Nanosensors for Exhaled Breath Condensate: Explored Models, Analytes, and Prospects

Exhaled breath condensate (EBC) has gained attention as a diagnostic gateway for lung diseases, brain–gut microbiota dysbiosis, and biobanking. Due to its non-invasive and fast collection method, EBC collection is not under temporal or volume limitations. Nonetheless, conventional EBC screening methods are complex and require high operational costs and expertise. Thus, the advent of nanotechnology has introduced efforts for using nanosensors as EBC analyzers. Over the past decade, multiple EBC-based studies reported the successful use of functionalized nanosensors to trace oxidative stress, tissue damage, and respiratory diseases. The EBC signature includes biomarkers such as gases (H2O2 and VOCs), cations (polyamines), fatty acids, cytokines, and aldehydes, in addition to traces of drugs and antibiotics. A common feature of nanosensors is their ability to amplify signals and rapidly detect EBC analytes with high sensitivity and specificity. Based on the collected data, standardizing the collection protocol and read-out methods across laboratories is essential for optimal data comparability. Larger cohorts should be considered to ensure a reliable reproducibility of the reported outputs. Future research directions should employ EBC-based nanosensors to unravel the unexplored omics of lung diseases, especially those linked to the brain–gut microbiota that might influence airway immunity.