Background: Inhalation of particulate matter (PM) tends to induce inflammation and endogenous reactive oxygen species (ROS) production. ROS overproduction, in turn, lead to oxidative stress and increase the risk of respiratory diseases, including chronic obstructive pulmonary disease (COPD). The diagnosis of COPD currently relies on respiratory functional exploration test using spirometry. However, this technique does not allow early diagnosis nor early detection of exacerbation episodes. In a complementary approach we have developed a portable photonic system able to determine the oxidative potential in the exhaled air (OPEA). The fast and non-invasive determination of OPEA provides access to biochemical information related to oxidative stress occurring in the lung.
Methods: The system is based on the amplification of the absorbance through multiscaterring-enhanced absorbance strategy (EU/US patent) that combines multiscattering and reflection in a compact photonic cell. Optimization and analytical validation of the OPEA analyzer system aims to achieve robust and sensitive measurements adapted for clinical studies.
Results: Several aspects of the OPEA system have been optimized: i) sample introduction in the reaction vial (bubbling flow rate, drop pressure reduction); ii) optimal light source/ photodetector for improved sensitivity (narrow LED spectrum); iii) Temperature stabilization (35°C); improved specificity (near-IR internal reference to avoid optical interferences.) The achieved limit-ofdetection stands in the pmol range for H2O2 equivalents.
Short discussion/conclusions: The developed method will be further characterized through the analysis of exhaled air samples from control and COPD subjects in order to evaluate the inter and within-subject variability over time; the influence of potential exogenous interfering compounds from outdoor urban environment (traffic-related air pollution) on the measured level; and the best sample storage conditions for field studies. Later on, the optimal context-of-use of the OPEA detection – early diagnosis, personalized treatment and early-phase exacerbation alert – will be determined in the frame of further clinical studies.