Поступила в редакцию 4 ноября 2017 г. Принята 17 ноября 2017 г.Актуальность. На сегодняшний день вопрос детектирования различных штаммов бактерии H. pylori приобрел большую значимость ввиду распространенности этой бактерии по всему миру и той роли, которую она играет в развитии множества серьезных желудочных и внежелудочных заболеваний. При этом не все штаммы бактерии H. pylori являются агрессивными и требуют лечения с использованием антибиотиков. Таким образом, возникает вопрос о необходимости дифференциации этих бактерий по их факторам вирулентности. Недорогой и общедоступной технологией для решения этой задачи могут стать современные сенсорные устройства. Цель работы. Цель работы состоит в разработке сенсорного устройства нового типа для дифференциального распознавания штаммов H. pylori на основе анализа смеси газов, выдыхаемых человеком. Такое устройство может быть создано на основе точечно-контактного газового сенсора. Материалы и методы. Фундаментальные свойства точечных контактов, используемых в микроконтактной спектроскопии Янсона, позволили сформировать на основе соединений TCNQ точечно-контактную мезоскопическую матрицу, чувствительную к малым концентрациям веществ в составе сложной газовой смеси. Анализируемым веществом служил газ, выдыхаемый человеком. Результаты. Газочувствительные точечно-контактные сенсоры на основе соединений TCNQ имеют сложные кривые отклика с двумя экстремумами, которые можно называть спектральными профилями сложной газовой смеси. Используя спектральные профили выдыхаемого газа различных пациентов можно дифференцировать различные состояния организма человека, вызванные бактерией H. pylori. Выводы. Показано, что продукты метаболизма канцерогенных штаммов бактерии H. pylori доминантно влияют на электропроводность сенсора и предопределяют поведение особенностей на кривых отклика сенсоров. В результате, используя точечно-контактные сенсоры на основе соединений TCNQ возможно дифференцировать штаммы H. pylori по их канцерогенному Background: The problem of detecting the different strains of H. pylori has gained great importance today due to the worldwide prevalence of this bacterium and its role in the pathogenesis of a number of serious gastric and extragastric diseases. However, not all H. pylori strains are aggressive and require antibiotic treatment. Thus, the question arises about the necessity of differentiating these bacterium strains with respect to their virulence factors. In accordance with the IV Maastricht Consensus Report, among the variety of ways to diagnose H. pylori infection, non-invasive methods should be given preference. Most of them are based on the analysis of gas which is exhaled by a human. Mass spectrometry, gas chromatography, and IR spectroscopy are currently the mostly used ones. However, despite the obvious advantages, these techniques have a number of disadvantages that make them difficult to use in everyday medical practice. Modern sensor devices can become an inexpensive and easy to access alternative to these technologies. Objectives: The aim of the w...
Original fundamental properties of Yanson point contacts allow their application to research and technology development at a wide range of surrounding conditions. At low temperature these nanoobjects can be used as a main instrument of Yanson point-contact spectroscopy. At room temperature they can serve as a sensitive element of advanced nanosensors with excellent performance. The most important advantage of point-contact sensors in investigating complex gas media is the spectral nature of the response signal. The discovery of the spectral capabilities of point-contact sensors in the analysis of complex gas media allows us to speak in terms of spectral multifunctionality of Yanson point contacts and the expansion of the possibilities of their spectral application from the spectroscopy of electron-phonon interaction at low temperatures to spectroscopy of gaseous media at room temperatures. Using the spectral response of point-contact sensors, in this work we propose a new non-invasive method for the determination of melatonin, one of the important hormones characterizing the state of the human body. A series of procedures was proposed to find melatonin concentration in the human body as function of the response of a point-contact sensor to the action of the exhaled breath. It has been shown that the proposed method is accurate enough to be used for medical purposes in real time. The results of the study suggest that the problem of non-invasive determination of melatonin concentration in the human body can be successfully solved by using breath tests based on Yanson point contacts.
The 7,7,8,8-tetracyanoquinodimethane (TCNQ) radical anion salt compound was used as the sensitive material of gas point contact sensors. The phase composition and surface morphology of the obtained sensor films were established. It was found correlation between surface morphology of the point-contact transducer and definite type of the sensor response curve observed under action of the human breath gas. If the sensor sample is formed from numerical crystals of the same or similar sizes having a uniform shape, similar to a shell, and clearly defined external borders it indicates to the creation of defect-free Yanson point contacts in the process of soft electrochemical synthesis. As a result, the surface of the sensor is a complex multistructure of a numerous number of Yanson point contacts, which generates a large output signal from the sensor in response to the action of the analyte. When crystals of Cu-TCNQ compound forming samples under investigation have lower density, large size, distorted and full of fractures boundaries, it prevents the formation of high-quality point contacts. These morphologic peculiarities are typical for samples with low level of response signal. In the case of extremely low density of Cu-TCNQ crystals observed in the sample surface the sample does not show any response to the action of the human breath gas.
The electric conductivity of point-contact multistructured sensors in a complex medium of the human breath gas has been studied. Considering a large number of parameters which characterize response curves of point-contact sensors, we proved the possibility of using a statistical procedure to assess the reproducibility of sensor operation. To select sensors with similar parameters from a studied set of sensors, the method of cluster analysis was employed. As a result, we first propose a criterion for selection of uniform sensors from sample sets based on sensing arrays, each containing over 200 point-contact sensing elements. We demonstrate the effectiveness of the proposed approach for the selection of uniform sensors in experiments with breath gas exhaled by a volunteer. In this case, pairs of random elements from the formed cluster show a good reproducibility of their sensor images. The selected elements are thus proved to be uniform samples which can be used to study complex gas media, for example, in clinical practice to develop methods of noninvasive diagnosis based on breath analysis.
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