Ethanol vapours above lacrimal fluid in the rabbit

Eyeglasses-based tear biosensing system: Non-invasive detection of alcohol, vitamins and glucose

We report on a wearable tear bioelectronic platform, integrating a microfluidic electrochemical detector into an eyeglasses nose-bridge pad, for non-invasive monitoring of key tear biomarkers. The alcohol-oxidase (AOx) biosensing fluidic system allowed real-time tear collection and direct alcohol measurements in stimulated tears, leading to the first wearable platform for tear alcohol monitoring. Placed outside the eye region this fully wearable tear-sensing platform addresses drawbacks of sensor systems involving direct contact with the eye as the contact lenses platform. Integrating the wireless electronic circuitry into the eyeglasses frame thus yielded a fully portable, convenient-to-use fashionable sensing device. The tear alcohol sensing concept was demonstrated for monitoring of alcohol intake in human subjects over multiple drinking courses, displaying good correlation to parallel BAC measurements. We also demonstrate for the first time the ability to monitor tear glucose outside the eye and the utility of wearable devices for monitoring vitamin nutrients in connection to enzymatic flow detector and rapid voltammetric scanning, respectively. These developments pave the way to build an effective eyeglasses system capable of chemical tear analysis.

Noninvasive estimation of blood alcohol concentrations by eye vapor analysis using an electrochemical fuel cell detector

A widely used breath analysis instrument was adapted for the noninvasive determination of blood alcohol in small animals. The instrument's response to ethanol in vapor above the lacrimal fluid was analyzed subsequent to taking vapor samples from a small eye cup for 15 sec. After ethanol administration (1.5 g/kg, orally) to rats, eye vapor measurements and venous blood samples were obtained over 5 hr. Eye vapor measurements were transposed into blood alcohol concentrations and compared with concentrations obtained by gas chromatographic analysis of blood. The correlation of concentrations obtained by the two methods yielded correlation coefficients of 0.93 and 0.95 depending on the calculation used. Eye vapor response and blood alcohol concentration were also found to be highly correlated (r = 0.96) after alcohol administration to mice and sampling for 2.5 hr after ethanol administration. Kinetic profiles obtained by eye vapor analysis and gas chromatography are virtually identical. The method described allows widespread use of a new, noninvasive approach to alcohol analysis in laboratory animals.