Chemical Assisted Opto-Electrical Nitrate Sensor for Detection of Inflammatory Disorder of Lungs

Abstract

Human breath is a noninvasive, information-rich bio-specimen containing disease specific biomarkers. Current exhaled breath (EB) analyzers have several limitations, including high cost, complexity and unavailability in clinical settings. This work develops and characterizes an inexpensive, rapid and reproducible Nitrate sensing system to monitor and diagnose the Asthmatic conditions using EB condensate (EBC) as a biosample. Elevated nitrate concentration in EBC reflects an increased nitric oxide (NO) metabolism. In this work, the EB is collected in a medicated polypropylene bag and placed in a laboratory standard refrigerator to produce a condensate containing Nitrate as one component. Nitrate reacts with the Brucine sulfate solution showing a distinct color change (yellowish). The intensity of the color formed was linearly dependent on the nitrate concentration. The proposed system, using an optical transceiver, responded instantly to the nitrate concentration. The performance indices of the portable device like sensitivity (3.56 mV/ppm of nitrate concentration in EBC), repeatability, response time ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 10$ </tex-math></inline-formula> s), etc. were assessed. The detection limit was found 0.1 ppm. The clinical performance of the device was compared with the standard nitrate tests using blood samples from 130 male volunteers. The statistical analysis of the data pairs using Bland Altman plot showed a significant agreement within ±5% confidence interval and correlation ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${r}^{{2}}=0.989$ </tex-math></inline-formula> ).