This Spotlight discusses optical sensing strategies and applications for early diagnostics in exhaled breath (EB) analyses. These sensors can noninvasively assess relevant biomarkers in EB, enabling early diagnosis of several diseases (e.g., cancer, asthma, diabetes) and the monitoring of breath metabolites in hospitalized patients after drug administration. Gas sensors with suitable selectivity, sensitivity, and a short response time are essential; in particular, optical-sensor-based transductions (e.g., UV-Vis absorbance, luminescence, infrared) are ideal for building portable dedicated devices, such as lab-on-a-chip and microfluidics devices.
Since Paracelsus in the late medieval ages, the analysis of exhaled breath has served to determine the health condition of patients. Steady progress in analytical instrumentation and, more recently, sensing technologies has translated qualitative odor diagnostics into precise and reliable tools ready for clinical usage, providing quantitative molecular information. Despite the complexity of the exhaled breath matrix, diseases as well as therapeutically relevant biomarker panels are readily accessible in a noninvasive fashion to provide insight into the physiological condition of the patient, disease status, and therapeutic progress. Recent progress in optics, photonics, and system miniaturization and integration has given optical sensors the potential to lead the field of breath analysis into routinely applied and, ultimately, low-cost diagnostics for point-of-care application scenarios.