Towards E-Nose Detection of Volatile Organic Compounds as Disease Biomarkers with Complementary Cardiovascular Assessment

Monitoring of volatile organic compounds (VOCs) in body fluids (blood, urine, sweat and saliva) or exhaled breath is a recent trend in medical research with the potential to unveil information about internal body processes or metabolic pathways dysregulated due to bacterial infection, tissue cancer, inflammation, and injury. Typically, these low-weight chemical compounds are analyzed from collected samples by expensive methods involving gas chromatography-mass spectrometry, proton-transfer-reaction mass spectrometry or ion mobility-spectrometry, which makes it difficult to translate into wearable technology for day-to-day use by patients. Recently, E-noses have been proposed to sense chemicals and/or odors from gas exchanges taking place in the upper body part, in an attempt to replace the human nose, with different degrees of success. In this paper, we propose a prototype for an E-nose device with sensing modules for VOCs detection by graphene-field effect transistor (GFET) technology, combined with modules for the detection of body temperature, motion and sounds produced by the cardiovascular system. We successfully tested the prototype in the neck region (carotid artery) for monitorization of the latter variables, whereas 12 clinically relevant VOCs were monitored inside a controlled setup for metrics such as the change of graphene’s resistance and spectral noise upon exposure to these vapors. This can then constitute the basis for development of a fully integrated system that directly correlates physiological variables with disease biomarkers sensed from gas exchanges.