56 Monitoring Diesel Exhaust Particles by Lock-in Thermography

Abstract

Abstract Diesel exhaust particles (DEPs) can deposit onto the respiratory epithelial surface upon inhalation. In vitro exposures of various lung models to DEPs have been performed under the air-liquid interface (ALI) conditions in previous studies, however, methods to quantify DEPs onto/into cells during and after exposure are still challenging and not well established. In our study, a new particle detection system, i.e. lock-in thermography (LIT), was explored. LIT is a heat- sensitive imaging method that applies the light illumination to induce the heat of carbon-based particles for detection. By testing a standard DEPs sample (SRM2975), a positive linear relationship (R2 = 0.98) was established between the thermal emission signals and DEPs levels ranging from 0 to 30 µg/mL, with limit of detection (LOD) at 1.00 µg/mL. Moreover, phototoxicity tests showed that no cytotoxic effects were observed on human lung epithelial (A549) cells upon excitation light wavelength of 525 and 660 nm for 1 – 2 mins. Taken together, it suggests that the LIT can be used for detecting DEPs exposed with A549 cells at the relatively low concentration. Further improvement and optimization of the LIT system are ongoing to evaluate DEPs exposed lung cells.