Rapid and sensitive detection of wood smoke exposure biomarkers using europium fluorescent nanoparticle label/lateral flow immunoassay

Exposure to wood smoke is associated with various adverse health problems. Biomonitoring of smoke exposureassociated biomarkers provides accurate measurements of personally absorbed doses. As a specific metabolite of benzene, the quantitative measurement of S-phenylmercapturic acid (S-PMA) plays a vital role in evaluating human exposure to wood smoke. In this study, we developed an efficient lateral flow immunoassay (LFIA) approach for accurately and rapidly measuring S-PMA levels. Europium chelate nanoparticles (EuNPs) conjugated with purified polyclonal sheep anti-S-PMA antibodies were employed as the fluorescent detection probe. This work is based on a competitive immunoassay, where the target S-PMA competes with the immobilized antigen on the test lines for the limited antigen-binding sites on EuNP-conjugated antibodies. Due to this competition, the fluorescent intensity of the EuNPs is inversely proportional to the concentration of the target SPMA in the sample, enabling quantitative measurement. Owing to the large Stokes shift, superior fluorescent brightness, and saturation of the EuNPs, S-PMA levels can be measured with a limit of detection of 0.32 ng/mL, a detectable range of 0.10-30 ng/mL, and a linear detection range of 0.25-30 ng/mL under optimized conditions. Stability testing revealed that the LFIA strips can be stored at room temperature for up to one year while maintaining excellent detection performance for S-PMA. These results demonstrate that the EuNP-based LFIA is a promising tool for accurate preclinical and point-of-care evaluation of wood smoke exposure. A major advantage of this approach is its ability to accurately analyze smoke biomarkers at anticipated low concentrations. The sensor system allows low-cost, rapid, and on-site data collection and quantification of wood smoke exposure.