Combined cellular (Cells-on-Particles) and acellular (DTT) assessment of indoor vs outdoor PM_2.5 toxicity

Air pollution is a complex mixture of particles and gases, and its characterization by physical and chemical methods may not fully capture health-relevant effects. Assessing how pollutants interact with living cells provides complementary insight into their potential harmful effects. An integrated "Cells-on-Particles" platform was employed to assess the cytotoxicity of indoor and outdoor PM_2.5 using human bronchial epithelial BEAS-2B cells. In this model, cells are directly cultured on collected aerosol particles, enabling an assessment of particle-induced cellular responses. The biological assay was complemented by an acellular dithiothreitol (DTT) assay, which quantifies the oxidative activity of particles and provides insight into their redox activity. Both indoor and outdoor PM_2.5 induced dose-dependent cytotoxicity, with outdoor particles showing stronger effects and higher DTT activity. A strong inverse linear association between DTT activity and cell viability was observed (for indoor R² = 0.96; for outdoor R² = 0.99), consistent with oxidative activity contributing to the observed cellular effects within this dataset. Under the indoor sampling conditions and PM_2.5 size-selective collection, indoor PM_2.5 was consistent with predominantly infiltrated outdoor fine particles. The indoor-outdoor differences may reflect infiltration and indoor residence processes. These results demonstrate that integrating the "Cells-on-Particles" exposure model with the DTT assay provides an integrated, a deposition-relevant approach for evaluating the toxicological impact of complex aerosol mixtures.