Exhaled breath analysis (EBA) is an advanced, non-invasive diagnostic technique that utilizes volatile organic compounds (VOCs) to detect and monitor various diseases. This review examines EBA’s historical development and current status as a promising diagnostic tool. It highlights the significant contributions of modern methods such as gas chromatography–mass spectrometry (GC-MS), ion mobility spectrometry (IMS), and electronic noses in enhancing the sensitivity and specificity of EBA. Furthermore, it emphasizes the transformative role of nanotechnology and machine learning in improving the diagnostic accuracy of EBA. Despite challenges such as standardization and environmental factors, which must be addressed for the widespread adoption of this technique, EBA shows excellent potential for early disease detection and personalized medicine. The review also highlights the potential of photonic crystal fiber (PCF) sensors, known for their superior sensitivity, in the field of EBA.

The g-C3N4/CS biosensor was designed, fabricated, and tested using compounds such as glucose, urine, lactose, and flutamide at a molarity of 10 µM, which could demonstrate a high sensitivity of 200 μm-1 for flutamide. Powerful effective medium theory and FDTD simulation were used to predict the most favorable mode and plasmonic properties of a graphite carbon nitride and chitosan nanocomposite. The research also explores the characteristics of surface plasmon resonance exhibited by the nanocomposite as the chitosan content is adjusted. Subsequent simulations are conducted on nanocomposites incorporating a thin layer and a modified gold structure. The intricate simulations ultimately reveal the optimal combination, tested under three different pH conditions (6.2, 7.2, and 8). In acidic conditions, the kinetic profile yielded a K_D= 3.45 × 10⁻⁷, surpassing the K_D value of a thin film. The Au significantly outperformed the alternative material. The biosensor demonstrated linear behavior across a wide concentration range from 1 to 150 µM, achieving a detection limit of 120 nM with its high sensitivity.