Highly sensitive flux-type non-invasive alcohol biosensor based on direct electron transfer of PQQ-dependent alcohol dehydrogenases adsorbed on carbon nanotubes†

Ethanol gas excreted by human skin can be used to determine auto-brewery syndrome (drunken disease), blood alcohol levels, and/or a body state of alcoholism. Considering the limitations of continuous non-invasive alcohol gas monitoring based on the electrochemical method, which requires high sensitivity and selectivity, a CNF film sensor was developed. This sensor was developed by utilizing pyrroloquinoline quinone-dependent alcohol dehydrogenase (PQQ-ADH) and multiwalled carbon nanotubes (MWCNTs) based on cellulose nanofiber (CNF) film platform. With a compact design, a PQQ-ADH/MWCNTs/CNF film sensor was built in a three-electrode system. This system could continuously detect ethanol gas with ultra-high sensitivity, a wide detection range (24 ppb–25 ppm), and high selectivity for ethanol. Finally, the CNF film sensor was used for ethanol gas monitoring in the human subject, and we were able to detect metabolism abnormalities of the subject by analyzing the declining slope (detoxification rate) of the ethanol gas concentration monitored. The CNF film sensor aims to gain valuable insights and enhance future standard health screening practices through non-invasive wearable daily monitoring sensors.