External ears for non-invasive and stable monitoring of volatile organic compounds in human blood

Koji Toma,Yasuhiko Iwasaki,Kohji Mitsubayashi,Takahiro Arakawa,Shota Suzuki

doi:10.1038/s41598-021-90146-1

Koji Toma, Yasuhiko Iwasaki + Show 3 more

Open Access

https://doi.org/10.1038/s41598-021-90146-1

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Abstract

Volatile organic compounds (VOCs) released through skin (transcutaneous gas) has been increasing in importance for the continuous and real-time assessment of diseases or metabolisms. For stable monitoring of transcutaneous gas, finding a body part with little interference on the measurement is essential. In this study, we have investigated the possibility of external ears for stable and real-time measurement of ethanol vapour by developing a monitoring system that consisted with an over-ear gas collection cell and a biochemical gas sensor (bio-sniffer). The high sensitivity with the broad dynamic range (26 ppb–554 ppm), the high selectivity to ethanol, and the capability of the continuous measurement of the monitoring system uncovered three important characteristics of external ear-derived ethanol with alcohol intake for the first time: there is little interference from sweat glands to a sensor signal at the external ear; similar temporal change in ethanol concentration to that of breath with delayed peak time (avg. 13 min); relatively high concentration of ethanol relative to other parts of a body (external ear-derived ethanol:breath ethanol = 1:590). These features indicated the suitability of external ears for non-invasive monitoring of blood VOCs.

Highlights

Volatile organic compounds (VOCs) released through skin has been increasing in importance for the continuous and real-time assessment of diseases or metabolisms
When the ethanol vapor reaches the Alcohol dehydrogenase (ADH) membrane, the catalysed redox reaction occurs at the membrane together with N AD+ in the buffer solution running above the membrane, which produces NADH in the buffer solution
We have examined the possibility of the external ear for stable monitoring of transcutaneous VOC by developing the monitoring system

Summary

Introduction

Volatile organic compounds (VOCs) released through skin (transcutaneous gas) has been increasing in importance for the continuous and real-time assessment of diseases or metabolisms. 13 min); relatively high concentration of ethanol relative to other parts of a body (external ear-derived ethanol:breath ethanol = 1:590) These features indicated the suitability of external ears for non-invasive monitoring of blood VOCs. Exhaled breath and transcutaneous gas contain volatile organic compounds (VOCs) from b lood[1]. There are highly sensitive analytical methods for VOCs in exhaled breath and transcutaneous gas, such as gas chromatography mass spectrometry (GC–MS)[7], proton-transfer-reaction mass spectrometry (PTR-MS)[8] that is often coupled with time of flight mass analyser (PTR–TOF–MS)[9], and selected-ion flow-tube mass spectrometry (SIFT-MS)[10] Their capability of identifying VOC composition is powerful for comprehensive analysis of the gas, the size and complexity of the system are drawbacks for monitoring transcutaneous VOC. Yamada et al presented a semiconductor-based portable sensor for transcutaneous blood acetone, which utilized zeolite to concentrate acetone before measurement[13,14]

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