Exhaled breath condensate as bioanalyte: from collection considerations to biomarker sensing.

Since the SARS-CoV-2 pandemic, the potential of exhaled breath (EB) to provide valuable information and insight into the health status of a person has been revisited. Mass spectrometry (MS) has gained increasing attention as a powerful analytical tool for clinical diagnostics of exhaled breath aerosols (EBA) and exhaled breath condensates (EBC) due to its high sensitivity and specificity. Although MS will continue to play an important role in biomarker discovery in EB, its use in clinical setting is rather limited. EB analysis is moving toward online sampling with portable, room temperature operable, and inexpensive point-of-care devices capable of real-time measurements. This transition is happening due to the availability of highly performing biosensors and the use of wearable EB collection tools, mostly in the form of face masks. This feature article will outline the last developments in the field, notably the novel ways of EBA and EBC collection and the analytical aspects of the collected samples. The inherit non-invasive character of the sample collection approach might open new doors for efficient ways for a fast, non-invasive, and better diagnosis.

A mask-based diagnostic platform for point-of-care screening of Covid-19.

Diagnostics of SARS-CoV-2 infection using real-time reverse-transcription polymerase chain reaction (RT-PCR) on nasopharyngeal swabs is now well-established, with saliva-based testing being lately more widely implemented for being more adapted for self-testing approaches. In this study, we introduce a different concept based on exhaled breath condensate (EBC), readily collected by a mask-based sampling device, and detection with an electrochemical biosensor with a modular architecture that enables fast and specific detection and quantification of COVID-19. The face mask forms an exhaled breath vapor containment volume to hold the exhaled breath vapor in proximity to the EBC collector to enable a condensate-forming surface, cooled by a thermal mass, to coalesce the exhaled breath into a 200-500 µL fluid sample in 2 min. EBC RT-PCR for SARS-CoV-2 genes (E, ORF1ab) on samples collected from 7 SARS-CoV-2 positive and 7 SARS-CoV-2 negative patients were performed. The presence of SARS-CoV-2 could be detected in 5 out of 7 SARS-CoV-2 positive patients. Furthermore, the EBC samples were screened on an electrochemical aptamer biosensor, which detects SARS-CoV-2 viral particles down to 10 pfu mL-1 in cultured SARS-CoV-2 suspensions. Using a "turn off" assay via ferrocenemethanol redox mediator, results about the infectivity state of the patient are obtained in 10 min.