A modified KN95 mask has brought exhaled nitric oxide (NO) detection into a wearable mass spectrometry format, offering a more practical route to on-site analysis of one of the best-established breath biomarkers for airway inflammation.
Exhaled NO is already used clinically, particularly in inflammatory airway disease, but most existing detection platforms remain poorly suited to portable, near-patient testing. The new study instead builds the assay around wearable collection and direct miniature-MS readout.
Their approach used paper strips preloaded with amlodipine inside the mask, together with a cooling device that condensed exhaled vapor onto the sampling surface. In that wet microenvironment, nitric oxide reacted with amlodipine to form dehydro amlodipine, which the researchers then detected directly by paper spray ionization miniature mass spectrometry. Tandem MS was used to confirm both the reagent and product ions.
The paper substrate, reagent concentration, and loading volume were then optimized so that the product signal could serve as a reliable readout of exhaled NO. Under those conditions, the assay delivered reproducible measurements and a detection limit low enough to cover typical exhaled NO screening ranges within minutes.
The workflow was also tested under more realistic sampling conditions. Humidity had little effect across the tested range, although ambient temperature did influence NO capture and detection performance, highlighting one of the main variables that would need tighter control in future point-of-care use.
For breath validation, healthy volunteers wore the modified mask after rinsing with either pure water or ascorbic acid, the latter chosen because it is known to elevate exhaled NO. The method detected clear DAM signals directly from breath, and showed significantly higher NO levels after ascorbic acid rinsing, supporting its ability to distinguish changes in exhaled NO under different conditions.
Because exhaled NO is already used to assess inflammatory airway disease, the authors suggest the mask-based workflow could provide a more practical route to on-site screening and follow-up in future clinical settings.
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