Electrochemical Sensing of Nitrite, a Biomarker of Oxidative Stress, in Exhaled Breath Condensate

摘要

We have developed a portable sensor for measuring nitrite levels in exhaled breath condensate (EBC), a biomarker of inflammation and oxidative stress in the respiratory tract. EBC is collected in a non-invasively by breathing into cold tube. The miniaturized electrochemical sensor for detecting nitrite was fabricated using reduced graphene oxide. The unique properties of reduced Graphene Oxide (rGO) is its being resilient to corrosion while exhibiting rapid electron transfer with electrolytes allowing for highly sensitive electrochemical detection and minimal fouling. The rGO sensor was housed in an electrochemical cell fabricated from Polydimethyl Siloxane (PDMS), to facilitate its ability to analyze small EBC sample volumes (<0.1 mL). The sensor is capable of detecting nitrite at a low over-potential of 0.7 V with respect to Ag/AgCI reference electrode. The sensor demonstrated a sensitivity of 0.21 μA μM~(-1) cm~(-2) in the range of 20-100 μM and 0.1 μA μM~(-1) cm~(-2) in the range of 100-1000 μM nitrite concentration with a low detection limit of 830 nM in the EBC matrix. The performance of the sensors was characterized using standard nitrite solutions in buffer, nitrite spiked into EBC, and also clinical EBC samples as well as compared to nitrite measured using a colometric method. The two colormetric and sensor method characterized the same trend in nitrite concentration in both fresh and frozen EBC samples, with the results being within a factor of two across nitrite concentrations ranging between 0.14-6.5 μM. This enzyme-free and label-free method of detecting biomarkers in EBC can pave the way for development of portable breath analyzers for use in studies of the effect of air pollution on oxidative stress and respiratory inflammation.