Novel correlative microscopy approach for nano-bio interface studies of nanoparticle-induced lung epithelial cell damage

Correlated light and electron microscopy (CLEM) has become essential in life sciences due to advancements in imaging resolution, sensitivity, and sample preservation. In nanotoxicology— specifically, studying the health effects of particulate matter exposure—CLEM can enable molecular-level structural as well as functional analysis of nanoparticle interactions with lung tissue, key for the understanding of modes of action. In our study, we for the first time implement an integrated high-resolution fluorescence lifetime imaging microscopy (FLIM) and hyperspectral fluorescence imaging (fHSI), scanning electron microscopy (SEM), ultra-high resolution helium ion microscopy (HIM) and synchrotron micro X-ray fluorescence (SR µXRF), to characterize the nano-bio interface and to better elucidate the modes of action of lung epithelial cells response to known inflammatory titanium dioxide nanotubes (TiO₂ NTs). Morpho-functional assessment uncovered several mechanisms associated with the extensive DNA, essential minerals and iron accumulation, cellular surface immobilization, and the localized formation of fibrous structures, all confirming immunomodulatory responses. These findings advance our understanding of the early cellular processes leading to inflammation development after lung epithelium exposure to these, high-aspect-ratio nanoparticles. The novel experimental approach, exploiting light, ion and electron sources, provides a robust framework for future research into nanoparticle toxicity and its impact on human health.