Wearable Sensor for Real-Time Monitoring of Hydrogen Peroxide in Simulated Exhaled Air

In this work, an innovative and cheap electrochemical sensor for hydrogen peroxide quantification in exhaled breath was developed. H2O2 is the most used biomarker among the Reactive Oxygen Species (ROS) for monitoring the level of oxidative stress in the respiratory system. This is due to its stability and ability to cross biological membranes and also because it is detectable in extracellular space. The electrochemical sensor was obtained using the silver layer of wasted compact discs (CDs). All three electrodes, working (WE), counter (CE), and pseudo-reference electrode (RE), were fabricated using a laser cutter. The working electrode was used directly, while an Ag/AgCl paste and a graphite paste were applied respectively on the RE and the CE. In addition, a chitosan layer was deposited by Electro-Phoretic Deposition (EPD) on the surface of the sensor. This biopolymer improves the wettability of the sensor in presence of a humid atmosphere such as that given by exhaled air. The sensor was tested in both liquid and nebulized solutions containing different concentrations of hydrogen peroxide. The detection of H2O2 was evaluated using Linear Sweep Voltammetry (LSV) as electrochemical technique. The results show that the peak current increases linearly with hydrogen peroxide concentration from 100 to 500 μM with a sensitivity of 0.068 µA µM−1 cm−2 and 0.108 µA µM−1 cm−2, a Limit Of Detection (LOD) of 60 μM and 30 μM respectively for liquid and nebulized solutions. Therefore, the use of the electrochemical sensor can allow the monitoring of hydrogen peroxide in real time with good results.