Paper-based device functionalized with molecularly imprinted polymer in a face mask for active sampling and smart analysis of pH and ethyl acetate in exhaled breath.

Patients with Cystic fibrosis (CF) require frequent monitoring in evaluating lung infections, but current diagnostic approaches are invasive and resource-intensive. Ethyl acetate (EA) and pH changes in exhaled breath have emerged as promising non-invasive biomarkers. In this context, we report a smart face mask that integrates a dual-function paper-based analytical device (PAD) for sampling exhaled breath and detecting pH and EA after the mask is worn. The system combines molecularly imprinted polymers for selective EA adsorption, Candida antarctica lipase for enzymatic hydrolysis of EA into acetic acid, and an iridium oxide-modified electrode for sensitive pH monitoring. The (bio)sensing platform demonstrated high sensitivity and reproducibility across solution and aerosol, with linear ranges of pH 5.3-9 and EA concentrations from 0.01 to 2.5 mM, and a detection limit of 1.5 μM under breath-like conditions. Tests in human saliva aerosol confirmed high accuracy (89.7-106.8%recovery) and precision (<4.3% RSD), while selectivity studies showed no interference from common breath metabolites. By enabling rapid pH and EA quantification in a portable, low-cost format, this platform provides a robust and non-invasive tool for point-of-care CF diagnostics.