally, separative analysis by HS-PTV-GC/MS was performed for confirmatory purposes and both methods provided similar results. The main advantage of the proposed methodology is that no prior chromatographic separation and no sample manipulation are required.

Noninvasive analysis of volatile biomarkers in human emanations for health and early disease diagnosis

Early disease diagnosis is crucial for human healthcare and successful therapy. Since any changes in homeostatic balance can alter human emanations, the components of breath exhalations and skin emissions may be diagnostic biomarkers for various diseases and metabolic disorders. Since hundreds of endogenous and exogenous volatile organic compounds (VOCs) are released from the human body, analysis of these VOCs may be a noninvasive, painless, and easy diagnostic tool. Sampling and preconcentration by sorbent tubes/traps and solid-phase microextraction, in combination with GC or GC–MS, are usually used to analyze VOCs. In addition, GC–MS-olfactometry is useful for simultaneous analysis of odorants and odor quality. Direct MS techniques are also useful for the online real-time detection of VOCs. This review focuses on recent developments in sampling and analysis of volatile biomarkers in human odors and/or emanations, and discusses future use of VOC analysis.