Dynamic Breath Limonene Sensing at High Selectivity

Liver diseases (e.g., cirrhosis, cancer) cause more thantwo milliondeaths per year worldwide. This is partly attributed to late diagnosisand insufficient screening techniques. A promising biomarker for noninvasiveand inexpensive liver disease screening is breath limonene that canindicate a deficiency of the cytochrome P450 liver enzymes. Here,we introduce a compact and low-cost detector for dynamic and selectivebreath limonene sensing. It comprises a chemoresistive sensor basedon Si/WO3 nanoparticles pre-screened by a packed bed Tenaxseparation column at room temperature. We demonstrate selective limonenedetection down to 20 parts per billion over up to three orders ofmagnitude higher concentrated acetone, ethanol, hydrogen, methanol,and 2-propanol in gas mixtures, as well as robustness to 10-90%relative humidity. Most importantly, this detector recognizes theindividual breath limonene dynamics of four healthy volunteers followingthe ingestion (swallowing or chewing) of a limonene capsule. Limonenerelease and subsequent metabolization are monitored from breath measurementsin real time and in excellent agreement (R (2) = 0.98) with high-resolution proton transfer reaction mass spectrometry.This study demonstrates the potential of the detector as a simple-to-useand noninvasive device for the routine monitoring of limonene levelsin exhaled breath to facilitate early diagnosis of liver dysfunction.